diff options
Diffstat (limited to 'doc/gawk.info')
| -rw-r--r-- | doc/gawk.info | 12682 |
1 files changed, 6702 insertions, 5980 deletions
diff --git a/doc/gawk.info b/doc/gawk.info index a5ef90b9..e60d0038 100644 --- a/doc/gawk.info +++ b/doc/gawk.info @@ -1,4 +1,4 @@ -This is gawk.info, produced by makeinfo version 4.5 from gawk.texi. +This is gawk.info, produced by makeinfo version 4.6 from gawk.texi. INFO-DIR-SECTION Text creation and manipulation START-INFO-DIR-ENTRY @@ -14,7 +14,7 @@ Copyright (C) 1989, 1991, 1992, 1993, 1996, 1997, 1998, 1999, 2000, This is Edition 3 of `GAWK: Effective AWK Programming: A User's -Guide for GNU Awk', for the 3.1.3 (or later) version of the GNU +Guide for GNU Awk', for the 3.1.4 (or later) version of the GNU implementation of AWK. Permission is granted to copy, distribute and/or modify this document @@ -30,14 +30,14 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) b. "You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development." - + File: gawk.info, Node: Top, Next: Foreword, Up: (dir) General Introduction ******************** - This file documents `awk', a program that you can use to select +This file documents `awk', a program that you can use to select particular records in a file and perform operations upon them. Copyright (C) 1989, 1991, 1992, 1993, 1996, 1997, 1998, 1999, 2000, @@ -45,7 +45,7 @@ Copyright (C) 1989, 1991, 1992, 1993, 1996, 1997, 1998, 1999, 2000, This is Edition 3 of `GAWK: Effective AWK Programming: A User's -Guide for GNU Awk', for the 3.1.3 (or later) version of the GNU +Guide for GNU Awk', for the 3.1.4 (or later) version of the GNU implementation of AWK. Permission is granted to copy, distribute and/or modify this document @@ -61,7 +61,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) b. "You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development." - + * Menu: * Foreword:: Some nice words about this @@ -456,6 +456,7 @@ texts being (a) (see below), and with the Back-Cover Texts being (b) To Nachum, for the added dimension. To Malka, for the new beginning. + File: gawk.info, Node: Foreword, Next: Preface, Prev: Top, Up: Top @@ -463,8 +464,8 @@ File: gawk.info, Node: Foreword, Next: Preface, Prev: Top, Up: Top Foreword ******** - Arnold Robbins and I are good friends. We were introduced 11 years -ago by circumstances--and our favorite programming language, AWK. The +Arnold Robbins and I are good friends. We were introduced 11 years ago +by circumstances--and our favorite programming language, AWK. The circumstances started a couple of years earlier. I was working at a new job and noticed an unplugged Unix computer sitting in the corner. No one knew how to use it, and neither did I. However, a couple of days @@ -549,7 +550,7 @@ File: gawk.info, Node: Preface, Next: Getting Started, Prev: Foreword, Up: T Preface ******* - Several kinds of tasks occur repeatedly when working with text files. +Several kinds of tasks occur repeatedly when working with text files. You might want to extract certain lines and discard the rest. Or you may need to make changes wherever certain patterns appear, but leave the rest of the file alone. Writing single-use programs for these @@ -558,14 +559,14 @@ inconvenient. Such jobs are often easier with `awk'. The `awk' utility interprets a special-purpose programming language that makes it easy to handle simple data-reformatting jobs. - The GNU implementation of `awk' is called `gawk'; it is fully +The GNU implementation of `awk' is called `gawk'; it is fully compatible with the System V Release 4 version of `awk'. `gawk' is also compatible with the POSIX specification of the `awk' language. This means that all properly written `awk' programs should work with `gawk'. Thus, we usually don't distinguish between `gawk' and other `awk' implementations. - Using `awk' allows you to: +Using `awk' allows you to: * Manage small, personal databases @@ -578,7 +579,7 @@ This means that all properly written `awk' programs should work with * Experiment with algorithms that you can adapt later to other computer languages - In addition, `gawk' provides facilities that make it easy to: +In addition, `gawk' provides facilities that make it easy to: * Extract bits and pieces of data for processing @@ -586,15 +587,15 @@ This means that all properly written `awk' programs should work with * Perform simple network communications - This Info file teaches you about the `awk' language and how you can -use it effectively. You should already be familiar with basic system +This Info file teaches you about the `awk' language and how you can use +it effectively. You should already be familiar with basic system commands, such as `cat' and `ls',(1) as well as basic shell facilities, such as input/output (I/O) redirection and pipes. - Implementations of the `awk' language are available for many -different computing environments. This Info file, while describing the -`awk' language in general, also describes the particular implementation -of `awk' called `gawk' (which stands for "GNU awk"). `gawk' runs on a +Implementations of the `awk' language are available for many different +computing environments. This Info file, while describing the `awk' +language in general, also describes the particular implementation of +`awk' called `gawk' (which stands for "GNU awk"). `gawk' runs on a broad range of Unix systems, ranging from 80386 PC-based computers up through large-scale systems, such as Crays. `gawk' has also been ported to Mac OS X, MS-DOS, Microsoft Windows (all versions) and OS/2 PCs, @@ -613,10 +614,10 @@ Atari and Amiga microcomputers, BeOS, Tandem D20, and VMS. * How To Contribute:: Helping to save the world. * Acknowledgments:: Acknowledgments. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) These commands are available on POSIX-compliant systems, as well -as on traditional Unix-based systems. If you are using some other +(1) These commands are available on POSIX-compliant systems, as well as +on traditional Unix-based systems. If you are using some other operating system, you still need to be familiar with the ideas of I/O redirection and pipes. @@ -636,7 +637,7 @@ History of `awk' and `gawk' After eight years, add another part `egrep' and two more parts C. Document very well and release. - The name `awk' comes from the initials of its designers: Alfred V. +The name `awk' comes from the initials of its designers: Alfred V. Aho, Peter J. Weinberger and Brian W. Kernighan. The original version of `awk' was written in 1977 at AT&T Bell Laboratories. In 1985, a new version made the programming language more powerful, introducing @@ -649,23 +650,23 @@ and Utilities standard further clarified the language. Both the `gawk' designers and the original Bell Laboratories `awk' designers provided feedback for the POSIX specification. - Paul Rubin wrote the GNU implementation, `gawk', in 1986. Jay -Fenlason completed it, with advice from Richard Stallman. John Woods +Paul Rubin wrote the GNU implementation, `gawk', in 1986. Jay Fenlason +completed it, with advice from Richard Stallman. John Woods contributed parts of the code as well. In 1988 and 1989, David Trueman, with help from me, thoroughly reworked `gawk' for compatibility with the newer `awk'. Circa 1995, I became the primary maintainer. Current development focuses on bug fixes, performance improvements, standards compliance, and occasionally, new features. - In May of 1997, Ju"rgen Kahrs felt the need for network access from +In May of 1997, Ju"rgen Kahrs felt the need for network access from `awk', and with a little help from me, set about adding features to do this for `gawk'. At that time, he also wrote the bulk of `TCP/IP Internetworking with `gawk'' (a separate document, available as part of the `gawk' distribution). His code finally became part of the main `gawk' distribution with `gawk' version 3.1. - *Note Contributors::, for a complete list of those who made -important contributions to `gawk'. +*Note Contributors::, for a complete list of those who made important +contributions to `gawk'. File: gawk.info, Node: Names, Next: This Manual, Prev: History, Up: Preface @@ -673,18 +674,18 @@ File: gawk.info, Node: Names, Next: This Manual, Prev: History, Up: Preface A Rose by Any Other Name ======================== - The `awk' language has evolved over the years. Full details are +The `awk' language has evolved over the years. Full details are provided in *Note Language History::. The language described in this Info file is often referred to as "new `awk'" (`nawk'). - Because of this, many systems have multiple versions of `awk'. Some +Because of this, many systems have multiple versions of `awk'. Some systems have an `awk' utility that implements the original version of the `awk' language and a `nawk' utility for the new version. Others have an `oawk' version for the "old `awk'" language and plain `awk' for the new one. Still others only have one version, which is usually the new one.(1) - All in all, this makes it difficult for you to know which version of +All in all, this makes it difficult for you to know which version of `awk' you should run when writing your programs. The best advice I can give here is to check your local documentation. Look for `awk', `oawk', and `nawk', as well as for `gawk'. It is likely that you already have @@ -692,14 +693,14 @@ some version of new `awk' on your system, which is what you should use when running your programs. (Of course, if you're reading this Info file, chances are good that you have `gawk'!) - Throughout this Info file, whenever we refer to a language feature -that should be available in any complete implementation of POSIX `awk', -we simply use the term `awk'. When referring to a feature that is +Throughout this Info file, whenever we refer to a language feature that +should be available in any complete implementation of POSIX `awk', we +simply use the term `awk'. When referring to a feature that is specific to the GNU implementation, we use the term `gawk'. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Often, these systems use `gawk' for their `awk' implementation! +(1) Often, these systems use `gawk' for their `awk' implementation! File: gawk.info, Node: This Manual, Next: Conventions, Prev: Names, Up: Preface @@ -707,107 +708,106 @@ File: gawk.info, Node: This Manual, Next: Conventions, Prev: Names, Up: Pref Using This Book =============== - The term `awk' refers to a particular program as well as to the +The term `awk' refers to a particular program as well as to the language you use to tell this program what to do. When we need to be careful, we call the language "the `awk' language," and the program "the `awk' utility." This Info file explains both the `awk' language and how to run the `awk' utility. The term "`awk' program" refers to a program written by you in the `awk' programming language. - Primarily, this Info file explains the features of `awk', as defined -in the POSIX standard. It does so in the context of the `gawk' +Primarily, this Info file explains the features of `awk', as defined in +the POSIX standard. It does so in the context of the `gawk' implementation. While doing so, it also attempts to describe important differences between `gawk' and other `awk' implementations.(1) Finally, any `gawk' features that are not in the POSIX standard for `awk' are noted. - There are subsections labelled as *Advanced Notes* scattered -throughout the Info file. They add a more complete explanation of -points that are relevant, but not likely to be of interest on first -reading. All appear in the index, under the heading "advanced -features." +There are subsections labelled as *Advanced Notes* scattered throughout +the Info file. They add a more complete explanation of points that are +relevant, but not likely to be of interest on first reading. All +appear in the index, under the heading "advanced features." - Most of the time, the examples use complete `awk' programs. In some -of the more advanced sections, only the part of the `awk' program that +Most of the time, the examples use complete `awk' programs. In some of +the more advanced sections, only the part of the `awk' program that illustrates the concept currently being described is shown. - While this Info file is aimed principally at people who have not been +While this Info file is aimed principally at people who have not been exposed to `awk', there is a lot of information here that even the `awk' expert should find useful. In particular, the description of POSIX `awk' and the example programs in *Note Library Functions::, and in *Note Sample Programs::, should be of interest. - *Note Getting Started::, provides the essentials you need to know to +*Note Getting Started::, provides the essentials you need to know to begin using `awk'. - *Note Regexp::, introduces regular expressions in general, and in +*Note Regexp::, introduces regular expressions in general, and in particular the flavors supported by POSIX `awk' and `gawk'. - *Note Reading Files::, describes how `awk' reads your data. It +*Note Reading Files::, describes how `awk' reads your data. It introduces the concepts of records and fields, as well as the `getline' command. I/O redirection is first described here. - *Note Printing::, describes how `awk' programs can produce output -with `print' and `printf'. +*Note Printing::, describes how `awk' programs can produce output with +`print' and `printf'. - *Note Expressions::, describes expressions, which are the basic +*Note Expressions::, describes expressions, which are the basic building blocks for getting most things done in a program. - *Note Patterns and Actions::, describes how to write patterns for +*Note Patterns and Actions::, describes how to write patterns for matching records, actions for doing something when a record is matched, and the built-in variables `awk' and `gawk' use. - *Note Arrays::, covers `awk''s one-and-only data structure: -associative arrays. Deleting array elements and whole arrays is also -described, as well as sorting arrays in `gawk'. +*Note Arrays::, covers `awk''s one-and-only data structure: associative +arrays. Deleting array elements and whole arrays is also described, as +well as sorting arrays in `gawk'. - *Note Functions::, describes the built-in functions `awk' and `gawk' +*Note Functions::, describes the built-in functions `awk' and `gawk' provide, as well as how to define your own functions. - *Note Internationalization::, describes special features in `gawk' -for translating program messages into different languages at runtime. +*Note Internationalization::, describes special features in `gawk' for +translating program messages into different languages at runtime. - *Note Advanced Features::, describes a number of `gawk'-specific +*Note Advanced Features::, describes a number of `gawk'-specific advanced features. Of particular note are the abilities to have two-way communications with another process, perform TCP/IP networking, and profile your `awk' programs. - *Note Invoking Gawk::, describes how to run `gawk', the meaning of -its command-line options, and how it finds `awk' program source files. +*Note Invoking Gawk::, describes how to run `gawk', the meaning of its +command-line options, and how it finds `awk' program source files. - *Note Library Functions::, and *Note Sample Programs::, provide many +*Note Library Functions::, and *Note Sample Programs::, provide many sample `awk' programs. Reading them allows you to see `awk' solving real problems. - *Note Language History::, describes how the `awk' language has -evolved since first release to present. It also describes how `gawk' -has acquired features over time. +*Note Language History::, describes how the `awk' language has evolved +since first release to present. It also describes how `gawk' has +acquired features over time. - *Note Installation::, describes how to get `gawk', how to compile it +*Note Installation::, describes how to get `gawk', how to compile it under Unix, and how to compile and use it on different non-Unix systems. It also describes how to report bugs in `gawk' and where to get three other freely available implementations of `awk'. - *Note Notes::, describes how to disable `gawk''s extensions, as well -as how to contribute new code to `gawk', how to write extension -libraries, and some possible future directions for `gawk' development. +*Note Notes::, describes how to disable `gawk''s extensions, as well as +how to contribute new code to `gawk', how to write extension libraries, +and some possible future directions for `gawk' development. - *Note Basic Concepts::, provides some very cursory background -material for those who are completely unfamiliar with computer -programming. Also centralized there is a discussion of some of the -issues surrounding floating-point numbers. +*Note Basic Concepts::, provides some very cursory background material +for those who are completely unfamiliar with computer programming. +Also centralized there is a discussion of some of the issues +surrounding floating-point numbers. - The *Note Glossary::, defines most, if not all, the significant -terms used throughout the book. If you find terms that you aren't -familiar with, try looking them up here. +The *Note Glossary::, defines most, if not all, the significant terms +used throughout the book. If you find terms that you aren't familiar +with, try looking them up here. - *Note Copying::, and *Note GNU Free Documentation License::, present +*Note Copying::, and *Note GNU Free Documentation License::, present the licenses that cover the `gawk' source code and this Info file, respectively. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) All such differences appear in the index under the entry +(1) All such differences appear in the index under the entry "differences in `awk' and `gawk'." @@ -816,15 +816,15 @@ File: gawk.info, Node: Conventions, Next: Manual History, Prev: This Manual, Typographical Conventions ========================= - This Info file is written using Texinfo, the GNU documentation +This Info file is written using Texinfo, the GNU documentation formatting language. A single Texinfo source file is used to produce both the printed and online versions of the documentation. This minor node briefly documents the typographical conventions used in Texinfo. - Examples you would type at the command-line are preceded by the -common shell primary and secondary prompts, `$' and `>'. Output from -the command is preceded by the glyph "-|". This typically represents -the command's standard output. Error messages, and other output on the +Examples you would type at the command-line are preceded by the common +shell primary and secondary prompts, `$' and `>'. Output from the +command is preceded by the glyph "-|". This typically represents the +command's standard output. Error messages, and other output on the command's standard error, are preceded by the glyph "error-->". For example: @@ -833,7 +833,7 @@ example: $ echo hello on stderr 1>&2 error--> hello on stderr - Characters that you type at the keyboard look `like this'. In +Characters that you type at the keyboard look `like this'. In particular, there are special characters called "control characters." These are characters that you type by holding down both the `CONTROL' key and another key, at the same time. For example, a `Ctrl-d' is typed @@ -847,14 +847,14 @@ Dark Corners illuminate, there's always a smaller but darker one. Brian Kernighan - Until the POSIX standard (and `The Gawk Manual'), many features of +Until the POSIX standard (and `The Gawk Manual'), many features of `awk' were either poorly documented or not documented at all. Descriptions of such features (often called "dark corners") are noted in this Info file with "(d.c.)". They also appear in the index under the heading "dark corner." - As noted by the opening quote, though, any coverage of dark corners -is, by definition, something that is incomplete. +As noted by the opening quote, though, any coverage of dark corners is, +by definition, something that is incomplete. File: gawk.info, Node: Manual History, Next: How To Contribute, Prev: Conventions, Up: Preface @@ -862,30 +862,28 @@ File: gawk.info, Node: Manual History, Next: How To Contribute, Prev: Convent The GNU Project and This Book ============================= - The Free Software Foundation (FSF) is a nonprofit organization -dedicated to the production and distribution of freely distributable -software. It was founded by Richard M. Stallman, the author of the -original Emacs editor. GNU Emacs is the most widely used version of -Emacs today. - - The GNU(1) Project is an ongoing effort on the part of the Free -Software Foundation to create a complete, freely distributable, -POSIX-compliant computing environment. The FSF uses the "GNU General -Public License" (GPL) to ensure that their software's source code is -always available to the end user. A copy of the GPL is included for -your reference (*note Copying::). The GPL applies to the C language -source code for `gawk'. To find out more about the FSF and the GNU -Project online, see the GNU Project's home page (http://www.gnu.org). -This Info file may also be read from their web site -(http://www.gnu.org/manual/gawk/). - - A shell, an editor (Emacs), highly portable optimizing C, C++, and +The Free Software Foundation (FSF) is a nonprofit organization dedicated +to the production and distribution of freely distributable software. +It was founded by Richard M. Stallman, the author of the original Emacs +editor. GNU Emacs is the most widely used version of Emacs today. + +The GNU(1) Project is an ongoing effort on the part of the Free Software +Foundation to create a complete, freely distributable, POSIX-compliant +computing environment. The FSF uses the "GNU General Public License" +(GPL) to ensure that their software's source code is always available +to the end user. A copy of the GPL is included for your reference +(*note Copying::). The GPL applies to the C language source code for +`gawk'. To find out more about the FSF and the GNU Project online, see +the GNU Project's home page (http://www.gnu.org). This Info file may +also be read from their web site (http://www.gnu.org/manual/gawk/). + +A shell, an editor (Emacs), highly portable optimizing C, C++, and Objective-C compilers, a symbolic debugger and dozens of large and small utilities (such as `gawk'), have all been completed and are freely available. The GNU operating system kernel (the HURD), has been released but is still in an early stage of development. - Until the GNU operating system is more fully developed, you should +Until the GNU operating system is more fully developed, you should consider using GNU/Linux, a freely distributable, Unix-like operating system for Intel 80386, DEC Alpha, Sun SPARC, IBM S/390, and other systems.(2) There are many books on GNU/Linux. One that is freely @@ -897,35 +895,35 @@ systems: NetBSD, FreeBSD, and OpenBSD. All are based on the 4.4-Lite Berkeley Software Distribution, and they use recent versions of `gawk' for their versions of `awk'.) - The Info file itself has gone through a number of previous editions. +The Info file itself has gone through a number of previous editions. Paul Rubin wrote the very first draft of `The GAWK Manual'; it was around 40 pages in size. Diane Close and Richard Stallman improved it, yielding a version that was around 90 pages long and barely described the original, "old" version of `awk'. - I started working with that version in the fall of 1988. As work on -it progressed, the FSF published several preliminary versions (numbered +I started working with that version in the fall of 1988. As work on it +progressed, the FSF published several preliminary versions (numbered 0.X). In 1996, Edition 1.0 was released with `gawk' 3.0.0. The FSF published the first two editions under the title `The GNU Awk User's Guide'. - This edition maintains the basic structure of Edition 1.0, but with +This edition maintains the basic structure of Edition 1.0, but with significant additional material, reflecting the host of new features in `gawk' version 3.1. Of particular note is *Note Array Sorting::, as well as *Note Bitwise Functions::, *Note Internationalization::, and also *Note Advanced Features::, and *Note Dynamic Extensions::. - `GAWK: Effective AWK Programming' will undoubtedly continue to -evolve. An electronic version comes with the `gawk' distribution from -the FSF. If you find an error in this Info file, please report it! -*Note Bugs::, for information on submitting problem reports -electronically, or write to me in care of the publisher. +`GAWK: Effective AWK Programming' will undoubtedly continue to evolve. +An electronic version comes with the `gawk' distribution from the FSF. +If you find an error in this Info file, please report it! *Note +Bugs::, for information on submitting problem reports electronically, +or write to me in care of the publisher. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) GNU stands for "GNU's not Unix." +(1) GNU stands for "GNU's not Unix." - (2) The terminology "GNU/Linux" is explained in the *Note Glossary::. +(2) The terminology "GNU/Linux" is explained in the *Note Glossary::. File: gawk.info, Node: How To Contribute, Next: Acknowledgments, Prev: Manual History, Up: Preface @@ -933,13 +931,13 @@ File: gawk.info, Node: How To Contribute, Next: Acknowledgments, Prev: Manual How to Contribute ================= - As the maintainer of GNU `awk', I am starting a collection of -publicly available `awk' programs. For more information, see +As the maintainer of GNU `awk', I am starting a collection of publicly +available `awk' programs. For more information, see `ftp://ftp.freefriends.org/arnold/Awkstuff'. If you have written an interesting `awk' program, or have written a `gawk' extension that you would like to share with the rest of the world, please contact me -(<arnold@gnu.org>). Making things available on the Internet helps keep -the `gawk' distribution down to manageable size. +(<arnold@skeeve.com>). Making things available on the Internet helps +keep the `gawk' distribution down to manageable size. File: gawk.info, Node: Acknowledgments, Prev: How To Contribute, Up: Preface @@ -947,7 +945,7 @@ File: gawk.info, Node: Acknowledgments, Prev: How To Contribute, Up: Preface Acknowledgments =============== - The initial draft of `The GAWK Manual' had the following +The initial draft of `The GAWK Manual' had the following acknowledgments: Many people need to be thanked for their assistance in producing @@ -959,59 +957,59 @@ acknowledgments: implementation and to this manual, that would otherwise have escaped us. - I would like to acknowledge Richard M. Stallman, for his vision of a +I would like to acknowledge Richard M. Stallman, for his vision of a better world and for his courage in founding the FSF and starting the GNU Project. - The following people (in alphabetical order) provided helpful -comments on various versions of this book, up to and including this -edition. Rick Adams, Nelson H.F. Beebe, Karl Berry, Dr. Michael -Brennan, Rich Burridge, Claire Cloutier, Diane Close, Scott Deifik, -Christopher ("Topher") Eliot, Jeffrey Friedl, Dr. Darrel Hankerson, -Michal Jaegermann, Dr. Richard J. LeBlanc, Michael Lijewski, Pat Rankin, +The following people (in alphabetical order) provided helpful comments +on various versions of this book, up to and including this edition. +Rick Adams, Nelson H.F. Beebe, Karl Berry, Dr. Michael Brennan, Rich +Burridge, Claire Cloutier, Diane Close, Scott Deifik, Christopher +("Topher") Eliot, Jeffrey Friedl, Dr. Darrel Hankerson, Michal +Jaegermann, Dr. Richard J. LeBlanc, Michael Lijewski, Pat Rankin, Miriam Robbins, Mary Sheehan, and Chuck Toporek. - Robert J. Chassell provided much valuable advice on the use of -Texinfo. He also deserves special thanks for convincing me _not_ to -title this Info file `How To Gawk Politely'. Karl Berry helped -significantly with the TeX part of Texinfo. +Robert J. Chassell provided much valuable advice on the use of Texinfo. +He also deserves special thanks for convincing me _not_ to title this +Info file `How To Gawk Politely'. Karl Berry helped significantly with +the TeX part of Texinfo. - I would like to thank Marshall and Elaine Hartholz of Seattle and -Dr. Bert and Rita Schreiber of Detroit for large amounts of quiet -vacation time in their homes, which allowed me to make significant -progress on this Info file and on `gawk' itself. +I would like to thank Marshall and Elaine Hartholz of Seattle and Dr. +Bert and Rita Schreiber of Detroit for large amounts of quiet vacation +time in their homes, which allowed me to make significant progress on +this Info file and on `gawk' itself. - Phil Hughes of SSC contributed in a very important way by loaning me +Phil Hughes of SSC contributed in a very important way by loaning me his laptop GNU/Linux system, not once, but twice, which allowed me to do a lot of work while away from home. - David Trueman deserves special credit; he has done a yeoman job of +David Trueman deserves special credit; he has done a yeoman job of evolving `gawk' so that it performs well and without bugs. Although he is no longer involved with `gawk', working with him on this project was a significant pleasure. - The intrepid members of the GNITS mailing list, and most notably -Ulrich Drepper, provided invaluable help and feedback for the design of -the internationalization features. +The intrepid members of the GNITS mailing list, and most notably Ulrich +Drepper, provided invaluable help and feedback for the design of the +internationalization features. - Nelson Beebe, Martin Brown, Andreas Buening, Scott Deifik, Darrel +Nelson Beebe, Martin Brown, Andreas Buening, Scott Deifik, Darrel Hankerson, Isamu Hasegawa, Michal Jaegermann, Ju"rgen Kahrs, Pat Rankin, Kai Uwe Rommel, and Eli Zaretskii (in alphabetical order) make up the `gawk' "crack portability team." Without their hard work and help, `gawk' would not be nearly the fine program it is today. It has been and continues to be a pleasure working with this team of fine people. - David and I would like to thank Brian Kernighan of Bell Laboratories -for invaluable assistance during the testing and debugging of `gawk', -and for help in clarifying numerous points about the language. We -could not have done nearly as good a job on either `gawk' or its +David and I would like to thank Brian Kernighan of Bell Laboratories for +invaluable assistance during the testing and debugging of `gawk', and +for help in clarifying numerous points about the language. We could +not have done nearly as good a job on either `gawk' or its documentation without his help. - Chuck Toporek, Mary Sheehan, and Claire Coutier of O'Reilly & +Chuck Toporek, Mary Sheehan, and Claire Coutier of O'Reilly & Associates contributed significant editorial help for this Info file for the 3.1 release of `gawk'. - I must thank my wonderful wife, Miriam, for her patience through the +I must thank my wonderful wife, Miriam, for her patience through the many versions of this project, for her proofreading, and for sharing me with the computer. I would like to thank my parents for their love, and for the grace with which they raised and educated me. Finally, I @@ -1028,32 +1026,32 @@ March, 2001 File: gawk.info, Node: Getting Started, Next: Regexp, Prev: Preface, Up: Top -Getting Started with `awk' -************************** +1 Getting Started with `awk' +**************************** - The basic function of `awk' is to search files for lines (or other +The basic function of `awk' is to search files for lines (or other units of text) that contain certain patterns. When a line matches one of the patterns, `awk' performs specified actions on that line. `awk' keeps processing input lines in this way until it reaches the end of the input files. - Programs in `awk' are different from programs in most other -languages, because `awk' programs are "data-driven"; that is, you -describe the data you want to work with and then what to do when you -find it. Most other languages are "procedural"; you have to describe, -in great detail, every step the program is to take. When working with -procedural languages, it is usually much harder to clearly describe the -data your program will process. For this reason, `awk' programs are -often refreshingly easy to read and write. +Programs in `awk' are different from programs in most other languages, +because `awk' programs are "data-driven"; that is, you describe the +data you want to work with and then what to do when you find it. Most +other languages are "procedural"; you have to describe, in great +detail, every step the program is to take. When working with procedural +languages, it is usually much harder to clearly describe the data your +program will process. For this reason, `awk' programs are often +refreshingly easy to read and write. - When you run `awk', you specify an `awk' "program" that tells `awk' +When you run `awk', you specify an `awk' "program" that tells `awk' what to do. The program consists of a series of "rules". (It may also contain "function definitions", an advanced feature that we will ignore for now. *Note User-defined::.) Each rule specifies one pattern to search for and one action to perform upon finding the pattern. - Syntactically, a rule consists of a pattern followed by an action. -The action is enclosed in curly braces to separate it from the pattern. +Syntactically, a rule consists of a pattern followed by an action. The +action is enclosed in curly braces to separate it from the pattern. Newlines usually separate rules. Therefore, an `awk' program looks like this: @@ -1080,21 +1078,21 @@ like this: File: gawk.info, Node: Running gawk, Next: Sample Data Files, Up: Getting Started -How to Run `awk' Programs -========================= +1.1 How to Run `awk' Programs +============================= - There are several ways to run an `awk' program. If the program is +There are several ways to run an `awk' program. If the program is short, it is easiest to include it in the command that runs `awk', like this: awk 'PROGRAM' INPUT-FILE1 INPUT-FILE2 ... - When the program is long, it is usually more convenient to put it in -a file and run it with a command like this: +When the program is long, it is usually more convenient to put it in a +file and run it with a command like this: awk -f PROGRAM-FILE INPUT-FILE1 INPUT-FILE2 ... - This minor node discusses both mechanisms, along with several +This minor node discusses both mechanisms, along with several variations of each. * Menu: @@ -1113,10 +1111,10 @@ variations of each. File: gawk.info, Node: One-shot, Next: Read Terminal, Up: Running gawk -One-Shot Throwaway `awk' Programs ---------------------------------- +1.1.1 One-Shot Throwaway `awk' Programs +--------------------------------------- - Once you are familiar with `awk', you will often type in simple +Once you are familiar with `awk', you will often type in simple programs the moment you want to use them. Then you can write the program as the first argument of the `awk' command, like this: @@ -1125,27 +1123,27 @@ program as the first argument of the `awk' command, like this: where PROGRAM consists of a series of PATTERNS and ACTIONS, as described earlier. - This command format instructs the "shell", or command interpreter, -to start `awk' and use the PROGRAM to process records in the input +This command format instructs the "shell", or command interpreter, to +start `awk' and use the PROGRAM to process records in the input file(s). There are single quotes around PROGRAM so the shell won't interpret any `awk' characters as special shell characters. The quotes also cause the shell to treat all of PROGRAM as a single argument for `awk', and allow PROGRAM to be more than one line long. - This format is also useful for running short or medium-sized `awk' +This format is also useful for running short or medium-sized `awk' programs from shell scripts, because it avoids the need for a separate file for the `awk' program. A self-contained shell script is more reliable because there are no other files to misplace. - *Note Very Simple::, presents several short, self-contained programs. +*Note Very Simple::, presents several short, self-contained programs. File: gawk.info, Node: Read Terminal, Next: Long, Prev: One-shot, Up: Running gawk -Running `awk' Without Input Files ---------------------------------- +1.1.2 Running `awk' Without Input Files +--------------------------------------- - You can also run `awk' without any input files. If you type the +You can also run `awk' without any input files. If you type the following command line: awk 'PROGRAM' @@ -1156,20 +1154,19 @@ end-of-file by typing `Ctrl-d'. (On other operating systems, the end-of-file character may be different. For example, on OS/2 and MS-DOS, it is `Ctrl-z'.) - As an example, the following program prints a friendly piece of -advice (from Douglas Adams's `The Hitchhiker's Guide to the Galaxy'), -to keep you from worrying about the complexities of computer programming +As an example, the following program prints a friendly piece of advice +(from Douglas Adams's `The Hitchhiker's Guide to the Galaxy'), to keep +you from worrying about the complexities of computer programming (`BEGIN' is a feature we haven't discussed yet): $ awk "BEGIN { print \"Don't Panic!\" }" -| Don't Panic! - This program does not read any input. The `\' before each of the -inner double quotes is necessary because of the shell's quoting -rules--in particular because it mixes both single quotes and double -quotes.(1) +This program does not read any input. The `\' before each of the inner +double quotes is necessary because of the shell's quoting rules--in +particular because it mixes both single quotes and double quotes.(1) - This next simple `awk' program emulates the `cat' utility; it copies +This next simple `awk' program emulates the `cat' utility; it copies whatever you type on the keyboard to its standard output (why this works is explained shortly). @@ -1184,26 +1181,26 @@ works is explained shortly). -| What, me worry? Ctrl-d - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Although we generally recommend the use of single quotes around -the program text, double quotes are needed here in order to put the -single quote into the message. +(1) Although we generally recommend the use of single quotes around the +program text, double quotes are needed here in order to put the single +quote into the message. File: gawk.info, Node: Long, Next: Executable Scripts, Prev: Read Terminal, Up: Running gawk -Running Long Programs ---------------------- +1.1.3 Running Long Programs +--------------------------- - Sometimes your `awk' programs can be very long. In this case, it is +Sometimes your `awk' programs can be very long. In this case, it is more convenient to put the program into a separate file. In order to tell `awk' to use that file for its program, you type: awk -f SOURCE-FILE INPUT-FILE1 INPUT-FILE2 ... - The `-f' instructs the `awk' utility to get the `awk' program from -the file SOURCE-FILE. Any file name can be used for SOURCE-FILE. For +The `-f' instructs the `awk' utility to get the `awk' program from the +file SOURCE-FILE. Any file name can be used for SOURCE-FILE. For example, you could put the program: BEGIN { print "Don't Panic!" } @@ -1223,24 +1220,23 @@ special characters. Notice that in `advice', the `awk' program did not have single quotes around it. The quotes are only needed for programs that are provided on the `awk' command line. - If you want to identify your `awk' program files clearly as such, -you can add the extension `.awk' to the file name. This doesn't affect -the execution of the `awk' program but it does make "housekeeping" -easier. +If you want to identify your `awk' program files clearly as such, you +can add the extension `.awk' to the file name. This doesn't affect the +execution of the `awk' program but it does make "housekeeping" easier. File: gawk.info, Node: Executable Scripts, Next: Comments, Prev: Long, Up: Running gawk -Executable `awk' Programs -------------------------- +1.1.4 Executable `awk' Programs +------------------------------- - Once you have learned `awk', you may want to write self-contained -`awk' scripts, using the `#!' script mechanism. You can do this on -many Unix systems(1) as well as on the GNU system. For example, you -could update the file `advice' to look like this: +Once you have learned `awk', you may want to write self-contained `awk' +scripts, using the `#!' script mechanism. You can do this on many Unix +systems(1) as well as on the GNU system. For example, you could update +the file `advice' to look like this: #! /bin/awk -f - + BEGIN { print "Don't Panic!" } After making this file executable (with the `chmod' utility), simply @@ -1255,35 +1251,35 @@ if you had typed `awk -f advice': variable (typically `$PATH'). If not, you may need to type `./advice' at the shell.) - Self-contained `awk' scripts are useful when you want to write a +Self-contained `awk' scripts are useful when you want to write a program that users can invoke without their having to know that the program is written in `awk'. Advanced Notes: Portability Issues with `#!' -------------------------------------------- - Some systems limit the length of the interpreter name to 32 -characters. Often, this can be dealt with by using a symbolic link. +Some systems limit the length of the interpreter name to 32 characters. +Often, this can be dealt with by using a symbolic link. - You should not put more than one argument on the `#!' line after the +You should not put more than one argument on the `#!' line after the path to `awk'. It does not work. The operating system treats the rest of the line as a single argument and passes it to `awk'. Doing this leads to confusing behavior--most likely a usage diagnostic of some sort from `awk'. - Finally, the value of `ARGV[0]' (*note Built-in Variables::) varies +Finally, the value of `ARGV[0]' (*note Built-in Variables::) varies depending upon your operating system. Some systems put `awk' there, some put the full pathname of `awk' (such as `/bin/awk'), and some put the name of your script (`advice'). Don't rely on the value of `ARGV[0]' to provide your script name. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) The `#!' mechanism works on Linux systems, systems derived from -the 4.4-Lite Berkeley Software Distribution, and most commercial Unix +(1) The `#!' mechanism works on Linux systems, systems derived from the +4.4-Lite Berkeley Software Distribution, and most commercial Unix systems. - (2) The line beginning with `#!' lists the full file name of an +(2) The line beginning with `#!' lists the full file name of an interpreter to run and an optional initial command-line argument to pass to that interpreter. The operating system then runs the interpreter with the given argument and the full argument list of the @@ -1294,64 +1290,63 @@ options to `awk', or data files, or both. File: gawk.info, Node: Comments, Next: Quoting, Prev: Executable Scripts, Up: Running gawk -Comments in `awk' Programs --------------------------- +1.1.6 Comments in `awk' Programs +-------------------------------- - A "comment" is some text that is included in a program for the sake -of human readers; it is not really an executable part of the program. +A "comment" is some text that is included in a program for the sake of +human readers; it is not really an executable part of the program. Comments can explain what the program does and how it works. Nearly all programming languages have provisions for comments, as programs are typically hard to understand without them. - In the `awk' language, a comment starts with the sharp sign -character (`#') and continues to the end of the line. The `#' does not -have to be the first character on the line. The `awk' language ignores -the rest of a line following a sharp sign. For example, we could have -put the following into `advice': +In the `awk' language, a comment starts with the sharp sign character +(`#') and continues to the end of the line. The `#' does not have to +be the first character on the line. The `awk' language ignores the rest +of a line following a sharp sign. For example, we could have put the +following into `advice': # This program prints a nice friendly message. It helps # keep novice users from being afraid of the computer. BEGIN { print "Don't Panic!" } - You can put comment lines into keyboard-composed throwaway `awk' +You can put comment lines into keyboard-composed throwaway `awk' programs, but this usually isn't very useful; the purpose of a comment is to help you or another person understand the program when reading it at a later time. - *Caution:* As mentioned in *Note One-shot::, you can enclose small -to medium programs in single quotes, in order to keep your shell -scripts self-contained. When doing so, _don't_ put an apostrophe -(i.e., a single quote) into a comment (or anywhere else in your -program). The shell interprets the quote as the closing quote for the -entire program. As a result, usually the shell prints a message about -mismatched quotes, and if `awk' actually runs, it will probably print -strange messages about syntax errors. For example, look at the -following: +*Caution:* As mentioned in *Note One-shot::, you can enclose small to +medium programs in single quotes, in order to keep your shell scripts +self-contained. When doing so, _don't_ put an apostrophe (i.e., a +single quote) into a comment (or anywhere else in your program). The +shell interprets the quote as the closing quote for the entire program. +As a result, usually the shell prints a message about mismatched +quotes, and if `awk' actually runs, it will probably print strange +messages about syntax errors. For example, look at the following: $ awk '{ print "hello" } # let's be cute' > - The shell sees that the first two quotes match, and that a new -quoted object begins at the end of the command line. It therefore -prompts with the secondary prompt, waiting for more input. With Unix -`awk', closing the quoted string produces this result: +The shell sees that the first two quotes match, and that a new quoted +object begins at the end of the command line. It therefore prompts +with the secondary prompt, waiting for more input. With Unix `awk', +closing the quoted string produces this result: $ awk '{ print "hello" } # let's be cute' > ' error--> awk: can't open file be error--> source line number 1 - Putting a backslash before the single quote in `let's' wouldn't help, +Putting a backslash before the single quote in `let's' wouldn't help, since backslashes are not special inside single quotes. The next node describes the shell's quoting rules. File: gawk.info, Node: Quoting, Prev: Comments, Up: Running gawk -Shell-Quoting Issues --------------------- +1.1.7 Shell-Quoting Issues +-------------------------- - For short to medium length `awk' programs, it is most convenient to +For short to medium length `awk' programs, it is most convenient to enter the program on the `awk' command line. This is best done by enclosing the entire program in single quotes. This is true whether you are entering the program interactively at the shell prompt, or @@ -1359,7 +1354,7 @@ writing it as part of a larger shell script: awk 'PROGRAM TEXT' INPUT-FILE1 INPUT-FILE2 ... - Once you are working with the shell, it is helpful to have a basic +Once you are working with the shell, it is helpful to have a basic knowledge of shell quoting rules. The following rules apply only to POSIX-compliant, Bourne-style shells (such as `bash', the GNU Bourne-Again Shell). If you use `csh', you're on your own. @@ -1412,7 +1407,7 @@ Bourne-Again Shell). If you use `csh', you're on your own. of the program! This results in syntax errors at best, and confusing behavior at worst. - Mixing single and double quotes is difficult. You have to resort to +Mixing single and double quotes is difficult. You have to resort to shell quoting tricks, like this: $ awk 'BEGIN { print "Here is a single quote <'"'"'>" }' @@ -1421,14 +1416,14 @@ shell quoting tricks, like this: This program consists of three concatenated quoted strings. The first and the third are single-quoted, the second is double-quoted. - This can be "simplified" to: +This can be "simplified" to: $ awk 'BEGIN { print "Here is a single quote <'\''>" }' -| Here is a single quote <'> Judge for yourself which of these two is the more readable. - Another option is to use double quotes, escaping the embedded, +Another option is to use double quotes, escaping the embedded, `awk'-level double quotes: $ awk "BEGIN { print \"Here is a single quote <'>\" }" @@ -1437,29 +1432,45 @@ Judge for yourself which of these two is the more readable. This option is also painful, because double quotes, backslashes, and dollar signs are very common in `awk' programs. - If you really need both single and double quotes in your `awk' -program, it is probably best to move it into a separate file, where the -shell won't be part of the picture, and you can say what you mean. +A third option is to use the octal escape sequence equivalents for the +single- and double-quote characters, like so: + + $ awk 'BEGIN { print "Here is a single quote <\47>" }' + -| Here is a single quote <'> + $ awk 'BEGIN { print "Here is a double quote <\42>" }' + -| Here is a double quote <"> + +This works nicely, except that you should comment clearly what the +escapes mean. + +A fourth option is to use command-line variable assignment, like this: + + $ awk -v sq="'" 'BEGIN { print "Here is a single quote <" sq ">" }' + -| Here is a single quote <'> + +If you really need both single and double quotes in your `awk' program, +it is probably best to move it into a separate file, where the shell +won't be part of the picture, and you can say what you mean. File: gawk.info, Node: Sample Data Files, Next: Very Simple, Prev: Running gawk, Up: Getting Started -Data Files for the Examples -=========================== +1.2 Data Files for the Examples +=============================== - Many of the examples in this Info file take their input from two -sample data files. The first, `BBS-list', represents a list of -computer bulletin board systems together with information about those -systems. The second data file, called `inventory-shipped', contains -information about monthly shipments. In both files, each line is -considered to be one "record". +Many of the examples in this Info file take their input from two sample +data files. The first, `BBS-list', represents a list of computer +bulletin board systems together with information about those systems. +The second data file, called `inventory-shipped', contains information +about monthly shipments. In both files, each line is considered to be +one "record". - In the data file `BBS-list', each record contains the name of a -computer bulletin board, its phone number, the board's baud rate(s), -and a code for the number of hours it is operational. An `A' in the -last column means the board operates 24 hours a day. A `B' in the last -column means the board only operates on evening and weekend hours. A -`C' means the board operates only on weekends: +In the data file `BBS-list', each record contains the name of a computer +bulletin board, its phone number, the board's baud rate(s), and a code +for the number of hours it is operational. An `A' in the last column +means the board operates 24 hours a day. A `B' in the last column +means the board only operates on evening and weekend hours. A `C' +means the board operates only on weekends: aardvark 555-5553 1200/300 B alpo-net 555-3412 2400/1200/300 A @@ -1473,7 +1484,7 @@ column means the board only operates on evening and weekend hours. A sdace 555-3430 2400/1200/300 A sabafoo 555-2127 1200/300 C - The data file `inventory-shipped' represents information about +The data file `inventory-shipped' represents information about shipments during the year. Each record contains the month, the number of green crates shipped, the number of red boxes shipped, the number of orange bags shipped, and the number of blue packages shipped, @@ -1492,13 +1503,13 @@ and the first four months of the current year. Oct 29 54 68 525 Nov 20 87 82 577 Dec 17 35 61 401 - + Jan 21 36 64 620 Feb 26 58 80 652 Mar 24 75 70 495 Apr 21 70 74 514 - If you are reading this in GNU Emacs using Info, you can copy the +If you are reading this in GNU Emacs using Info, you can copy the regions of text showing these sample files into your own test files. This way you can try out the examples shown in the remainder of this document. You do this by using the command `M-x write-region' to copy @@ -1507,17 +1518,17 @@ Miscellaneous File Operations: (emacs)Misc File Ops, for more information). Using this information, create your own `BBS-list' and `inventory-shipped' files and practice what you learn in this Info file. - If you are using the stand-alone version of Info, see *Note Extract +If you are using the stand-alone version of Info, see *Note Extract Program::, for an `awk' program that extracts these data files from `gawk.texi', the Texinfo source file for this Info file. File: gawk.info, Node: Very Simple, Next: Two Rules, Prev: Sample Data Files, Up: Getting Started -Some Simple Examples -==================== +1.3 Some Simple Examples +======================== - The following command runs a simple `awk' program that searches the +The following command runs a simple `awk' program that searches the input file `BBS-list' for the character string `foo' (a grouping of characters is usually called a "string"; the term "string" is based on similar usage in English, such as "a string of pearls," or "a string of @@ -1529,7 +1540,7 @@ When lines containing `foo' are found, they are printed because `print $0' means print the current line. (Just `print' by itself means the same thing, so we could have written that instead.) - You will notice that slashes (`/') surround the string `foo' in the +You will notice that slashes (`/') surround the string `foo' in the `awk' program. The slashes indicate that `foo' is the pattern to search for. This type of pattern is called a "regular expression", which is covered in more detail later (*note Regexp::). The pattern is @@ -1537,7 +1548,7 @@ allowed to match parts of words. There are single quotes around the `awk' program so that the shell won't interpret any of it as special shell characters. - Here is what this program prints: +Here is what this program prints: $ awk '/foo/ { print $0 }' BBS-list -| fooey 555-1234 2400/1200/300 B @@ -1545,18 +1556,18 @@ shell characters. -| macfoo 555-6480 1200/300 A -| sabafoo 555-2127 1200/300 C - In an `awk' rule, either the pattern or the action can be omitted, -but not both. If the pattern is omitted, then the action is performed -for _every_ input line. If the action is omitted, the default action -is to print all lines that match the pattern. +In an `awk' rule, either the pattern or the action can be omitted, but +not both. If the pattern is omitted, then the action is performed for +_every_ input line. If the action is omitted, the default action is to +print all lines that match the pattern. - Thus, we could leave out the action (the `print' statement and the -curly braces) in the previous example and the result would be the same: -all lines matching the pattern `foo' are printed. By comparison, -omitting the `print' statement but retaining the curly braces makes an -empty action that does nothing (i.e., no lines are printed). +Thus, we could leave out the action (the `print' statement and the curly +braces) in the previous example and the result would be the same: all +lines matching the pattern `foo' are printed. By comparison, omitting +the `print' statement but retaining the curly braces makes an empty +action that does nothing (i.e., no lines are printed). - Many practical `awk' programs are just a line or two. Following is a +Many practical `awk' programs are just a line or two. Following is a collection of useful, short programs to get you started. Some of these programs contain constructs that haven't been covered yet. (The description of the program will give you a good idea of what is going @@ -1630,20 +1641,20 @@ different ways to do the same things shown here: File: gawk.info, Node: Two Rules, Next: More Complex, Prev: Very Simple, Up: Getting Started -An Example with Two Rules -========================= +1.4 An Example with Two Rules +============================= - The `awk' utility reads the input files one line at a time. For -each line, `awk' tries the patterns of each of the rules. If several +The `awk' utility reads the input files one line at a time. For each +line, `awk' tries the patterns of each of the rules. If several patterns match, then several actions are run in the order in which they appear in the `awk' program. If no patterns match, then no actions are run. - After processing all the rules that match the line (and perhaps -there are none), `awk' reads the next line. (However, *note Next -Statement::, and also *note Nextfile Statement::). This continues -until the program reaches the end of the file. For example, the -following `awk' program contains two rules: +After processing all the rules that match the line (and perhaps there +are none), `awk' reads the next line. (However, *note Next Statement::, +and also *note Nextfile Statement::). This continues until the program +reaches the end of the file. For example, the following `awk' program +contains two rules: /12/ { print $0 } /21/ { print $0 } @@ -1653,11 +1664,11 @@ action. The second rule has the string `21' as the pattern and also has `print $0' as the action. Each rule's action is enclosed in its own pair of braces. - This program prints every line that contains the string `12' _or_ -the string `21'. If a line contains both strings, it is printed twice, +This program prints every line that contains the string `12' _or_ the +string `21'. If a line contains both strings, it is printed twice, once by each rule. - This is what happens if we run this program on our two sample data +This is what happens if we run this program on our two sample data files, `BBS-list' and `inventory-shipped': $ awk '/12/ { print $0 } @@ -1682,11 +1693,11 @@ twice, once for each rule. File: gawk.info, Node: More Complex, Next: Statements/Lines, Prev: Two Rules, Up: Getting Started -A More Complex Example -====================== +1.5 A More Complex Example +========================== - Now that we've mastered some simple tasks, let's look at what -typical `awk' programs do. This example shows how `awk' can be used to +Now that we've mastered some simple tasks, let's look at what typical +`awk' programs do. This example shows how `awk' can be used to summarize, select, and rearrange the output of another utility. It uses features that haven't been covered yet, so don't worry if you don't understand all the details: @@ -1694,7 +1705,7 @@ understand all the details: ls -l | awk '$6 == "Nov" { sum += $5 } END { print sum }' - This command prints the total number of bytes in all the files in the +This command prints the total number of bytes in all the files in the current directory that were last modified in November (of any year). (1) The `ls -l' part of this example is a system command that gives you a listing of the files in a directory, including each file's size and @@ -1717,7 +1728,7 @@ The sixth, seventh, and eighth fields contain the month, day, and time, respectively, that the file was last modified. Finally, the ninth field contains the name of the file.(2) - The `$6 == "Nov"' in our `awk' program is an expression that tests +The `$6 == "Nov"' in our `awk' program is an expression that tests whether the sixth field of the output from `ls -l' matches the string `Nov'. Each time a line has the string `Nov' for its sixth field, the action `sum += $5' is performed. This adds the fifth field (the file's @@ -1726,20 +1737,20 @@ reading all the input lines, `sum' is the total of the sizes of the files whose lines matched the pattern. (This works because `awk' variables are automatically initialized to zero.) - After the last line of output from `ls' has been processed, the -`END' rule executes and prints the value of `sum'. In this example, -the value of `sum' is 80600. +After the last line of output from `ls' has been processed, the `END' +rule executes and prints the value of `sum'. In this example, the +value of `sum' is 80600. - These more advanced `awk' techniques are covered in later sections +These more advanced `awk' techniques are covered in later sections (*note Action Overview::). Before you can move on to more advanced `awk' programming, you have to know how `awk' interprets your input and displays your output. By manipulating fields and using `print' statements, you can produce some very useful and impressive-looking reports. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) In the C shell (`csh'), you need to type a semicolon and then a +(1) In the C shell (`csh'), you need to type a semicolon and then a backslash at the end of the first line; see *Note Statements/Lines::, for an explanation. In a POSIX-compliant shell, such as the Bourne shell or `bash', you can type the example as shown. If the command @@ -1747,35 +1758,34 @@ shell or `bash', you can type the example as shown. If the command POSIX-compliant shell. Otherwise, you are probably using the C shell or a shell derived from it. - (2) On some very old systems, you may need to use `ls -lg' to get -this output. +(2) On some very old systems, you may need to use `ls -lg' to get this +output. File: gawk.info, Node: Statements/Lines, Next: Other Features, Prev: More Complex, Up: Getting Started -`awk' Statements Versus Lines -============================= +1.6 `awk' Statements Versus Lines +================================= - Most often, each line in an `awk' program is a separate statement or +Most often, each line in an `awk' program is a separate statement or separate rule, like this: awk '/12/ { print $0 } /21/ { print $0 }' BBS-list inventory-shipped - However, `gawk' ignores newlines after any of the following symbols -and keywords: +However, `gawk' ignores newlines after any of the following symbols and +keywords: , { ? : || && do else A newline at any other point is considered the end of the statement.(1) - If you would like to split a single statement into two lines at a -point where a newline would terminate it, you can "continue" it by -ending the first line with a backslash character (`\'). The backslash -must be the final character on the line in order to be recognized as a -continuation character. A backslash is allowed anywhere in the -statement, even in the middle of a string or regular expression. For -example: +If you would like to split a single statement into two lines at a point +where a newline would terminate it, you can "continue" it by ending the +first line with a backslash character (`\'). The backslash must be the +final character on the line in order to be recognized as a continuation +character. A backslash is allowed anywhere in the statement, even in +the middle of a string or regular expression. For example: awk '/This regular expression is too long, so continue it\ on the next line/ { print $1 }' @@ -1794,8 +1804,8 @@ constant using backslash continuation. Thus, for maximum portability of your `awk' programs, it is best not to split your lines in the middle of a regular expression or a string. - *Caution:* _Backslash continuation does not work as described with -the C shell._ It works for `awk' programs in files and for one-shot +*Caution:* _Backslash continuation does not work as described with the +C shell._ It works for `awk' programs in files and for one-shot programs, _provided_ you are using a POSIX-compliant shell, such as the Unix Bourne shell or `bash'. But the C shell behaves differently! There, you must use two backslashes in a row, followed by a newline. @@ -1811,8 +1821,8 @@ program must be escaped with a backslash. To illustrate: Here, the `%' and `?' are the C shell's primary and secondary prompts, analogous to the standard shell's `$' and `>'. - Compare the previous example to how it is done with a -POSIX-compliant shell: +Compare the previous example to how it is done with a POSIX-compliant +shell: $ awk 'BEGIN { > print \ @@ -1820,12 +1830,12 @@ POSIX-compliant shell: > }' -| hello, world - `awk' is a line-oriented language. Each rule's action has to begin -on the same line as the pattern. To have the pattern and action on +`awk' is a line-oriented language. Each rule's action has to begin on +the same line as the pattern. To have the pattern and action on separate lines, you _must_ use backslash continuation; there is no other option. - Another thing to keep in mind is that backslash continuation and +Another thing to keep in mind is that backslash continuation and comments do not mix. As soon as `awk' sees the `#' that starts a comment, it ignores _everything_ on the rest of the line. For example: @@ -1840,53 +1850,53 @@ onto the next line. However, the backslash-newline combination is never even noticed because it is "hidden" inside the comment. Thus, the `BEGIN' is noted as a syntax error. - When `awk' statements within one rule are short, you might want to -put more than one of them on a line. This is accomplished by -separating the statements with a semicolon (`;'). This also applies to -the rules themselves. Thus, the program shown at the start of this -minor node could also be written this way: +When `awk' statements within one rule are short, you might want to put +more than one of them on a line. This is accomplished by separating +the statements with a semicolon (`;'). This also applies to the rules +themselves. Thus, the program shown at the start of this minor node +could also be written this way: /12/ { print $0 } ; /21/ { print $0 } -*Note:* The requirement that states that rules on the same line must be -separated with a semicolon was not in the original `awk' language; it -was added for consistency with the treatment of statements within an -action. + NOTE: The requirement that states that rules on the same line must + be separated with a semicolon was not in the original `awk' + language; it was added for consistency with the treatment of + statements within an action. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) The `?' and `:' referred to here is the three-operand -conditional expression described in *Note Conditional Exp::. Splitting -lines after `?' and `:' is a minor `gawk' extension; if `--posix' is -specified (*note Options::), then this extension is disabled. +(1) The `?' and `:' referred to here is the three-operand conditional +expression described in *Note Conditional Exp::. Splitting lines after +`?' and `:' is a minor `gawk' extension; if `--posix' is specified +(*note Options::), then this extension is disabled. File: gawk.info, Node: Other Features, Next: When, Prev: Statements/Lines, Up: Getting Started -Other Features of `awk' -======================= +1.7 Other Features of `awk' +=========================== - The `awk' language provides a number of predefined, or "built-in", +The `awk' language provides a number of predefined, or "built-in", variables that your programs can use to get information from `awk'. There are other variables your program can set as well to control how `awk' processes your data. - In addition, `awk' provides a number of built-in functions for doing +In addition, `awk' provides a number of built-in functions for doing common computational and string-related operations. `gawk' provides built-in functions for working with timestamps, performing bit manipulation, and for runtime string translation. - As we develop our presentation of the `awk' language, we introduce -most of the variables and many of the functions. They are defined +As we develop our presentation of the `awk' language, we introduce most +of the variables and many of the functions. They are defined systematically in *Note Built-in Variables::, and *Note Built-in::. File: gawk.info, Node: When, Prev: Other Features, Up: Getting Started -When to Use `awk' -================= +1.8 When to Use `awk' +===================== - Now that you've seen some of what `awk' can do, you might wonder how +Now that you've seen some of what `awk' can do, you might wonder how `awk' could be useful for you. By using utility programs, advanced patterns, field separators, arithmetic statements, and other selection criteria, you can produce much more complex output. The `awk' language @@ -1894,20 +1904,23 @@ is very useful for producing reports from large amounts of raw data, such as summarizing information from the output of other utility programs like `ls'. (*Note More Complex::.) - Programs written with `awk' are usually much smaller than they would -be in other languages. This makes `awk' programs easy to compose and -use. Often, `awk' programs can be quickly composed at your terminal, -used once, and thrown away. Because `awk' programs are interpreted, you -can avoid the (usually lengthy) compilation part of the typical +Programs written with `awk' are usually much smaller than they would be +in other languages. This makes `awk' programs easy to compose and use. +Often, `awk' programs can be quickly composed at your terminal, used +once, and thrown away. Because `awk' programs are interpreted, you can +avoid the (usually lengthy) compilation part of the typical edit-compile-test-debug cycle of software development. - Complex programs have been written in `awk', including a complete +Complex programs have been written in `awk', including a complete retargetable assembler for eight-bit microprocessors (*note Glossary::, for more information), and a microcode assembler for a special-purpose -Prolog computer. However, `awk''s capabilities are strained by tasks of -such complexity. +Prolog computer. More recently, `gawk' was used for writing a Wiki +clone.(1) While the original `awk''s capabilities were strained by tasks +of such complexity, modern versions are more capable. Even the Bell +Labs version of `awk' has fewer predefined limits, and those that it +has are much larger than they used to be. - If you find yourself writing `awk' scripts of more than, say, a few +If you find yourself writing `awk' scripts of more than, say, a few hundred lines, you might consider using a different programming language. Emacs Lisp is a good choice if you need sophisticated string or pattern matching capabilities. The shell is also good at string and @@ -1918,18 +1931,23 @@ of large programs. Programs in these languages may require more lines of source code than the equivalent `awk' programs, but they are easier to maintain and usually run more efficiently. +---------- Footnotes ---------- + +(1) Yet Another Wiki Clone +(http://www.awk-scripting.de/cgi/wiki.cgi/yawk/). + File: gawk.info, Node: Regexp, Next: Reading Files, Prev: Getting Started, Up: Top -Regular Expressions -******************* +2 Regular Expressions +********************* - A "regular expression", or "regexp", is a way of describing a set of +A "regular expression", or "regexp", is a way of describing a set of strings. Because regular expressions are such a fundamental part of `awk' programming, their format and use deserve a separate major node. - A regular expression enclosed in slashes (`/') is an `awk' pattern -that matches every input record whose text belongs to that set. The +A regular expression enclosed in slashes (`/') is an `awk' pattern that +matches every input record whose text belongs to that set. The simplest regular expression is a sequence of letters, numbers, or both. Such a regexp matches any string that contains that sequence. Thus, the regexp `foo' matches any string containing `foo'. Therefore, the @@ -1952,10 +1970,10 @@ you specify more complicated classes of strings. File: gawk.info, Node: Regexp Usage, Next: Escape Sequences, Up: Regexp -How to Use Regular Expressions -============================== +2.1 How to Use Regular Expressions +================================== - A regular expression can be used as a pattern by enclosing it in +A regular expression can be used as a pattern by enclosing it in slashes. Then the regular expression is tested against the entire text of each record. (Normally, it only needs to match some part of the text in order to succeed.) For example, the following prints the @@ -1968,7 +1986,7 @@ it: -| 555-6480 -| 555-2127 - `~' (tilde), `~' operator Regular expressions can also be used in +`~' (tilde), `~' operator Regular expressions can also be used in matching expressions. These expressions allow you to specify the string to match against; it need not be the entire current input record. The two operators `~' and `!~' perform regular expression @@ -1988,16 +2006,16 @@ uppercase letter `J' somewhere in the first field: -| Jul 24 34 67 436 -| Jan 21 36 64 620 - So does this: +So does this: awk '{ if ($1 ~ /J/) print }' inventory-shipped - This next example is true if the expression EXP (taken as a -character string) does _not_ match REGEXP: +This next example is true if the expression EXP (taken as a character +string) does _not_ match REGEXP: EXP !~ /REGEXP/ - The following example matches, or selects, all input records whose +The following example matches, or selects, all input records whose first field _does not_ contain the uppercase letter `J': $ awk '$1 !~ /J/' inventory-shipped @@ -2007,17 +2025,17 @@ first field _does not_ contain the uppercase letter `J': -| May 16 34 29 208 ... - When a regexp is enclosed in slashes, such as `/foo/', we call it a +When a regexp is enclosed in slashes, such as `/foo/', we call it a "regexp constant", much like `5.27' is a numeric constant and `"foo"' is a string constant. File: gawk.info, Node: Escape Sequences, Next: Regexp Operators, Prev: Regexp Usage, Up: Regexp -Escape Sequences -================ +2.2 Escape Sequences +==================== - Some characters cannot be included literally in string constants +Some characters cannot be included literally in string constants (`"foo"') or regexp constants (`/foo/'). Instead, they should be represented with "escape sequences", which are character sequences beginning with a backslash (`\'). One use of an escape sequence is to @@ -2028,17 +2046,17 @@ double-quote character as a part of the string. For example: $ awk 'BEGIN { print "He said \"hi!\" to her." }' -| He said "hi!" to her. - The backslash character itself is another character that cannot be +The backslash character itself is another character that cannot be included normally; you must write `\\' to put one backslash in the string or regexp. Thus, the string whose contents are the two characters `"' and `\' must be written `"\"\\"'. - Backslash also represents unprintable characters such as TAB or +Backslash also represents unprintable characters such as TAB or newline. While there is nothing to stop you from entering most unprintable characters directly in a string constant or regexp constant, they may look ugly. - The following table lists all the escape sequences used in `awk' and +The following table lists all the escape sequences used in `awk' and what they represent. Unless noted otherwise, all these escape sequences apply to both string constants and regexp constants: @@ -2095,20 +2113,20 @@ apply to both string constants and regexp constants: string, in order to tell `awk' to keep processing the rest of the string. - In `gawk', a number of additional two-character sequences that begin +In `gawk', a number of additional two-character sequences that begin with a backslash have special meaning in regexps. *Note GNU Regexp Operators::. - In a regexp, a backslash before any character that is not in the +In a regexp, a backslash before any character that is not in the previous list and not listed in *Note GNU Regexp Operators::, means that the next character should be taken literally, even if it would normally be a regexp operator. For example, `/a\+b/' matches the three characters `a+b'. - For complete portability, do not use a backslash before any -character not shown in the previous list. +For complete portability, do not use a backslash before any character +not shown in the previous list. - To summarize: +To summarize: * The escape sequences in the table above are always processed first, for both string constants and regexp constants. This happens very @@ -2124,8 +2142,8 @@ character not shown in the previous list. Advanced Notes: Backslash Before Regular Characters --------------------------------------------------- - If you place a backslash in a string constant before something that -is not one of the characters previously listed, POSIX `awk' purposely +If you place a backslash in a string constant before something that is +not one of the characters previously listed, POSIX `awk' purposely leaves what happens as undefined. There are two choices: Strip the backslash out @@ -2143,13 +2161,13 @@ Leave the backslash alone Advanced Notes: Escape Sequences for Metacharacters --------------------------------------------------- - Suppose you use an octal or hexadecimal escape to represent a regexp +Suppose you use an octal or hexadecimal escape to represent a regexp metacharacter. (See *Note Regexp Operators::.) Does `awk' treat the character as a literal character or as a regexp operator? - Historically, such characters were taken literally. (d.c.) -However, the POSIX standard indicates that they should be treated as -real metacharacters, which is what `gawk' does. In compatibility mode +Historically, such characters were taken literally. (d.c.) However, +the POSIX standard indicates that they should be treated as real +metacharacters, which is what `gawk' does. In compatibility mode (*note Options::), `gawk' treats the characters represented by octal and hexadecimal escape sequences literally when used in regexp constants. Thus, `/a\52b/' is equivalent to `/a\*b/'. @@ -2157,19 +2175,19 @@ constants. Thus, `/a\52b/' is equivalent to `/a\*b/'. File: gawk.info, Node: Regexp Operators, Next: Character Lists, Prev: Escape Sequences, Up: Regexp -Regular Expression Operators -============================ +2.3 Regular Expression Operators +================================ - You can combine regular expressions with special characters, called +You can combine regular expressions with special characters, called "regular expression operators" or "metacharacters", to increase the power and versatility of regular expressions. - The escape sequences described in *Note Escape Sequences::, are -valid inside a regexp. They are introduced by a `\' and are recognized -and converted into corresponding real characters as the very first step -in processing regexps. +The escape sequences described in *Note Escape Sequences::, are valid +inside a regexp. They are introduced by a `\' and are recognized and +converted into corresponding real characters as the very first step in +processing regexps. - Here is a list of metacharacters. All characters that are not escape +Here is a list of metacharacters. All characters that are not escape sequences and that are not listed in the table stand for themselves: `\' @@ -2303,36 +2321,36 @@ sequences and that are not listed in the table stand for themselves: regexp constants are valid and work the way you want them to, using any version of `awk'.(2) - In regular expressions, the `*', `+', and `?' operators, as well as -the braces `{' and `}', have the highest precedence, followed by +In regular expressions, the `*', `+', and `?' operators, as well as the +braces `{' and `}', have the highest precedence, followed by concatenation, and finally by `|'. As in arithmetic, parentheses can change how operators are grouped. - In POSIX `awk' and `gawk', the `*', `+', and `?' operators stand for +In POSIX `awk' and `gawk', the `*', `+', and `?' operators stand for themselves when there is nothing in the regexp that precedes them. For example, `/+/' matches a literal plus sign. However, many other versions of `awk' treat such a usage as a syntax error. - If `gawk' is in compatibility mode (*note Options::), POSIX -character classes and interval expressions are not available in regular +If `gawk' is in compatibility mode (*note Options::), POSIX character +classes and interval expressions are not available in regular expressions. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) In other literature, you may see a character list referred to as +(1) In other literature, you may see a character list referred to as either a "character set", a "character class", or a "bracket expression". - (2) Use two backslashes if you're using a string constant with a -regexp operator or function. +(2) Use two backslashes if you're using a string constant with a regexp +operator or function. File: gawk.info, Node: Character Lists, Next: GNU Regexp Operators, Prev: Regexp Operators, Up: Regexp -Using Character Lists -===================== +2.4 Using Character Lists +========================= - Within a character list, a "range expression" consists of two +Within a character list, a "range expression" consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, using the locale's collating sequence and character set. For example, in the default C locale, `[a-dx-z]' is @@ -2343,47 +2361,63 @@ example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the `LC_ALL' environment variable to the value `C'. - To include one of the characters `\', `]', `-', or `^' in a -character list, put a `\' in front of it. For example: +To include one of the characters `\', `]', `-', or `^' in a character +list, put a `\' in front of it. For example: [d\]] matches either `d' or `]'. - This treatment of `\' in character lists is compatible with other -`awk' implementations and is also mandated by POSIX. The regular -expressions in `awk' are a superset of the POSIX specification for -Extended Regular Expressions (EREs). POSIX EREs are based on the -regular expressions accepted by the traditional `egrep' utility. +This treatment of `\' in character lists is compatible with other `awk' +implementations and is also mandated by POSIX. The regular expressions +in `awk' are a superset of the POSIX specification for Extended Regular +Expressions (EREs). POSIX EREs are based on the regular expressions +accepted by the traditional `egrep' utility. - "Character classes" are a new feature introduced in the POSIX -standard. A character class is a special notation for describing lists -of characters that have a specific attribute, but the actual characters +"Character classes" are a new feature introduced in the POSIX standard. +A character class is a special notation for describing lists of +characters that have a specific attribute, but the actual characters can vary from country to country and/or from character set to character set. For example, the notion of what is an alphabetic character differs between the United States and France. - A character class is only valid in a regexp _inside_ the brackets of -a character list. Character classes consist of `[:', a keyword -denoting the class, and `:]'. Here are the character classes defined -by the POSIX standard. - -`[:alnum:]' Alphanumeric characters. -`[:alpha:]' Alphabetic characters. -`[:blank:]' Space and TAB characters. -`[:cntrl:]' Control characters. -`[:digit:]' Numeric characters. -`[:graph:]' Characters that are both printable and visible. (A space is - printable but not visible, whereas an `a' is both.) -`[:lower:]' Lowercase alphabetic characters. -`[:print:]' Printable characters (characters that are not control - characters). -`[:punct:]' Punctuation characters (characters that are not letters, - digits, control characters, or space characters). -`[:space:]' Space characters (such as space, TAB, and formfeed, to name a - few). -`[:upper:]' Uppercase alphabetic characters. -`[:xdigit:]' Characters that are hexadecimal digits. +A character class is only valid in a regexp _inside_ the brackets of a +character list. Character classes consist of `[:', a keyword denoting +the class, and `:]'. *Note table-char-classes:: lists the character +classes defined by the POSIX standard. + +Class Meaning +-------------------------------------------------------------------------- +`[:alnum:]' Alphanumeric characters. +-------------------------------------------------------------------------- +`[:alpha:]' Alphabetic characters. +-------------------------------------------------------------------------- +`[:blank:]' Space and TAB characters. +-------------------------------------------------------------------------- +`[:cntrl:]' Control characters. +-------------------------------------------------------------------------- +`[:digit:]' Numeric characters. +-------------------------------------------------------------------------- +`[:graph:]' Characters that are both printable and visible. (A space is + printable but not visible, whereas an `a' is both.) +-------------------------------------------------------------------------- +`[:lower:]' Lowercase alphabetic characters. +-------------------------------------------------------------------------- +`[:print:]' Printable characters (characters that are not control + characters). +-------------------------------------------------------------------------- +`[:punct:]' Punctuation characters (characters that are not letters, + digits, control characters, or space characters). +-------------------------------------------------------------------------- +`[:space:]' Space characters (such as space, TAB, and formfeed, to name + a few). +-------------------------------------------------------------------------- +`[:upper:]' Uppercase alphabetic characters. +-------------------------------------------------------------------------- +`[:xdigit:]'Characters that are hexadecimal digits. +-------------------------------------------------------------------------- + +Table 2.1: POSIX Character Classes For example, before the POSIX standard, you had to write `/[A-Za-z0-9]/' to match alphanumeric characters. If your character @@ -2421,10 +2455,10 @@ they do not recognize collating symbols or equivalence classes. File: gawk.info, Node: GNU Regexp Operators, Next: Case-sensitivity, Prev: Character Lists, Up: Regexp -`gawk'-Specific Regexp Operators -================================ +2.5 `gawk'-Specific Regexp Operators +==================================== - GNU software that deals with regular expressions provides a number of +GNU software that deals with regular expressions provides a number of additional regexp operators. These operators are described in this minor node and are specific to `gawk'; they are not available in other `awk' implementations. Most of the additional operators deal with word @@ -2509,13 +2543,13 @@ No options File: gawk.info, Node: Case-sensitivity, Next: Leftmost Longest, Prev: GNU Regexp Operators, Up: Regexp -Case Sensitivity in Matching -============================ +2.6 Case Sensitivity in Matching +================================ - Case is normally significant in regular expressions, both when -matching ordinary characters (i.e., not metacharacters) and inside -character sets. Thus, a `w' in a regular expression matches only a -lowercase `w' and not an uppercase `W'. +Case is normally significant in regular expressions, both when matching +ordinary characters (i.e., not metacharacters) and inside character +sets. Thus, a `w' in a regular expression matches only a lowercase `w' +and not an uppercase `W'. The simplest way to do a case-independent match is to use a character list--for example, `[Ww]'. However, this can be cumbersome if you need @@ -2532,50 +2566,53 @@ discussed yet; *note String Functions::). For example: converts the first field to lowercase before matching against it. This works in any POSIX-compliant `awk'. - Another method, specific to `gawk', is to set the variable -`IGNORECASE' to a nonzero value (*note Built-in Variables::). When -`IGNORECASE' is not zero, _all_ regexp and string operations ignore -case. Changing the value of `IGNORECASE' dynamically controls the -case-sensitivity of the program as it runs. Case is significant by -default because `IGNORECASE' (like most variables) is initialized to -zero: +Another method, specific to `gawk', is to set the variable `IGNORECASE' +to a nonzero value (*note Built-in Variables::). When `IGNORECASE' is +not zero, _all_ regexp and string operations ignore case. Changing the +value of `IGNORECASE' dynamically controls the case-sensitivity of the +program as it runs. Case is significant by default because +`IGNORECASE' (like most variables) is initialized to zero: x = "aB" if (x ~ /ab/) ... # this test will fail - + IGNORECASE = 1 if (x ~ /ab/) ... # now it will succeed - In general, you cannot use `IGNORECASE' to make certain rules +In general, you cannot use `IGNORECASE' to make certain rules case-insensitive and other rules case-sensitive, because there is no straightforward way to set `IGNORECASE' just for the pattern of a particular rule.(1) To do this, use either character lists or `tolower'. However, one thing you can do with `IGNORECASE' only is dynamically turn case-sensitivity on or off for all the rules at once. - `IGNORECASE' can be set on the command line or in a `BEGIN' rule -(*note Other Arguments::; also *note Using BEGIN/END::). Setting -`IGNORECASE' from the command line is a way to make a program -case-insensitive without having to edit it. +`IGNORECASE' can be set on the command line or in a `BEGIN' rule (*note +Other Arguments::; also *note Using BEGIN/END::). Setting `IGNORECASE' +from the command line is a way to make a program case-insensitive +without having to edit it. - Prior to `gawk' 3.0, the value of `IGNORECASE' affected regexp +Prior to `gawk' 3.0, the value of `IGNORECASE' affected regexp operations only. It did not affect string comparison with `==', `!=', and so on. Beginning with version 3.0, both regexp and string comparison operations are also affected by `IGNORECASE'. - Beginning with `gawk' 3.0, the equivalences between upper- and +Beginning with `gawk' 3.0, the equivalences between upper- and lowercase characters are based on the ISO-8859-1 (ISO Latin-1) character set. This character set is a superset of the traditional 128 ASCII characters, which also provides a number of characters suitable for use with European languages. - The value of `IGNORECASE' has no effect if `gawk' is in -compatibility mode (*note Options::). Case is always significant in -compatibility mode. +As of `gawk' 3.1.4, the case equivalencies are fully locale-aware. +They are based on the C `<ctype.h>' facilities, such as `isalpha()' and +`toupper()'. - ---------- Footnotes ---------- +The value of `IGNORECASE' has no effect if `gawk' is in compatibility +mode (*note Options::). Case is always significant in compatibility +mode. - (1) Experienced C and C++ programmers will note that it is possible, +---------- Footnotes ---------- + +(1) Experienced C and C++ programmers will note that it is possible, using something like `IGNORECASE = 1 && /foObAr/ { ... }' and `IGNORECASE = 0 || /foobar/ { ... }'. However, this is somewhat obscure and we don't recommend it. @@ -2583,19 +2620,19 @@ obscure and we don't recommend it. File: gawk.info, Node: Leftmost Longest, Next: Computed Regexps, Prev: Case-sensitivity, Up: Regexp -How Much Text Matches? -====================== +2.7 How Much Text Matches? +========================== - Consider the following: +Consider the following: echo aaaabcd | awk '{ sub(/a+/, "<A>"); print }' - This example uses the `sub' function (which we haven't discussed yet; +This example uses the `sub' function (which we haven't discussed yet; *note String Functions::) to make a change to the input record. Here, the regexp `/a+/' indicates "one or more `a' characters," and the replacement text is `<A>'. - The input contains four `a' characters. `awk' (and POSIX) regular +The input contains four `a' characters. `awk' (and POSIX) regular expressions always match the leftmost, _longest_ sequence of input characters that can match. Thus, all four `a' characters are replaced with `<A>' in this example: @@ -2603,7 +2640,7 @@ with `<A>' in this example: $ echo aaaabcd | awk '{ sub(/a+/, "<A>"); print }' -| <A>bcd - For simple match/no-match tests, this is not so important. But when +For simple match/no-match tests, this is not so important. But when doing text matching and substitutions with the `match', `sub', `gsub', and `gensub' functions, it is very important. *Note String Functions::, for more information on these functions. Understanding this principle @@ -2613,10 +2650,10 @@ Records::, and also *note Field Separators::). File: gawk.info, Node: Computed Regexps, Next: Locales, Prev: Leftmost Longest, Up: Regexp -Using Dynamic Regexps -===================== +2.8 Using Dynamic Regexps +========================= - The righthand side of a `~' or `!~' operator need not be a regexp +The righthand side of a `~' or `!~' operator need not be a regexp constant (i.e., a string of characters between slashes). It may be any expression. The expression is evaluated and converted to a string if necessary; the contents of the string are used as the regexp. A regexp @@ -2628,27 +2665,26 @@ that is computed in this way is called a "dynamic regexp": This sets `digits_regexp' to a regexp that describes one or more digits, and tests whether the input record matches this regexp. - When using the `~' and `!~' *Caution:* When using the `~' and `!~' -operators, there is a difference between a regexp constant enclosed in -slashes and a string constant enclosed in double quotes. If you are -going to use a string constant, you have to understand that the string -is, in essence, scanned _twice_: the first time when `awk' reads your -program, and the second time when it goes to match the string on the -lefthand side of the operator with the pattern on the right. This is -true of any string-valued expression (such as `digits_regexp', shown -previously), not just string constants. - - What difference does it make if the string is scanned twice? The -answer has to do with escape sequences, and particularly with -backslashes. To get a backslash into a regular expression inside a -string, you have to type two backslashes. - - For example, `/\*/' is a regexp constant for a literal `*'. Only -one backslash is needed. To do the same thing with a string, you have -to type `"\\*"'. The first backslash escapes the second one so that -the string actually contains the two characters `\' and `*'. - - Given that you can use both regexp and string constants to describe +*Caution:* When using the `~' and `!~' operators, there is a difference +between a regexp constant enclosed in slashes and a string constant +enclosed in double quotes. If you are going to use a string constant, +you have to understand that the string is, in essence, scanned _twice_: +the first time when `awk' reads your program, and the second time when +it goes to match the string on the lefthand side of the operator with +the pattern on the right. This is true of any string-valued expression +(such as `digits_regexp', shown previously), not just string constants. + +What difference does it make if the string is scanned twice? The answer +has to do with escape sequences, and particularly with backslashes. To +get a backslash into a regular expression inside a string, you have to +type two backslashes. + +For example, `/\*/' is a regexp constant for a literal `*'. Only one +backslash is needed. To do the same thing with a string, you have to +type `"\\*"'. The first backslash escapes the second one so that the +string actually contains the two characters `\' and `*'. + +Given that you can use both regexp and string constants to describe regular expressions, which should you use? The answer is "regexp constants," for several reasons: @@ -2669,8 +2705,8 @@ constants," for several reasons: Advanced Notes: Using `\n' in Character Lists of Dynamic Regexps ---------------------------------------------------------------- - Some commercial versions of `awk' do not allow the newline character -to be used inside a character list for a dynamic regexp: +Some commercial versions of `awk' do not allow the newline character to +be used inside a character list for a dynamic regexp: $ awk '$0 ~ "[ \t\n]"' error--> awk: newline in character class [ @@ -2679,29 +2715,29 @@ to be used inside a character list for a dynamic regexp: error--> context is error--> >>> <<< - But a newline in a regexp constant works with no problem: +But a newline in a regexp constant works with no problem: $ awk '$0 ~ /[ \t\n]/' here is a sample line -| here is a sample line Ctrl-d - `gawk' does not have this problem, and it isn't likely to occur -often in practice, but it's worth noting for future reference. +`gawk' does not have this problem, and it isn't likely to occur often +in practice, but it's worth noting for future reference. File: gawk.info, Node: Locales, Prev: Computed Regexps, Up: Regexp -Where You Are Makes A Difference -================================ +2.9 Where You Are Makes A Difference +==================================== - Modern systems support the notion of "locales": a way to tell the +Modern systems support the notion of "locales": a way to tell the system about the local character set and language. The current locale setting can affect the way regexp matching works, often in surprising ways. In particular, many locales do case-insensitive matching, even when you may have specified characters of only one particular case. - The following example uses the `sub' function, which does text +The following example uses the `sub' function, which does text replacement (*note String Functions::). Here, the intent is to remove trailing uppercase characters: @@ -2719,17 +2755,17 @@ statements: LANG=C LC_ALL=C export LANG LC_ALL - The setting `C' forces `gawk' to behave in the traditional Unix -manner, where case distinctions do matter. You may wish to put these +The setting `C' forces `gawk' to behave in the traditional Unix manner, +where case distinctions do matter. You may wish to put these statements into your shell startup file, e.g., `$HOME/.profile'. - Similar considerations apply to other ranges. For example, `["-/]' -is perfectly valid in ASCII, but is not valid in many Unicode locales, +Similar considerations apply to other ranges. For example, `["-/]' is +perfectly valid in ASCII, but is not valid in many Unicode locales, such as `en_US.UTF-8'. (In general, such ranges should be avoided; either list the characters individually, or use a POSIX character class such as `[[:punct:]]'.) - For the normal case of `RS = "\n"', the locale is largely irrelevant. +For the normal case of `RS = "\n"', the locale is largely irrelevant. For other single byte record separators, using `LC_ALL=C' will give you much better performance when reading records. Otherwise, `gawk' has to make several function calls, _per input character_ to find the record @@ -2738,10 +2774,10 @@ terminator. File: gawk.info, Node: Reading Files, Next: Printing, Prev: Regexp, Up: Top -Reading Input Files -******************* +3 Reading Input Files +********************* - In the typical `awk' program, all input is read either from the +In the typical `awk' program, all input is read either from the standard input (by default, this is the keyboard, but often it is a pipe from another command) or from files whose names you specify on the `awk' command line. If you specify input files, `awk' reads them in @@ -2749,13 +2785,13 @@ order, processing all the data from one before going on to the next. The name of the current input file can be found in the built-in variable `FILENAME' (*note Built-in Variables::). - The input is read in units called "records", and is processed by the +The input is read in units called "records", and is processed by the rules of your program one record at a time. By default, each record is one line. Each record is automatically split into chunks called "fields". This makes it more convenient for programs to work on the parts of a record. - On rare occasions, you may need to use the `getline' command. The +On rare occasions, you may need to use the `getline' command. The `getline' command is valuable, both because it can do explicit input from any number of files, and because the files used with it do not have to be named on the `awk' command line (*note Getline::). @@ -2775,31 +2811,30 @@ have to be named on the `awk' command line (*note Getline::). File: gawk.info, Node: Records, Next: Fields, Up: Reading Files -How Input Is Split into Records -=============================== +3.1 How Input Is Split into Records +=================================== - The `awk' utility divides the input for your `awk' program into -records and fields. `awk' keeps track of the number of records that -have been read so far from the current input file. This value is -stored in a built-in variable called `FNR'. It is reset to zero when a -new file is started. Another built-in variable, `NR', is the total -number of input records read so far from all data files. It starts at -zero, but is never automatically reset to zero. +The `awk' utility divides the input for your `awk' program into records +and fields. `awk' keeps track of the number of records that have been +read so far from the current input file. This value is stored in a +built-in variable called `FNR'. It is reset to zero when a new file is +started. Another built-in variable, `NR', is the total number of input +records read so far from all data files. It starts at zero, but is +never automatically reset to zero. - Records are separated by a character called the "record separator". -By default, the record separator is the newline character. This is why +Records are separated by a character called the "record separator". By +default, the record separator is the newline character. This is why records are, by default, single lines. A different character can be used for the record separator by assigning the character to the built-in variable `RS'. - Like any other variable, the value of `RS' can be changed in the -`awk' program with the assignment operator, `=' (*note Assignment -Ops::). The new record-separator character should be enclosed in -quotation marks, which indicate a string constant. Often the right -time to do this is at the beginning of execution, before any input is -processed, so that the very first record is read with the proper -separator. To do this, use the special `BEGIN' pattern (*note -BEGIN/END::). For example: +Like any other variable, the value of `RS' can be changed in the `awk' +program with the assignment operator, `=' (*note Assignment Ops::). +The new record-separator character should be enclosed in quotation +marks, which indicate a string constant. Often the right time to do +this is at the beginning of execution, before any input is processed, +so that the very first record is read with the proper separator. To do +this, use the special `BEGIN' pattern (*note BEGIN/END::). For example: awk 'BEGIN { RS = "/" } { print $0 }' BBS-list @@ -2853,38 +2888,37 @@ record is treated as part of the record for the `core' BBS; the newline separating them in the output is the original newline in the data file, not the one added by `awk' when it printed the record! - Another way to change the record separator is on the command line, +Another way to change the record separator is on the command line, using the variable-assignment feature (*note Other Arguments::): awk '{ print $0 }' RS="/" BBS-list This sets `RS' to `/' before processing `BBS-list'. - Using an unusual character such as `/' for the record separator +Using an unusual character such as `/' for the record separator produces correct behavior in the vast majority of cases. However, the following (extreme) pipeline prints a surprising `1': $ echo | awk 'BEGIN { RS = "a" } ; { print NF }' -| 1 - There is one field, consisting of a newline. The value of the -built-in variable `NF' is the number of fields in the current record. +There is one field, consisting of a newline. The value of the built-in +variable `NF' is the number of fields in the current record. - Reaching the end of an input file terminates the current input -record, even if the last character in the file is not the character in -`RS'. (d.c.) +Reaching the end of an input file terminates the current input record, +even if the last character in the file is not the character in `RS'. +(d.c.) - The empty string `""' (a string without any characters) has a -special meaning as the value of `RS'. It means that records are -separated by one or more blank lines and nothing else. *Note Multiple -Line::, for more details. +The empty string `""' (a string without any characters) has a special +meaning as the value of `RS'. It means that records are separated by +one or more blank lines and nothing else. *Note Multiple Line::, for +more details. - If you change the value of `RS' in the middle of an `awk' run, the -new value is used to delimit subsequent records, but the record -currently being processed, as well as records already processed, are not -affected. +If you change the value of `RS' in the middle of an `awk' run, the new +value is used to delimit subsequent records, but the record currently +being processed, as well as records already processed, are not affected. - After the end of the record has been determined, `gawk' sets the +After the end of the record has been determined, `gawk' sets the variable `RT' to the text in the input that matched `RS'. When using `gawk', the value of `RS' is not limited to a one-character string. It can be any regular expression (*note Regexp::). In general, each record @@ -2896,14 +2930,14 @@ newline in the input), and the following record starts just after the end of this string (at the first character of the following line). The newline, because it matches `RS', is not part of either record. - When `RS' is a single character, `RT' contains the same single +When `RS' is a single character, `RT' contains the same single character. However, when `RS' is a regular expression, `RT' contains the actual input text that matched the regular expression. - The following example illustrates both of these features. It sets -`RS' equal to a regular expression that matches either a newline or a -series of one or more uppercase letters with optional leading and/or -trailing whitespace: +The following example illustrates both of these features. It sets `RS' +equal to a regular expression that matches either a newline or a series +of one or more uppercase letters with optional leading and/or trailing +whitespace: $ echo record 1 AAAA record 2 BBBB record 3 | > gawk 'BEGIN { RS = "\n|( *[[:upper:]]+ *)" } @@ -2918,15 +2952,15 @@ value of `RT' is a newline, and the `print' statement supplies its own terminating newline. *Note Simple Sed::, for a more useful example of `RS' as a regexp and `RT'. - If you set `RS' to a regular expression that allows optional -trailing text, such as `RS = "abc(XYZ)?"' it is possible, due to -implementation constraints, that `gawk' may match the leading part of -the regular expression, but not the trailing part, particularly if the -input text that could match the trailing part is fairly long. `gawk' -attempts to avoid this problem, but currently, there's no guarantee -that this will never happen. +If you set `RS' to a regular expression that allows optional trailing +text, such as `RS = "abc(XYZ)?"' it is possible, due to implementation +constraints, that `gawk' may match the leading part of the regular +expression, but not the trailing part, particularly if the input text +that could match the trailing part is fairly long. `gawk' attempts to +avoid this problem, but currently, there's no guarantee that this will +never happen. - The use of `RS' as a regular expression and the `RT' variable are +The use of `RS' as a regular expression and the `RT' variable are `gawk' extensions; they are not available in compatibility mode (*note Options::). In compatibility mode, only the first character of the value of `RS' is used to determine the end of the record. @@ -2934,55 +2968,55 @@ value of `RS' is used to determine the end of the record. Advanced Notes: `RS = "\0"' Is Not Portable ------------------------------------------- - There are times when you might want to treat an entire data file as a +There are times when you might want to treat an entire data file as a single record. The only way to make this happen is to give `RS' a value that you know doesn't occur in the input file. This is hard to do in a general way, such that a program always works for arbitrary input files. - You might think that for text files, the NUL character, which -consists of a character with all bits equal to zero, is a good value to -use for `RS' in this case: +You might think that for text files, the NUL character, which consists +of a character with all bits equal to zero, is a good value to use for +`RS' in this case: BEGIN { RS = "\0" } # whole file becomes one record? - `gawk' in fact accepts this, and uses the NUL character for the -record separator. However, this usage is _not_ portable to other `awk' +`gawk' in fact accepts this, and uses the NUL character for the record +separator. However, this usage is _not_ portable to other `awk' implementations. - All other `awk' implementations(1) store strings internally as -C-style strings. C strings use the NUL character as the string -terminator. In effect, this means that `RS = "\0"' is the same as `RS -= ""'. (d.c.) +All other `awk' implementations(1) store strings internally as C-style +strings. C strings use the NUL character as the string terminator. In +effect, this means that `RS = "\0"' is the same as `RS = ""'. +(d.c.) - The best way to treat a whole file as a single record is to simply -read the file in, one record at a time, concatenating each record onto -the end of the previous ones. +The best way to treat a whole file as a single record is to simply read +the file in, one record at a time, concatenating each record onto the +end of the previous ones. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) At least that we know about. +(1) At least that we know about. File: gawk.info, Node: Fields, Next: Nonconstant Fields, Prev: Records, Up: Reading Files -Examining Fields -================ +3.2 Examining Fields +==================== - When `awk' reads an input record, the record is automatically -"parsed" or separated by the interpreter into chunks called "fields". -By default, fields are separated by "whitespace", like words in a line. +When `awk' reads an input record, the record is automatically "parsed" +or separated by the interpreter into chunks called "fields". By +default, fields are separated by "whitespace", like words in a line. Whitespace in `awk' means any string of one or more spaces, tabs, or newlines;(1) other characters, such as formfeed, vertical tab, etc. that are considered whitespace by other languages, are _not_ considered whitespace by `awk'. - The purpose of fields is to make it more convenient for you to refer -to these pieces of the record. You don't have to use them--you can +The purpose of fields is to make it more convenient for you to refer to +these pieces of the record. You don't have to use them--you can operate on the whole record if you want--but fields are what make simple `awk' programs so powerful. - A dollar-sign (`$') is used to refer to a field in an `awk' program, +A dollar-sign (`$') is used to refer to a field in an `awk' program, followed by the number of the field you want. Thus, `$1' refers to the first field, `$2' to the second, and so on. (Unlike the Unix shells, the field numbers are not limited to single digits. `$127' is the one @@ -2996,17 +3030,17 @@ Here the first field, or `$1', is `This', the second field, or `$2', is Because there is no space between the `e' and the `.', the period is considered part of the seventh field. - `NF' is a built-in variable whose value is the number of fields in -the current record. `awk' automatically updates the value of `NF' each +`NF' is a built-in variable whose value is the number of fields in the +current record. `awk' automatically updates the value of `NF' each time it reads a record. No matter how many fields there are, the last field in a record can be represented by `$NF'. So, `$NF' is the same as `$7', which is `example.'. If you try to reference a field beyond the last one (such as `$8' when the record has only seven fields), you get the empty string. (If used in a numeric operation, you get zero.) - The use of `$0', which looks like a reference to the "zero-th" -field, is a special case: it represents the whole input record when you -are not interested in specific fields. Here are some more examples: +The use of `$0', which looks like a reference to the "zero-th" field, is +a special case: it represents the whole input record when you are not +interested in specific fields. Here are some more examples: $ awk '$1 ~ /foo/ { print $0 }' BBS-list -| fooey 555-1234 2400/1200/300 B @@ -3019,7 +3053,7 @@ field contains the string `foo'. The operator `~' is called a "matching operator" (*note Regexp Usage::); it tests whether a string (here, the field `$1') matches a given regular expression. - By contrast, the following example looks for `foo' in _the entire +By contrast, the following example looks for `foo' in _the entire record_ and prints the first field and the last field for each matching input record: @@ -3029,22 +3063,22 @@ input record: -| macfoo A -| sabafoo C - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) In POSIX `awk', newlines are not considered whitespace for +(1) In POSIX `awk', newlines are not considered whitespace for separating fields. File: gawk.info, Node: Nonconstant Fields, Next: Changing Fields, Prev: Fields, Up: Reading Files -Nonconstant Field Numbers -========================= +3.3 Nonconstant Field Numbers +============================= - The number of a field does not need to be a constant. Any -expression in the `awk' language can be used after a `$' to refer to a -field. The value of the expression specifies the field number. If the -value is a string, rather than a number, it is converted to a number. -Consider this example: +The number of a field does not need to be a constant. Any expression in +the `awk' language can be used after a `$' to refer to a field. The +value of the expression specifies the field number. If the value is a +string, rather than a number, it is converted to a number. Consider +this example: awk '{ print $NR }' @@ -3057,24 +3091,23 @@ another example of using expressions as field numbers: awk '{ print $(2*2) }' BBS-list - `awk' evaluates the expression `(2*2)' and uses its value as the -number of the field to print. The `*' sign represents multiplication, -so the expression `2*2' evaluates to four. The parentheses are used so -that the multiplication is done before the `$' operation; they are -necessary whenever there is a binary operator in the field-number -expression. This example, then, prints the hours of operation (the -fourth field) for every line of the file `BBS-list'. (All of the `awk' -operators are listed, in order of decreasing precedence, in *Note -Precedence::.) - - If the field number you compute is zero, you get the entire record. +`awk' evaluates the expression `(2*2)' and uses its value as the number +of the field to print. The `*' sign represents multiplication, so the +expression `2*2' evaluates to four. The parentheses are used so that +the multiplication is done before the `$' operation; they are necessary +whenever there is a binary operator in the field-number expression. +This example, then, prints the hours of operation (the fourth field) +for every line of the file `BBS-list'. (All of the `awk' operators are +listed, in order of decreasing precedence, in *Note Precedence::.) + +If the field number you compute is zero, you get the entire record. Thus, `$(2-2)' has the same value as `$0'. Negative field numbers are not allowed; trying to reference one usually terminates the program. (The POSIX standard does not define what happens when you reference a negative field number. `gawk' notices this and terminates your program. Other `awk' implementations may behave differently.) - As mentioned in *Note Fields::, `awk' stores the current record's +As mentioned in *Note Fields::, `awk' stores the current record's number of fields in the built-in variable `NF' (also *note Built-in Variables::). The expression `$NF' is not a special feature--it is the direct consequence of evaluating `NF' and using its value as a field @@ -3083,10 +3116,10 @@ number. File: gawk.info, Node: Changing Fields, Next: Field Separators, Prev: Nonconstant Fields, Up: Reading Files -Changing the Contents of a Field -================================ +3.4 Changing the Contents of a Field +==================================== - The contents of a field, as seen by `awk', can be changed within an +The contents of a field, as seen by `awk', can be changed within an `awk' program; this changes what `awk' perceives as the current input record. (The actual input is untouched; `awk' _never_ modifies the input file.) Consider the following example and its output: @@ -3105,15 +3138,15 @@ three minus ten: `$3 - 10'. (*Note Arithmetic Ops::.) Then it prints the original and new values for field three. (Someone in the warehouse made a consistent mistake while inventorying the red boxes.) - For this to work, the text in field `$3' must make sense as a -number; the string of characters must be converted to a number for the -computer to do arithmetic on it. The number resulting from the -subtraction is converted back to a string of characters that then -becomes field three. *Note Conversion::. +For this to work, the text in field `$3' must make sense as a number; +the string of characters must be converted to a number for the computer +to do arithmetic on it. The number resulting from the subtraction is +converted back to a string of characters that then becomes field three. +*Note Conversion::. - When the value of a field is changed (as perceived by `awk'), the -text of the input record is recalculated to contain the new field where -the old one was. In other words, `$0' changes to reflect the altered +When the value of a field is changed (as perceived by `awk'), the text +of the input record is recalculated to contain the new field where the +old one was. In other words, `$0' changes to reflect the altered field. Thus, this program prints a copy of the input file, with 10 subtracted from the second field of each line: @@ -3123,8 +3156,8 @@ subtracted from the second field of each line: -| Mar 5 24 34 228 ... - It is also possible to also assign contents to fields that are out -of range. For example: +It is also possible to also assign contents to fields that are out of +range. For example: $ awk '{ $6 = ($5 + $4 + $3 + $2) > print $6 }' inventory-shipped @@ -3138,20 +3171,20 @@ We've just created `$6', whose value is the sum of fields `$2', `$3', `inventory-shipped', `$6' represents the total number of parcels shipped for a particular month. - Creating a new field changes `awk''s internal copy of the current -input record, which is the value of `$0'. Thus, if you do `print $0' -after adding a field, the record printed includes the new field, with -the appropriate number of field separators between it and the previously +Creating a new field changes `awk''s internal copy of the current input +record, which is the value of `$0'. Thus, if you do `print $0' after +adding a field, the record printed includes the new field, with the +appropriate number of field separators between it and the previously existing fields. - This recomputation affects and is affected by `NF' (the number of +This recomputation affects and is affected by `NF' (the number of fields; *note Fields::). For example, the value of `NF' is set to the number of the highest field you create. The exact format of `$0' is also affected by a feature that has not been discussed yet: the "output field separator", `OFS', used to separate the fields (*note Output Separators::). - Note, however, that merely _referencing_ an out-of-range field does +Note, however, that merely _referencing_ an out-of-range field does _not_ change the value of either `$0' or `NF'. Referencing an out-of-range field only produces an empty string. For example: @@ -3165,9 +3198,9 @@ out of range. (*Note If Statement::, for more information about `awk''s `if-else' statements. *Note Typing and Comparison::, for more information about the `!=' operator.) - It is important to note that making an assignment to an existing -field changes the value of `$0' but does not change the value of `NF', -even when you assign the empty string to a field. For example: +It is important to note that making an assignment to an existing field +changes the value of `$0' but does not change the value of `NF', even +when you assign the empty string to a field. For example: $ echo a b c d | awk '{ OFS = ":"; $2 = "" > print $0; print NF }' @@ -3187,7 +3220,7 @@ The intervening field, `$5', is created with an empty value (indicated by the second pair of adjacent colons), and `NF' is updated with the value six. - Decrementing `NF' throws away the values of the fields after the new +Decrementing `NF' throws away the values of the fields after the new value of `NF' and recomputes `$0'. (d.c.) Here is an example: $ echo a b c d e f | awk '{ print "NF =", NF; @@ -3195,10 +3228,10 @@ value of `NF' and recomputes `$0'. (d.c.) Here is an example: -| NF = 6 -| a b c - *Caution:* Some versions of `awk' don't rebuild `$0' when `NF' is +*Caution:* Some versions of `awk' don't rebuild `$0' when `NF' is decremented. Caveat emptor. - Finally, there are times when it is convenient to force `awk' to +Finally, there are times when it is convenient to force `awk' to rebuild the entire record, using the current value of the fields and `OFS'. To do this, use the seemingly innocuous assignment: @@ -3208,17 +3241,17 @@ rebuild the entire record, using the current value of the fields and This forces `awk' rebuild the record. It does help to add a comment, as we've shown here. - There is a flip side to the relationship between `$0' and the -fields. Any assignment to `$0' causes the record to be reparsed into -fields using the _current_ value of `FS'. This also applies to any -built-in function that updates `$0', such as `sub' and `gsub' (*note -String Functions::). +There is a flip side to the relationship between `$0' and the fields. +Any assignment to `$0' causes the record to be reparsed into fields +using the _current_ value of `FS'. This also applies to any built-in +function that updates `$0', such as `sub' and `gsub' (*note String +Functions::). File: gawk.info, Node: Field Separators, Next: Constant Size, Prev: Changing Fields, Up: Reading Files -Specifying How Fields Are Separated -=================================== +3.5 Specifying How Fields Are Separated +======================================= * Menu: @@ -3227,27 +3260,26 @@ Specifying How Fields Are Separated * Command Line Field Separator:: Setting `FS' from the command-line. * Field Splitting Summary:: Some final points and a summary table. - The "field separator", which is either a single character or a -regular expression, controls the way `awk' splits an input record into -fields. `awk' scans the input record for character sequences that -match the separator; the fields themselves are the text between the -matches. +The "field separator", which is either a single character or a regular +expression, controls the way `awk' splits an input record into fields. +`awk' scans the input record for character sequences that match the +separator; the fields themselves are the text between the matches. - In the examples that follow, we use the bullet symbol (*) to -represent spaces in the output. If the field separator is `oo', then -the following line: +In the examples that follow, we use the bullet symbol (*) to represent +spaces in the output. If the field separator is `oo', then the +following line: moo goo gai pan is split into three fields: `m', `*g', and `*gai*pan'. Note the leading spaces in the values of the second and third fields. - The field separator is represented by the built-in variable `FS'. +The field separator is represented by the built-in variable `FS'. Shell programmers take note: `awk' does _not_ use the name `IFS' that is used by the POSIX-compliant shells (such as the Unix Bourne shell, `sh', or `bash'). - The value of `FS' can be changed in the `awk' program with the +The value of `FS' can be changed in the `awk' program with the assignment operator, `=' (*note Assignment Ops::). Often the right time to do this is at the beginning of execution before any input has been processed, so that the very first record is read with the proper @@ -3263,7 +3295,7 @@ Given the input line: this `awk' program extracts and prints the string `*29*Oak*St.'. - Sometimes the input data contains separator characters that don't +Sometimes the input data contains separator characters that don't separate fields the way you thought they would. For instance, the person's name in the example we just used might have a title or suffix attached, such as: @@ -3277,7 +3309,7 @@ characters carefully to prevent such problems. (If the data is not in a form that is easy to process, perhaps you can massage it first with a separate `awk' program.) - Fields are normally separated by whitespace sequences (spaces, tabs, +Fields are normally separated by whitespace sequences (spaces, tabs, and newlines), not by single spaces. Two spaces in a row do not delimit an empty field. The default value of the field separator `FS' is a string containing a single space, `" "'. If `awk' interpreted @@ -3287,7 +3319,7 @@ The reason this does not happen is that a single space as the value of `FS' is a special case--it is taken to specify the default manner of delimiting fields. - If `FS' is any other single character, such as `","', then each +If `FS' is any other single character, such as `","', then each occurrence of that character separates two fields. Two consecutive occurrences delimit an empty field. If the character occurs at the beginning or the end of the line, that too delimits an empty field. The @@ -3297,10 +3329,10 @@ rules. File: gawk.info, Node: Regexp Field Splitting, Next: Single Character Fields, Up: Field Separators -Using Regular Expressions to Separate Fields --------------------------------------------- +3.5.1 Using Regular Expressions to Separate Fields +-------------------------------------------------- - The previous node discussed the use of single characters or simple +The previous node discussed the use of single characters or simple strings as the value of `FS'. More generally, the value of `FS' may be a string containing any regular expression. In this case, each match in the record for the regular expression separates fields. For @@ -3313,19 +3345,18 @@ space and a TAB into a field separator. (`\t' is an "escape sequence" that stands for a TAB; *note Escape Sequences::, for the complete list of similar escape sequences.) - For a less trivial example of a regular expression, try using single +For a less trivial example of a regular expression, try using single spaces to separate fields the way single commas are used. `FS' can be set to `"[ ]"' (left bracket, space, right bracket). This regular expression matches a single space and nothing else (*note Regexp::). - There is an important difference between the two cases of `FS = " "' -(a single space) and `FS = "[ \t\n]+"' (a regular expression matching -one or more spaces, tabs, or newlines). For both values of `FS', -fields are separated by "runs" (multiple adjacent occurrences) of -spaces, tabs, and/or newlines. However, when the value of `FS' is -`" "', `awk' first strips leading and trailing whitespace from the -record and then decides where the fields are. For example, the -following pipeline prints `b': +There is an important difference between the two cases of `FS = " "' (a +single space) and `FS = "[ \t\n]+"' (a regular expression matching one +or more spaces, tabs, or newlines). For both values of `FS', fields +are separated by "runs" (multiple adjacent occurrences) of spaces, tabs, +and/or newlines. However, when the value of `FS' is `" "', `awk' first +strips leading and trailing whitespace from the record and then decides +where the fields are. For example, the following pipeline prints `b': $ echo ' a b c d ' | awk '{ print $2 }' -| b @@ -3339,8 +3370,8 @@ letter): In this case, the first field is "null" or empty. - The stripping of leading and trailing whitespace also comes into -play whenever `$0' is recomputed. For instance, study this pipeline: +The stripping of leading and trailing whitespace also comes into play +whenever `$0' is recomputed. For instance, study this pipeline: $ echo ' a b c d' | awk '{ print; $2 = $2; print }' -| a b c d @@ -3356,13 +3387,13 @@ prints the new `$0'. File: gawk.info, Node: Single Character Fields, Next: Command Line Field Separator, Prev: Regexp Field Splitting, Up: Field Separators -Making Each Character a Separate Field --------------------------------------- +3.5.2 Making Each Character a Separate Field +-------------------------------------------- - There are times when you may want to examine each character of a -record separately. This can be done in `gawk' by simply assigning the -null string (`""') to `FS'. In this case, each individual character in -the record becomes a separate field. For example: +There are times when you may want to examine each character of a record +separately. This can be done in `gawk' by simply assigning the null +string (`""') to `FS'. In this case, each individual character in the +record becomes a separate field. For example: $ echo a b | gawk 'BEGIN { FS = "" } > { @@ -3373,8 +3404,8 @@ the record becomes a separate field. For example: -| Field 2 is -| Field 3 is b - Traditionally, the behavior of `FS' equal to `""' was not defined. -In this case, most versions of Unix `awk' simply treat the entire record +Traditionally, the behavior of `FS' equal to `""' was not defined. In +this case, most versions of Unix `awk' simply treat the entire record as only having one field. (d.c.) In compatibility mode (*note Options::), if `FS' is the null string, then `gawk' also behaves this way. @@ -3382,10 +3413,10 @@ way. File: gawk.info, Node: Command Line Field Separator, Next: Field Splitting Summary, Prev: Single Character Fields, Up: Field Separators -Setting `FS' from the Command Line ----------------------------------- +3.5.3 Setting `FS' from the Command Line +---------------------------------------- - `FS' can be set on the command line. Use the `-F' option to do so. +`FS' can be set on the command line. Use the `-F' option to do so. For example: awk -F, 'PROGRAM' INPUT-FILES @@ -3397,7 +3428,7 @@ command-line options: the `-F' and `-f' options have nothing to do with each other. You can use both options at the same time to set the `FS' variable _and_ get an `awk' program from a file. - The value used for the argument to `-F' is processed in exactly the +The value used for the argument to `-F' is processed in exactly the same way as assignments to the built-in variable `FS'. Any special characters in the field separator must be escaped appropriately. For example, to use a `\' as the field separator on the command line, you @@ -3411,22 +3442,22 @@ Because `\' is used for quoting in the shell, `awk' sees `-F\\'. Then Sequences::), finally yielding a single `\' to use for the field separator. - As a special case, in compatibility mode (*note Options::), if the +As a special case, in compatibility mode (*note Options::), if the argument to `-F' is `t', then `FS' is set to the TAB character. If you type `-F\t' at the shell, without any quotes, the `\' gets deleted, so `awk' figures that you really want your fields to be separated with tabs and not `t's. Use `-v FS="t"' or `-F"[t]"' on the command line if you really do want to separate your fields with `t's. - For example, let's use an `awk' program file called `baud.awk' that +For example, let's use an `awk' program file called `baud.awk' that contains the pattern `/300/' and the action `print $1': /300/ { print $1 } - Let's also set `FS' to be the `-' character and run the program on -the file `BBS-list'. The following command prints a list of the names -of the bulletin boards that operate at 300 baud and the first three -digits of their phone numbers: +Let's also set `FS' to be the `-' character and run the program on the +file `BBS-list'. The following command prints a list of the names of +the bulletin boards that operate at 300 baud and the first three digits +of their phone numbers: $ awk -F- -f baud.awk BBS-list -| aardvark 555 @@ -3446,12 +3477,12 @@ looked like this: alpo-net 555-3412 2400/1200/300 A - The `-' as part of the system's name was used as the field -separator, instead of the `-' in the phone number that was originally -intended. This demonstrates why you have to be careful in choosing -your field and record separators. +The `-' as part of the system's name was used as the field separator, +instead of the `-' in the phone number that was originally intended. +This demonstrates why you have to be careful in choosing your field and +record separators. - Perhaps the most common use of a single character as the field +Perhaps the most common use of a single character as the field separator occurs when processing the Unix system password file. On many Unix systems, each user has a separate entry in the system password file, one line per user. The information in these lines is separated @@ -3461,19 +3492,19 @@ look like this: arnold:xyzzy:2076:10:Arnold Robbins:/home/arnold:/bin/bash - The following program searches the system password file and prints -the entries for users who have no password: +The following program searches the system password file and prints the +entries for users who have no password: awk -F: '$2 == ""' /etc/passwd File: gawk.info, Node: Field Splitting Summary, Prev: Command Line Field Separator, Up: Field Separators -Field-Splitting Summary ------------------------ +3.5.4 Field-Splitting Summary +----------------------------- - It is important to remember that when you assign a string constant -as the value of `FS', it undergoes normal `awk' string processing. For +It is important to remember that when you assign a string constant as +the value of `FS', it undergoes normal `awk' string processing. For example, with Unix `awk' and `gawk', the assignment `FS = "\.."' assigns the character string `".."' to `FS' (the backslash is stripped). This creates a regexp meaning "fields are separated by @@ -3481,8 +3512,8 @@ occurrences of any two characters." If instead you want fields to be separated by a literal period followed by any single character, use `FS = "\\.."'. - The following table summarizes how fields are split, based on the -value of `FS' (`==' means "is equal to"): +The following table summarizes how fields are split, based on the value +of `FS' (`==' means "is equal to"): `FS == " "' Fields are separated by runs of whitespace. Leading and trailing @@ -3507,18 +3538,18 @@ value of `FS' (`==' means "is equal to"): Advanced Notes: Changing `FS' Does Not Affect the Fields -------------------------------------------------------- - According to the POSIX standard, `awk' is supposed to behave as if -each record is split into fields at the time it is read. In -particular, this means that if you change the value of `FS' after a -record is read, the value of the fields (i.e., how they were split) -should reflect the old value of `FS', not the new one. +According to the POSIX standard, `awk' is supposed to behave as if each +record is split into fields at the time it is read. In particular, +this means that if you change the value of `FS' after a record is read, +the value of the fields (i.e., how they were split) should reflect the +old value of `FS', not the new one. - However, many implementations of `awk' do not work this way. -Instead, they defer splitting the fields until a field is actually -referenced. The fields are split using the _current_ value of `FS'! -(d.c.) This behavior can be difficult to diagnose. The following -example illustrates the difference between the two methods. (The -`sed'(1) command prints just the first line of `/etc/passwd'.) +However, many implementations of `awk' do not work this way. Instead, +they defer splitting the fields until a field is actually referenced. +The fields are split using the _current_ value of `FS'! (d.c.) This +behavior can be difficult to diagnose. The following example +illustrates the difference between the two methods. (The `sed'(1) +command prints just the first line of `/etc/passwd'.) sed 1q /etc/passwd | awk '{ FS = ":" ; print $1 }' @@ -3534,7 +3565,7 @@ like: Advanced Notes: `FS' and `IGNORECASE' ------------------------------------- - The `IGNORECASE' variable (*note User-modified::) affects field +The `IGNORECASE' variable (*note User-modified::) affects field splitting _only_ when the value of `FS' is a regexp. It has no effect when `FS' is a single character, even if that character is a letter. Thus, in the following code: @@ -3549,42 +3580,41 @@ alphabetic character while ignoring case, use a regexp that will do it for you. E.g., `FS = "[c]"'. In this case, `IGNORECASE' will take effect. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) The `sed' utility is a "stream editor." Its behavior is also +(1) The `sed' utility is a "stream editor." Its behavior is also defined by the POSIX standard. File: gawk.info, Node: Constant Size, Next: Multiple Line, Prev: Field Separators, Up: Reading Files -Reading Fixed-Width Data -======================== +3.6 Reading Fixed-Width Data +============================ - (This minor node discusses an advanced feature of `awk'. If you are -a novice `awk' user, you might want to skip it on the first reading.) +(This minor node discusses an advanced feature of `awk'. If you are a +novice `awk' user, you might want to skip it on the first reading.) - `gawk' version 2.13 introduced a facility for dealing with -fixed-width fields with no distinctive field separator. For example, -data of this nature arises in the input for old Fortran programs where -numbers are run together, or in the output of programs that did not -anticipate the use of their output as input for other programs. +`gawk' version 2.13 introduced a facility for dealing with fixed-width +fields with no distinctive field separator. For example, data of this +nature arises in the input for old Fortran programs where numbers are +run together, or in the output of programs that did not anticipate the +use of their output as input for other programs. - An example of the latter is a table where all the columns are lined -up by the use of a variable number of spaces and _empty fields are just +An example of the latter is a table where all the columns are lined up +by the use of a variable number of spaces and _empty fields are just spaces_. Clearly, `awk''s normal field splitting based on `FS' does not work well in this case. Although a portable `awk' program can use a series of `substr' calls on `$0' (*note String Functions::), this is awkward and inefficient for a large number of fields. - The splitting of an input record into fixed-width fields is -specified by assigning a string containing space-separated numbers to -the built-in variable `FIELDWIDTHS'. Each number specifies the width -of the field, _including_ columns between fields. If you want to -ignore the columns between fields, you can specify the width as a -separate field that is subsequently ignored. It is a fatal error to -supply a field width that is not a positive number. The following data -is the output of the Unix `w' utility. It is useful to illustrate the -use of `FIELDWIDTHS': +The splitting of an input record into fixed-width fields is specified by +assigning a string containing space-separated numbers to the built-in +variable `FIELDWIDTHS'. Each number specifies the width of the field, +_including_ columns between fields. If you want to ignore the columns +between fields, you can specify the width as a separate field that is +subsequently ignored. It is a fatal error to supply a field width that +is not a positive number. The following data is the output of the Unix +`w' utility. It is useful to illustrate the use of `FIELDWIDTHS': 10:06pm up 21 days, 14:04, 23 users User tty login idle JCPU PCPU what @@ -3597,12 +3627,12 @@ use of `FIELDWIDTHS': brent ttyp0 26Jun91 4:46 26:46 4:41 bash dave ttyq4 26Jun9115days 46 46 wnewmail - The following program takes the above input, converts the idle time -to number of seconds, and prints out the first two fields and the +The following program takes the above input, converts the idle time to +number of seconds, and prints out the first two fields and the calculated idle time: - *Note:* This program uses a number of `awk' features that haven't -been introduced yet. + NOTE: This program uses a number of `awk' features that haven't + been introduced yet. BEGIN { FIELDWIDTHS = "9 6 10 6 7 7 35" } NR > 2 { @@ -3616,11 +3646,11 @@ been introduced yet. } if (idle ~ /days/) idle *= 24 * 60 * 60 - + print $1, $2, idle } - Running the program on the data produces the following results: +Running the program on the data produces the following results: hzuo ttyV0 0 hzang ttyV3 50 @@ -3631,21 +3661,21 @@ been introduced yet. brent ttyp0 286 dave ttyq4 1296000 - Another (possibly more practical) example of fixed-width input data -is the input from a deck of balloting cards. In some parts of the -United States, voters mark their choices by punching holes in computer -cards. These cards are then processed to count the votes for any -particular candidate or on any particular issue. Because a voter may -choose not to vote on some issue, any column on the card may be empty. -An `awk' program for processing such data could use the `FIELDWIDTHS' -feature to simplify reading the data. (Of course, getting `gawk' to -run on a system with card readers is another story!) - - Assigning a value to `FS' causes `gawk' to use `FS' for field -splitting again. Use `FS = FS' to make this happen, without having to -know the current value of `FS'. In order to tell which kind of field -splitting is in effect, use `PROCINFO["FS"]' (*note Auto-set::). The -value is `"FS"' if regular field splitting is being used, or it is +Another (possibly more practical) example of fixed-width input data is +the input from a deck of balloting cards. In some parts of the United +States, voters mark their choices by punching holes in computer cards. +These cards are then processed to count the votes for any particular +candidate or on any particular issue. Because a voter may choose not to +vote on some issue, any column on the card may be empty. An `awk' +program for processing such data could use the `FIELDWIDTHS' feature to +simplify reading the data. (Of course, getting `gawk' to run on a +system with card readers is another story!) + +Assigning a value to `FS' causes `gawk' to use `FS' for field splitting +again. Use `FS = FS' to make this happen, without having to know the +current value of `FS'. In order to tell which kind of field splitting +is in effect, use `PROCINFO["FS"]' (*note Auto-set::). The value is +`"FS"' if regular field splitting is being used, or it is `"FIELDWIDTHS"' if fixed-width field splitting is being used: if (PROCINFO["FS"] == "FS") @@ -3653,7 +3683,7 @@ value is `"FS"' if regular field splitting is being used, or it is else FIXED-WIDTH FIELD SPLITTING ... - This information is useful when writing a function that needs to +This information is useful when writing a function that needs to temporarily change `FS' or `FIELDWIDTHS', read some records, and then restore the original settings (*note Passwd Functions::, for an example of such a function). @@ -3661,30 +3691,30 @@ of such a function). File: gawk.info, Node: Multiple Line, Next: Getline, Prev: Constant Size, Up: Reading Files -Multiple-Line Records -===================== +3.7 Multiple-Line Records +========================= - In some databases, a single line cannot conveniently hold all the +In some databases, a single line cannot conveniently hold all the information in one entry. In such cases, you can use multiline records. The first step in doing this is to choose your data format. - One technique is to use an unusual character or string to separate +One technique is to use an unusual character or string to separate records. For example, you could use the formfeed character (written `\f' in `awk', as in C) to separate them, making each record a page of the file. To do this, just set the variable `RS' to `"\f"' (a string containing the formfeed character). Any other character could equally well be used, as long as it won't be part of the data in a record. - Another technique is to have blank lines separate records. By a -special dispensation, an empty string as the value of `RS' indicates -that records are separated by one or more blank lines. When `RS' is set -to the empty string, each record always ends at the first blank line +Another technique is to have blank lines separate records. By a special +dispensation, an empty string as the value of `RS' indicates that +records are separated by one or more blank lines. When `RS' is set to +the empty string, each record always ends at the first blank line encountered. The next record doesn't start until the first nonblank line that follows. No matter how many blank lines appear in a row, they all act as one record separator. (Blank lines must be completely empty; lines that contain only whitespace do not count.) - You can achieve the same effect as `RS = ""' by assigning the string +You can achieve the same effect as `RS = ""' by assigning the string `"\n\n+"' to `RS'. This regexp matches the newline at the end of the record and one or more blank lines after the record. In addition, a regular expression always matches the longest possible sequence when @@ -3693,13 +3723,13 @@ doesn't start until the first nonblank line that follows--no matter how many blank lines appear in a row, they are considered one record separator. - There is an important difference between `RS = ""' and `RS = -"\n\n+"'. In the first case, leading newlines in the input data file -are ignored, and if a file ends without extra blank lines after the -last record, the final newline is removed from the record. In the -second case, this special processing is not done. (d.c.) +There is an important difference between `RS = ""' and `RS = "\n\n+"'. +In the first case, leading newlines in the input data file are ignored, +and if a file ends without extra blank lines after the last record, the +final newline is removed from the record. In the second case, this +special processing is not done. (d.c.) - Now that the input is separated into records, the second step is to +Now that the input is separated into records, the second step is to separate the fields in the record. One way to do this is to divide each of the lines into fields in the normal manner. This happens by default as the result of a special feature. When `RS' is set to the empty @@ -3707,7 +3737,7 @@ string, _and_ `FS' is a set to a single character, the newline character _always_ acts as a field separator. This is in addition to whatever field separations result from `FS'.(1) - The original motivation for this special exception was probably to +The original motivation for this special exception was probably to provide useful behavior in the default case (i.e., `FS' is equal to `" "'). This feature can be a problem if you really don't want the newline character to separate fields, because there is no way to @@ -3718,17 +3748,17 @@ special feature in a different way, by making `FS' into a regexp for that single character. For example, if the field separator is a percent character, instead of `FS = "%"', use `FS = "[%]"'. - Another way to separate fields is to put each field on a separate -line: to do this, just set the variable `FS' to the string `"\n"'. -(This single character seperator matches a single newline.) A -practical example of a data file organized this way might be a mailing -list, where each entry is separated by blank lines. Consider a mailing -list in a file named `addresses', which looks like this: +Another way to separate fields is to put each field on a separate line: +to do this, just set the variable `FS' to the string `"\n"'. (This +single character seperator matches a single newline.) A practical +example of a data file organized this way might be a mailing list, +where each entry is separated by blank lines. Consider a mailing list +in a file named `addresses', which looks like this: Jane Doe 123 Main Street Anywhere, SE 12345-6789 - + John Smith 456 Tree-lined Avenue Smallville, MW 98765-4321 @@ -3737,11 +3767,11 @@ list in a file named `addresses', which looks like this: A simple program to process this file is as follows: # addrs.awk --- simple mailing list program - + # Records are separated by blank lines. # Each line is one field. BEGIN { RS = "" ; FS = "\n" } - + { print "Name is:", $1 print "Address is:", $2 @@ -3749,7 +3779,7 @@ A simple program to process this file is as follows: print "" } - Running the program produces the following output: +Running the program produces the following output: $ awk -f addrs.awk addresses -| Name is: Jane Doe @@ -3762,7 +3792,7 @@ A simple program to process this file is as follows: -| ... - *Note Labels Program::, for a more realistic program that deals with +*Note Labels Program::, for a more realistic program that deals with address lists. The following table summarizes how records are split, based on the value of `RS'. (`==' means "is equal to.") @@ -3787,41 +3817,41 @@ based on the value of `RS'. (`==' means "is equal to.") records. (This is a `gawk' extension; it is not specified by the POSIX standard.) - In all cases, `gawk' sets `RT' to the input text that matched the -value specified by `RS'. +In all cases, `gawk' sets `RT' to the input text that matched the value +specified by `RS'. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) When `FS' is the null string (`""') or a regexp, this special +(1) When `FS' is the null string (`""') or a regexp, this special feature of `RS' does not apply. It does apply to the default field separator of a single space: `FS = " "'. File: gawk.info, Node: Getline, Prev: Multiple Line, Up: Reading Files -Explicit Input with `getline' -============================= +3.8 Explicit Input with `getline' +================================= - So far we have been getting our input data from `awk''s main input +So far we have been getting our input data from `awk''s main input stream--either the standard input (usually your terminal, sometimes the output from another program) or from the files specified on the command line. The `awk' language has a special built-in command called `getline' that can be used to read input under your explicit control. - The `getline' command is used in several different ways and should +The `getline' command is used in several different ways and should _not_ be used by beginners. The examples that follow the explanation of the `getline' command include material that has not been covered yet. Therefore, come back and study the `getline' command _after_ you have reviewed the rest of this Info file and have a good knowledge of how `awk' works. - The `getline' command returns one if it finds a record and zero if -it encounters the end of the file. If there is some error in getting a +The `getline' command returns one if it finds a record and zero if it +encounters the end of the file. If there is some error in getting a record, such as a file that cannot be opened, then `getline' returns -1. In this case, `gawk' sets the variable `ERRNO' to a string describing the error that occurred. - In the following examples, COMMAND stands for a string value that +In the following examples, COMMAND stands for a string value that represents a shell command. * Menu: @@ -3843,11 +3873,11 @@ represents a shell command. File: gawk.info, Node: Plain Getline, Next: Getline/Variable, Up: Getline -Using `getline' with No Arguments ---------------------------------- +3.8.1 Using `getline' with No Arguments +--------------------------------------- - The `getline' command can be used without arguments to read input -from the current input file. All it does in this case is read the next +The `getline' command can be used without arguments to read input from +the current input file. All it does in this case is read the next input record and split it up into fields. This is useful if you've finished processing the current record, but want to do some special processing on the next record _right now_. For example: @@ -3874,29 +3904,30 @@ processing on the next record _right now_. For example: print $0 } - This `awk' program deletes all C-style comments (`/* ... */') from -the input. By replacing the `print $0' with other statements, you -could perform more complicated processing on the decommented input, -such as searching for matches of a regular expression. (This program -has a subtle problem--it does not work if one comment ends and another -begins on the same line.) +This `awk' program deletes all C-style comments (`/* ... */') from the +input. By replacing the `print $0' with other statements, you could +perform more complicated processing on the decommented input, such as +searching for matches of a regular expression. (This program has a +subtle problem--it does not work if one comment ends and another begins +on the same line.) - This form of the `getline' command sets `NF', `NR', `FNR', and the +This form of the `getline' command sets `NF', `NR', `FNR', and the value of `$0'. - *Note:* The new value of `$0' is used to test the patterns of any -subsequent rules. The original value of `$0' that triggered the rule -that executed `getline' is lost. By contrast, the `next' statement -reads a new record but immediately begins processing it normally, -starting with the first rule in the program. *Note Next Statement::. + NOTE: The new value of `$0' is used to test the patterns of any + subsequent rules. The original value of `$0' that triggered the + rule that executed `getline' is lost. By contrast, the `next' + statement reads a new record but immediately begins processing it + normally, starting with the first rule in the program. *Note Next + Statement::. File: gawk.info, Node: Getline/Variable, Next: Getline/File, Prev: Plain Getline, Up: Getline -Using `getline' into a Variable -------------------------------- +3.8.2 Using `getline' into a Variable +------------------------------------- - You can use `getline VAR' to read the next record from `awk''s input +You can use `getline VAR' to read the next record from `awk''s input into the variable VAR. No other processing is done. For example, suppose the next line is a comment or a special string, and you want to read it without triggering any rules. This form of `getline' allows @@ -3926,20 +3957,20 @@ and produces these results: phore free - The `getline' command used in this way sets only the variables `NR' -and `FNR' (and of course, VAR). The record is not split into fields, -so the values of the fields (including `$0') and the value of `NF' do -not change. +The `getline' command used in this way sets only the variables `NR' and +`FNR' (and of course, VAR). The record is not split into fields, so +the values of the fields (including `$0') and the value of `NF' do not +change. File: gawk.info, Node: Getline/File, Next: Getline/Variable/File, Prev: Getline/Variable, Up: Getline -Using `getline' from a File ---------------------------- +3.8.3 Using `getline' from a File +--------------------------------- - Use `getline < FILE' to read the next record from FILE. Here FILE -is a string-valued expression that specifies the file name. `< FILE' -is called a "redirection" because it directs input to come from a +Use `getline < FILE' to read the next record from FILE. Here FILE is a +string-valued expression that specifies the file name. `< FILE' is +called a "redirection" because it directs input to come from a different place. For example, the following program reads its input record from the file `secondary.input' when it encounters a first field with a value equal to 10 in the current input file: @@ -3952,29 +3983,29 @@ with a value equal to 10 in the current input file: print } - Because the main input stream is not used, the values of `NR' and -`FNR' are not changed. However, the record it reads is split into -fields in the normal manner, so the values of `$0' and the other fields -are changed, resulting in a new value of `NF'. +Because the main input stream is not used, the values of `NR' and `FNR' +are not changed. However, the record it reads is split into fields in +the normal manner, so the values of `$0' and the other fields are +changed, resulting in a new value of `NF'. - According to POSIX, `getline < EXPRESSION' is ambiguous if -EXPRESSION contains unparenthesized operators other than `$'; for -example, `getline < dir "/" file' is ambiguous because the -concatenation operator is not parenthesized. You should write it as -`getline < (dir "/" file)' if you want your program to be portable to -other `awk' implementations. +According to POSIX, `getline < EXPRESSION' is ambiguous if EXPRESSION +contains unparenthesized operators other than `$'; for example, +`getline < dir "/" file' is ambiguous because the concatenation +operator is not parenthesized. You should write it as `getline < (dir +"/" file)' if you want your program to be portable to other `awk' +implementations. File: gawk.info, Node: Getline/Variable/File, Next: Getline/Pipe, Prev: Getline/File, Up: Getline -Using `getline' into a Variable from a File -------------------------------------------- +3.8.4 Using `getline' into a Variable from a File +------------------------------------------------- - Use `getline VAR < FILE' to read input from the file FILE, and put -it in the variable VAR. As above, FILE is a string-valued expression -that specifies the file from which to read. +Use `getline VAR < FILE' to read input from the file FILE, and put it +in the variable VAR. As above, FILE is a string-valued expression that +specifies the file from which to read. - In this version of `getline', none of the built-in variables are +In this version of `getline', none of the built-in variables are changed and the record is not split into fields. The only variable changed is VAR. For example, the following program copies all the input files to the output, except for records that say @@ -3990,15 +4021,15 @@ file FILENAME: print } - Note here how the name of the extra input file is not built into the +Note here how the name of the extra input file is not built into the program; it is taken directly from the data, specifically from the second field on the `@include' line. - The `close' function is called to ensure that if two identical +The `close' function is called to ensure that if two identical `@include' lines appear in the input, the entire specified file is included twice. *Note Close Files And Pipes::. - One deficiency of this program is that it does not process nested +One deficiency of this program is that it does not process nested `@include' statements (i.e., `@include' statements in included files) the way a true macro preprocessor would. *Note Igawk Program::, for a program that does handle nested `@include' statements. @@ -4006,10 +4037,10 @@ program that does handle nested `@include' statements. File: gawk.info, Node: Getline/Pipe, Next: Getline/Variable/Pipe, Prev: Getline/Variable/File, Up: Getline -Using `getline' from a Pipe ---------------------------- +3.8.5 Using `getline' from a Pipe +--------------------------------- - The output of a command can also be piped into `getline', using +The output of a command can also be piped into `getline', using `COMMAND | getline'. In this case, the string COMMAND is run as a shell command and its output is piped into `awk' to be used as input. This form of `getline' reads one record at a time from the pipe. For @@ -4051,24 +4082,24 @@ Notice that this program ran the command `who' and printed the previous result. (If you try this program yourself, you will of course get different results, depending upon who is logged in on your system.) - This variation of `getline' splits the record into fields, sets the +This variation of `getline' splits the record into fields, sets the value of `NF', and recomputes the value of `$0'. The values of `NR' and `FNR' are not changed. - According to POSIX, `EXPRESSION | getline' is ambiguous if -EXPRESSION contains unparenthesized operators other than `$'--for -example, `"echo " "date" | getline' is ambiguous because the -concatenation operator is not parenthesized. You should write it as -`("echo " "date") | getline' if you want your program to be portable to -other `awk' implementations. +According to POSIX, `EXPRESSION | getline' is ambiguous if EXPRESSION +contains unparenthesized operators other than `$'--for example, +`"echo " "date" | getline' is ambiguous because the concatenation +operator is not parenthesized. You should write it as `("echo " +"date") | getline' if you want your program to be portable to other +`awk' implementations. File: gawk.info, Node: Getline/Variable/Pipe, Next: Getline/Coprocess, Prev: Getline/Pipe, Up: Getline -Using `getline' into a Variable from a Pipe -------------------------------------------- +3.8.6 Using `getline' into a Variable from a Pipe +------------------------------------------------- - When you use `COMMAND | getline VAR', the output of COMMAND is sent +When you use `COMMAND | getline VAR', the output of COMMAND is sent through a pipe to `getline' and into the variable VAR. For example, the following program reads the current date and time into the variable `current_time', using the `date' utility, and then prints it: @@ -4079,10 +4110,10 @@ following program reads the current date and time into the variable print "Report printed on " current_time } - In this version of `getline', none of the built-in variables are +In this version of `getline', none of the built-in variables are changed and the record is not split into fields. - According to POSIX, `EXPRESSION | getline VAR' is ambiguous if +According to POSIX, `EXPRESSION | getline VAR' is ambiguous if EXPRESSION contains unparenthesized operators other than `$'; for example, `"echo " "date" | getline VAR' is ambiguous because the concatenation operator is not parenthesized. You should write it as @@ -4092,14 +4123,14 @@ portable to other `awk' implementations. File: gawk.info, Node: Getline/Coprocess, Next: Getline/Variable/Coprocess, Prev: Getline/Variable/Pipe, Up: Getline -Using `getline' from a Coprocess --------------------------------- +3.8.7 Using `getline' from a Coprocess +-------------------------------------- - Input into `getline' from a pipe is a one-way operation. The -command that is started with `COMMAND | getline' only sends data _to_ -your `awk' program. +Input into `getline' from a pipe is a one-way operation. The command +that is started with `COMMAND | getline' only sends data _to_ your +`awk' program. - On occasion, you might want to send data to another program for +On occasion, you might want to send data to another program for processing and then read the results back. `gawk' allows you start a "coprocess", with which two-way communications are possible. This is done with the `|&' operator. Typically, you write data to the @@ -4110,41 +4141,41 @@ coprocess first and then read results back, as shown in the following: which sends a query to `db_server' and then reads the results. - The values of `NR' and `FNR' are not changed, because the main input +The values of `NR' and `FNR' are not changed, because the main input stream is not used. However, the record is split into fields in the normal manner, thus changing the values of `$0', of the other fields, and of `NF'. - Coprocesses are an advanced feature. They are discussed here only +Coprocesses are an advanced feature. They are discussed here only because this is the minor node on `getline'. *Note Two-way I/O::, where coprocesses are discussed in more detail. File: gawk.info, Node: Getline/Variable/Coprocess, Next: Getline Notes, Prev: Getline/Coprocess, Up: Getline -Using `getline' into a Variable from a Coprocess ------------------------------------------------- +3.8.8 Using `getline' into a Variable from a Coprocess +------------------------------------------------------ - When you use `COMMAND |& getline VAR', the output from the coprocess +When you use `COMMAND |& getline VAR', the output from the coprocess COMMAND is sent through a two-way pipe to `getline' and into the variable VAR. - In this version of `getline', none of the built-in variables are +In this version of `getline', none of the built-in variables are changed and the record is not split into fields. The only variable changed is VAR. - Coprocesses are an advanced feature. They are discussed here only +Coprocesses are an advanced feature. They are discussed here only because this is the minor node on `getline'. *Note Two-way I/O::, where coprocesses are discussed in more detail. File: gawk.info, Node: Getline Notes, Next: Getline Summary, Prev: Getline/Variable/Coprocess, Up: Getline -Points to Remember About `getline' ----------------------------------- +3.8.9 Points to Remember About `getline' +---------------------------------------- - Here are some miscellaneous points about `getline' that you should -bear in mind: +Here are some miscellaneous points about `getline' that you should bear +in mind: * When `getline' changes the value of `$0' and `NF', `awk' does _not_ automatically jump to the start of the program and start @@ -4174,29 +4205,40 @@ bear in mind: File: gawk.info, Node: Getline Summary, Prev: Getline Notes, Up: Getline -Summary of `getline' Variants ------------------------------ +3.8.10 Summary of `getline' Variants +------------------------------------ - The following table summarizes the eight variants of `getline', -listing which built-in variables are set by each one. +*Note table-getline-variants:: summarizes the eight variants of +`getline', listing which built-in variables are set by each one. -`getline' Sets `$0', `NF', `FNR', and `NR' -`getline' VAR Sets VAR, `FNR', and `NR' -`getline <' FILE Sets `$0' and `NF' -`getline VAR < FILE' Sets VAR -COMMAND `| getline' Sets `$0' and `NF' -COMMAND `| getline' VAR Sets VAR -COMMAND `|& getline' Sets `$0' and `NF'. This is a `gawk' - extension -COMMAND `|& getline' VAR Sets VAR. This is a `gawk' extension +Variant Effect +-------------------------------------------------------------------------- +`getline' Sets `$0', `NF', `FNR', and `NR' +-------------------------------------------------------------------------- +`getline' VAR Sets VAR, `FNR', and `NR' +-------------------------------------------------------------------------- +`getline <' FILE Sets `$0' and `NF' +-------------------------------------------------------------------------- +`getline VAR < FILE' Sets VAR +-------------------------------------------------------------------------- +COMMAND `| getline' Sets `$0' and `NF' +-------------------------------------------------------------------------- +COMMAND `| getline' VAR Sets VAR +-------------------------------------------------------------------------- +COMMAND `|& getline' Sets `$0' and `NF'. This is a `gawk' extension +-------------------------------------------------------------------------- +COMMAND `|& getline' VAR Sets VAR. This is a `gawk' extension +-------------------------------------------------------------------------- + +Table 3.1: getline Variants and What They Set File: gawk.info, Node: Printing, Next: Expressions, Prev: Reading Files, Up: Top -Printing Output -*************** +4 Printing Output +***************** - One of the most common programming actions is to "print", or output, +One of the most common programming actions is to "print", or output, some or all of the input. Use the `print' statement for simple output, and the `printf' statement for fancier formatting. The `print' statement is not limited when computing _which_ values to print. @@ -4228,10 +4270,10 @@ function. File: gawk.info, Node: Print, Next: Print Examples, Up: Printing -The `print' Statement -===================== +4.1 The `print' Statement +========================= - The `print' statement is used to produce output with simple, +The `print' statement is used to produce output with simple, standardized formatting. Specify only the strings or numbers to print, in a list separated by commas. They are output, separated by single spaces, followed by a newline. The statement looks like this: @@ -4243,42 +4285,41 @@ parentheses are necessary if any of the item expressions uses the `>' relational operator; otherwise it could be confused with a redirection (*note Redirection::). - The items to print can be constant strings or numbers, fields of the +The items to print can be constant strings or numbers, fields of the current record (such as `$1'), variables, or any `awk' expression. Numeric values are converted to strings and then printed. - The simple statement `print' with no items is equivalent to `print -$0': it prints the entire current record. To print a blank line, use -`print ""', where `""' is the empty string. To print a fixed piece of -text, use a string constant, such as `"Don't Panic"', as one item. If -you forget to use the double-quote characters, your text is taken as an +The simple statement `print' with no items is equivalent to `print $0': +it prints the entire current record. To print a blank line, use `print +""', where `""' is the empty string. To print a fixed piece of text, +use a string constant, such as `"Don't Panic"', as one item. If you +forget to use the double-quote characters, your text is taken as an `awk' expression, and you will probably get an error. Keep in mind that a space is printed between any two items. File: gawk.info, Node: Print Examples, Next: Output Separators, Prev: Print, Up: Printing -Examples of `print' Statements -============================== +4.2 Examples of `print' Statements +================================== - Each `print' statement makes at least one line of output. However, -it isn't limited to only one line. If an item value is a string that +Each `print' statement makes at least one line of output. However, it +isn't limited to only one line. If an item value is a string that contains a newline, the newline is output along with the rest of the string. A single `print' statement can make any number of lines this way. - The following is an example of printing a string that contains -embedded newlines (the `\n' is an escape sequence, used to represent -the newline character; *note Escape Sequences::): +The following is an example of printing a string that contains embedded +newlines (the `\n' is an escape sequence, used to represent the newline +character; *note Escape Sequences::): $ awk 'BEGIN { print "line one\nline two\nline three" }' -| line one -| line two -| line three - The next example, which is run on the `inventory-shipped' file, -prints the first two fields of each input record, with a space between -them: +The next example, which is run on the `inventory-shipped' file, prints +the first two fields of each input record, with a space between them: $ awk '{ print $1, $2 }' inventory-shipped -| Jan 13 @@ -4286,7 +4327,7 @@ them: -| Mar 15 ... - A common mistake in using the `print' statement is to omit the comma +A common mistake in using the `print' statement is to omit the comma between two items. This often has the effect of making the items run together in the output, with no space. The reason for this is that juxtaposing two string expressions in `awk' means to concatenate them. @@ -4298,7 +4339,7 @@ Here is the same program, without the comma: -| Mar15 ... - To someone unfamiliar with the `inventory-shipped' file, neither +To someone unfamiliar with the `inventory-shipped' file, neither example's output makes much sense. A heading line at the beginning would make it clearer. Let's add some headings to our table of months (`$1') and green crates shipped (`$2'). We do this using the `BEGIN' @@ -4325,38 +4366,39 @@ fields: print "----- ------" } { print $1, " ", $2 }' inventory-shipped - Lining up columns this way can get pretty complicated when there are +Lining up columns this way can get pretty complicated when there are many columns to fix. Counting spaces for two or three columns is simple, but any more than this can take up a lot of time. This is why the `printf' statement was created (*note Printf::); one of its specialties is lining up columns of data. - *Note:* You can continue either a `print' or `printf' statement -simply by putting a newline after any comma (*note Statements/Lines::). + NOTE: You can continue either a `print' or `printf' statement + simply by putting a newline after any comma (*note + Statements/Lines::). File: gawk.info, Node: Output Separators, Next: OFMT, Prev: Print Examples, Up: Printing -Output Separators -================= +4.3 Output Separators +===================== - As mentioned previously, a `print' statement contains a list of -items separated by commas. In the output, the items are normally -separated by single spaces. However, this doesn't need to be the case; -a single space is only the default. Any string of characters may be -used as the "output field separator" by setting the built-in variable -`OFS'. The initial value of this variable is the string `" "'--that -is, a single space. +As mentioned previously, a `print' statement contains a list of items +separated by commas. In the output, the items are normally separated +by single spaces. However, this doesn't need to be the case; a single +space is only the default. Any string of characters may be used as the +"output field separator" by setting the built-in variable `OFS'. The +initial value of this variable is the string `" "'--that is, a single +space. - The output from an entire `print' statement is called an "output +The output from an entire `print' statement is called an "output record". Each `print' statement outputs one output record, and then outputs a string called the "output record separator" (or `ORS'). The initial value of `ORS' is the string `"\n"'; i.e., a newline character. Thus, each `print' statement normally makes a separate line. - In order to change how output fields and records are separated, -assign new values to the variables `OFS' and `ORS'. The usual place to -do this is in the `BEGIN' rule (*note BEGIN/END::), so that it happens +In order to change how output fields and records are separated, assign +new values to the variables `OFS' and `ORS'. The usual place to do +this is in the `BEGIN' rule (*note BEGIN/END::), so that it happens before any input is processed. It can also be done with assignments on the command line, before the names of the input files, or using the `-v' command-line option (*note Options::). The following example @@ -4372,16 +4414,16 @@ semicolon, with a blank line added after each newline: -| barfly;555-7685 ... - If the value of `ORS' does not contain a newline, the program's -output is run together on a single line. +If the value of `ORS' does not contain a newline, the program's output +is run together on a single line. File: gawk.info, Node: OFMT, Next: Printf, Prev: Output Separators, Up: Printing -Controlling Numeric Output with `print' -======================================= +4.4 Controlling Numeric Output with `print' +=========================================== - When the `print' statement is used to print numeric values, `awk' +When the `print' statement is used to print numeric values, `awk' internally converts the number to a string of characters and prints that string. `awk' uses the `sprintf' function to do this conversion (*note String Functions::). For now, it suffices to say that the @@ -4390,12 +4432,12 @@ to format numbers (or strings), and that there are a number of different ways in which numbers can be formatted. The different format specifications are discussed more fully in *Note Control Letters::. - The built-in variable `OFMT' contains the default format -specification that `print' uses with `sprintf' when it wants to convert -a number to a string for printing. The default value of `OFMT' is -`"%.6g"'. The way `print' prints numbers can be changed by supplying -different format specifications as the value of `OFMT', as shown in the -following example: +The built-in variable `OFMT' contains the default format specification +that `print' uses with `sprintf' when it wants to convert a number to a +string for printing. The default value of `OFMT' is `"%.6g"'. The way +`print' prints numbers can be changed by supplying different format +specifications as the value of `OFMT', as shown in the following +example: $ awk 'BEGIN { > OFMT = "%.0f" # print numbers as integers (rounds) @@ -4409,17 +4451,16 @@ According to the POSIX standard, `awk''s behavior is undefined if File: gawk.info, Node: Printf, Next: Redirection, Prev: OFMT, Up: Printing -Using `printf' Statements for Fancier Printing -============================================== +4.5 Using `printf' Statements for Fancier Printing +================================================== - For more precise control over the output format than what is -normally provided by `print', use `printf'. `printf' can be used to -specify the width to use for each item, as well as various formatting -choices for numbers (such as what output base to use, whether to print -an exponent, whether to print a sign, and how many digits to print -after the decimal point). This is done by supplying a string, called -the "format string", that controls how and where to print the other -arguments. +For more precise control over the output format than what is normally +provided by `print', use `printf'. `printf' can be used to specify the +width to use for each item, as well as various formatting choices for +numbers (such as what output base to use, whether to print an exponent, +whether to print a sign, and how many digits to print after the decimal +point). This is done by supplying a string, called the "format +string", that controls how and where to print the other arguments. * Menu: @@ -4431,10 +4472,10 @@ arguments. File: gawk.info, Node: Basic Printf, Next: Control Letters, Up: Printf -Introduction to the `printf' Statement --------------------------------------- +4.5.1 Introduction to the `printf' Statement +-------------------------------------------- - A simple `printf' statement looks like this: +A simple `printf' statement looks like this: printf FORMAT, ITEM1, ITEM2, ... @@ -4443,19 +4484,19 @@ The parentheses are necessary if any of the item expressions use the `>' relational operator; otherwise, it can be confused with a redirection (*note Redirection::). - The difference between `printf' and `print' is the FORMAT argument. +The difference between `printf' and `print' is the FORMAT argument. This is an expression whose value is taken as a string; it specifies how to output each of the other arguments. It is called the "format string". - The format string is very similar to that in the ISO C library -function `printf'. Most of FORMAT is text to output verbatim. -Scattered among this text are "format specifiers"--one per item. Each -format specifier says to output the next item in the argument list at -that place in the format. +The format string is very similar to that in the ISO C library function +`printf'. Most of FORMAT is text to output verbatim. Scattered among +this text are "format specifiers"--one per item. Each format specifier +says to output the next item in the argument list at that place in the +format. - The `printf' statement does not automatically append a newline to -its output. It outputs only what the format string specifies. So if a +The `printf' statement does not automatically append a newline to its +output. It outputs only what the format string specifies. So if a newline is needed, you must include one in the format string. The output separator variables `OFS' and `ORS' have no effect on `printf' statements. For example: @@ -4472,10 +4513,10 @@ Here, neither the `+' nor the `OUCH' appear when the message is printed. File: gawk.info, Node: Control Letters, Next: Format Modifiers, Prev: Basic Printf, Up: Printf -Format-Control Letters ----------------------- +4.5.2 Format-Control Letters +---------------------------- - A format specifier starts with the character `%' and ends with a +A format specifier starts with the character `%' and ends with a "format-control letter"--it tells the `printf' statement how to output one item. The format-control letter specifies what _kind_ of value to print. The rest of the format specifier is made up of optional @@ -4511,6 +4552,18 @@ width. Here is a list of the format-control letters: of which follow the decimal point. (The `4.3' represents two modifiers, discussed in the next node.) + On systems supporting IEEE 754 floating point format, values + representing negative infinity are formatted as `-inf' or + `-infinity', and positive infinity as `inf' and `-infinity'. The + special "not a number" value formats as `-nan' or `nan'. + +`%F' + Like `%f' but the infinity and "not a number" values are spelled + using uppercase letters. + + The `%F' format is a POSIX extension to ISO C; not all systems + support. On those that don't, `gawk' uses `%f' instead. + `%g, %G' These print a number in either scientific notation or in floating-point notation, whichever uses fewer characters; if the @@ -4537,20 +4590,20 @@ width. Here is a list of the format-control letters: sequence `%%' outputs one `%'; it does not consume an argument and it ignores any modifiers. - *Note:* When using the integer format-control letters for values -that are outside the range of the widest C integer type, `gawk' -switches to the the `%g' format specifier. If `--lint' is provided on -the command line (*note Options::), `gawk' warns about this. Other -versions of `awk' may print invalid values or do something else -entirely. (d.c.) + NOTE: When using the integer format-control letters for values + that are outside the range of the widest C integer type, `gawk' + switches to the the `%g' format specifier. If `--lint' is provided + on the command line (*note Options::), `gawk' warns about this. + Other versions of `awk' may print invalid values or do something + else entirely. (d.c.) File: gawk.info, Node: Format Modifiers, Next: Printf Examples, Prev: Control Letters, Up: Printf -Modifiers for `printf' Formats ------------------------------- +4.5.3 Modifiers for `printf' Formats +------------------------------------ - A format specification can also include "modifiers" that can control +A format specification can also include "modifiers" that can control how much of the item's value is printed, as well as how much space it gets. The modifiers come between the `%' and the format-control letter. We will use the bullet symbol "*" in the following examples to represent @@ -4609,6 +4662,28 @@ which they may appear: to non-numeric output formats. (d.c.) This flag only has an effect when the field width is wider than the value to print. +`'' + A single quote or apostrohe character is a POSIX extension to ISO + C. It indicates that the integer part of a floating point value, + or the entire part of an integer decimal value, should have a + thousands-separator character in it. This only works in locales + that support such characters. For example: + + $ cat thousands.awk Show source program + -| BEGIN { printf "%'d\n", 1234567 } + $ LC_ALL=C gawk -f thousands.awk Run it in "C" locale + -| 1234567 + $ LC_ALL=en_US.UTF-8 gawk -f thousands.awk Run in US English UTF locale + -| 1,234,567 + + For more information about locales and internationalization issues, + *FIXME: see xxxx*. + + NOTE: The `'' flag is a nice feature, but its use complicates + things: it now becomes difficult to use it in command-line + programs. For information on appropriate quoting tricks, + *FIXME: see XXXX*. + `WIDTH' This is a number specifying the desired minimum width of a field. Inserting any number between the `%' sign and the format-control @@ -4654,7 +4729,7 @@ which they may appear: prints `foob'. - The C library `printf''s dynamic WIDTH and PREC capability (for +The C library `printf''s dynamic WIDTH and PREC capability (for example, `"%*.*s"') is supported. Instead of supplying explicit WIDTH and/or PREC values in the format string, they are passed in the argument list. For example: @@ -4681,7 +4756,7 @@ string, like so: This is not particularly easy to read but it does work. - C programmers may be used to supplying additional `l', `L', and `h' +C programmers may be used to supplying additional `l', `L', and `h' modifiers in `printf' format strings. These are not valid in `awk'. Most `awk' implementations silently ignore these modifiers. If `--lint' is provided on the command line (*note Options::), `gawk' @@ -4691,10 +4766,10 @@ error. File: gawk.info, Node: Printf Examples, Prev: Format Modifiers, Up: Printf -Examples Using `printf' ------------------------ +4.5.4 Examples Using `printf' +----------------------------- - The following is a simple example of how to use `printf' to make an +The following is a simple example of how to use `printf' to make an aligned table: awk '{ printf "%-10s %s\n", $1, $2 }' BBS-list @@ -4717,16 +4792,16 @@ an aligned two-column table of names and phone numbers, as shown here: -| sdace 555-3430 -| sabafoo 555-2127 - In this case, the phone numbers had to be printed as strings because +In this case, the phone numbers had to be printed as strings because the numbers are separated by a dash. Printing the phone numbers as numbers would have produced just the first three digits: `555'. This would have been pretty confusing. - It wasn't necessary to specify a width for the phone numbers because +It wasn't necessary to specify a width for the phone numbers because they are last on their lines. They don't need to have spaces after them. - The table could be made to look even nicer by adding headings to the +The table could be made to look even nicer by adding headings to the tops of the columns. This is done using the `BEGIN' pattern (*note BEGIN/END::) so that the headers are only printed once, at the beginning of the `awk' program: @@ -4735,7 +4810,7 @@ beginning of the `awk' program: print "---- ------" } { printf "%-10s %s\n", $1, $2 }' BBS-list - The above example mixed `print' and `printf' statements in the same +The above example mixed `print' and `printf' statements in the same program. Using just `printf' statements can produce the same results: awk 'BEGIN { printf "%-10s %s\n", "Name", "Number" @@ -4746,15 +4821,15 @@ Printing each column heading with the same format specification used for the column elements ensures that the headings are aligned just like the columns. - The fact that the same format specification is used three times can -be emphasized by storing it in a variable, like this: +The fact that the same format specification is used three times can be +emphasized by storing it in a variable, like this: awk 'BEGIN { format = "%-10s %s\n" printf format, "Name", "Number" printf format, "----", "------" } { printf format, $1, $2 }' BBS-list - At this point, it would be a worthwhile exercise to use the `printf' +At this point, it would be a worthwhile exercise to use the `printf' statement to line up the headings and table data for the `inventory-shipped' example that was covered earlier in the minor node on the `print' statement (*note Print::). @@ -4762,18 +4837,18 @@ on the `print' statement (*note Print::). File: gawk.info, Node: Redirection, Next: Special Files, Prev: Printf, Up: Printing -Redirecting Output of `print' and `printf' -========================================== +4.6 Redirecting Output of `print' and `printf' +============================================== - So far, the output from `print' and `printf' has gone to the standard +So far, the output from `print' and `printf' has gone to the standard output, usually the terminal. Both `print' and `printf' can also send their output to other places. This is called "redirection". - A redirection appears after the `print' or `printf' statement. +A redirection appears after the `print' or `printf' statement. Redirections in `awk' are written just like redirections in shell commands, except that they are written inside the `awk' program. - There are four forms of output redirection: output to a file, output +There are four forms of output redirection: output to a file, output appended to a file, output through a pipe to another command, and output to a coprocess. They are all shown for the `print' statement, but they work identically for `printf': @@ -4868,13 +4943,13 @@ work identically for `printf': This feature is a `gawk' extension, and is not available in POSIX `awk'. *Note Two-way I/O::, for a more complete discussion. - Redirecting output using `>', `>>', `|', or `|&' asks the system to +Redirecting output using `>', `>>', `|', or `|&' asks the system to open a file, pipe, or coprocess only if the particular FILE or COMMAND you specify has not already been written to by your program or if it has been closed since it was last written to. - It is a common error to use `>' redirection for the first `print' to -a file, and then to use `>>' for subsequent output: +It is a common error to use `>' redirection for the first `print' to a +file, and then to use `>>' for subsequent output: # clear the file print "Don't panic" > "guide.txt" @@ -4887,36 +4962,36 @@ This is indeed how redirections must be used from the shell. But in `>' for all the `print' statements, since the output file is only opened once. - Many `awk' implementations limit the number of pipelines that an -`awk' program may have open to just one! In `gawk', there is no such -limit. `gawk' allows a program to open as many pipelines as the -underlying operating system permits. +Many `awk' implementations limit the number of pipelines that an `awk' +program may have open to just one! In `gawk', there is no such limit. +`gawk' allows a program to open as many pipelines as the underlying +operating system permits. Advanced Notes: Piping into `sh' -------------------------------- - A particularly powerful way to use redirection is to build command -lines and pipe them into the shell, `sh'. For example, suppose you -have a list of files brought over from a system where all the file names -are stored in uppercase, and you wish to rename them to have names in -all lowercase. The following program is both simple and efficient: +A particularly powerful way to use redirection is to build command lines +and pipe them into the shell, `sh'. For example, suppose you have a +list of files brought over from a system where all the file names are +stored in uppercase, and you wish to rename them to have names in all +lowercase. The following program is both simple and efficient: { printf("mv %s %s\n", $0, tolower($0)) | "sh" } - + END { close("sh") } - The `tolower' function returns its argument string with all -uppercase characters converted to lowercase (*note String Functions::). -The program builds up a list of command lines, using the `mv' utility -to rename the files. It then sends the list to the shell for execution. +The `tolower' function returns its argument string with all uppercase +characters converted to lowercase (*note String Functions::). The +program builds up a list of command lines, using the `mv' utility to +rename the files. It then sends the list to the shell for execution. File: gawk.info, Node: Special Files, Next: Close Files And Pipes, Prev: Redirection, Up: Printing -Special File Names in `gawk' -============================ +4.7 Special File Names in `gawk' +================================ - `gawk' provides a number of special file names that it interprets +`gawk' provides a number of special file names that it interprets internally. These file names provide access to standard file descriptors, process-related information, and TCP/IP networking. @@ -4930,10 +5005,10 @@ descriptors, process-related information, and TCP/IP networking. File: gawk.info, Node: Special FD, Next: Special Process, Up: Special Files -Special Files for Standard Descriptors --------------------------------------- +4.7.1 Special Files for Standard Descriptors +-------------------------------------------- - Running programs conventionally have three input and output streams +Running programs conventionally have three input and output streams already available to them for reading and writing. These are known as the "standard input", "standard output", and "standard error output". These streams are, by default, connected to your terminal, but they are @@ -4942,7 +5017,7 @@ and `|' operators. Standard error is typically used for writing error messages; the reason there are two separate streams, standard output and standard error, is so that they can be redirected separately. - In other implementations of `awk', the only way to write an error +In other implementations of `awk', the only way to write an error message to standard error in an `awk' program is as follows: print "Serious error detected!" | "cat 1>&2" @@ -4961,7 +5036,7 @@ happens, writing to the terminal is not correct. In fact, if `awk' is run from a background job, it may not have a terminal at all. Then opening `/dev/tty' fails. - `gawk' provides special file names for accessing the three standard +`gawk' provides special file names for accessing the three standard streams, as well as any other inherited open files. If the file name matches one of these special names when `gawk' redirects input or output, then it directly uses the stream that the file name stands for. @@ -4983,28 +5058,28 @@ been ported to, not just those that are POSIX-compliant: the shell). Unless special pains are taken in the shell from which `gawk' is invoked, only descriptors 0, 1, and 2 are available. - The file names `/dev/stdin', `/dev/stdout', and `/dev/stderr' are +The file names `/dev/stdin', `/dev/stdout', and `/dev/stderr' are aliases for `/dev/fd/0', `/dev/fd/1', and `/dev/fd/2', respectively. However, they are more self-explanatory. The proper way to write an error message in a `gawk' program is to use `/dev/stderr', like this: print "Serious error detected!" > "/dev/stderr" - Note the use of quotes around the file name. Like any other +Note the use of quotes around the file name. Like any other redirection, the value must be a string. It is a common error to omit the quotes, which leads to confusing results. File: gawk.info, Node: Special Process, Next: Special Network, Prev: Special FD, Up: Special Files -Special Files for Process-Related Information ---------------------------------------------- +4.7.2 Special Files for Process-Related Information +--------------------------------------------------- - `gawk' also provides special file names that give access to -information about the running `gawk' process. Each of these "files" -provides a single record of information. To read them more than once, -they must first be closed with the `close' function (*note Close Files -And Pipes::). The file names are: +`gawk' also provides special file names that give access to information +about the running `gawk' process. Each of these "files" provides a +single record of information. To read them more than once, they must +first be closed with the `close' function (*note Close Files And +Pipes::). The file names are: `/dev/pid' Reading this file returns the process ID of the current process, @@ -5043,29 +5118,29 @@ And Pipes::). The file names are: returned by the `getgroups' system call. (Multiple groups may not be supported on all systems.) - These special file names may be used on the command line as data -files, as well as for I/O redirections within an `awk' program. They -may not be used as source files with the `-f' option. +These special file names may be used on the command line as data files, +as well as for I/O redirections within an `awk' program. They may not +be used as source files with the `-f' option. - *Note:* The special files that provide process-related information -are now considered obsolete and will disappear entirely in the next -release of `gawk'. `gawk' prints a warning message every time you use -one of these files. To obtain process-related information, use the -`PROCINFO' array. *Note Auto-set::. + NOTE: The special files that provide process-related information + are now considered obsolete and will disappear entirely in the + next release of `gawk'. `gawk' prints a warning message every + time you use one of these files. To obtain process-related + information, use the `PROCINFO' array. *Note Auto-set::. File: gawk.info, Node: Special Network, Next: Special Caveats, Prev: Special Process, Up: Special Files -Special Files for Network Communications ----------------------------------------- +4.7.3 Special Files for Network Communications +---------------------------------------------- - Starting with version 3.1 of `gawk', `awk' programs can open a -two-way TCP/IP connection, acting as either a client or a server. This -is done using a special file name of the form: +Starting with version 3.1 of `gawk', `awk' programs can open a two-way +TCP/IP connection, acting as either a client or a server. This is done +using a special file name of the form: `/inet/PROTOCOL/LOCAL-PORT/REMOTE-HOST/REMOTE-PORT' - The PROTOCOL is one of `tcp', `udp', or `raw', and the other fields +The PROTOCOL is one of `tcp', `udp', or `raw', and the other fields represent the other essential pieces of information for making a networking connection. These file names are used with the `|&' operator for communicating with a coprocess (*note Two-way I/O::). @@ -5075,10 +5150,10 @@ Full discussion is delayed until *Note TCP/IP Networking::. File: gawk.info, Node: Special Caveats, Prev: Special Network, Up: Special Files -Special File Name Caveats -------------------------- +4.7.4 Special File Name Caveats +------------------------------- - Here is a list of things to bear in mind when using the special file +Here is a list of things to bear in mind when using the special file names that `gawk' provides: * Recognition of these special file names is disabled if `gawk' is in @@ -5098,9 +5173,9 @@ names that `gawk' provides: any of the files related to file descriptors 0, 1, and 2. Doing so results in unpredictable behavior. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Older versions of `gawk' would interpret these names internally +(1) Older versions of `gawk' would interpret these names internally only if the system did not actually have a `/dev/fd' directory or any of the other special files listed earlier. Usually this didn't make a difference, but sometimes it did; thus, it was decided to make `gawk''s @@ -5110,25 +5185,25 @@ special file names itself. File: gawk.info, Node: Close Files And Pipes, Prev: Special Files, Up: Printing -Closing Input and Output Redirections -===================================== +4.8 Closing Input and Output Redirections +========================================= - If the same file name or the same shell command is used with -`getline' more than once during the execution of an `awk' program -(*note Getline::), the file is opened (or the command is executed) the -first time only. At that time, the first record of input is read from -that file or command. The next time the same file or command is used -with `getline', another record is read from it, and so on. +If the same file name or the same shell command is used with `getline' +more than once during the execution of an `awk' program (*note +Getline::), the file is opened (or the command is executed) the first +time only. At that time, the first record of input is read from that +file or command. The next time the same file or command is used with +`getline', another record is read from it, and so on. - Similarly, when a file or pipe is opened for output, the file name or +Similarly, when a file or pipe is opened for output, the file name or command associated with it is remembered by `awk', and subsequent writes to the same file or command are appended to the previous writes. The file or pipe stays open until `awk' exits. - This implies that special steps are necessary in order to read the -same file again from the beginning, or to rerun a shell command (rather -than reading more output from the same command). The `close' function -makes these things possible: +This implies that special steps are necessary in order to read the same +file again from the beginning, or to rerun a shell command (rather than +reading more output from the same command). The `close' function makes +these things possible: close(FILENAME) @@ -5136,9 +5211,9 @@ or: close(COMMAND) - The argument FILENAME or COMMAND can be any expression. Its value -must _exactly_ match the string that was used to open the file or start -the command (spaces and other "irrelevant" characters included). For +The argument FILENAME or COMMAND can be any expression. Its value must +_exactly_ match the string that was used to open the file or start the +command (spaces and other "irrelevant" characters included). For example, if you open a pipe with this: "sort -r names" | getline foo @@ -5147,13 +5222,13 @@ then you must close it with this: close("sort -r names") - Once this function call is executed, the next `getline' from that -file or command, or the next `print' or `printf' to that file or -command, reopens the file or reruns the command. Because the -expression that you use to close a file or pipeline must exactly match -the expression used to open the file or run the command, it is good -practice to use a variable to store the file name or command. The -previous example becomes the following: +Once this function call is executed, the next `getline' from that file +or command, or the next `print' or `printf' to that file or command, +reopens the file or reruns the command. Because the expression that +you use to close a file or pipeline must exactly match the expression +used to open the file or run the command, it is good practice to use a +variable to store the file name or command. The previous example +becomes the following: sortcom = "sort -r names" sortcom | getline foo @@ -5188,9 +5263,9 @@ programs. Here are some of the reasons for closing an output file: the program closes the pipe after each line of output, then each line makes a separate message. - If you use more files than the system allows you to have open, -`gawk' attempts to multiplex the available open files among your data -files. `gawk''s ability to do this depends upon the facilities of your +If you use more files than the system allows you to have open, `gawk' +attempts to multiplex the available open files among your data files. +`gawk''s ability to do this depends upon the facilities of your operating system, so it may not always work. It is therefore both good practice and good portability advice to always use `close' on your files when you are done with them. In fact, if you are using a lot of @@ -5206,25 +5281,25 @@ consider something like this: # need close(command) here } - This example creates a new pipeline based on data in _each_ record. +This example creates a new pipeline based on data in _each_ record. Without the call to `close' indicated in the comment, `awk' creates child processes to run the commands, until it eventually runs out of file descriptors for more pipelines. - Even though each command has finished (as indicated by the -end-of-file return status from `getline'), the child process is not -terminated;(1) more importantly, the file descriptor for the pipe is -not closed and released until `close' is called or `awk' exits. +Even though each command has finished (as indicated by the end-of-file +return status from `getline'), the child process is not terminated;(1) +more importantly, the file descriptor for the pipe is not closed and +released until `close' is called or `awk' exits. - `close' will silently do nothing if given an argument that does not +`close' will silently do nothing if given an argument that does not represent a file, pipe or coprocess that was opened with a redirection. - Note also that `close(FILENAME)' has no "magic" effects on the -implicit loop that reads through the files named on the command line. -It is, more likely, a close of a file that was never opened, so `awk' -silently does nothing. +Note also that `close(FILENAME)' has no "magic" effects on the implicit +loop that reads through the files named on the command line. It is, +more likely, a close of a file that was never opened, so `awk' silently +does nothing. - When using the `|&' operator to communicate with a coprocess, it is +When using the `|&' operator to communicate with a coprocess, it is occasionally useful to be able to close one end of the two-way pipe without closing the other. This is done by supplying a second argument to `close'. As in any other call to `close', the first argument is the @@ -5237,7 +5312,7 @@ discusses it in more detail and gives an example. Advanced Notes: Using `close''s Return Value -------------------------------------------- - In many versions of Unix `awk', the `close' function is actually a +In many versions of Unix `awk', the `close' function is actually a statement. It is a syntax error to try and use the return value from `close': (d.c.) @@ -5245,45 +5320,43 @@ statement. It is a syntax error to try and use the return value from command | getline info retval = close(command) # syntax error in most Unix awks - `gawk' treats `close' as a function. The return value is -1 if the +`gawk' treats `close' as a function. The return value is -1 if the argument names something that was never opened with a redirection, or if there is a system problem closing the file or process. In these cases, `gawk' sets the built-in variable `ERRNO' to a string describing the problem. - In `gawk', when closing a pipe or coprocess, the return value is the +In `gawk', when closing a pipe or coprocess, the return value is the exit status of the command.(2) Otherwise, it is the return value from the system's `close' or `fclose' C functions when closing input or output files, respectively. This value is zero if the close succeeds, or -1 if it fails. - The POSIX standard is very vague; it says that `close' returns zero -on success and non-zero otherwise. In general, different -implementations vary in what they report when closing pipes; thus the -return value cannot be used portably. (d.c.) +The POSIX standard is very vague; it says that `close' returns zero on +success and non-zero otherwise. In general, different implementations +vary in what they report when closing pipes; thus the return value +cannot be used portably. (d.c.) - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) The technical terminology is rather morbid. The finished child -is called a "zombie," and cleaning up after it is referred to as -"reaping." +(1) The technical terminology is rather morbid. The finished child is +called a "zombie," and cleaning up after it is referred to as "reaping." - (2) This is a full 16-bit value as returned by the `wait' system -call. See the system manual pages for information on how to decode this -value. +(2) This is a full 16-bit value as returned by the `wait' system call. +See the system manual pages for information on how to decode this value. File: gawk.info, Node: Expressions, Next: Patterns and Actions, Prev: Printing, Up: Top -Expressions -*********** +5 Expressions +************* - Expressions are the basic building blocks of `awk' patterns and +Expressions are the basic building blocks of `awk' patterns and actions. An expression evaluates to a value that you can print, test, or pass to a function. Additionally, an expression can assign a new value to a variable or a field by using an assignment operator. - An expression can serve as a pattern or action statement on its own. +An expression can serve as a pattern or action statement on its own. Most other kinds of statements contain one or more expressions that specify the data on which to operate. As in other languages, expressions in `awk' include variables, array references, constants, @@ -5318,16 +5391,16 @@ operators. File: gawk.info, Node: Constants, Next: Using Constant Regexps, Up: Expressions -Constant Expressions -==================== +5.1 Constant Expressions +======================== - The simplest type of expression is the "constant", which always has -the same value. There are three types of constants: numeric, string, -and regular expression. +The simplest type of expression is the "constant", which always has the +same value. There are three types of constants: numeric, string, and +regular expression. - Each is used in the appropriate context when you need a data value -that isn't going to change. Numeric constants can have different -forms, but are stored identically internally. +Each is used in the appropriate context when you need a data value that +isn't going to change. Numeric constants can have different forms, but +are stored identically internally. * Menu: @@ -5338,10 +5411,10 @@ forms, but are stored identically internally. File: gawk.info, Node: Scalar Constants, Next: Nondecimal-numbers, Up: Constants -Numeric and String Constants ----------------------------- +5.1.1 Numeric and String Constants +---------------------------------- - A "numeric constant" stands for a number. This number can be an +A "numeric constant" stands for a number. This number can be an integer, a decimal fraction, or a number in scientific (exponential) notation.(1) Here are some examples of numeric constants that all have the same value: @@ -5350,7 +5423,7 @@ the same value: 1.05e+2 1050e-1 - A string constant consists of a sequence of characters enclosed in +A string constant consists of a sequence of characters enclosed in double-quotation marks. For example: "parrot" @@ -5361,19 +5434,19 @@ eight-bit ASCII characters including ASCII NUL (character code zero). Other `awk' implementations may have difficulty with some character codes. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) The internal representation of all numbers, including integers, +(1) The internal representation of all numbers, including integers, uses double-precision floating-point numbers. On most modern systems, these are in IEEE 754 standard format. File: gawk.info, Node: Nondecimal-numbers, Next: Regexp Constants, Prev: Scalar Constants, Up: Constants -Octal and Hexadecimal Numbers ------------------------------ +5.1.2 Octal and Hexadecimal Numbers +----------------------------------- - In `awk', all numbers are in decimal; i.e., base 10. Many other +In `awk', all numbers are in decimal; i.e., base 10. Many other programming languages allow you to specify numbers in other bases, often octal (base 8) and hexadecimal (base 16). In octal, the numbers go 0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, etc. Just as `11', in decimal, is 1 @@ -5385,8 +5458,8 @@ usually irrelevant; hexadecimal `a' and `A' have the same value.) Thus, `11', in hexadecimal, is 1 times 16 plus 1, which equals 17 in decimal. - Just by looking at plain `11', you can't tell what base it's in. -So, in C, C++, and other languages derived from C, there is a special +Just by looking at plain `11', you can't tell what base it's in. So, +in C, C++, and other languages derived from C, there is a special notation to help signify the base. Octal numbers start with a leading `0', and hexadecimal numbers start with a leading `0x' or `0X': @@ -5399,17 +5472,17 @@ notation to help signify the base. Octal numbers start with a leading `0x11' Hexadecimal 11, decimal value 17. - This example shows the difference: +This example shows the difference: $ gawk 'BEGIN { printf "%d, %d, %d\n", 011, 11, 0x11 }' -| 9, 11, 17 - Being able to use octal and hexadecimal constants in your programs -is most useful when working with data that cannot be represented +Being able to use octal and hexadecimal constants in your programs is +most useful when working with data that cannot be represented conveniently as characters or as regular numbers, such as binary data of various sorts. - `gawk' allows the use of octal and hexadecimal constants in your +`gawk' allows the use of octal and hexadecimal constants in your program text. However, such numbers in the input data are not treated differently; doing so by default would break old programs. (If you really need to do this, use the `--non-decimal-data' command-line @@ -5420,21 +5493,21 @@ octal or hexadecimal constants when working with the built-in bit manipulation functions; see *Note Bitwise Functions::, for more information. - Unlike some early C implementations, `8' and `9' are not valid in -octal constants; e.g., `gawk' treats `018' as decimal 18: +Unlike some early C implementations, `8' and `9' are not valid in octal +constants; e.g., `gawk' treats `018' as decimal 18: $ gawk 'BEGIN { print "021 is", 021 ; print 018 }' -| 021 is 17 -| 18 - Octal and hexadecimal source code constants are a `gawk' extension. -If `gawk' is in compatibility mode (*note Options::), they are not +Octal and hexadecimal source code constants are a `gawk' extension. If +`gawk' is in compatibility mode (*note Options::), they are not available. Advanced Notes: A Constant's Base Does Not Affect Its Value ----------------------------------------------------------- - Once a numeric constant has been converted internally into a number, +Once a numeric constant has been converted internally into a number, `gawk' no longer remembers what the original form of the constant was; the internal value is always used. This has particular consequences for conversion of numbers to strings: @@ -5445,10 +5518,10 @@ for conversion of numbers to strings: File: gawk.info, Node: Regexp Constants, Prev: Nondecimal-numbers, Up: Constants -Regular Expression Constants ----------------------------- +5.1.4 Regular Expression Constants +---------------------------------- - A regexp constant is a regular expression description enclosed in +A regexp constant is a regular expression description enclosed in slashes, such as `/^beginning and end$/'. Most regexps used in `awk' programs are constant, but the `~' and `!~' matching operators can also match computed or "dynamic" regexps (which are just ordinary strings or @@ -5457,16 +5530,15 @@ variables that contain a regexp). File: gawk.info, Node: Using Constant Regexps, Next: Variables, Prev: Constants, Up: Expressions -Using Regular Expression Constants -================================== +5.2 Using Regular Expression Constants +====================================== - When used on the righthand side of the `~' or `!~' operators, a -regexp constant merely stands for the regexp that is to be matched. -However, regexp constants (such as `/foo/') may be used like simple -expressions. When a regexp constant appears by itself, it has the same -meaning as if it appeared in a pattern, i.e., `($0 ~ /foo/)' (d.c.) -*Note Expression Patterns::. This means that the following two code -segments: +When used on the righthand side of the `~' or `!~' operators, a regexp +constant merely stands for the regexp that is to be matched. However, +regexp constants (such as `/foo/') may be used like simple expressions. +When a regexp constant appears by itself, it has the same meaning as if +it appeared in a pattern, i.e., `($0 ~ /foo/)' (d.c.) *Note Expression +Patterns::. This means that the following two code segments: if ($0 ~ /barfly/ || $0 ~ /camelot/) print "found" @@ -5499,7 +5571,7 @@ assigns either zero or one to the variable `matches', depending upon the contents of the current input record. This feature of the language has never been well documented until the POSIX specification. - Constant regular expressions are also used as the first argument for +Constant regular expressions are also used as the first argument for the `gensub', `sub', and `gsub' functions, and as the second argument of the `match' function (*note String Functions::). Modern implementations of `awk', including `gawk', allow the third argument of @@ -5516,7 +5588,7 @@ For example: sub(pat, repl, str) return str } - + { ... text = "hi! hi yourself!" @@ -5524,8 +5596,8 @@ For example: ... } - In this example, the programmer wants to pass a regexp constant to -the user-defined function `mysub', which in turn passes it on to either +In this example, the programmer wants to pass a regexp constant to the +user-defined function `mysub', which in turn passes it on to either `sub' or `gsub'. However, what really happens is that the `pat' parameter is either one or zero, depending upon whether or not `$0' matches `/hi/'. `gawk' issues a warning when it sees a regexp constant @@ -5535,10 +5607,10 @@ value in this way is probably not what was intended. File: gawk.info, Node: Variables, Next: Conversion, Prev: Using Constant Regexps, Up: Expressions -Variables -========= +5.3 Variables +============= - Variables are ways of storing values at one point in your program for +Variables are ways of storing values at one point in your program for use later in another part of your program. They can be manipulated entirely within the program text, and they can also be assigned values on the `awk' command line. @@ -5553,29 +5625,29 @@ on the `awk' command line. File: gawk.info, Node: Using Variables, Next: Assignment Options, Up: Variables -Using Variables in a Program ----------------------------- +5.3.1 Using Variables in a Program +---------------------------------- - Variables let you give names to values and refer to them later. +Variables let you give names to values and refer to them later. Variables have already been used in many of the examples. The name of a variable must be a sequence of letters, digits, or underscores, and it may not begin with a digit. Case is significant in variable names; `a' and `A' are distinct variables. - A variable name is a valid expression by itself; it represents the +A variable name is a valid expression by itself; it represents the variable's current value. Variables are given new values with "assignment operators", "increment operators", and "decrement operators". *Note Assignment Ops::. - A few variables have special built-in meanings, such as `FS' (the -field separator), and `NF' (the number of fields in the current input +A few variables have special built-in meanings, such as `FS' (the field +separator), and `NF' (the number of fields in the current input record). *Note Built-in Variables::, for a list of the built-in variables. These built-in variables can be used and assigned just like all other variables, but their values are also used or changed automatically by `awk'. All built-in variables' names are entirely uppercase. - Variables in `awk' can be assigned either numeric or string values. +Variables in `awk' can be assigned either numeric or string values. The kind of value a variable holds can change over the life of a program. By default, variables are initialized to the empty string, which is zero if converted to a number. There is no need to @@ -5585,10 +5657,10 @@ do in C and in most other traditional languages. File: gawk.info, Node: Assignment Options, Prev: Using Variables, Up: Variables -Assigning Variables on the Command Line ---------------------------------------- +5.3.2 Assigning Variables on the Command Line +--------------------------------------------- - Any `awk' variable can be set by including a "variable assignment" +Any `awk' variable can be set by including a "variable assignment" among the arguments on the command line when `awk' is invoked (*note Other Arguments::). Such an assignment has the following form: @@ -5625,7 +5697,7 @@ second field is printed in lines from `BBS-list': -| 555-3412 ... - Command-line arguments are made available for explicit examination by +Command-line arguments are made available for explicit examination by the `awk' program in the `ARGV' array (*note ARGC and ARGV::). `awk' processes the values of command-line assignments for escape sequences (*note Escape Sequences::). (d.c.) @@ -5633,15 +5705,15 @@ processes the values of command-line assignments for escape sequences File: gawk.info, Node: Conversion, Next: Arithmetic Ops, Prev: Variables, Up: Expressions -Conversion of Strings and Numbers -================================= +5.4 Conversion of Strings and Numbers +===================================== - Strings are converted to numbers and numbers are converted to -strings, if the context of the `awk' program demands it. For example, -if the value of either `foo' or `bar' in the expression `foo + bar' -happens to be a string, it is converted to a number before the addition -is performed. If numeric values appear in string concatenation, they -are converted to strings. Consider the following: +Strings are converted to numbers and numbers are converted to strings, +if the context of the `awk' program demands it. For example, if the +value of either `foo' or `bar' in the expression `foo + bar' happens to +be a string, it is converted to a number before the addition is +performed. If numeric values appear in string concatenation, they are +converted to strings. Consider the following: two = 2; three = 3 print (two three) + 4 @@ -5651,7 +5723,7 @@ variables `two' and `three' are converted to strings and concatenated together. The resulting string is converted back to the number 23, to which 4 is then added. - If, for some reason, you need to force a number to be converted to a +If, for some reason, you need to force a number to be converted to a string, concatenate the empty string, `""', with that number. To force a string to be converted to a number, add zero to that string. A string is converted to a number by interpreting any numeric prefix of @@ -5659,24 +5731,24 @@ the string as numerals: `"2.5"' converts to 2.5, `"1e3"' converts to 1000, and `"25fix"' has a numeric value of 25. Strings that can't be interpreted as valid numbers convert to zero. - The exact manner in which numbers are converted into strings is +The exact manner in which numbers are converted into strings is controlled by the `awk' built-in variable `CONVFMT' (*note Built-in Variables::). Numbers are converted using the `sprintf' function with `CONVFMT' as the format specifier (*note String Functions::). - `CONVFMT''s default value is `"%.6g"', which prints a value with at +`CONVFMT''s default value is `"%.6g"', which prints a value with at least six significant digits. For some applications, you might want to change it to specify more precision. On most modern machines, 17 digits is enough to capture a floating-point number's value exactly, most of the time.(1) - Strange results can occur if you set `CONVFMT' to a string that -doesn't tell `sprintf' how to format floating-point numbers in a useful -way. For example, if you forget the `%' in the format, `awk' converts -all numbers to the same constant string. As a special case, if a -number is an integer, then the result of converting it to a string is -_always_ an integer, no matter what the value of `CONVFMT' may be. -Given the following code fragment: +Strange results can occur if you set `CONVFMT' to a string that doesn't +tell `sprintf' how to format floating-point numbers in a useful way. +For example, if you forget the `%' in the format, `awk' converts all +numbers to the same constant string. As a special case, if a number is +an integer, then the result of converting it to a string is _always_ an +integer, no matter what the value of `CONVFMT' may be. Given the +following code fragment: CONVFMT = "%2.2f" a = 12 @@ -5684,7 +5756,7 @@ Given the following code fragment: `b' has the value `"12"', not `"12.00"'. (d.c.) - Prior to the POSIX standard, `awk' used the value of `OFMT' for +Prior to the POSIX standard, `awk' used the value of `OFMT' for converting numbers to strings. `OFMT' specifies the output format to use when printing numbers with `print'. `CONVFMT' was introduced in order to separate the semantics of conversion from the semantics of @@ -5696,7 +5768,7 @@ older implementations of `awk'. We recommend that instead of changing your programs, just port `gawk' itself. *Note Print::, for more information on the `print' statement. - Finally, once again, where you are can matter when it comes to +Finally, once again, where you are can matter when it comes to converting between numbers and strings. In *Note Locales::, we mentioned that the local character set and language (the locale) can affect how `gawk' matches characters. The locale also affects numeric @@ -5706,10 +5778,10 @@ use the period character (`.') as the decimal point. However, many (if not most) European and non-English locales use the comma (`,') as the decimal point character. - The POSIX standard says that `awk' always uses the period as the -decimal point when reading the `awk' program source code, and for -command-line variable assignments (*note Other Arguments::). However, -when interpreting input data, for `print' and `printf' output, and for +The POSIX standard says that `awk' always uses the period as the decimal +point when reading the `awk' program source code, and for command-line +variable assignments (*note Other Arguments::). However, when +interpreting input data, for `print' and `printf' output, and for number to string conversion, the local decimal point character is used. As of version 3.1.3, `gawk' fully complies with this aspect of the standard. Here are some examples indicating the difference in behavior, @@ -5729,24 +5801,24 @@ the decimal point separator. In the normal `"C"' locale, `gawk' treats `4,321' as `4', while in the Danish locale, it's treated as the full number, `4.321'. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Pathological cases can require up to 752 digits (!), but we -doubt that you need to worry about this. +(1) Pathological cases can require up to 752 digits (!), but we doubt +that you need to worry about this. File: gawk.info, Node: Arithmetic Ops, Next: Concatenation, Prev: Conversion, Up: Expressions -Arithmetic Operators -==================== +5.5 Arithmetic Operators +======================== - The `awk' language uses the common arithmetic operators when -evaluating expressions. All of these arithmetic operators follow normal +The `awk' language uses the common arithmetic operators when evaluating +expressions. All of these arithmetic operators follow normal precedence rules and work as you would expect them to. - The following example uses a file named `grades', which contains a -list of student names as well as three test scores per student (it's a -small class): +The following example uses a file named `grades', which contains a list +of student names as well as three test scores per student (it's a small +class): Pat 100 97 58 Sandy 84 72 93 @@ -5761,8 +5833,8 @@ scores: -| Sandy 83 -| Chris 84.3333 - The following list provides the arithmetic operators in `awk', in -order from the highest precedence to the lowest: +The following list provides the arithmetic operators in `awk', in order +from the highest precedence to the lowest: `- X' Negation. @@ -5796,57 +5868,58 @@ order from the highest precedence to the lowest: `X - Y' Subtraction. - Unary plus and minus have the same precedence, the multiplication +Unary plus and minus have the same precedence, the multiplication operators all have the same precedence, and addition and subtraction have the same precedence. - When computing the remainder of `X % Y', the quotient is rounded -toward zero to an integer and multiplied by Y. This result is -subtracted from X; this operation is sometimes known as "trunc-mod." -The following relation always holds: +When computing the remainder of `X % Y', the quotient is rounded toward +zero to an integer and multiplied by Y. This result is subtracted from +X; this operation is sometimes known as "trunc-mod." The following +relation always holds: b * int(a / b) + (a % b) == a - One possibly undesirable effect of this definition of remainder is -that `X % Y' is negative if X is negative. Thus: +One possibly undesirable effect of this definition of remainder is that +`X % Y' is negative if X is negative. Thus: -17 % 8 = -1 - In other `awk' implementations, the signedness of the remainder may -be machine-dependent. +In other `awk' implementations, the signedness of the remainder may be +machine-dependent. - *Note:* The POSIX standard only specifies the use of `^' for -exponentiation. For maximum portability, do not use the `**' operator. + NOTE: The POSIX standard only specifies the use of `^' for + exponentiation. For maximum portability, do not use the `**' + operator. File: gawk.info, Node: Concatenation, Next: Assignment Ops, Prev: Arithmetic Ops, Up: Expressions -String Concatenation -==================== +5.6 String Concatenation +======================== It seemed like a good idea at the time. Brian Kernighan - There is only one string operation: concatenation. It does not have -a specific operator to represent it. Instead, concatenation is -performed by writing expressions next to one another, with no operator. -For example: +There is only one string operation: concatenation. It does not have a +specific operator to represent it. Instead, concatenation is performed +by writing expressions next to one another, with no operator. For +example: $ awk '{ print "Field number one: " $1 }' BBS-list -| Field number one: aardvark -| Field number one: alpo-net ... - Without the space in the string constant after the `:', the line -runs together. For example: +Without the space in the string constant after the `:', the line runs +together. For example: $ awk '{ print "Field number one:" $1 }' BBS-list -| Field number one:aardvark -| Field number one:alpo-net ... - Because string concatenation does not have an explicit operator, it -is often necessary to insure that it happens at the right time by using +Because string concatenation does not have an explicit operator, it is +often necessary to insure that it happens at the right time by using parentheses to enclose the items to concatenate. For example, the following code fragment does not concatenate `file' and `name' as you might expect: @@ -5859,7 +5932,7 @@ It is necessary to use the following: print "something meaningful" > (file name) - Parentheses should be used around concatenation in all but the most +Parentheses should be used around concatenation in all but the most common contexts, such as on the righthand side of `='. Be careful about the kinds of expressions used in string concatenation. In particular, the order of evaluation of expressions used for @@ -5880,43 +5953,42 @@ counter-intuitive. Consider this example: $ awk 'BEGIN { print -12 " " -24 }' -| -12-24 - This "obviously" is concatenating -12, a space, and -24. But where -did the space disappear to? The answer lies in the combination of -operator precedences and `awk''s automatic conversion rules. To get -the desired result, write the program in the following manner: +This "obviously" is concatenating -12, a space, and -24. But where did +the space disappear to? The answer lies in the combination of operator +precedences and `awk''s automatic conversion rules. To get the desired +result, write the program in the following manner: $ awk 'BEGIN { print -12 " " (-24) }' -| -12 -24 - This forces `awk' to treat the `-' on the `-24' as unary. -Otherwise, it's parsed as follows: +This forces `awk' to treat the `-' on the `-24' as unary. Otherwise, +it's parsed as follows: -12 (`" "' - 24) => -12 (0 - 24) => -12 (-24) => -12-24 - As mentioned earlier, when doing concatenation, _parenthesize_. +As mentioned earlier, when doing concatenation, _parenthesize_. Otherwise, you're never quite sure what you'll get. File: gawk.info, Node: Assignment Ops, Next: Increment Ops, Prev: Concatenation, Up: Expressions -Assignment Expressions -====================== +5.7 Assignment Expressions +========================== - An "assignment" is an expression that stores a (usually different) +An "assignment" is an expression that stores a (usually different) value into a variable. For example, let's assign the value one to the variable `z': z = 1 - After this expression is executed, the variable `z' has the value -one. Whatever old value `z' had before the assignment is forgotten. +After this expression is executed, the variable `z' has the value one. +Whatever old value `z' had before the assignment is forgotten. - Assignments can also store string values. For example, the -following stores the value `"this food is good"' in the variable -`message': +Assignments can also store string values. For example, the following +stores the value `"this food is good"' in the variable `message': thing = "food" predicate = "good" @@ -5931,7 +6003,7 @@ An assignment operator is different; it does produce a value, but even if you ignore it, the assignment still makes itself felt through the alteration of the variable. We call this a "side effect". - The lefthand operand of an assignment need not be a variable (*note +The lefthand operand of an assignment need not be a variable (*note Variables::); it can also be a field (*note Changing Fields::) or an array element (*note Arrays::). These are all called "lvalues", which means they can appear on the lefthand side of an assignment operator. @@ -5939,7 +6011,7 @@ The righthand operand may be any expression; it produces the new value that the assignment stores in the specified variable, field, or array element. (Such values are called "rvalues".) - It is important to note that variables do _not_ have permanent types. +It is important to note that variables do _not_ have permanent types. A variable's type is simply the type of whatever value it happens to hold at the moment. In the following program fragment, the variable `foo' has a numeric value at first, and a string value later on: @@ -5952,20 +6024,21 @@ hold at the moment. In the following program fragment, the variable When the second assignment gives `foo' a string value, the fact that it previously had a numeric value is forgotten. - String values that do not begin with a digit have a numeric value of +String values that do not begin with a digit have a numeric value of zero. After executing the following code, the value of `foo' is five: foo = "a string" foo = foo + 5 -*Note:* Using a variable as a number and then later as a string can be -confusing and is poor programming style. The previous two examples -illustrate how `awk' works, _not_ how you should write your programs! + NOTE: Using a variable as a number and then later as a string can + be confusing and is poor programming style. The previous two + examples illustrate how `awk' works, _not_ how you should write + your programs! - An assignment is an expression, so it has a value--the same value -that is assigned. Thus, `z = 1' is an expression with the value one. -One consequence of this is that you can write multiple assignments -together, such as: +An assignment is an expression, so it has a value--the same value that +is assigned. Thus, `z = 1' is an expression with the value one. One +consequence of this is that you can write multiple assignments together, +such as: x = y = z = 5 @@ -5974,13 +6047,13 @@ and `z'). It does so because the value of `z = 5', which is five, is stored into `y' and then the value of `y = z = 5', which is five, is stored into `x'. - Assignments may be used anywhere an expression is called for. For +Assignments may be used anywhere an expression is called for. For example, it is valid to write `x != (y = 1)' to set `y' to one, and then test whether `x' equals one. But this style tends to make programs hard to read; such nesting of assignments should be avoided, except perhaps in a one-shot program. - Aside from `=', there are several other assignment operators that do +Aside from `=', there are several other assignment operators that do arithmetic with the old value of the variable. For example, the operator `+=' computes a new value by adding the righthand value to the old value of the variable. Thus, the following assignment adds five to @@ -5994,8 +6067,8 @@ This is equivalent to the following: Use whichever makes the meaning of your program clearer. - There are situations where using `+=' (or any assignment operator) -is _not_ the same as simply repeating the lefthand operand in the +There are situations where using `+=' (or any assignment operator) is +_not_ the same as simply repeating the lefthand operand in the righthand expression. For example: # Thanks to Pat Rankin for this example @@ -6003,7 +6076,7 @@ righthand expression. For example: foo[rand()] += 5 for (x in foo) print x, foo[x] - + bar[rand()] = bar[rand()] + 5 for (x in bar) print x, bar[x] @@ -6023,28 +6096,39 @@ Consider this example: The value of `a[3]' could be either two or four. - Here is a table of the arithmetic assignment operators. In each -case, the righthand operand is an expression whose value is converted -to a number. +*Note table-assign-ops:: lists the arithmetic assignment operators. In +each case, the righthand operand is an expression whose value is +converted to a number. + +Operator Effect +-------------------------------------------------------------------------- +LVALUE `+=' INCREMENT Adds INCREMENT to the value of LVALUE. +-------------------------------------------------------------------------- +LVALUE `-=' DECREMENT Subtracts DECREMENT from the value of LVALUE. +-------------------------------------------------------------------------- +LVALUE `*=' Multiplies the value of LVALUE by COEFFICIENT. +COEFFICIENT +-------------------------------------------------------------------------- +LVALUE `/=' DIVISOR Divides the value of LVALUE by DIVISOR. +-------------------------------------------------------------------------- +LVALUE `%=' MODULUS Sets LVALUE to its remainder by MODULUS. +-------------------------------------------------------------------------- +LVALUE `^=' POWER +-------------------------------------------------------------------------- +LVALUE `**=' POWER Raises LVALUE to the power POWER. +-------------------------------------------------------------------------- -LVALUE `+=' INCREMENT Adds INCREMENT to the value of LVALUE. -LVALUE `-=' DECREMENT Subtracts DECREMENT from the value of LVALUE. -LVALUE `*=' Multiplies the value of LVALUE by COEFFICIENT. -COEFFICIENT -LVALUE `/=' DIVISOR Divides the value of LVALUE by DIVISOR. -LVALUE `%=' MODULUS Sets LVALUE to its remainder by MODULUS. -LVALUE `^=' POWER -LVALUE `**=' POWER Raises LVALUE to the power POWER. +Table 5.1: Arithmetic Assignment Operators - *Note:* Only the `^=' operator is specified by POSIX. For maximum -portability, do not use the `**=' operator. + NOTE: Only the `^=' operator is specified by POSIX. For maximum + portability, do not use the `**=' operator. Advanced Notes: Syntactic Ambiguities Between `/=' and Regular Expressions -------------------------------------------------------------------------- - There is a syntactic ambiguity between the `/=' assignment operator -and regexp constants whose first character is an `='. (d.c.) This is -most notable in commercial `awk' versions. For example: +There is a syntactic ambiguity between the `/=' assignment operator and +regexp constants whose first character is an `='. (d.c.) This is most +notable in commercial `awk' versions. For example: $ awk /==/ /dev/null error--> awk: syntax error at source line 1 @@ -6056,21 +6140,21 @@ A workaround is: awk '/[=]=/' /dev/null - `gawk' does not have this problem, nor do the other freely available +`gawk' does not have this problem, nor do the other freely available versions described in *Note Other Versions::. File: gawk.info, Node: Increment Ops, Next: Truth Values, Prev: Assignment Ops, Up: Expressions -Increment and Decrement Operators -================================= +5.8 Increment and Decrement Operators +===================================== - "Increment" and "decrement operators" increase or decrease the value -of a variable by one. An assignment operator can do the same thing, so +"Increment" and "decrement operators" increase or decrease the value of +a variable by one. An assignment operator can do the same thing, so the increment operators add no power to the `awk' language; however, they are convenient abbreviations for very common operations. - The operator used for adding one is written `++'. It can be used to +The operator used for adding one is written `++'. It can be used to increment a variable either before or after taking its value. To pre-increment a variable `v', write `++v'. This adds one to the value of `v'--that new value is also the value of the expression. (The @@ -6083,18 +6167,18 @@ four, but it changes the value of `foo' to five. In other words, the operator returns the old value of the variable, but with the side effect of incrementing it. - The post-increment `foo++' is nearly the same as writing `(foo += 1) -- 1'. It is not perfectly equivalent because all numbers in `awk' are +The post-increment `foo++' is nearly the same as writing `(foo += 1) - +1'. It is not perfectly equivalent because all numbers in `awk' are floating-point--in floating-point, `foo + 1 - 1' does not necessarily equal `foo'. But the difference is minute as long as you stick to numbers that are fairly small (less than 10e12). - Fields and array elements are incremented just like variables. (Use +Fields and array elements are incremented just like variables. (Use `$(i++)' when you want to do a field reference and a variable increment at the same time. The parentheses are necessary because of the precedence of the field reference operator `$'.) - The decrement operator `--' works just like `++', except that it +The decrement operator `--' works just like `++', except that it subtracts one instead of adding it. As with `++', it can be used before the lvalue to pre-decrement or after it to post-decrement. Following is a summary of increment and decrement expressions: @@ -6135,23 +6219,23 @@ Or something even stranger? b += ++b + b++ print b - In other words, when do the various side effects prescribed by the +In other words, when do the various side effects prescribed by the postfix operators (`b++') take effect? When side effects happen is "implementation defined". In other words, it is up to the particular version of `awk'. The result for the first example may be 12 or 13, and for the second, it may be 22 or 23. - In short, doing things like this is not recommended and definitely -not anything that you can rely upon for portability. You should avoid -such things in your own programs. +In short, doing things like this is not recommended and definitely not +anything that you can rely upon for portability. You should avoid such +things in your own programs. File: gawk.info, Node: Truth Values, Next: Typing and Comparison, Prev: Increment Ops, Up: Expressions -True and False in `awk' -======================= +5.9 True and False in `awk' +=========================== - Many programming languages have a special representation for the +Many programming languages have a special representation for the concepts of "true" and "false." Such languages usually use the special constants `true' and `false', or perhaps their uppercase equivalents. However, `awk' is different. It borrows a very simple concept of true @@ -6169,29 +6253,29 @@ value' three times: print "A strange truth value" } - There is a surprising consequence of the "nonzero or non-null" rule: +There is a surprising consequence of the "nonzero or non-null" rule: the string constant `"0"' is actually true, because it is non-null. (d.c.) File: gawk.info, Node: Typing and Comparison, Next: Boolean Ops, Prev: Truth Values, Up: Expressions -Variable Typing and Comparison Expressions -========================================== +5.10 Variable Typing and Comparison Expressions +=============================================== The Guide is definitive. Reality is frequently inaccurate. The Hitchhiker's Guide to the Galaxy - Unlike other programming languages, `awk' variables do not have a -fixed type. Instead, they can be either a number or a string, depending -upon the value that is assigned to them. +Unlike other programming languages, `awk' variables do not have a fixed +type. Instead, they can be either a number or a string, depending upon +the value that is assigned to them. - The 1992 POSIX standard introduced the concept of a "numeric -string", which is simply a string that looks like a number--for -example, `" +2"'. This concept is used for determining the type of a -variable. The type of the variable is important because the types of -two variables determine how they are compared. In `gawk', variable -typing follows these rules: +The 1992 POSIX standard introduced the concept of a "numeric string", +which is simply a string that looks like a number--for example, +`" +2"'. This concept is used for determining the type of a variable. +The type of the variable is important because the types of two variables +determine how they are compared. In `gawk', variable typing follows +these rules: * A numeric constant or the result of a numeric operation has the NUMERIC attribute. @@ -6208,9 +6292,8 @@ typing follows these rules: * Attributes propagate across assignments but are not changed by any use. - The last rule is particularly important. In the following program, -`a' has numeric type, even though it is later used in a string -operation: +The last rule is particularly important. In the following program, `a' +has numeric type, even though it is later used in a string operation: BEGIN { a = 12.345 @@ -6218,63 +6301,60 @@ operation: print b } - When two operands are compared, either string comparison or numeric +When two operands are compared, either string comparison or numeric comparison may be used. This depends upon the attributes of the operands, according to the following symmetric matrix: - +---------------------------------------------- + +--------------------------------------------- | STRING NUMERIC STRNUM - --------+---------------------------------------------- + -------+--------------------------------------------- | STRING | string string string | NUMERIC | string numeric numeric | STRNUM | string numeric numeric - --------+---------------------------------------------- + -------+--------------------------------------------- - The basic idea is that user input that looks numeric--and _only_ -user input--should be treated as numeric, even though it is actually -made of characters and is therefore also a string. Thus, for example, -the string constant `" +3.14"' is a string, even though it looks -numeric, and is _never_ treated as number for comparison purposes. +The basic idea is that user input that looks numeric--and _only_ user +input--should be treated as numeric, even though it is actually made of +characters and is therefore also a string. Thus, for example, the +string constant `" +3.14"' is a string, even though it looks numeric, +and is _never_ treated as number for comparison purposes. - In short, when one operand is a "pure" string, such as a string +In short, when one operand is a "pure" string, such as a string constant, then a string comparison is performed. Otherwise, a numeric comparison is performed.(1) - "Comparison expressions" compare strings or numbers for -relationships such as equality. They are written using "relational -operators", which are a superset of those in C. Here is a table of -them: - -`X < Y' - True if X is less than Y. - -`X <= Y' - True if X is less than or equal to Y. - -`X > Y' - True if X is greater than Y. - -`X >= Y' - True if X is greater than or equal to Y. - -`X == Y' - True if X is equal to Y. - -`X != Y' - True if X is not equal to Y. - -`X ~ Y' - True if the string X matches the regexp denoted by Y. +"Comparison expressions" compare strings or numbers for relationships +such as equality. They are written using "relational operators", which +are a superset of those in C. *Note table-relational-ops:: describes +them. -`X !~ Y' - True if the string X does not match the regexp denoted by Y. +Expression Result +-------------------------------------------------------------------------- +X `<' Y True if X is less than Y. +-------------------------------------------------------------------------- +X `<=' Y True if X is less than or equal to Y. +-------------------------------------------------------------------------- +X `>' Y True if X is greater than Y. +-------------------------------------------------------------------------- +X `>=' Y True if X is greater than or equal to Y. +-------------------------------------------------------------------------- +X `==' Y True if X is equal to Y. +-------------------------------------------------------------------------- +X `!=' Y True if X is not equal to Y. +-------------------------------------------------------------------------- +X `~' Y True if the string X matches the regexp denoted by Y. +-------------------------------------------------------------------------- +X `!~' Y True if the string X does not match the regexp + denoted by Y. +-------------------------------------------------------------------------- +SUBSCRIPT `in' True if the array ARRAY has an element with the +ARRAY subscript SUBSCRIPT. +-------------------------------------------------------------------------- -`SUBSCRIPT in ARRAY' - True if the array ARRAY has an element with the subscript - SUBSCRIPT. +Table 5.2: Relational Operators Comparison expressions have the value one if true and zero if false. When comparing operands of mixed types, numeric operands are converted @@ -6299,7 +6379,7 @@ Unless `b' happens to be zero or the null string, the `if' part of the test always succeeds. Because the operators are so similar, this kind of error is very difficult to spot when scanning the source code. - The following table of expressions illustrates the kind of comparison +The following table of expressions illustrates the kind of comparison `gawk' performs, as well as what the result of the comparison is: `1.5 <= 2.0' @@ -6323,7 +6403,7 @@ of error is very difficult to spot when scanning the source code. `a == b' string comparison (false) - In the next example: +In the next example: $ echo 1e2 3 | awk '{ print ($1 < $2) ? "true" : "false" }' -| false @@ -6346,48 +6426,47 @@ By contrast: has the value one if `x' contains `foo', such as `"Oh, what a fool am I!"'. - The righthand operand of the `~' and `!~' operators may be either a +The righthand operand of the `~' and `!~' operators may be either a regexp constant (`/.../') or an ordinary expression. In the latter case, the value of the expression as a string is used as a dynamic regexp (*note Regexp Usage::; also *note Computed Regexps::). - In modern implementations of `awk', a constant regular expression in +In modern implementations of `awk', a constant regular expression in slashes by itself is also an expression. The regexp `/REGEXP/' is an abbreviation for the following comparison expression: $0 ~ /REGEXP/ - One special place where `/foo/' is _not_ an abbreviation for `$0 ~ +One special place where `/foo/' is _not_ an abbreviation for `$0 ~ /foo/' is when it is the righthand operand of `~' or `!~'. *Note Using Constant Regexps::, where this is discussed in more detail. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) The POSIX standard is under revision. The revised standard's -rules for typing and comparison are the same as just described for -`gawk'. +(1) The POSIX standard is under revision. The revised standard's rules +for typing and comparison are the same as just described for `gawk'. File: gawk.info, Node: Boolean Ops, Next: Conditional Exp, Prev: Typing and Comparison, Up: Expressions -Boolean Expressions -=================== +5.11 Boolean Expressions +======================== - A "Boolean expression" is a combination of comparison expressions or +A "Boolean expression" is a combination of comparison expressions or matching expressions, using the Boolean operators "or" (`||'), "and" (`&&'), and "not" (`!'), along with parentheses to control nesting. The truth value of the Boolean expression is computed by combining the truth values of the component expressions. Boolean expressions are also referred to as "logical expressions". The terms are equivalent. - Boolean expressions can be used wherever comparison and matching +Boolean expressions can be used wherever comparison and matching expressions can be used. They can be used in `if', `while', `do', and `for' statements (*note Statements::). They have numeric values (one if true, zero if false) that come into play if the result of the Boolean expression is stored in a variable or used in arithmetic. - In addition, every Boolean expression is also a valid pattern, so -you can use one as a pattern to control the execution of rules. The +In addition, every Boolean expression is also a valid pattern, so you +can use one as a pattern to control the execution of rules. The Boolean operators are: `BOOLEAN1 && BOOLEAN2' @@ -6424,22 +6503,21 @@ Boolean operators are: (The `in' operator is described in *Note Reference to Elements::.) - The `&&' and `||' operators are called "short-circuit" operators +The `&&' and `||' operators are called "short-circuit" operators because of the way they work. Evaluation of the full expression is "short-circuited" if the result can be determined part way through its evaluation. - Statements that use `&&' or `||' can be continued simply by putting -a newline after them. But you cannot put a newline in front of either -of these operators without using backslash continuation (*note +Statements that use `&&' or `||' can be continued simply by putting a +newline after them. But you cannot put a newline in front of either of +these operators without using backslash continuation (*note Statements/Lines::). - The actual value of an expression using the `!' operator is either -one or zero, depending upon the truth value of the expression it is -applied to. The `!' operator is often useful for changing the sense of -a flag variable from false to true and back again. For example, the -following program is one way to print lines in between special -bracketing lines: +The actual value of an expression using the `!' operator is either one +or zero, depending upon the truth value of the expression it is applied +to. The `!' operator is often useful for changing the sense of a flag +variable from false to true and back again. For example, the following +program is one way to print lines in between special bracketing lines: $1 == "START" { interested = ! interested; next } interested == 1 { print } @@ -6452,18 +6530,19 @@ using `!'. The next rule prints lines as long as `interested' is true. When a line is seen whose first field is `END', `interested' is toggled back to false. - *Note:* The `next' statement is discussed in *Note Next Statement::. -`next' tells `awk' to skip the rest of the rules, get the next record, -and start processing the rules over again at the top. The reason it's -there is to avoid printing the bracketing `START' and `END' lines. + NOTE: The `next' statement is discussed in *Note Next Statement::. + `next' tells `awk' to skip the rest of the rules, get the next + record, and start processing the rules over again at the top. The + reason it's there is to avoid printing the bracketing `START' and + `END' lines. File: gawk.info, Node: Conditional Exp, Next: Function Calls, Prev: Boolean Ops, Up: Expressions -Conditional Expressions -======================= +5.12 Conditional Expressions +============================ - A "conditional expression" is a special kind of expression that has +A "conditional expression" is a special kind of expression that has three operands. It allows you to use one expression's value to select one of two other expressions. The conditional expression is the same as in the C language, as shown here: @@ -6479,7 +6558,7 @@ following expression produces the absolute value of `x': x >= 0 ? x : -x - Each time the conditional expression is computed, only one of +Each time the conditional expression is computed, only one of IF-TRUE-EXP and IF-FALSE-EXP is used; the other is ignored. This is important when the expressions have side effects. For example, this conditional expression examines element `i' of either array `a' or @@ -6491,7 +6570,7 @@ This is guaranteed to increment `i' exactly once, because each time only one of the two increment expressions is executed and the other is not. *Note Arrays::, for more information about arrays. - As a minor `gawk' extension, a statement that uses `?:' can be +As a minor `gawk' extension, a statement that uses `?:' can be continued simply by putting a newline after either character. However, putting a newline in front of either character does not work without using backslash continuation (*note Statements/Lines::). If `--posix' @@ -6500,21 +6579,21 @@ is specified (*note Options::), then this extension is disabled. File: gawk.info, Node: Function Calls, Next: Precedence, Prev: Conditional Exp, Up: Expressions -Function Calls -============== +5.13 Function Calls +=================== - A "function" is a name for a particular calculation. This enables -you to ask for it by name at any point in the program. For example, -the function `sqrt' computes the square root of a number. +A "function" is a name for a particular calculation. This enables you +to ask for it by name at any point in the program. For example, the +function `sqrt' computes the square root of a number. - A fixed set of functions are "built-in", which means they are -available in every `awk' program. The `sqrt' function is one of these. -*Note Built-in::, for a list of built-in functions and their -descriptions. In addition, you can define functions for use in your -program. *Note User-defined::, for instructions on how to do this. +A fixed set of functions are "built-in", which means they are available +in every `awk' program. The `sqrt' function is one of these. *Note +Built-in::, for a list of built-in functions and their descriptions. +In addition, you can define functions for use in your program. *Note +User-defined::, for instructions on how to do this. - The way to use a function is with a "function call" expression, -which consists of the function name followed immediately by a list of +The way to use a function is with a "function call" expression, which +consists of the function name followed immediately by a list of "arguments" in parentheses. The arguments are expressions that provide the raw materials for the function's calculations. When there is more than one argument, they are separated by commas. If there are no @@ -6525,28 +6604,27 @@ examples show function calls with and without arguments: atan2(y, x) two arguments rand() no arguments - *Caution:* Do not put any space between the function name and the +*Caution:* Do not put any space between the function name and the open-parenthesis! A user-defined function name looks just like the name of a variable--a space would make the expression look like concatenation of a variable with an expression inside parentheses. - With built-in functions, space before the parenthesis is harmless, -but it is best not to get into the habit of using space to avoid -mistakes with user-defined functions. Each function expects a -particular number of arguments. For example, the `sqrt' function must -be called with a single argument, the number of which to take the -square root: +With built-in functions, space before the parenthesis is harmless, but +it is best not to get into the habit of using space to avoid mistakes +with user-defined functions. Each function expects a particular number +of arguments. For example, the `sqrt' function must be called with a +single argument, the number of which to take the square root: sqrt(ARGUMENT) - Some of the built-in functions have one or more optional arguments. -If those arguments are not supplied, the functions use a reasonable +Some of the built-in functions have one or more optional arguments. If +those arguments are not supplied, the functions use a reasonable default value. *Note Built-in::, for full details. If arguments are omitted in calls to user-defined functions, then those arguments are treated as local variables and initialized to the empty string (*note User-defined::). - Like every other expression, the function call has a value, which is +Like every other expression, the function call has a value, which is computed by the function based on the arguments you give it. In this example, the value of `sqrt(ARGUMENT)' is the square root of ARGUMENT. A function can also have side effects, such as assigning values to @@ -6565,15 +6643,15 @@ one number per line, and prints the square root of each one: File: gawk.info, Node: Precedence, Prev: Function Calls, Up: Expressions -Operator Precedence (How Operators Nest) -======================================== +5.14 Operator Precedence (How Operators Nest) +============================================= - "Operator precedence" determines how operators are grouped when +"Operator precedence" determines how operators are grouped when different operators appear close by in one expression. For example, `*' has higher precedence than `+'; thus, `a + b * c' means to multiply `b' and `c', and then add `a' to the product (i.e., `a + (b * c)'). - The normal precedence of the operators can be overruled by using +The normal precedence of the operators can be overruled by using parentheses. Think of the precedence rules as saying where the parentheses are assumed to be. In fact, it is wise to always use parentheses whenever there is an unusual combination of operators, @@ -6582,20 +6660,20 @@ precedence is in this case. Even experienced programmers occasionally forget the exact rules, which leads to mistakes. Explicit parentheses help prevent any such mistakes. - When operators of equal precedence are used together, the leftmost +When operators of equal precedence are used together, the leftmost operator groups first, except for the assignment, conditional, and exponentiation operators, which group in the opposite order. Thus, `a - b + c' groups as `(a - b) + c' and `a = b = c' groups as `a = (b = c)'. - The precedence of prefix unary operators does not matter as long as -only unary operators are involved, because there is only one way to -interpret them: innermost first. Thus, `$++i' means `$(++i)' and -`++$x' means `++($x)'. However, when another operator follows the -operand, then the precedence of the unary operators can matter. `$x^2' -means `($x)^2', but `-x^2' means `-(x^2)', because `-' has lower -precedence than `^', whereas `$' has higher precedence. This table -presents `awk''s operators, in order of highest to lowest precedence: +The precedence of prefix unary operators does not matter as long as only +unary operators are involved, because there is only one way to interpret +them: innermost first. Thus, `$++i' means `$(++i)' and `++$x' means +`++($x)'. However, when another operator follows the operand, then the +precedence of the unary operators can matter. `$x^2' means `($x)^2', +but `-x^2' means `-(x^2)', because `-' has lower precedence than `^', +whereas `$' has higher precedence. This table presents `awk''s +operators, in order of highest to lowest precedence: `(...)' Grouping. @@ -6657,21 +6735,21 @@ presents `awk''s operators, in order of highest to lowest precedence: `/= %= ^= **=' Assignment. These operators group right to left. - *Note:* The `|&', `**', and `**=' operators are not specified by -POSIX. For maximum portability, do not use them. + NOTE: The `|&', `**', and `**=' operators are not specified by + POSIX. For maximum portability, do not use them. File: gawk.info, Node: Patterns and Actions, Next: Arrays, Prev: Expressions, Up: Top -Patterns, Actions, and Variables -******************************** +6 Patterns, Actions, and Variables +********************************** - As you have already seen, each `awk' statement consists of a pattern +As you have already seen, each `awk' statement consists of a pattern with an associated action. This major node describes how you build patterns and actions, what kinds of things you can do within actions, and `awk''s built-in variables. - The pattern-action rules and the statements available for use within +The pattern-action rules and the statements available for use within actions form the core of `awk' programming. In a sense, everything covered up to here has been the foundation that programs are built on top of. Now it's time to start building something useful. @@ -6688,8 +6766,8 @@ top of. Now it's time to start building something useful. File: gawk.info, Node: Pattern Overview, Next: Using Shell Variables, Up: Patterns and Actions -Pattern Elements -================ +6.1 Pattern Elements +==================== * Menu: @@ -6699,7 +6777,7 @@ Pattern Elements * BEGIN/END:: Specifying initialization and cleanup rules. * Empty:: The empty pattern, which matches every record. - Patterns in `awk' control the execution of rules--a rule is executed +Patterns in `awk' control the execution of rules--a rule is executed when its pattern matches the current input record. The following is a summary of the types of `awk' patterns: @@ -6727,11 +6805,11 @@ summary of the types of `awk' patterns: File: gawk.info, Node: Regexp Patterns, Next: Expression Patterns, Up: Pattern Overview -Regular Expressions as Patterns -------------------------------- +6.1.1 Regular Expressions as Patterns +------------------------------------- - Regular expressions are one of the first kinds of patterns presented -in this book. This kind of pattern is simply a regexp constant in the +Regular expressions are one of the first kinds of patterns presented in +this book. This kind of pattern is simply a regexp constant in the pattern part of a rule. Its meaning is `$0 ~ /PATTERN/'. The pattern matches when the input record matches the regexp. For example: @@ -6741,18 +6819,18 @@ matches when the input record matches the regexp. For example: File: gawk.info, Node: Expression Patterns, Next: Ranges, Prev: Regexp Patterns, Up: Pattern Overview -Expressions as Patterns ------------------------ +6.1.2 Expressions as Patterns +----------------------------- - Any `awk' expression is valid as an `awk' pattern. The pattern -matches if the expression's value is nonzero (if a number) or non-null -(if a string). The expression is reevaluated each time the rule is -tested against a new input record. If the expression uses fields such -as `$1', the value depends directly on the new input record's text; +Any `awk' expression is valid as an `awk' pattern. The pattern matches +if the expression's value is nonzero (if a number) or non-null (if a +string). The expression is reevaluated each time the rule is tested +against a new input record. If the expression uses fields such as +`$1', the value depends directly on the new input record's text; otherwise, it depends on only what has happened so far in the execution of the `awk' program. - Comparison expressions, using the comparison operators described in +Comparison expressions, using the comparison operators described in *Note Typing and Comparison::, are a very common kind of pattern. Regexp matching and nonmatching are also very common expressions. The left operand of the `~' and `!~' operators is a string. The right @@ -6774,12 +6852,12 @@ which accepts any record with a first field that contains `foo': -| 555-6480 -| 555-2127 - A regexp constant as a pattern is also a special case of an -expression pattern. The expression `/foo/' has the value one if `foo' -appears in the current input record. Thus, as a pattern, `/foo/' -matches any record containing `foo'. +A regexp constant as a pattern is also a special case of an expression +pattern. The expression `/foo/' has the value one if `foo' appears in +the current input record. Thus, as a pattern, `/foo/' matches any +record containing `foo'. - Boolean expressions are also commonly used as patterns. Whether the +Boolean expressions are also commonly used as patterns. Whether the pattern matches an input record depends on whether its subexpressions match. For example, the following command prints all the records in `BBS-list' that contain both `2400' and `foo': @@ -6787,7 +6865,7 @@ match. For example, the following command prints all the records in $ awk '/2400/ && /foo/' BBS-list -| fooey 555-1234 2400/1200/300 B - The following command prints all records in `BBS-list' that contain +The following command prints all records in `BBS-list' that contain _either_ `2400' or `foo' (or both, of course): $ awk '/2400/ || /foo/' BBS-list @@ -6799,7 +6877,7 @@ _either_ `2400' or `foo' (or both, of course): -| sdace 555-3430 2400/1200/300 A -| sabafoo 555-2127 1200/300 C - The following command prints all records in `BBS-list' that do _not_ +The following command prints all records in `BBS-list' that do _not_ contain the string `foo': $ awk '! /foo/' BBS-list @@ -6811,30 +6889,30 @@ contain the string `foo': -| core 555-2912 1200/300 C -| sdace 555-3430 2400/1200/300 A - The subexpressions of a Boolean operator in a pattern can be -constant regular expressions, comparisons, or any other `awk' -expressions. Range patterns are not expressions, so they cannot appear -inside Boolean patterns. Likewise, the special patterns `BEGIN' and -`END', which never match any input record, are not expressions and -cannot appear inside Boolean patterns. +The subexpressions of a Boolean operator in a pattern can be constant +regular expressions, comparisons, or any other `awk' expressions. Range +patterns are not expressions, so they cannot appear inside Boolean +patterns. Likewise, the special patterns `BEGIN' and `END', which +never match any input record, are not expressions and cannot appear +inside Boolean patterns. File: gawk.info, Node: Ranges, Next: BEGIN/END, Prev: Expression Patterns, Up: Pattern Overview -Specifying Record Ranges with Patterns --------------------------------------- +6.1.3 Specifying Record Ranges with Patterns +-------------------------------------------- - A "range pattern" is made of two patterns separated by a comma, in -the form `BEGPAT, ENDPAT'. It is used to match ranges of consecutive -input records. The first pattern, BEGPAT, controls where the range -begins, while ENDPAT controls where the pattern ends. For example, the +A "range pattern" is made of two patterns separated by a comma, in the +form `BEGPAT, ENDPAT'. It is used to match ranges of consecutive input +records. The first pattern, BEGPAT, controls where the range begins, +while ENDPAT controls where the pattern ends. For example, the following: awk '$1 == "on", $1 == "off"' myfile prints every record in `myfile' between `on'/`off' pairs, inclusive. - A range pattern starts out by matching BEGPAT against every input +A range pattern starts out by matching BEGPAT against every input record. When a record matches BEGPAT, the range pattern is "turned on" and the range pattern matches this record as well. As long as the range pattern stays turned on, it automatically matches every input @@ -6843,12 +6921,12 @@ record; when this succeeds, the range pattern is turned off again for the following record. Then the range pattern goes back to checking BEGPAT against each record. - The record that turns on the range pattern and the one that turns it +The record that turns on the range pattern and the one that turns it off both match the range pattern. If you don't want to operate on these records, you can write `if' statements in the rule's action to distinguish them from the records you are interested in. - It is possible for a pattern to be turned on and off by the same +It is possible for a pattern to be turned on and off by the same record. If the record satisfies both conditions, then the action is executed for just that record. For example, suppose there is text between two identical markers (e.g., the `%' symbol), each on its own @@ -6869,13 +6947,13 @@ a flag: /^%$/ { skip = ! skip; next } skip == 1 { next } # skip lines with `skip' set - In a range pattern, the comma (`,') has the lowest precedence of all +In a range pattern, the comma (`,') has the lowest precedence of all the operators (i.e., it is evaluated last). Thus, the following program attempts to combine a range pattern with another, simpler test: echo Yes | awk '/1/,/2/ || /Yes/' - The intent of this program is `(/1/,/2/) || /Yes/'. However, `awk' +The intent of this program is `(/1/,/2/) || /Yes/'. However, `awk' interprets this as `/1/, (/2/ || /Yes/)'. This cannot be changed or worked around; range patterns do not combine with other patterns: @@ -6888,16 +6966,16 @@ worked around; range patterns do not combine with other patterns: File: gawk.info, Node: BEGIN/END, Next: Empty, Prev: Ranges, Up: Pattern Overview -The `BEGIN' and `END' Special Patterns --------------------------------------- +6.1.4 The `BEGIN' and `END' Special Patterns +-------------------------------------------- - All the patterns described so far are for matching input records. -The `BEGIN' and `END' special patterns are different. They supply -startup and cleanup actions for `awk' programs. `BEGIN' and `END' -rules must have actions; there is no default action for these rules -because there is no current record when they run. `BEGIN' and `END' -rules are often referred to as "`BEGIN' and `END' blocks" by long-time -`awk' programmers. +All the patterns described so far are for matching input records. The +`BEGIN' and `END' special patterns are different. They supply startup +and cleanup actions for `awk' programs. `BEGIN' and `END' rules must +have actions; there is no default action for these rules because there +is no current record when they run. `BEGIN' and `END' rules are often +referred to as "`BEGIN' and `END' blocks" by long-time `awk' +programmers. * Menu: @@ -6907,11 +6985,11 @@ rules are often referred to as "`BEGIN' and `END' blocks" by long-time File: gawk.info, Node: Using BEGIN/END, Next: I/O And BEGIN/END, Up: BEGIN/END -Startup and Cleanup Actions -........................... +6.1.4.1 Startup and Cleanup Actions +................................... - A `BEGIN' rule is executed once only, before the first input record -is read. Likewise, an `END' rule is executed once only, after all the +A `BEGIN' rule is executed once only, before the first input record is +read. Likewise, an `END' rule is executed once only, after all the input is read. For example: $ awk ' @@ -6921,7 +6999,7 @@ input is read. For example: -| Analysis of "foo" -| "foo" appears 4 times. - This program finds the number of records in the input file `BBS-list' +This program finds the number of records in the input file `BBS-list' that contain the string `foo'. The `BEGIN' rule prints a title for the report. There is no need to use the `BEGIN' rule to initialize the counter `n' to zero, since `awk' does this automatically (*note @@ -6929,11 +7007,11 @@ Variables::). The second rule increments the variable `n' every time a record containing the pattern `foo' is read. The `END' rule prints the value of `n' at the end of the run. - The special patterns `BEGIN' and `END' cannot be used in ranges or -with Boolean operators (indeed, they cannot be used with any operators). -An `awk' program may have multiple `BEGIN' and/or `END' rules. They -are executed in the order in which they appear: all the `BEGIN' rules -at startup and all the `END' rules at termination. `BEGIN' and `END' +The special patterns `BEGIN' and `END' cannot be used in ranges or with +Boolean operators (indeed, they cannot be used with any operators). An +`awk' program may have multiple `BEGIN' and/or `END' rules. They are +executed in the order in which they appear: all the `BEGIN' rules at +startup and all the `END' rules at termination. `BEGIN' and `END' rules may be intermixed with other rules. This feature was added in the 1987 version of `awk' and is included in the POSIX standard. The original (1978) version of `awk' required the `BEGIN' rule to be placed @@ -6942,7 +7020,7 @@ end, and only allowed one of each. This is no longer required, but it is a good idea to follow this template in terms of program organization and readability. - Multiple `BEGIN' and `END' rules are useful for writing library +Multiple `BEGIN' and `END' rules are useful for writing library functions, because each library file can have its own `BEGIN' and/or `END' rule to do its own initialization and/or cleanup. The order in which library functions are named on the command line controls the @@ -6952,44 +7030,44 @@ the order in which they are executed doesn't matter. *Note Options::, for more information on using library functions. *Note Library Functions::, for a number of useful library functions. - If an `awk' program has only a `BEGIN' rule and no other rules, then +If an `awk' program has only a `BEGIN' rule and no other rules, then the program exits after the `BEGIN' rule is run.(1) However, if an `END' rule exists, then the input is read, even if there are no other rules in the program. This is necessary in case the `END' rule checks the `FNR' and `NR' variables. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) The original version of `awk' used to keep reading and ignoring +(1) The original version of `awk' used to keep reading and ignoring input until the end of the file was seen. File: gawk.info, Node: I/O And BEGIN/END, Prev: Using BEGIN/END, Up: BEGIN/END -Input/Output from `BEGIN' and `END' Rules -......................................... +6.1.4.2 Input/Output from `BEGIN' and `END' Rules +................................................. - There are several (sometimes subtle) points to remember when doing -I/O from a `BEGIN' or `END' rule. The first has to do with the value -of `$0' in a `BEGIN' rule. Because `BEGIN' rules are executed before -any input is read, there simply is no input record, and therefore no +There are several (sometimes subtle) points to remember when doing I/O +from a `BEGIN' or `END' rule. The first has to do with the value of +`$0' in a `BEGIN' rule. Because `BEGIN' rules are executed before any +input is read, there simply is no input record, and therefore no fields, when executing `BEGIN' rules. References to `$0' and the fields yield a null string or zero, depending upon the context. One way to give `$0' a real value is to execute a `getline' command without a variable (*note Getline::). Another way is simply to assign a value to `$0'. - The second point is similar to the first but from the other -direction. Traditionally, due largely to implementation issues, `$0' -and `NF' were _undefined_ inside an `END' rule. The POSIX standard -specifies that `NF' is available in an `END' rule. It contains the -number of fields from the last input record. Most probably due to an -oversight, the standard does not say that `$0' is also preserved, -although logically one would think that it should be. In fact, `gawk' -does preserve the value of `$0' for use in `END' rules. Be aware, -however, that Unix `awk', and possibly other implementations, do not. - - The third point follows from the first two. The meaning of `print' +The second point is similar to the first but from the other direction. +Traditionally, due largely to implementation issues, `$0' and `NF' were +_undefined_ inside an `END' rule. The POSIX standard specifies that +`NF' is available in an `END' rule. It contains the number of fields +from the last input record. Most probably due to an oversight, the +standard does not say that `$0' is also preserved, although logically +one would think that it should be. In fact, `gawk' does preserve the +value of `$0' for use in `END' rules. Be aware, however, that Unix +`awk', and possibly other implementations, do not. + +The third point follows from the first two. The meaning of `print' inside a `BEGIN' or `END' rule is the same as always: `print $0'. If `$0' is the null string, then this prints an empty line. Many long time `awk' programmers use an unadorned `print' in `BEGIN' and `END' @@ -6999,7 +7077,7 @@ idea in `END' rules, at least in `gawk'. It is also poor style, since if an empty line is needed in the output, the program should print one explicitly. - Finally, the `next' and `nextfile' statements are not allowed in a +Finally, the `next' and `nextfile' statements are not allowed in a `BEGIN' rule, because the implicit read-a-record-and-match-against-the-rules loop has not started yet. Similarly, those statements are not valid in an `END' rule, since all @@ -7009,10 +7087,10 @@ Nextfile Statement::.) File: gawk.info, Node: Empty, Prev: BEGIN/END, Up: Pattern Overview -The Empty Pattern ------------------ +6.1.5 The Empty Pattern +----------------------- - An empty (i.e., nonexistent) pattern is considered to match _every_ +An empty (i.e., nonexistent) pattern is considered to match _every_ input record. For example, the program: awk '{ print $1 }' BBS-list @@ -7022,16 +7100,16 @@ prints the first field of every record. File: gawk.info, Node: Using Shell Variables, Next: Action Overview, Prev: Pattern Overview, Up: Patterns and Actions -Using Shell Variables in Programs -================================= +6.2 Using Shell Variables in Programs +===================================== - `awk' programs are often used as components in larger programs -written in shell. For example, it is very common to use a shell -variable to hold a pattern that the `awk' program searches for. There -are two ways to get the value of the shell variable into the body of -the `awk' program. +`awk' programs are often used as components in larger programs written +in shell. For example, it is very common to use a shell variable to +hold a pattern that the `awk' program searches for. There are two ways +to get the value of the shell variable into the body of the `awk' +program. - The most common method is to use shell quoting to substitute the +The most common method is to use shell quoting to substitute the variable's value into the program inside the script. For example, in the following program: @@ -7045,12 +7123,12 @@ concatenated together to form the program. The first part is double-quoted, which allows substitution of the `pattern' variable inside the quotes. The second part is single-quoted. - Variable substitution via quoting works, but can be potentially -messy. It requires a good understanding of the shell's quoting rules -(*note Quoting::), and it's often difficult to correctly match up the -quotes when reading the program. +Variable substitution via quoting works, but can be potentially messy. +It requires a good understanding of the shell's quoting rules (*note +Quoting::), and it's often difficult to correctly match up the quotes +when reading the program. - A better method is to use `awk''s variable assignment feature (*note +A better method is to use `awk''s variable assignment feature (*note Assignment Options::) to assign the shell variable's value to an `awk' variable's value. Then use dynamic regexps to match the pattern (*note Computed Regexps::). The following shows how to redo the previous @@ -7073,15 +7151,15 @@ at every point in the program. File: gawk.info, Node: Action Overview, Next: Statements, Prev: Using Shell Variables, Up: Patterns and Actions -Actions -======= +6.3 Actions +=========== - An `awk' program or script consists of a series of rules and -function definitions interspersed. (Functions are described later. -*Note User-defined::.) A rule contains a pattern and an action, either -of which (but not both) may be omitted. The purpose of the "action" is -to tell `awk' what to do once a match for the pattern is found. Thus, -in outline, an `awk' program generally looks like this: +An `awk' program or script consists of a series of rules and function +definitions interspersed. (Functions are described later. *Note +User-defined::.) A rule contains a pattern and an action, either of +which (but not both) may be omitted. The purpose of the "action" is to +tell `awk' what to do once a match for the pattern is found. Thus, in +outline, an `awk' program generally looks like this: [PATTERN] [{ ACTION }] [PATTERN] [{ ACTION }] @@ -7089,8 +7167,8 @@ in outline, an `awk' program generally looks like this: function NAME(ARGS) { ... } ... - An action consists of one or more `awk' "statements", enclosed in -curly braces (`{...}'). Each statement specifies one thing to do. The +An action consists of one or more `awk' "statements", enclosed in curly +braces (`{...}'). Each statement specifies one thing to do. The statements are separated by newlines or semicolons. The curly braces around an action must be used even if the action contains only one statement, or if it contains no statements at all. However, if you @@ -7100,7 +7178,7 @@ action is equivalent to `{ print $0 }': /foo/ { } match `foo', do nothing -- empty action /foo/ match `foo', print the record -- omitted action - The following types of statements are supported in `awk': +The following types of statements are supported in `awk': Expressions Call functions or assign values to variables (*note @@ -7132,14 +7210,14 @@ Deletion statements File: gawk.info, Node: Statements, Next: Built-in Variables, Prev: Action Overview, Up: Patterns and Actions -Control Statements in Actions -============================= +6.4 Control Statements in Actions +================================= - "Control statements", such as `if', `while', and so on, control the +"Control statements", such as `if', `while', and so on, control the flow of execution in `awk' programs. Most of the control statements in `awk' are patterned on similar statements in C. - All the control statements start with special keywords, such as `if' +All the control statements start with special keywords, such as `if' and `while', to distinguish them from simple expressions. Many control statements contain other statements. For example, the `if' statement contains another statement that may or may not be executed. The @@ -7168,10 +7246,10 @@ with curly braces, separating them with newlines or semicolons. File: gawk.info, Node: If Statement, Next: While Statement, Up: Statements -The `if'-`else' Statement -------------------------- +6.4.1 The `if'-`else' Statement +------------------------------- - The `if'-`else' statement is `awk''s decision-making statement. It +The `if'-`else' statement is `awk''s decision-making statement. It looks like this: if (CONDITION) THEN-BODY [else ELSE-BODY] @@ -7188,7 +7266,7 @@ following: else print "x is odd" - In this example, if the expression `x % 2 == 0' is true (that is, if +In this example, if the expression `x % 2 == 0' is true (that is, if the value of `x' is evenly divisible by two), then the first `print' statement is executed; otherwise, the second `print' statement is executed. If the `else' keyword appears on the same line as THEN-BODY @@ -7207,10 +7285,10 @@ first thing on its line. File: gawk.info, Node: While Statement, Next: Do Statement, Prev: If Statement, Up: Statements -The `while' Statement ---------------------- +6.4.2 The `while' Statement +--------------------------- - In programming, a "loop" is a part of a program that can be executed +In programming, a "loop" is a part of a program that can be executed two or more times in succession. The `while' statement is the simplest looping statement in `awk'. It repeatedly executes a statement as long as a condition is true. For example: @@ -7245,19 +7323,19 @@ tests whether `i' is less than or equal to three. This is true when increments the value of `i' and the loop repeats. The loop terminates when `i' reaches four. - A newline is not required between the condition and the body; -however using one makes the program clearer unless the body is a -compound statement or else is very simple. The newline after the -open-brace that begins the compound statement is not required either, -but the program is harder to read without it. +A newline is not required between the condition and the body; however +using one makes the program clearer unless the body is a compound +statement or else is very simple. The newline after the open-brace +that begins the compound statement is not required either, but the +program is harder to read without it. File: gawk.info, Node: Do Statement, Next: For Statement, Prev: While Statement, Up: Statements -The `do'-`while' Statement --------------------------- +6.4.3 The `do'-`while' Statement +-------------------------------- - The `do' loop is a variation of the `while' looping statement. The +The `do' loop is a variation of the `while' looping statement. The `do' loop executes the BODY once and then repeats the BODY as long as the CONDITION is true. It looks like this: @@ -7265,7 +7343,7 @@ the CONDITION is true. It looks like this: BODY while (CONDITION) - Even if the CONDITION is false at the start, the BODY is executed at +Even if the CONDITION is false at the start, the BODY is executed at least once (and only once, unless executing BODY makes CONDITION true). Contrast this with the corresponding `while' statement: @@ -7290,10 +7368,10 @@ occasionally is there a real use for a `do' statement. File: gawk.info, Node: For Statement, Next: Switch Statement, Prev: Do Statement, Up: Statements -The `for' Statement -------------------- +6.4.4 The `for' Statement +------------------------- - The `for' statement makes it more convenient to count iterations of a +The `for' statement makes it more convenient to count iterations of a loop. The general form of the `for' statement looks like this: for (INITIALIZATION; CONDITION; INCREMENT) @@ -7302,8 +7380,8 @@ loop. The general form of the `for' statement looks like this: The INITIALIZATION, CONDITION, and INCREMENT parts are arbitrary `awk' expressions, and BODY stands for any `awk' statement. - The `for' statement starts by executing INITIALIZATION. Then, as -long as the CONDITION is true, it repeatedly executes BODY and then +The `for' statement starts by executing INITIALIZATION. Then, as long +as the CONDITION is true, it repeatedly executes BODY and then INCREMENT. Typically, INITIALIZATION sets a variable to either zero or one, INCREMENT adds one to it, and CONDITION compares it against the desired number of iterations. For example: @@ -7315,19 +7393,18 @@ desired number of iterations. For example: This prints the first three fields of each input record, with one field per line. - It isn't possible to set more than one variable in the -INITIALIZATION part without using a multiple assignment statement such -as `x = y = 0'. This makes sense only if all the initial values are -equal. (But it is possible to initialize additional variables by -writing their assignments as separate statements preceding the `for' -loop.) +It isn't possible to set more than one variable in the INITIALIZATION +part without using a multiple assignment statement such as `x = y = 0'. +This makes sense only if all the initial values are equal. (But it is +possible to initialize additional variables by writing their +assignments as separate statements preceding the `for' loop.) - The same is true of the INCREMENT part. Incrementing additional +The same is true of the INCREMENT part. Incrementing additional variables requires separate statements at the end of the loop. The C compound expression, using C's comma operator, is useful in this context but it is not supported in `awk'. - Most often, INCREMENT is an increment expression, as in the previous +Most often, INCREMENT is an increment expression, as in the previous example. But this is not required; it can be any expression whatsoever. For example, the following statement prints all the powers of two between 1 and 100: @@ -7335,14 +7412,14 @@ of two between 1 and 100: for (i = 1; i <= 100; i *= 2) print i - If there is nothing to be done, any of the three expressions in the +If there is nothing to be done, any of the three expressions in the parentheses following the `for' keyword may be omitted. Thus, `for (; x > 0;)' is equivalent to `while (x > 0)'. If the CONDITION is omitted, it is treated as true, effectively yielding an "infinite loop" (i.e., a loop that never terminates). - In most cases, a `for' loop is an abbreviation for a `while' loop, -as shown here: +In most cases, a `for' loop is an abbreviation for a `while' loop, as +shown here: INITIALIZATION while (CONDITION) { @@ -7355,14 +7432,14 @@ Statement::) is used inside the loop. Changing a `for' statement to a `while' statement in this way can change the effect of the `continue' statement inside the loop. - The `awk' language has a `for' statement in addition to a `while' +The `awk' language has a `for' statement in addition to a `while' statement because a `for' loop is often both less work to type and more natural to think of. Counting the number of iterations is very common in loops. It can be easier to think of this counting as part of looping rather than as something to do inside the loop. - There is an alternate version of the `for' loop, for iterating over -all the indices of an array: +There is an alternate version of the `for' loop, for iterating over all +the indices of an array: for (i in array) DO SOMETHING WITH array[i] @@ -7373,20 +7450,27 @@ all the indices of an array: File: gawk.info, Node: Switch Statement, Next: Break Statement, Prev: For Statement, Up: Statements -The `switch' Statement ----------------------- +6.4.5 The `switch' Statement +---------------------------- - *NOTE:* This node describes an experimental feature added in `gawk' +*NOTE:* This node describes an experimental feature added in `gawk' 3.1.3. It is _not_ enabled by default. To enable it, use the `--enable-switch' option to `configure' when `gawk' is being configured and built. *Note Additional Configuration Options::, for more information. - The `switch' statement allows the evaluation of an expression and -the execution of statements based on a `case' match. Case statements -are checked for a match in the order they are defined. If no suitable -`case' is found, the `default' section is executed, if supplied. The -general form of the `switch' statement looks like this: +The `switch' statement allows the evaluation of an expression and the +execution of statements based on a `case' match. Case statements are +checked for a match in the order they are defined. If no suitable +`case' is found, the `default' section is executed, if supplied. + +Each `case' contains a single constant, be it numeric, string, or +regexp. The `switch' expression is evaluated, and then each `case''s +constant is compared against the result in turn. The type of constant +determines the comparison: numeric or string do the usual comparisons. +A regexp constant does a regular expression match against the string +value of the original expression. The general form of the `switch' +statement looks like this: switch (EXPRESSION) { case VALUE OR REGULAR EXPRESSION: @@ -7395,30 +7479,30 @@ general form of the `switch' statement looks like this: DEFAULT-BODY } - The `switch' statement works as it does in C. Once a match to a given -case is made, case statement bodies are executed until a `break', -`continue', `next', `nextfile' or `exit' is encountered, or the end of -the `switch' statement itself. For example: +Control flow in the `switch' statement works as it does in C. Once a +match to a given case is made, case statement bodies are executed until +a `break', `continue', `next', `nextfile' or `exit' is encountered, or +the end of the `switch' statement itself. For example: switch (NR * 2 + 1) { case 3: case "11": print NR - 1 break - + case /2[[:digit:]]+/: print NR - + default: print NR + 1 - + case -1: print NR * -1 } - Note that if none of the statements specified above halt execution -of a matched `case' statement, execution falls through to the next -`case' until execution halts. In the above example, for any case value +Note that if none of the statements specified above halt execution of a +matched `case' statement, execution falls through to the next `case' +until execution halts. In the above example, for any case value starting with `2' followed by one or more digits, the `print' statement is executed and then falls through into the `default' section, executing its `print' statement. In turn, the -1 case will also be @@ -7427,10 +7511,10 @@ executed since the `default' does not halt execution. File: gawk.info, Node: Break Statement, Next: Continue Statement, Prev: Switch Statement, Up: Statements -The `break' Statement ---------------------- +6.4.6 The `break' Statement +--------------------------- - The `break' statement jumps out of the innermost `for', `while', or +The `break' statement jumps out of the innermost `for', `while', or `do' loop that encloses it. The following example finds the smallest divisor of any integer, and also identifies prime numbers: @@ -7446,14 +7530,14 @@ divisor of any integer, and also identifies prime numbers: printf "%d is prime\n", num } - When the remainder is zero in the first `if' statement, `awk' +When the remainder is zero in the first `if' statement, `awk' immediately "breaks out" of the containing `for' loop. This means that `awk' proceeds immediately to the statement following the loop and continues processing. (This is very different from the `exit' statement, which stops the entire `awk' program. *Note Exit Statement::.) - Th following program illustrates how the CONDITION of a `for' or +Th following program illustrates how the CONDITION of a `for' or `while' statement could be replaced with a `break' inside an `if': # find smallest divisor of num @@ -7471,7 +7555,7 @@ Statement::.) } } - The `break' statement has no meaning when used outside the body of a +The `break' statement has no meaning when used outside the body of a loop. However, although it was never documented, historical implementations of `awk' treated the `break' statement outside of a loop as if it were a `next' statement (*note Next Statement::). Recent @@ -7484,16 +7568,16 @@ inside the body of a loop. (d.c.) File: gawk.info, Node: Continue Statement, Next: Next Statement, Prev: Break Statement, Up: Statements -The `continue' Statement ------------------------- +6.4.7 The `continue' Statement +------------------------------ - As with `break', the `continue' statement is used only inside `for', +As with `break', the `continue' statement is used only inside `for', `while', and `do' loops. It skips over the rest of the loop body, causing the next cycle around the loop to begin immediately. Contrast this with `break', which jumps out of the loop altogether. - The `continue' statement in a `for' loop directs `awk' to skip the -rest of the body of the loop and resume execution with the +The `continue' statement in a `for' loop directs `awk' to skip the rest +of the body of the loop and resume execution with the increment-expression of the `for' statement. The following program illustrates this fact: @@ -7524,8 +7608,8 @@ the previous example with the following `while' loop: This program loops forever once `x' reaches 5. - The `continue' statement has no meaning when used outside the body of -a loop. Historical versions of `awk' treated a `continue' statement +The `continue' statement has no meaning when used outside the body of a +loop. Historical versions of `awk' treated a `continue' statement outside a loop the same way they treated a `break' statement outside a loop: as if it were a `next' statement (*note Next Statement::). Recent versions of Unix `awk' no longer work this way, and `gawk' @@ -7537,28 +7621,28 @@ specifies that `continue' should only be used inside the body of a loop. File: gawk.info, Node: Next Statement, Next: Nextfile Statement, Prev: Continue Statement, Up: Statements -The `next' Statement --------------------- +6.4.8 The `next' Statement +-------------------------- - The `next' statement forces `awk' to immediately stop processing the +The `next' statement forces `awk' to immediately stop processing the current record and go on to the next record. This means that no further rules are executed for the current record, and the rest of the current rule's action isn't executed. - Contrast this with the effect of the `getline' function (*note +Contrast this with the effect of the `getline' function (*note Getline::). That also causes `awk' to read the next record immediately, but it does not alter the flow of control in any way (i.e., the rest of the current action executes with a new input record). - At the highest level, `awk' program execution is a loop that reads -an input record and then tests each rule's pattern against it. If you +At the highest level, `awk' program execution is a loop that reads an +input record and then tests each rule's pattern against it. If you think of this loop as a `for' statement whose body contains the rules, then the `next' statement is analogous to a `continue' statement. It skips to the end of the body of this implicit loop and executes the increment (which reads another record). - For example, suppose an `awk' program works only on records with -four fields, and it shouldn't fail when given bad input. To avoid +For example, suppose an `awk' program works only on records with four +fields, and it shouldn't fail when given bad input. To avoid complicating the rest of the program, write a "weed out" rule near the beginning, in the following manner: @@ -7573,7 +7657,7 @@ see the bad record. The error message is redirected to the standard error output stream, as error messages should be. For more detail see *Note Special Files::. - According to the POSIX standard, the behavior is undefined if the +According to the POSIX standard, the behavior is undefined if the `next' statement is used in a `BEGIN' or `END' rule. `gawk' treats it as a syntax error. Although POSIX permits it, some other `awk' implementations don't allow the `next' statement inside function bodies @@ -7586,19 +7670,19 @@ any `END' rules is executed. *Note BEGIN/END::. File: gawk.info, Node: Nextfile Statement, Next: Exit Statement, Prev: Next Statement, Up: Statements -Using `gawk''s `nextfile' Statement ------------------------------------ +6.4.9 Using `gawk''s `nextfile' Statement +----------------------------------------- - `gawk' provides the `nextfile' statement, which is similar to the +`gawk' provides the `nextfile' statement, which is similar to the `next' statement. However, instead of abandoning processing of the current record, the `nextfile' statement instructs `gawk' to stop processing the current data file. - The `nextfile' statement is a `gawk' extension. In most other `awk' +The `nextfile' statement is a `gawk' extension. In most other `awk' implementations, or if `gawk' is in compatibility mode (*note Options::), `nextfile' is not special. - Upon execution of the `nextfile' statement, `FILENAME' is updated to +Upon execution of the `nextfile' statement, `FILENAME' is updated to the name of the next data file listed on the command line, `FNR' is reset to one, `ARGIND' is incremented, and processing starts over with the first rule in the program. (`ARGIND' hasn't been introduced yet. @@ -7606,30 +7690,30 @@ the first rule in the program. (`ARGIND' hasn't been introduced yet. end of the input to be reached, then the code in any `END' rules is executed. *Note BEGIN/END::. - The `nextfile' statement is useful when there are many data files to +The `nextfile' statement is useful when there are many data files to process but it isn't necessary to process every record in every file. Normally, in order to move on to the next data file, a program has to continue scanning the unwanted records. The `nextfile' statement accomplishes this much more efficiently. - While one might think that `close(FILENAME)' would accomplish the -same as `nextfile', this isn't true. `close' is reserved for closing -files, pipes, and coprocesses that are opened with redirections. It is -not related to the main processing that `awk' does with the files -listed in `ARGV'. +While one might think that `close(FILENAME)' would accomplish the same +as `nextfile', this isn't true. `close' is reserved for closing files, +pipes, and coprocesses that are opened with redirections. It is not +related to the main processing that `awk' does with the files listed in +`ARGV'. - If it's necessary to use an `awk' version that doesn't support +If it's necessary to use an `awk' version that doesn't support `nextfile', see *Note Nextfile Function::, for a user-defined function that simulates the `nextfile' statement. - The current version of the Bell Laboratories `awk' (*note Other +The current version of the Bell Laboratories `awk' (*note Other Versions::) also supports `nextfile'. However, it doesn't allow the `nextfile' statement inside function bodies (*note User-defined::). `gawk' does; a `nextfile' inside a function body reads the next record and starts processing it with the first rule in the program, just as any other `nextfile' statement. - *Caution:* Versions of `gawk' prior to 3.0 used two words (`next +*Caution:* Versions of `gawk' prior to 3.0 used two words (`next file') for the `nextfile' statement. In version 3.0, this was changed to one word, because the treatment of `file' was inconsistent. When it appeared after `next', `file' was a keyword; otherwise, it was a @@ -7639,40 +7723,40 @@ generates a syntax error. File: gawk.info, Node: Exit Statement, Prev: Nextfile Statement, Up: Statements -The `exit' Statement --------------------- +6.4.10 The `exit' Statement +--------------------------- - The `exit' statement causes `awk' to immediately stop executing the +The `exit' statement causes `awk' to immediately stop executing the current rule and to stop processing input; any remaining input is ignored. The `exit' statement is written as follows: exit [RETURN CODE] - When an `exit' statement is executed from a `BEGIN' rule, the -program stops processing everything immediately. No input records are -read. However, if an `END' rule is present, as part of executing the -`exit' statement, the `END' rule is executed (*note BEGIN/END::). If -`exit' is used as part of an `END' rule, it causes the program to stop +When an `exit' statement is executed from a `BEGIN' rule, the program +stops processing everything immediately. No input records are read. +However, if an `END' rule is present, as part of executing the `exit' +statement, the `END' rule is executed (*note BEGIN/END::). If `exit' +is used as part of an `END' rule, it causes the program to stop immediately. - An `exit' statement that is not part of a `BEGIN' or `END' rule -stops the execution of any further automatic rules for the current -record, skips reading any remaining input records, and executes the -`END' rule if there is one. +An `exit' statement that is not part of a `BEGIN' or `END' rule stops +the execution of any further automatic rules for the current record, +skips reading any remaining input records, and executes the `END' rule +if there is one. - In such a case, if you don't want the `END' rule to do its job, set -a variable to nonzero before the `exit' statement and check that -variable in the `END' rule. *Note Assert Function::, for an example -that does this. +In such a case, if you don't want the `END' rule to do its job, set a +variable to nonzero before the `exit' statement and check that variable +in the `END' rule. *Note Assert Function::, for an example that does +this. - If an argument is supplied to `exit', its value is used as the exit +If an argument is supplied to `exit', its value is used as the exit status code for the `awk' process. If no argument is supplied, `exit' returns status zero (success). In the case where an argument is supplied to a first `exit' statement, and then `exit' is called a second time from an `END' rule with no argument, `awk' uses the previously supplied exit value. (d.c.) - For example, suppose an error condition occurs that is difficult or +For example, suppose an error condition occurs that is difficult or impossible to handle. Conventionally, programs report this by exiting with a nonzero status. An `awk' program can do this using an `exit' statement with a nonzero argument, as shown in the following example: @@ -7689,20 +7773,19 @@ statement with a nonzero argument, as shown in the following example: File: gawk.info, Node: Built-in Variables, Prev: Statements, Up: Patterns and Actions -Built-in Variables -================== +6.5 Built-in Variables +====================== - Most `awk' variables are available to use for your own purposes; -they never change unless your program assigns values to them, and they -never affect anything unless your program examines them. However, a -few variables in `awk' have special built-in meanings. `awk' examines -some of these automatically, so that they enable you to tell `awk' how -to do certain things. Others are set automatically by `awk', so that -they carry information from the internal workings of `awk' to your -program. +Most `awk' variables are available to use for your own purposes; they +never change unless your program assigns values to them, and they never +affect anything unless your program examines them. However, a few +variables in `awk' have special built-in meanings. `awk' examines some +of these automatically, so that they enable you to tell `awk' how to do +certain things. Others are set automatically by `awk', so that they +carry information from the internal workings of `awk' to your program. - This minor node documents all the built-in variables of `gawk', most -of which are also documented in the chapters describing their areas of +This minor node documents all the built-in variables of `gawk', most of +which are also documented in the chapters describing their areas of activity. * Menu: @@ -7716,11 +7799,11 @@ activity. File: gawk.info, Node: User-modified, Next: Auto-set, Up: Built-in Variables -Built-in Variables That Control `awk' -------------------------------------- +6.5.1 Built-in Variables That Control `awk' +------------------------------------------- - The following is an alphabetical list of variables that you can -change to control how `awk' does certain things. The variables that are +The following is an alphabetical list of variables that you can change +to control how `awk' does certain things. The variables that are specific to `gawk' are marked with a pound sign (`#'). `BINMODE #' @@ -7863,17 +7946,17 @@ specific to `gawk' are marked with a pound sign (`#'). implementations, or if `gawk' is in compatibility mode (*note Options::), it is not special. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) In POSIX `awk', newline does not count as whitespace. +(1) In POSIX `awk', newline does not count as whitespace. File: gawk.info, Node: Auto-set, Next: ARGC and ARGV, Prev: User-modified, Up: Built-in Variables -Built-in Variables That Convey Information ------------------------------------------- +6.5.2 Built-in Variables That Convey Information +------------------------------------------------ - The following is an alphabetical list of variables that `awk' sets +The following is an alphabetical list of variables that `awk' sets automatically on certain occasions in order to provide information to your program. The variables that are specific to `gawk' are marked with a pound sign (`#'). @@ -7944,6 +8027,13 @@ with a pound sign (`#'). during a read for `getline', or during a `close' operation, then `ERRNO' contains a string describing the error. + `ERRNO' works similarly to the C variable `errno'. In particular + `gawk' _never_ clears it (sets it to zero or `""'). Thus, you + should only expect its value to be meaningful when an I/O + operation returns a failure value, such as `getline' returning -1. + You are, of course, free to clear it yourself before doing an I/O + operation. + This variable is a `gawk' extension. In other `awk' implementations, or if `gawk' is in compatibility mode (*note Options::), it is not special. @@ -8010,6 +8100,10 @@ with a pound sign (`#'). `PROCINFO["uid"]' The value of the `getuid' system call. + `PROCINFO["version"]' + The version of `gawk'. This is available from version 3.1.4 + and later. + On some systems, there may be elements in the array, `"group1"' through `"groupN"' for some N. N is the number of supplementary groups that the process has. Use the `in' operator to test for @@ -8043,11 +8137,11 @@ with a pound sign (`#'). Advanced Notes: Changing `NR' and `FNR' --------------------------------------- - `awk' increments `NR' and `FNR' each time it reads a record, instead -of setting them to the absolute value of the number of records read. -This means that a program can change these variables and their new -values are incremented for each record. (d.c.) This is demonstrated -in the following example: +`awk' increments `NR' and `FNR' each time it reads a record, instead of +setting them to the absolute value of the number of records read. This +means that a program can change these variables and their new values +are incremented for each record. (d.c.) This is demonstrated in the +following example: $ echo '1 > 2 @@ -8063,19 +8157,19 @@ Before `FNR' was added to the `awk' language (*note V7/SVR3.1::), many `awk' programs used this feature to track the number of records in a file by resetting `NR' to zero when `FILENAME' changed. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Some early implementations of Unix `awk' initialized `FILENAME' -to `"-"', even if there were data files to be processed. This behavior -was incorrect and should not be relied upon in your programs. +(1) Some early implementations of Unix `awk' initialized `FILENAME' to +`"-"', even if there were data files to be processed. This behavior was +incorrect and should not be relied upon in your programs. File: gawk.info, Node: ARGC and ARGV, Prev: Auto-set, Up: Built-in Variables -Using `ARGC' and `ARGV' ------------------------ +6.5.4 Using `ARGC' and `ARGV' +----------------------------- - *Note Auto-set::, presented the following program describing the +*Note Auto-set::, presented the following program describing the information contained in `ARGC' and `ARGV': $ awk 'BEGIN { @@ -8108,25 +8202,25 @@ treated as arguments and do show up in the `ARGV' array: -| ARGV[2] = /dev/null -| A=1, B=2 - A program can alter `ARGC' and the elements of `ARGV'. Each time -`awk' reaches the end of an input file, it uses the next element of -`ARGV' as the name of the next input file. By storing a different -string there, a program can change which files are read. Use `"-"' to -represent the standard input. Storing additional elements and -incrementing `ARGC' causes additional files to be read. - - If the value of `ARGC' is decreased, that eliminates input files -from the end of the list. By recording the old value of `ARGC' -elsewhere, a program can treat the eliminated arguments as something -other than file names. - - To eliminate a file from the middle of the list, store the null -string (`""') into `ARGV' in place of the file's name. As a special -feature, `awk' ignores file names that have been replaced with the null -string. Another option is to use the `delete' statement to remove -elements from `ARGV' (*note Delete::). - - All of these actions are typically done in the `BEGIN' rule, before +A program can alter `ARGC' and the elements of `ARGV'. Each time `awk' +reaches the end of an input file, it uses the next element of `ARGV' as +the name of the next input file. By storing a different string there, +a program can change which files are read. Use `"-"' to represent the +standard input. Storing additional elements and incrementing `ARGC' +causes additional files to be read. + +If the value of `ARGC' is decreased, that eliminates input files from +the end of the list. By recording the old value of `ARGC' elsewhere, a +program can treat the eliminated arguments as something other than file +names. + +To eliminate a file from the middle of the list, store the null string +(`""') into `ARGV' in place of the file's name. As a special feature, +`awk' ignores file names that have been replaced with the null string. +Another option is to use the `delete' statement to remove elements from +`ARGV' (*note Delete::). + +All of these actions are typically done in the `BEGIN' rule, before actual processing of the input begins. *Note Split Program::, and see *Note Tee Program::, for examples of each way of removing elements from `ARGV'. The following fragment processes `ARGV' in order to examine, @@ -8148,17 +8242,17 @@ and then remove, command-line options: } } - To actually get the options into the `awk' program, end the `awk' +To actually get the options into the `awk' program, end the `awk' options with `--' and then supply the `awk' program's options, in the following manner: awk -f myprog -- -v -d file1 file2 ... - This is not necessary in `gawk'. Unless `--posix' has been -specified, `gawk' silently puts any unrecognized options into `ARGV' -for the `awk' program to deal with. As soon as it sees an unknown -option, `gawk' stops looking for other options that it might otherwise -recognize. The previous example with `gawk' would be: +This is not necessary in `gawk'. Unless `--posix' has been specified, +`gawk' silently puts any unrecognized options into `ARGV' for the `awk' +program to deal with. As soon as it sees an unknown option, `gawk' +stops looking for other options that it might otherwise recognize. The +previous example with `gawk' would be: gawk -f myprog -d -v file1 file2 ... @@ -8168,21 +8262,21 @@ are passed on to the `awk' program. File: gawk.info, Node: Arrays, Next: Functions, Prev: Patterns and Actions, Up: Top -Arrays in `awk' -*************** +7 Arrays in `awk' +***************** - An "array" is a table of values called "elements". The elements of -an array are distinguished by their indices. "Indices" may be either +An "array" is a table of values called "elements". The elements of an +array are distinguished by their indices. "Indices" may be either numbers or strings. - This major node describes how arrays work in `awk', how to use array +This major node describes how arrays work in `awk', how to use array elements, how to scan through every element in an array, and how to remove array elements. It also describes how `awk' simulates multidimensional arrays, as well as some of the less obvious points about array usage. The major node finishes with a discussion of `gawk''s facility for sorting an array based on its indices. - `awk' maintains a single set of names that may be used for naming +`awk' maintains a single set of names that may be used for naming variables, arrays, and functions (*note User-defined::). Thus, you cannot have a variable and an array with the same name in the same `awk' program. @@ -8209,23 +8303,22 @@ cannot have a variable and an array with the same name in the same File: gawk.info, Node: Array Intro, Next: Reference to Elements, Up: Arrays -Introduction to Arrays -====================== +7.1 Introduction to Arrays +========================== - The `awk' language provides one-dimensional arrays for storing -groups of related strings or numbers. Every `awk' array must have a -name. Array names have the same syntax as variable names; any valid -variable name would also be a valid array name. But one name cannot be -used in both ways (as an array and as a variable) in the same `awk' -program. +The `awk' language provides one-dimensional arrays for storing groups +of related strings or numbers. Every `awk' array must have a name. +Array names have the same syntax as variable names; any valid variable +name would also be a valid array name. But one name cannot be used in +both ways (as an array and as a variable) in the same `awk' program. - Arrays in `awk' superficially resemble arrays in other programming +Arrays in `awk' superficially resemble arrays in other programming languages, but there are fundamental differences. In `awk', it isn't necessary to specify the size of an array before starting to use it. Additionally, any number or string in `awk', not just consecutive integers, may be used as an array index. - In most other languages, arrays must be "declared" before use, +In most other languages, arrays must be "declared" before use, including a specification of how many elements or components they contain. In such languages, the declaration causes a contiguous block of memory to be allocated for that many elements. Usually, an index in @@ -8239,7 +8332,7 @@ languages allow arbitrary starting and ending indices--e.g., `15 .. 27'--but the size of the array is still fixed when the array is declared.) - A contiguous array of four elements might look like the following +A contiguous array of four elements might look like the following example, conceptually, if the element values are 8, `"foo"', `""', and 30: @@ -8252,8 +8345,8 @@ Only the values are stored; the indices are implicit from the order of the values. Here, 8 is the value at index zero, because 8 appears in the position with zero elements before it. - Arrays in `awk' are different--they are "associative". This means -that each array is a collection of pairs: an index and its corresponding +Arrays in `awk' are different--they are "associative". This means that +each array is a collection of pairs: an index and its corresponding array element value: Element 3 Value 30 @@ -8263,8 +8356,8 @@ array element value: The pairs are shown in jumbled order because their order is irrelevant. - One advantage of associative arrays is that new pairs can be added -at any time. For example, suppose a tenth element is added to the array +One advantage of associative arrays is that new pairs can be added at +any time. For example, suppose a tenth element is added to the array whose value is `"number ten"'. The result is: Element 10 Value "number ten" @@ -8277,7 +8370,7 @@ Now the array is "sparse", which just means some indices are missing. It has elements 0-3 and 10, but doesn't have elements 4, 5, 6, 7, 8, or 9. - Another consequence of associative arrays is that the indices don't +Another consequence of associative arrays is that the indices don't have to be positive integers. Any number, or even a string, can be an index. For example, the following is an array that translates words from English to French: @@ -8294,22 +8387,22 @@ strings; this is discussed in more detail in *Note Numeric Array Subscripts::. Here, the number `1' isn't double-quoted, since `awk' automatically converts it to a string. - The value of `IGNORECASE' has no effect upon array subscripting. -The identical string value used to store an array element must be used -to retrieve it. When `awk' creates an array (e.g., with the `split' +The value of `IGNORECASE' has no effect upon array subscripting. The +identical string value used to store an array element must be used to +retrieve it. When `awk' creates an array (e.g., with the `split' built-in function), that array's indices are consecutive integers starting at one. (*Note String Functions::.) - `awk''s arrays are efficient--the time to access an element is +`awk''s arrays are efficient--the time to access an element is independent of the number of elements in the array. File: gawk.info, Node: Reference to Elements, Next: Assigning Elements, Prev: Array Intro, Up: Arrays -Referring to an Array Element -============================= +7.2 Referring to an Array Element +================================= - The principal way to use an array is to refer to one of its elements. +The principal way to use an array is to refer to one of its elements. An array reference is an expression as follows: ARRAY[INDEX] @@ -8317,19 +8410,19 @@ An array reference is an expression as follows: Here, ARRAY is the name of an array. The expression INDEX is the index of the desired element of the array. - The value of the array reference is the current value of that array +The value of the array reference is the current value of that array element. For example, `foo[4.3]' is an expression for the element of array `foo' at index `4.3'. - A reference to an array element that has no recorded value yields a +A reference to an array element that has no recorded value yields a value of `""', the null string. This includes elements that have not been assigned any value as well as elements that have been deleted (*note Delete::). Such a reference automatically creates that array element, with the null string as its value. (In some cases, this is unfortunate, because it might waste memory inside `awk'.) - To determine whether an element exists in an array at a certain -index, use the following expression: +To determine whether an element exists in an array at a certain index, +use the following expression: INDEX in ARRAY @@ -8342,7 +8435,7 @@ whether the array `frequencies' contains the index `2': if (2 in frequencies) print "Subscript 2 is present." - Note that this is _not_ a test of whether the array `frequencies' +Note that this is _not_ a test of whether the array `frequencies' contains an element whose _value_ is two. There is no way to do that except to scan all the elements. Also, this _does not_ create `frequencies[2]', while the following (incorrect) alternative does: @@ -8353,10 +8446,10 @@ except to scan all the elements. Also, this _does not_ create File: gawk.info, Node: Assigning Elements, Next: Array Example, Prev: Reference to Elements, Up: Arrays -Assigning Array Elements -======================== +7.3 Assigning Array Elements +============================ - Array elements can be assigned values just like `awk' variables: +Array elements can be assigned values just like `awk' variables: ARRAY[SUBSCRIPT] = VALUE @@ -8367,31 +8460,31 @@ VALUE is the value to assign to that element of the array. File: gawk.info, Node: Array Example, Next: Scanning an Array, Prev: Assigning Elements, Up: Arrays -Basic Array Example -=================== +7.4 Basic Array Example +======================= - The following program takes a list of lines, each beginning with a -line number, and prints them out in order of line number. The line -numbers are not in order when they are first read--instead they are -scrambled. This program sorts the lines by making an array using the -line numbers as subscripts. The program then prints out the lines in -sorted order of their numbers. It is a very simple program and gets -confused upon encountering repeated numbers, gaps, or lines that don't -begin with a number: +The following program takes a list of lines, each beginning with a line +number, and prints them out in order of line number. The line numbers +are not in order when they are first read--instead they are scrambled. +This program sorts the lines by making an array using the line numbers +as subscripts. The program then prints out the lines in sorted order +of their numbers. It is a very simple program and gets confused upon +encountering repeated numbers, gaps, or lines that don't begin with a +number: { if ($1 > max) max = $1 arr[$1] = $0 } - + END { for (x = 1; x <= max; x++) print arr[x] } - The first rule keeps track of the largest line number seen so far; -it also stores each line into the array `arr', at an index that is the +The first rule keeps track of the largest line number seen so far; it +also stores each line into the array `arr', at an index that is the line's number. The second rule runs after all the input has been read, to print out all the lines. When this program is run with the following input: @@ -8410,7 +8503,7 @@ Its output is: 4 . . . And four on the floor 5 I am the Five man - If a line number is repeated, the last line with a given number +If a line number is repeated, the last line with a given number overrides the others. Gaps in the line numbers can be handled with an easy improvement to the program's `END' rule, as follows: @@ -8423,10 +8516,10 @@ easy improvement to the program's `END' rule, as follows: File: gawk.info, Node: Scanning an Array, Next: Delete, Prev: Array Example, Up: Arrays -Scanning All Elements of an Array -================================= +7.5 Scanning All Elements of an Array +===================================== - In programs that use arrays, it is often necessary to use a loop that +In programs that use arrays, it is often necessary to use a loop that executes once for each element of an array. In other languages, where arrays are contiguous and indices are limited to positive integers, this is easy: all the valid indices can be found by counting from the @@ -8440,21 +8533,21 @@ has a special kind of `for' statement for scanning an array: This loop executes BODY once for each index in ARRAY that the program has previously used, with the variable VAR set to that index. - The following program uses this form of the `for' statement. The -first rule scans the input records and notes which words appear (at -least once) in the input, by storing a one into the array `used' with -the word as index. The second rule scans the elements of `used' to -find all the distinct words that appear in the input. It prints each -word that is more than 10 characters long and also prints the number of -such words. *Note String Functions::, for more information on the -built-in function `length'. +The following program uses this form of the `for' statement. The first +rule scans the input records and notes which words appear (at least +once) in the input, by storing a one into the array `used' with the +word as index. The second rule scans the elements of `used' to find +all the distinct words that appear in the input. It prints each word +that is more than 10 characters long and also prints the number of such +words. *Note String Functions::, for more information on the built-in +function `length'. # Record a 1 for each word that is used at least once { for (i = 1; i <= NF; i++) used[$i] = 1 } - + # Find number of distinct words more than 10 characters long END { for (x in used) @@ -8467,29 +8560,28 @@ built-in function `length'. *Note Word Sorting::, for a more detailed example of this type. - The order in which elements of the array are accessed by this -statement is determined by the internal arrangement of the array -elements within `awk' and cannot be controlled or changed. This can -lead to problems if new elements are added to ARRAY by statements in -the loop body; it is not predictable whether the `for' loop will reach -them. Similarly, changing VAR inside the loop may produce strange -results. It is best to avoid such things. +The order in which elements of the array are accessed by this statement +is determined by the internal arrangement of the array elements within +`awk' and cannot be controlled or changed. This can lead to problems +if new elements are added to ARRAY by statements in the loop body; it +is not predictable whether the `for' loop will reach them. Similarly, +changing VAR inside the loop may produce strange results. It is best +to avoid such things. File: gawk.info, Node: Delete, Next: Numeric Array Subscripts, Prev: Scanning an Array, Up: Arrays -The `delete' Statement -====================== +7.6 The `delete' Statement +========================== - To remove an individual element of an array, use the `delete' -statement: +To remove an individual element of an array, use the `delete' statement: delete ARRAY[INDEX] - Once an array element has been deleted, any value the element once -had is no longer available. It is as if the element had never been -referred to or had been given a value. The following is an example of -deleting elements in an array: +Once an array element has been deleted, any value the element once had +is no longer available. It is as if the element had never been referred +to or had been given a value. The following is an example of deleting +elements in an array: for (i in frequencies) delete frequencies[i] @@ -8503,62 +8595,62 @@ the presence of that element returns zero (i.e., false): if (4 in foo) print "This will never be printed" - It is important to note that deleting an element is _not_ the same -as assigning it a null value (the empty string, `""'). For example: +It is important to note that deleting an element is _not_ the same as +assigning it a null value (the empty string, `""'). For example: foo[4] = "" if (4 in foo) print "This is printed, even though foo[4] is empty" - It is not an error to delete an element that does not exist. If +It is not an error to delete an element that does not exist. If `--lint' is provided on the command line (*note Options::), `gawk' issues a warning message when an element that is not in the array is deleted. - All the elements of an array may be deleted with a single statement -by leaving off the subscript in the `delete' statement, as follows: +All the elements of an array may be deleted with a single statement by +leaving off the subscript in the `delete' statement, as follows: delete ARRAY - This ability is a `gawk' extension; it is not available in +This ability is a `gawk' extension; it is not available in compatibility mode (*note Options::). - Using this version of the `delete' statement is about three times -more efficient than the equivalent loop that deletes each element one -at a time. +Using this version of the `delete' statement is about three times more +efficient than the equivalent loop that deletes each element one at a +time. - The following statement provides a portable but nonobvious way to -clear out an array:(1) +The following statement provides a portable but nonobvious way to clear +out an array:(1) split("", array) - The `split' function (*note String Functions::) clears out the -target array first. This call asks it to split apart the null string. -Because there is no data to split out, the function simply clears the -array and then returns. +The `split' function (*note String Functions::) clears out the target +array first. This call asks it to split apart the null string. Because +there is no data to split out, the function simply clears the array and +then returns. - *Caution:* Deleting an array does not change its type; you cannot +*Caution:* Deleting an array does not change its type; you cannot delete an array and then use the array's name as a scalar (i.e., a regular variable). For example, the following does not work: a[1] = 3; delete a; a = 3 - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Thanks to Michael Brennan for pointing this out. +(1) Thanks to Michael Brennan for pointing this out. File: gawk.info, Node: Numeric Array Subscripts, Next: Uninitialized Subscripts, Prev: Delete, Up: Arrays -Using Numbers to Subscript Arrays -================================= +7.7 Using Numbers to Subscript Arrays +===================================== - An important aspect about arrays to remember is that _array -subscripts are always strings_. When a numeric value is used as a -subscript, it is converted to a string value before being used for -subscripting (*note Conversion::). This means that the value of the -built-in variable `CONVFMT' can affect how your program accesses -elements of an array. For example: +An important aspect about arrays to remember is that _array subscripts +are always strings_. When a numeric value is used as a subscript, it +is converted to a string value before being used for subscripting +(*note Conversion::). This means that the value of the built-in +variable `CONVFMT' can affect how your program accesses elements of an +array. For example: xyz = 12.153 data[xyz] = 1 @@ -8578,7 +8670,7 @@ assigned the value one. The program then changes the value of two significant digits. This test fails, since `"12.15"' is a different string from `"12.153"'. - According to the rules for conversions (*note Conversion::), integer +According to the rules for conversions (*note Conversion::), integer values are always converted to strings as integers, no matter what the value of `CONVFMT' may happen to be. So the usual case of the following works: @@ -8586,25 +8678,25 @@ following works: for (i = 1; i <= maxsub; i++) do something with array[i] - The "integer values always convert to strings as integers" rule has -an additional consequence for array indexing. Octal and hexadecimal +The "integer values always convert to strings as integers" rule has an +additional consequence for array indexing. Octal and hexadecimal constants (*note Nondecimal-numbers::) are converted internally into numbers, and their original form is forgotten. This means, for example, that `array[17]', `array[021]', and `array[0x11]' all refer to the same element! - As with many things in `awk', the majority of the time things work -as one would expect them to. But it is useful to have a precise -knowledge of the actual rules which sometimes can have a subtle effect -on your programs. +As with many things in `awk', the majority of the time things work as +one would expect them to. But it is useful to have a precise knowledge +of the actual rules which sometimes can have a subtle effect on your +programs. File: gawk.info, Node: Uninitialized Subscripts, Next: Multi-dimensional, Prev: Numeric Array Subscripts, Up: Arrays -Using Uninitialized Variables as Subscripts -=========================================== +7.8 Using Uninitialized Variables as Subscripts +=============================================== - Suppose it's necessary to write a program to print the input data in +Suppose it's necessary to write a program to print the input data in reverse order. A reasonable attempt to do so (with some test data) might look like this: @@ -8618,14 +8710,14 @@ might look like this: -| line 3 -| line 2 - Unfortunately, the very first line of input data did not come out in -the output! +Unfortunately, the very first line of input data did not come out in the +output! - At first glance, this program should have worked. The variable -`lines' is uninitialized, and uninitialized variables have the numeric -value zero. So, `awk' should have printed the value of `l[0]'. +At first glance, this program should have worked. The variable `lines' +is uninitialized, and uninitialized variables have the numeric value +zero. So, `awk' should have printed the value of `l[0]'. - The issue here is that subscripts for `awk' arrays are _always_ +The issue here is that subscripts for `awk' arrays are _always_ strings. Uninitialized variables, when used as strings, have the value `""', not zero. Thus, `line 1' ends up stored in `l[""]'. The following version of the program works correctly: @@ -8636,62 +8728,61 @@ following version of the program works correctly: print l[i] } - Here, the `++' forces `lines' to be numeric, thus making the "old +Here, the `++' forces `lines' to be numeric, thus making the "old value" numeric zero. This is then converted to `"0"' as the array subscript. - Even though it is somewhat unusual, the null string (`""') is a -valid array subscript. (d.c.) `gawk' warns about the use of the null -string as a subscript if `--lint' is provided on the command line -(*note Options::). +Even though it is somewhat unusual, the null string (`""') is a valid +array subscript. (d.c.) `gawk' warns about the use of the null string +as a subscript if `--lint' is provided on the command line (*note +Options::). File: gawk.info, Node: Multi-dimensional, Next: Multi-scanning, Prev: Uninitialized Subscripts, Up: Arrays -Multidimensional Arrays -======================= +7.9 Multidimensional Arrays +=========================== - A multidimensional array is an array in which an element is -identified by a sequence of indices instead of a single index. For -example, a two-dimensional array requires two indices. The usual way -(in most languages, including `awk') to refer to an element of a -two-dimensional array named `grid' is with `grid[X,Y]'. +A multidimensional array is an array in which an element is identified +by a sequence of indices instead of a single index. For example, a +two-dimensional array requires two indices. The usual way (in most +languages, including `awk') to refer to an element of a two-dimensional +array named `grid' is with `grid[X,Y]'. - Multidimensional arrays are supported in `awk' through concatenation -of indices into one string. `awk' converts the indices into strings +Multidimensional arrays are supported in `awk' through concatenation of +indices into one string. `awk' converts the indices into strings (*note Conversion::) and concatenates them together, with a separator between them. This creates a single string that describes the values of the separate indices. The combined string is used as a single index into an ordinary, one-dimensional array. The separator used is the value of the built-in variable `SUBSEP'. - For example, suppose we evaluate the expression `foo[5,12] = "value"' +For example, suppose we evaluate the expression `foo[5,12] = "value"' when the value of `SUBSEP' is `"@"'. The numbers 5 and 12 are converted to strings and concatenated with an `@' between them, yielding `"5@12"'; thus, the array element `foo["5@12"]' is set to `"value"'. - Once the element's value is stored, `awk' has no record of whether -it was stored with a single index or a sequence of indices. The two +Once the element's value is stored, `awk' has no record of whether it +was stored with a single index or a sequence of indices. The two expressions `foo[5,12]' and `foo[5 SUBSEP 12]' are always equivalent. - The default value of `SUBSEP' is the string `"\034"', which contains -a nonprinting character that is unlikely to appear in an `awk' program -or in most input data. The usefulness of choosing an unlikely -character comes from the fact that index values that contain a string -matching `SUBSEP' can lead to combined strings that are ambiguous. -Suppose that `SUBSEP' is `"@"'; then `foo["a@b", "c"]' and -`foo["a", "b@c"]' are indistinguishable because both are actually -stored as `foo["a@b@c"]'. +The default value of `SUBSEP' is the string `"\034"', which contains a +nonprinting character that is unlikely to appear in an `awk' program or +in most input data. The usefulness of choosing an unlikely character +comes from the fact that index values that contain a string matching +`SUBSEP' can lead to combined strings that are ambiguous. Suppose that +`SUBSEP' is `"@"'; then `foo["a@b", "c"]' and `foo["a", "b@c"]' are +indistinguishable because both are actually stored as `foo["a@b@c"]'. - To test whether a particular index sequence exists in a +To test whether a particular index sequence exists in a multidimensional array, use the same operator (`in') that is used for single dimensional arrays. Write the whole sequence of indices in parentheses, separated by commas, as the left operand: (SUBSCRIPT1, SUBSCRIPT2, ...) in ARRAY - The following example treats its input as a two-dimensional array of +The following example treats its input as a two-dimensional array of fields; it rotates this array 90 degrees clockwise and prints the result. It assumes that all lines have the same number of elements: @@ -8702,7 +8793,7 @@ result. It assumes that all lines have the same number of elements: for (x = 1; x <= NF; x++) vector[x, NR] = $x } - + END { for (x = 1; x <= max_nf; x++) { for (y = max_nr; y >= 1; --y) @@ -8730,15 +8821,15 @@ the program produces the following output: File: gawk.info, Node: Multi-scanning, Next: Array Sorting, Prev: Multi-dimensional, Up: Arrays -Scanning Multidimensional Arrays -================================ +7.10 Scanning Multidimensional Arrays +===================================== - There is no special `for' statement for scanning a -"multidimensional" array. There cannot be one, because, in truth, there -are no multidimensional arrays or elements--there is only a -multidimensional _way of accessing_ an array. +There is no special `for' statement for scanning a "multidimensional" +array. There cannot be one, because, in truth, there are no +multidimensional arrays or elements--there is only a multidimensional +_way of accessing_ an array. - However, if your program has an array that is always accessed as +However, if your program has an array that is always accessed as multidimensional, you can get the effect of scanning it by combining the scanning `for' statement (*note Scanning an Array::) with the built-in `split' function (*note String Functions::). It works in the @@ -8754,7 +8845,7 @@ in the array, and splits it into the individual indices by breaking it apart where the value of `SUBSEP' appears. The individual indices then become the elements of the array `separate'. - Thus, if a value is previously stored in `array[1, "foo"]'; then an +Thus, if a value is previously stored in `array[1, "foo"]'; then an element with index `"1\034foo"' exists in `array'. (Recall that the default value of `SUBSEP' is the character with code 034.) Sooner or later, the `for' statement finds that index and does an iteration with @@ -8770,12 +8861,12 @@ recovered. File: gawk.info, Node: Array Sorting, Prev: Multi-scanning, Up: Arrays -Sorting Array Values and Indices with `gawk' -============================================ +7.11 Sorting Array Values and Indices with `gawk' +================================================= - The order in which an array is scanned with a `for (i in array)' -loop is essentially arbitrary. In most `awk' implementations, sorting -an array requires writing a `sort' function. While this can be +The order in which an array is scanned with a `for (i in array)' loop +is essentially arbitrary. In most `awk' implementations, sorting an +array requires writing a `sort' function. While this can be educational for exploring different sorting algorithms, usually that's not the point of the program. `gawk' provides the built-in `asort' and `asorti' functions (*note String Functions::) for sorting arrays. For @@ -8786,13 +8877,13 @@ example: for (i = 1; i <= n; i++) DO SOMETHING WITH data[i] - After the call to `asort', the array `data' is indexed from 1 to -some number N, the total number of elements in `data'. (This count is +After the call to `asort', the array `data' is indexed from 1 to some +number N, the total number of elements in `data'. (This count is `asort''s return value.) `data[1]' <= `data[2]' <= `data[3]', and so on. The comparison of array elements is done using `gawk''s usual comparison rules (*note Typing and Comparison::). - An important side effect of calling `asort' is that _the array's +An important side effect of calling `asort' is that _the array's original indices are irrevocably lost_. As this isn't always desirable, `asort' accepts a second argument: @@ -8801,28 +8892,30 @@ desirable, `asort' accepts a second argument: for (i = 1; i <= n; i++) DO SOMETHING WITH dest[i] - In this case, `gawk' copies the `source' array into the `dest' array +In this case, `gawk' copies the `source' array into the `dest' array and then sorts `dest', destroying its indices. However, the `source' array is not affected. - Often, what's needed is to sort on the values of the _indices_ -instead of the values of the elements. To do that, starting with -`gawk' 3.1.2, use the `asorti' function. The interface is identical to -that of `asort', except that the index values are used for sorting, and -become the values of the result array: +Often, what's needed is to sort on the values of the _indices_ instead +of the values of the elements. To do that, starting with `gawk' 3.1.2, +use the `asorti' function. The interface is identical to that of +`asort', except that the index values are used for sorting, and become +the values of the result array: { source[$0] = some_func($0) } - + END { n = asorti(source, dest) - for (i = 1; i <= n; i++) - DO SOMETHING WITH dest[i] + for (i = 1; i <= n; i++) { + DO SOMETHING WITH dest[i] Work with sorted indices directly + ... + DO SOMETHING WITH source[dest[i]] Access original array via sorted indices + } } - If your version of `gawk' is 3.1.0 or 3.1.1, you don't have -`asorti'. Instead, use a helper array to hold the sorted index values, -and then access the original array's elements. It works in the -following way: +If your version of `gawk' is 3.1.0 or 3.1.1, you don't have `asorti'. +Instead, use a helper array to hold the sorted index values, and then +access the original array's elements. It works in the following way: POPULATE THE ARRAY data # copy indices @@ -8832,22 +8925,24 @@ following way: j++ } n = asort(ind) # index values are now sorted - for (i = 1; i <= n; i++) - DO SOMETHING WITH data[ind[i]] + for (i = 1; i <= n; i++) { + DO SOMETHING WITH ind[i] Work with sorted indices directly + ... + DO SOMETHING WITH data[ind[i]] Access original array via sorted indices + } - Sorting the array by replacing the indices provides maximal -flexibility. To traverse the elements in decreasing order, use a loop -that goes from N down to 1, either over the elements or over the -indices. +Sorting the array by replacing the indices provides maximal flexibility. +To traverse the elements in decreasing order, use a loop that goes from +N down to 1, either over the elements or over the indices. - Copying array indices and elements isn't expensive in terms of -memory. Internally, `gawk' maintains "reference counts" to data. For -example, when `asort' copies the first array to the second one, there -is only one copy of the original array elements' data, even though both -arrays use the values. Similarly, when copying the indices from `data' -to `ind', there is only one copy of the actual index strings. +Copying array indices and elements isn't expensive in terms of memory. +Internally, `gawk' maintains "reference counts" to data. For example, +when `asort' copies the first array to the second one, there is only +one copy of the original array elements' data, even though both arrays +use the values. Similarly, when copying the indices from `data' to +`ind', there is only one copy of the actual index strings. - We said previously that comparisons are done using `gawk''s "usual +We said previously that comparisons are done using `gawk''s "usual comparison rules." Because `IGNORECASE' affects string comparisons, the value of `IGNORECASE' also affects sorting for both `asort' and `asorti'. Caveat Emptor. @@ -8855,15 +8950,15 @@ the value of `IGNORECASE' also affects sorting for both `asort' and File: gawk.info, Node: Functions, Next: Internationalization, Prev: Arrays, Up: Top -Functions -********* +8 Functions +*********** - This major node describes `awk''s built-in functions, which fall -into three categories: numeric, string, and I/O. `gawk' provides -additional groups of functions to work with values that represent time, -do bit manipulation, and internationalize and localize programs. +This major node describes `awk''s built-in functions, which fall into +three categories: numeric, string, and I/O. `gawk' provides additional +groups of functions to work with values that represent time, do bit +manipulation, and internationalize and localize programs. - Besides the built-in functions, `awk' has provisions for writing new +Besides the built-in functions, `awk' has provisions for writing new functions that the rest of a program can use. The second half of this major node describes these "user-defined" functions. @@ -8875,10 +8970,10 @@ major node describes these "user-defined" functions. File: gawk.info, Node: Built-in, Next: User-defined, Up: Functions -Built-in Functions -================== +8.1 Built-in Functions +====================== - "Built-in" functions are always available for your `awk' program to +"Built-in" functions are always available for your `awk' program to call. This minor node defines all the built-in functions in `awk'; some of these are mentioned in other sections but are summarized here for your convenience. @@ -8898,29 +8993,29 @@ for your convenience. File: gawk.info, Node: Calling Built-in, Next: Numeric Functions, Up: Built-in -Calling Built-in Functions --------------------------- +8.1.1 Calling Built-in Functions +-------------------------------- - To call one of `awk''s built-in functions, write the name of the +To call one of `awk''s built-in functions, write the name of the function followed by arguments in parentheses. For example, `atan2(y + z, 1)' is a call to the function `atan2' and has two arguments. - Whitespace is ignored between the built-in function name and the -open parenthesis, and it is good practice to avoid using whitespace -there. User-defined functions do not permit whitespace in this way, and -it is easier to avoid mistakes by following a simple convention that -always works--no whitespace after a function name. +Whitespace is ignored between the built-in function name and the open +parenthesis, and it is good practice to avoid using whitespace there. +User-defined functions do not permit whitespace in this way, and it is +easier to avoid mistakes by following a simple convention that always +works--no whitespace after a function name. - Each built-in function accepts a certain number of arguments. In -some cases, arguments can be omitted. The defaults for omitted -arguments vary from function to function and are described under the -individual functions. In some `awk' implementations, extra arguments -given to built-in functions are ignored. However, in `gawk', it is a -fatal error to give extra arguments to a built-in function. +Each built-in function accepts a certain number of arguments. In some +cases, arguments can be omitted. The defaults for omitted arguments +vary from function to function and are described under the individual +functions. In some `awk' implementations, extra arguments given to +built-in functions are ignored. However, in `gawk', it is a fatal +error to give extra arguments to a built-in function. - When a function is called, expressions that create the function's -actual parameters are evaluated completely before the call is performed. -For example, in the following code fragment: +When a function is called, expressions that create the function's actual +parameters are evaluated completely before the call is performed. For +example, in the following code fragment: i = 4 j = sqrt(i++) @@ -8934,18 +9029,18 @@ are evaluated from left to right or from right to left. For example: i = 5 j = atan2(i++, i *= 2) - If the order of evaluation is left to right, then `i' first becomes -6, and then 12, and `atan2' is called with the two arguments 6 and 12. +If the order of evaluation is left to right, then `i' first becomes 6, +and then 12, and `atan2' is called with the two arguments 6 and 12. But if the order of evaluation is right to left, `i' first becomes 10, then 11, and `atan2' is called with the two arguments 11 and 10. File: gawk.info, Node: Numeric Functions, Next: String Functions, Prev: Calling Built-in, Up: Built-in -Numeric Functions ------------------ +8.1.2 Numeric Functions +----------------------- - The following list describes all of the built-in functions that work +The following list describes all of the built-in functions that work with numbers. Optional parameters are enclosed in square brackets ([ ]): @@ -9001,7 +9096,7 @@ brackets ([ ]): # Function to roll a simulated die. function roll(n) { return 1 + int(rand() * n) } - + # Roll 3 six-sided dice and # print total number of points. { @@ -9039,15 +9134,15 @@ brackets ([ ]): easy to keep track of the seeds in case you need to consistently reproduce sequences of random numbers. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) The C version of `rand' is known to produce fairly poor -sequences of random numbers. However, nothing requires that an `awk' +(1) The C version of `rand' is known to produce fairly poor sequences +of random numbers. However, nothing requires that an `awk' implementation use the C `rand' to implement the `awk' version of `rand'. In fact, `gawk' uses the BSD `random' function, which is considerably better than `rand', to produce random numbers. - (2) Computer-generated random numbers really are not truly random. +(2) Computer-generated random numbers really are not truly random. They are technically known as "pseudorandom." This means that while the numbers in a sequence appear to be random, you can in fact generate the same sequence of random numbers over and over again. @@ -9055,11 +9150,11 @@ the same sequence of random numbers over and over again. File: gawk.info, Node: String Functions, Next: I/O Functions, Prev: Numeric Functions, Up: Built-in -String-Manipulation Functions ------------------------------ +8.1.3 String-Manipulation Functions +----------------------------------- - The functions in this minor node look at or change the text of one -or more strings. Optional parameters are enclosed in square +The functions in this minor node look at or change the text of one or +more strings. Optional parameters are enclosed in square brackets ([ ]). Those functions that are specific to `gawk' are marked with a pound sign (`#'): @@ -9132,12 +9227,13 @@ with a pound sign (`#'): If no argument is supplied, `length' returns the length of `$0'. - *Note:* In older versions of `awk', the `length' function could be - called without any parentheses. Doing so is marked as - "deprecated" in the POSIX standard. This means that while a - program can do this, it is a feature that can eventually be - removed from a future version of the standard. Therefore, for - programs to be maximally portable, always supply the parentheses. + NOTE: In older versions of `awk', the `length' function could + be called without any parentheses. Doing so is marked as + "deprecated" in the POSIX standard. This means that while a + program can do this, it is a feature that can eventually be + removed from a future version of the standard. Therefore, + for programs to be maximally portable, always supply the + parentheses. `match(STRING, REGEXP [, ARRAY])' The `match' function searches STRING for the longest, leftmost @@ -9504,35 +9600,35 @@ with a pound sign (`#'): Nonalphabetic characters are left unchanged. For example, `toupper("MiXeD cAsE 123")' returns `"MIXED CASE 123"'. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Unless you use the `--non-decimal-data' option, which isn't +(1) Unless you use the `--non-decimal-data' option, which isn't recommended. *Note Nondecimal Data::, for more information. - (2) Note that this means that the record will first be regenerated +(2) Note that this means that the record will first be regenerated using the value of `OFS' if any fields have been changed, and that the fields will be updated after the substituion, even if the operation is a "no-op" such as `sub(/^/, "")'. - (3) This is different from C and C++, in which the first character -is number zero. +(3) This is different from C and C++, in which the first character is +number zero. File: gawk.info, Node: Gory Details, Up: String Functions -More About `\' and `&' with `sub', `gsub', and `gensub' -....................................................... +8.1.3.1 More About `\' and `&' with `sub', `gsub', and `gensub' +............................................................... - When using `sub', `gsub', or `gensub', and trying to get literal +When using `sub', `gsub', or `gensub', and trying to get literal backslashes and ampersands into the replacement text, you need to remember that there are several levels of "escape processing" going on. - First, there is the "lexical" level, which is when `awk' reads your +First, there is the "lexical" level, which is when `awk' reads your program and builds an internal copy of it that can be executed. Then there is the runtime level, which is when `awk' actually scans the replacement string to determine what to generate. - At both levels, `awk' looks for a defined set of characters that can +At both levels, `awk' looks for a defined set of characters that can come after a backslash. At the lexical level, it looks for the escape sequences listed in *Note Escape Sequences::. Thus, for every `\' that `awk' processes at the runtime level, type two backslashes at the @@ -9541,16 +9637,16 @@ sequence follows the `\', Unix `awk' and `gawk' both simply remove the initial `\' and put the next character into the string. Thus, for example, `"a\qb"' is treated as `"aqb"'. - At the runtime level, the various functions handle sequences of `\' -and `&' differently. The situation is (sadly) somewhat complex. +At the runtime level, the various functions handle sequences of `\' and +`&' differently. The situation is (sadly) somewhat complex. Historically, the `sub' and `gsub' functions treated the two character sequence `\&' specially; this sequence was replaced in the generated text with a single `&'. Any other `\' within the REPLACEMENT string -that did not precede an `&' was passed through unchanged. To -illustrate with a table: +that did not precede an `&' was passed through unchanged. This is +illustrated in *Note table-sub-escapes::. You type `sub' sees `sub' generates - -------- ---------- --------------- + ------- --------- -------------- `\&' `&' the matched text `\\&' `\&' a literal `&' `\\\&' `\&' a literal `&' @@ -9559,6 +9655,8 @@ illustrate with a table: `\\\\\\&' `\\\&' a literal `\\&' `\\q' `\q' a literal `\q' +Table 8.1: Historical Escape Sequence Processing for sub and gsub + This table shows both the lexical-level processing, where an odd number of backslashes becomes an even number at the runtime level, as well as the runtime processing done by `sub'. (For the sake of simplicity, the @@ -9568,18 +9666,21 @@ backslashes entered at the lexical level.) The problem with the historical approach is that there is no way to get a literal `\' followed by the matched text. - The 1992 POSIX standard attempted to fix this problem. The standard + The 1992 POSIX standard attempted to fix this problem. That standard says that `sub' and `gsub' look for either a `\' or an `&' after the `\'. If either one follows a `\', that character is output literally. -The interpretation of `\' and `&' then becomes: +The interpretation of `\' and `&' then becomes as shown in *Note +table-sub-posix-92::. You type `sub' sees `sub' generates - -------- ---------- --------------- + ------- --------- -------------- `&' `&' the matched text `\\&' `\&' a literal `&' `\\\\&' `\\&' a literal `\', then the matched text `\\\\\\&' `\\\&' a literal `\&' +Table 8.2: 1992 POSIX Rules for sub and gsub Escape Sequence Processing + This appears to solve the problem. Unfortunately, the phrasing of the standard is unusual. It says, in effect, that `\' turns off the special meaning of any following character, but for anything other than `\' and @@ -9592,18 +9693,22 @@ problems: * To make sure that an `awk' program is portable, _every_ character in the REPLACEMENT string must be preceded with a backslash.(1) - The POSIX standard is under revision. Because of the problems just -listed, proposed text for the revised standard reverts to rules that -correspond more closely to the original existing practice. The proposed -rules have special cases that make it possible to produce a `\' -preceding the matched text: + Because of the problems just listed, in 1996, the `gawk' maintainer +submitted proposed text for a revised standard that reverts to rules +that correspond more closely to the original existing practice. The +proposed rules have special cases that make it possible to produce a +`\' preceding the matched text. This is shown in *Note +table-sub-proposed::. You type `sub' sees `sub' generates - -------- ---------- --------------- + ------- --------- -------------- `\\\\\\&' `\\\&' a literal `\&' `\\\\&' `\\&' a literal `\', followed by the matched text `\\&' `\&' a literal `&' `\\q' `\q' a literal `\q' + `\\\\' `\\' `\\' + +Table 8.3: Propsosed rules for sub and backslash In a nutshell, at the runtime level, there are now three special sequences of characters (`\\\&', `\\&' and `\&') whereas historically @@ -9612,20 +9717,46 @@ is not part of one of these three sequences is not special and appears in the output literally. `gawk' 3.0 and 3.1 follow these proposed POSIX rules for `sub' and -`gsub'. Whether these proposed rules will actually become codified -into the standard is unknown at this point. Subsequent `gawk' releases -will track the standard and implement whatever the final version -specifies; this Info file will be updated as well.(2) +`gsub'. The POSIX standard took much longer to be revised than was +expected in 1996. The 2001 standard does not follow the above rules. +Instead, the rules there are somewhat simpler. The results are similar +except for one case. + + The 2001 POSIX rules state that `\&' in the replacement string +produces a literal `&', `\\' produces a literal `\', and `\' followed +by anything else is not special; the `\' is placed straight into the +output. These rules are presented in *Note table-posix-2001-sub::. + + You type `sub' sees `sub' generates + ------- --------- -------------- + `\\\\\\&' `\\\&' a literal `\&' + `\\\\&' `\\&' a literal `\', followed by the matched text + `\\&' `\&' a literal `&' + `\\q' `\q' a literal `\q' + `\\\\' `\\' `\' + +Table 8.4: POSIX 2001 rules for sub + + The only case where the difference is noticeable is the last one: +`\\\\' is seen as `\\' and produces `\' instead of `\\'. + + Starting with version 3.1.4, `gawk' follows the POSIX rules when +`--posix' is specified (*note Options::). Otherwise, it continues to +follow the 1996 proposed rules, since, as of this writing, that has +been its behavior for over seven years. + + NOTE: At the next major release, `gawk' will switch to using the + POSIX 2001 rules by default. The rules for `gensub' are considerably simpler. At the runtime level, whenever `gawk' sees a `\', if the following character is a digit, then the text that matched the corresponding parenthesized subexpression is placed in the generated output. Otherwise, no matter what character follows the `\', it appears in the generated text and -the `\' does not: +the `\' does not, as shown in *Note table-gensub-escapes::. You type `gensub' sees `gensub' generates - -------- ------------- ------------------ + ------- ------------ ----------------- `&' `&' the matched text `\\&' `\&' a literal `&' `\\\\' `\\' a literal `\' @@ -9633,6 +9764,8 @@ the `\' does not: `\\\\\\&' `\\\&' a literal `\&' `\\q' `\q' a literal `q' +Table 8.5: Escape Sequence Processing for gensub + Because of the complexity of the lexical and runtime level processing and the special cases for `sub' and `gsub', we recommend the use of `gawk' and `gensub' when you have to do substitutions. @@ -9640,7 +9773,7 @@ and the special cases for `sub' and `gsub', we recommend the use of Advanced Notes: Matching the Null String ---------------------------------------- - In `awk', the `*' operator can match the null string. This is +In `awk', the `*' operator can match the null string. This is particularly important for the `sub', `gsub', and `gensub' functions. For example: @@ -9649,21 +9782,17 @@ For example: Although this makes a certain amount of sense, it can be surprising. - ---------- Footnotes ---------- - - (1) This consequence was certainly unintended. +---------- Footnotes ---------- - (2) As this Info file was being finalized, we learned that the POSIX -standard will not use these rules. However, it was too late to change -`gawk' for the 3.1 release. `gawk' behaves as described here. +(1) This consequence was certainly unintended. File: gawk.info, Node: I/O Functions, Next: Time Functions, Prev: String Functions, Up: Built-in -Input/Output Functions ----------------------- +8.1.5 Input/Output Functions +---------------------------- - The following functions relate to input/output (I/O). Optional +The following functions relate to input/output (I/O). Optional parameters are enclosed in square brackets ([ ]): `close(FILENAME [, HOW])' @@ -9752,11 +9881,11 @@ parameters are enclosed in square brackets ([ ]): Advanced Notes: Interactive Versus Noninteractive Buffering ----------------------------------------------------------- - As a side point, buffering issues can be even more confusing, -depending upon whether your program is "interactive", i.e., -communicating with a user sitting at a keyboard.(1) +As a side point, buffering issues can be even more confusing, depending +upon whether your program is "interactive", i.e., communicating with a +user sitting at a keyboard.(1) - Interactive programs generally "line buffer" their output; i.e., they +Interactive programs generally "line buffer" their output; i.e., they write out every line. Noninteractive programs wait until they have a full buffer, which may be many lines of output. Here is an example of the difference: @@ -9784,11 +9913,10 @@ it is all buffered and sent down the pipe to `cat' in one shot. Advanced Notes: Controlling Output Buffering with `system' ---------------------------------------------------------- - The `fflush' function provides explicit control over output -buffering for individual files and pipes. However, its use is not -portable to many other `awk' implementations. An alternative method to -flush output buffers is to call `system' with a null string as its -argument: +The `fflush' function provides explicit control over output buffering +for individual files and pipes. However, its use is not portable to +many other `awk' implementations. An alternative method to flush output +buffers is to call `system' with a null string as its argument: system("") # flush output @@ -9801,7 +9929,7 @@ unnecessary shell. (Other implementations may only flush the buffer associated with the standard output and not necessarily all buffered output.) - If you think about what a programmer expects, it makes sense that +If you think about what a programmer expects, it makes sense that `system' should flush any pending output. The following program: BEGIN { @@ -9822,21 +9950,21 @@ and not: first print second print - If `awk' did not flush its buffers before calling `system', you -would see the latter (undesirable) output. +If `awk' did not flush its buffers before calling `system', you would +see the latter (undesirable) output. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) A program is interactive if the standard output is connected to -a terminal device. +(1) A program is interactive if the standard output is connected to a +terminal device. File: gawk.info, Node: Time Functions, Next: Bitwise Functions, Prev: I/O Functions, Up: Built-in -Using `gawk''s Timestamp Functions ----------------------------------- +8.1.8 Using `gawk''s Timestamp Functions +---------------------------------------- - `awk' programs are commonly used to process log files containing +`awk' programs are commonly used to process log files containing timestamp information, indicating when a particular log record was written. Many programs log their timestamp in the form returned by the `time' system call, which is the number of seconds since a particular @@ -9847,7 +9975,7 @@ which is sufficient to represent times through 2038-01-19 03:14:07 UTC. Many systems support a wider range of timestamps, including negative timestamps that represent times before the epoch. - In order to make it easier to process such log files and to produce +In order to make it easier to process such log files and to produce useful reports, `gawk' provides the following functions for working with timestamps. They are `gawk' extensions; they are not specified in the POSIX standard, nor are they in any other known version of `awk'.(2) @@ -9894,26 +10022,26 @@ Optional parameters are enclosed in square brackets ([ ]): that of the `date' utility. (Versions of `gawk' prior to 3.0 require the FORMAT argument.) - The `systime' function allows you to compare a timestamp from a log +The `systime' function allows you to compare a timestamp from a log file with the current time of day. In particular, it is easy to determine how long ago a particular record was logged. It also allows you to produce log records using the "seconds since the epoch" format. - The `mktime' function allows you to convert a textual representation -of a date and time into a timestamp. This makes it easy to do +The `mktime' function allows you to convert a textual representation of +a date and time into a timestamp. This makes it easy to do before/after comparisons of dates and times, particularly when dealing with date and time data coming from an external source, such as a log file. - The `strftime' function allows you to easily turn a timestamp into +The `strftime' function allows you to easily turn a timestamp into human-readable information. It is similar in nature to the `sprintf' function (*note String Functions::), in that it copies nonformat specification characters verbatim to the returned string, while substituting date and time values for format specifications in the FORMAT string. - `strftime' is guaranteed by the 1999 ISO C standard(4) to support -the following date format specifications: +`strftime' is guaranteed by the 1999 ISO C standard(4) to support the +following date format specifications: `%a' The locale's abbreviated weekday name. @@ -10053,10 +10181,10 @@ the following date format specifications: `%%' A literal `%'. - If a conversion specifier is not one of the above, the behavior is +If a conversion specifier is not one of the above, the behavior is undefined.(6) - Informally, a "locale" is the geographic place in which a program is +Informally, a "locale" is the geographic place in which a program is meant to run. For example, a common way to abbreviate the date September 4, 1991 in the United States is "9/4/91." In many countries in Europe, however, it is abbreviated "4.9.91." Thus, the `%x' @@ -10065,7 +10193,7 @@ specification in a `"US"' locale might produce `9/4/91', while in a defines a default `"C"' locale, which is an environment that is typical of what most C programmers are used to. - A public-domain C version of `strftime' is supplied with `gawk' for +A public-domain C version of `strftime' is supplied with `gawk' for systems that are not yet fully standards-compliant. It supports all of the just listed format specifications. If that version is used to compile `gawk' (*note Installation::), then the following additional @@ -10091,12 +10219,12 @@ format specifications are available: `%v' The date in VMS format (e.g., `20-JUN-1991'). - Additionally, the alternate representations are recognized but their +Additionally, the alternate representations are recognized but their normal representations are used. - This example is an `awk' implementation of the POSIX `date' utility. -Normally, the `date' utility prints the current date and time of day -in a well-known format. However, if you provide an argument to it that +This example is an `awk' implementation of the POSIX `date' utility. +Normally, the `date' utility prints the current date and time of day in +a well-known format. However, if you provide an argument to it that begins with a `+', `date' copies nonformat specifier characters to the standard output and interprets the current time according to the format specifiers in the string. For example: @@ -10104,24 +10232,24 @@ specifiers in the string. For example: $ date '+Today is %A, %B %d, %Y.' -| Today is Thursday, September 14, 2000. - Here is the `gawk' version of the `date' utility. It has a shell +Here is the `gawk' version of the `date' utility. It has a shell "wrapper" to handle the `-u' option, which requires that `date' run as if the time zone is set to UTC: #! /bin/sh # # date --- approximate the P1003.2 'date' command - + case $1 in -u) TZ=UTC0 # use UTC export TZ shift ;; esac - + gawk 'BEGIN { format = "%a %b %d %H:%M:%S %Z %Y" exitval = 0 - + if (ARGC > 2) exitval = 1 else if (ARGC == 2) { @@ -10133,26 +10261,26 @@ if the time zone is set to UTC: exit exitval }' "$@" - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) *Note Glossary::, especially the entries "Epoch" and "UTC." +(1) *Note Glossary::, especially the entries "Epoch" and "UTC." - (2) The GNU `date' utility can also do many of the things described +(2) The GNU `date' utility can also do many of the things described here. Its use may be preferable for simple time-related operations in shell scripts. - (3) Occasionally there are minutes in a year with a leap second, -which is why the seconds can go up to 60. +(3) Occasionally there are minutes in a year with a leap second, which +is why the seconds can go up to 60. - (4) As this is a recent standard, not every system's `strftime' +(4) As this is a recent standard, not every system's `strftime' necessarily supports all of the conversions listed here. - (5) If you don't understand any of this, don't worry about it; these +(5) If you don't understand any of this, don't worry about it; these facilities are meant to make it easier to "internationalize" programs. Other internationalization features are described in *Note Internationalization::. - (6) This is because ISO C leaves the behavior of the C version of +(6) This is because ISO C leaves the behavior of the C version of `strftime' undefined and `gawk' uses the system's version of `strftime' if it's there. Typically, the conversion specifier either does not appear in the returned string or appears literally. @@ -10160,26 +10288,28 @@ appear in the returned string or appears literally. File: gawk.info, Node: Bitwise Functions, Next: I18N Functions, Prev: Time Functions, Up: Built-in -Bit-Manipulation Functions of `gawk' ------------------------------------- +8.1.9 Bit-Manipulation Functions of `gawk' +------------------------------------------ I can explain it for you, but I can't understand it for you. Anonymous - Many languages provide the ability to perform "bitwise" operations -on two integer numbers. In other words, the operation is performed on +Many languages provide the ability to perform "bitwise" operations on +two integer numbers. In other words, the operation is performed on each successive pair of bits in the operands. Three common operations -are bitwise AND, OR, and XOR. The operations are described by the -following table: +are bitwise AND, OR, and XOR. The operations are described in *Note +table-bitwise-ops::. Bit Operator | AND | OR | XOR - |---+---+---+---+---+--- + |--+--+--+--+--+-- Operands | 0 | 1 | 0 | 1 | 0 | 1 - ----------+---+---+---+---+---+--- + ---------+--+--+--+--+--+-- 0 | 0 0 | 0 1 | 0 1 1 | 0 1 | 1 1 | 1 0 +Table 8.6: Bitwise Operations + As you can see, the result of an AND operation is 1 only when _both_ bits are 1. The result of an OR operation is 1 if _either_ bit is 1. The result of an XOR operation is 1 if either bit is 1, but not both. @@ -10206,30 +10336,32 @@ bitwise operations just described. They are: For all of these functions, first the double-precision floating-point value is converted to the widest C unsigned integer -type, then the bitwise operation is performed and then the result is -converted back into a C `double'. (If you don't understand this +type, then the bitwise operation is performed. If the result cannot be +represented exactly as a C `double', leading nonzero bits are removed +one by one until it can be represented exactly. The result is then +converted back into a C `double'. (If you don't understand this paragraph, don't worry about it.) Here is a user-defined function (*note User-defined::) that illustrates the use of these functions: # bits2str --- turn a byte into readable 1's and 0's - + function bits2str(bits, data, mask) { if (bits == 0) return "0" - + mask = 1 for (; bits != 0; bits = rshift(bits, 1)) data = (and(bits, mask) ? "1" : "0") data - + while ((length(data) % 8) != 0) data = "0" data - + return data } - + BEGIN { printf "123 = %s\n", bits2str(123) printf "0123 = %s\n", bits2str(0123) @@ -10252,7 +10384,7 @@ This program produces the following output when run: -| lshift(0x99, 2) = 0x264 = 0000001001100100 -| rshift(0x99, 2) = 0x26 = 00100110 - The `bits2str' function turns a binary number into a string. The +The `bits2str' function turns a binary number into a string. The number `1' represents a binary value where the rightmost bit is set to 1. Using this mask, the function repeatedly checks the rightmost bit. ANDing the mask with the value indicates whether the rightmost bit is 1 @@ -10260,28 +10392,28 @@ or not. If so, a `"1"' is concatenated onto the front of the string. Otherwise, a `"0"' is added. The value is then shifted right by one bit and the loop continues until there are no more 1 bits. - If the initial value is zero it returns a simple `"0"'. Otherwise, -at the end, it pads the value with zeros to represent multiples of -8-bit quantities. This is typical in modern computers. +If the initial value is zero it returns a simple `"0"'. Otherwise, at +the end, it pads the value with zeros to represent multiples of 8-bit +quantities. This is typical in modern computers. - The main code in the `BEGIN' rule shows the difference between the +The main code in the `BEGIN' rule shows the difference between the decimal and octal values for the same numbers (*note Nondecimal-numbers::), and then demonstrates the results of the `compl', `lshift', and `rshift' functions. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) This example shows that 0's come in on the left side. For -`gawk', this is always true, but in some languages, it's possible to -have the left side fill with 1's. Caveat emptor. +(1) This example shows that 0's come in on the left side. For `gawk', +this is always true, but in some languages, it's possible to have the +left side fill with 1's. Caveat emptor. File: gawk.info, Node: I18N Functions, Prev: Bitwise Functions, Up: Built-in -Using `gawk''s String-Translation Functions -------------------------------------------- +8.1.10 Using `gawk''s String-Translation Functions +-------------------------------------------------- - `gawk' provides facilities for internationalizing `awk' programs. +`gawk' provides facilities for internationalizing `awk' programs. These include the functions described in the following list. The descriptions here are purposely brief. *Note Internationalization::, for the full story. Optional parameters are enclosed in square @@ -10314,11 +10446,11 @@ brackets ([ ]): File: gawk.info, Node: User-defined, Prev: Built-in, Up: Functions -User-Defined Functions -====================== +8.2 User-Defined Functions +========================== - Complicated `awk' programs can often be simplified by defining your -own functions. User-defined functions can be called just like built-in +Complicated `awk' programs can often be simplified by defining your own +functions. User-defined functions can be called just like built-in ones (*note Function Calls::), but it is up to you to define them, i.e., to tell `awk' what they should do. @@ -10334,17 +10466,17 @@ i.e., to tell `awk' what they should do. File: gawk.info, Node: Definition Syntax, Next: Function Example, Up: User-defined -Function Definition Syntax --------------------------- +8.2.1 Function Definition Syntax +-------------------------------- - Definitions of functions can appear anywhere between the rules of an +Definitions of functions can appear anywhere between the rules of an `awk' program. Thus, the general form of an `awk' program is extended to include sequences of rules _and_ user-defined function definitions. There is no need to put the definition of a function before all uses of the function. This is because `awk' reads the entire program before starting to execute any of it. - The definition of a function named NAME looks like this: +The definition of a function named NAME looks like this: function NAME(PARAMETER-LIST) { @@ -10357,58 +10489,58 @@ underscores that doesn't start with a digit. Within a single `awk' program, any particular name can only be used as a variable, array, or function. - PARAMETER-LIST is a list of the function's arguments and local -variable names, separated by commas. When the function is called, the -argument names are used to hold the argument values given in the call. -The local variables are initialized to the empty string. A function -cannot have two parameters with the same name, nor may it have a -parameter with the same name as the function itself. +PARAMETER-LIST is a list of the function's arguments and local variable +names, separated by commas. When the function is called, the argument +names are used to hold the argument values given in the call. The +local variables are initialized to the empty string. A function cannot +have two parameters with the same name, nor may it have a parameter +with the same name as the function itself. - The BODY-OF-FUNCTION consists of `awk' statements. It is the most +The BODY-OF-FUNCTION consists of `awk' statements. It is the most important part of the definition, because it says what the function should actually _do_. The argument names exist to give the body a way to talk about the arguments; local variables exist to give the body places to keep temporary values. - Argument names are not distinguished syntactically from local -variable names. Instead, the number of arguments supplied when the -function is called determines how many argument variables there are. -Thus, if three argument values are given, the first three names in -PARAMETER-LIST are arguments and the rest are local variables. - - It follows that if the number of arguments is not the same in all -calls to the function, some of the names in PARAMETER-LIST may be -arguments on some occasions and local variables on others. Another way -to think of this is that omitted arguments default to the null string. - - Usually when you write a function, you know how many names you -intend to use for arguments and how many you intend to use as local -variables. It is conventional to place some extra space between the -arguments and the local variables, in order to document how your -function is supposed to be used. - - During execution of the function body, the arguments and local -variable values hide, or "shadow", any variables of the same names used -in the rest of the program. The shadowed variables are not accessible -in the function definition, because there is no way to name them while -their names have been taken away for the local variables. All other -variables used in the `awk' program can be referenced or set normally -in the function's body. - - The arguments and local variables last only as long as the function -body is executing. Once the body finishes, you can once again access -the variables that were shadowed while the function was running. - - The function body can contain expressions that call functions. They +Argument names are not distinguished syntactically from local variable +names. Instead, the number of arguments supplied when the function is +called determines how many argument variables there are. Thus, if three +argument values are given, the first three names in PARAMETER-LIST are +arguments and the rest are local variables. + +It follows that if the number of arguments is not the same in all calls +to the function, some of the names in PARAMETER-LIST may be arguments +on some occasions and local variables on others. Another way to think +of this is that omitted arguments default to the null string. + +Usually when you write a function, you know how many names you intend to +use for arguments and how many you intend to use as local variables. +It is conventional to place some extra space between the arguments and +the local variables, in order to document how your function is supposed +to be used. + +During execution of the function body, the arguments and local variable +values hide, or "shadow", any variables of the same names used in the +rest of the program. The shadowed variables are not accessible in the +function definition, because there is no way to name them while their +names have been taken away for the local variables. All other variables +used in the `awk' program can be referenced or set normally in the +function's body. + +The arguments and local variables last only as long as the function body +is executing. Once the body finishes, you can once again access the +variables that were shadowed while the function was running. + +The function body can contain expressions that call functions. They can even call this function, either directly or by way of another function. When this happens, we say the function is "recursive". The act of a function calling itself is called "recursion". - In many `awk' implementations, including `gawk', the keyword -`function' may be abbreviated `func'. However, POSIX only specifies -the use of the keyword `function'. This actually has some practical -implications. If `gawk' is in POSIX-compatibility mode (*note -Options::), then the following statement does _not_ define a function: +In many `awk' implementations, including `gawk', the keyword `function' +may be abbreviated `func'. However, POSIX only specifies the use of +the keyword `function'. This actually has some practical implications. +If `gawk' is in POSIX-compatibility mode (*note Options::), then the +following statement does _not_ define a function: func foo() { a = sqrt($1) ; print a } @@ -10419,16 +10551,16 @@ probably not what is desired. (`awk' accepts this input as syntactically valid, because functions may be used before they are defined in `awk' programs.) - To ensure that your `awk' programs are portable, always use the -keyword `function' when defining a function. +To ensure that your `awk' programs are portable, always use the keyword +`function' when defining a function. File: gawk.info, Node: Function Example, Next: Function Caveats, Prev: Definition Syntax, Up: User-defined -Function Definition Examples ----------------------------- +8.2.2 Function Definition Examples +---------------------------------- - Here is an example of a user-defined function, called `myprint', that +Here is an example of a user-defined function, called `myprint', that takes a number and prints it in a specific format: function myprint(num) @@ -10453,7 +10585,7 @@ this program, using our function to format the results, prints: 5.6 21.2 - This function deletes all the elements in an array: +This function deletes all the elements in an array: function delarray(a, i) { @@ -10461,15 +10593,15 @@ this program, using our function to format the results, prints: delete a[i] } - When working with arrays, it is often necessary to delete all the +When working with arrays, it is often necessary to delete all the elements in an array and start over with a new list of elements (*note Delete::). Instead of having to repeat this loop everywhere that you need to clear out an array, your program can just call `delarray'. (This guarantees portability. The use of `delete ARRAY' to delete the contents of an entire array is a nonstandard extension.) - The following is an example of a recursive function. It takes a -string as an input parameter and returns the string in backwards order. +The following is an example of a recursive function. It takes a string +as an input parameter and returns the string in backwards order. Recursive functions must always have a test that stops the recursion. In this case, the recursion terminates when the starting position is zero, i.e., when there are no more characters left in the string. @@ -10478,18 +10610,18 @@ zero, i.e., when there are no more characters left in the string. { if (start == 0) return "" - + return (substr(str, start, 1) rev(str, start - 1)) } - If this function is in a file named `rev.awk', it can be tested this +If this function is in a file named `rev.awk', it can be tested this way: $ echo "Don't Panic!" | > gawk --source '{ print rev($0, length($0)) }' -f rev.awk -| !cinaP t'noD - The C `ctime' function takes a timestamp and returns it in a string, +The C `ctime' function takes a timestamp and returns it in a string, formatted in a well-known fashion. The following example uses the built-in `strftime' function (*note Time Functions::) to create an `awk' version of `ctime': @@ -10497,7 +10629,7 @@ built-in `strftime' function (*note Time Functions::) to create an # ctime.awk # # awk version of C ctime(3) function - + function ctime(ts, format) { format = "%a %b %d %H:%M:%S %Z %Y" @@ -10509,30 +10641,30 @@ built-in `strftime' function (*note Time Functions::) to create an File: gawk.info, Node: Function Caveats, Next: Return Statement, Prev: Function Example, Up: User-defined -Calling User-Defined Functions ------------------------------- +8.2.3 Calling User-Defined Functions +------------------------------------ - "Calling a function" means causing the function to run and do its -job. A function call is an expression and its value is the value -returned by the function. +"Calling a function" means causing the function to run and do its job. +A function call is an expression and its value is the value returned by +the function. - A function call consists of the function name followed by the -arguments in parentheses. `awk' expressions are what you write in the -call for the arguments. Each time the call is executed, these -expressions are evaluated, and the values are the actual arguments. For -example, here is a call to `foo' with three arguments (the first being -a string concatenation): +A function call consists of the function name followed by the arguments +in parentheses. `awk' expressions are what you write in the call for +the arguments. Each time the call is executed, these expressions are +evaluated, and the values are the actual arguments. For example, here +is a call to `foo' with three arguments (the first being a string +concatenation): foo(x y, "lose", 4 * z) - *Caution:* Whitespace characters (spaces and tabs) are not allowed +*Caution:* Whitespace characters (spaces and tabs) are not allowed between the function name and the open-parenthesis of the argument list. If you write whitespace by mistake, `awk' might think that you mean to concatenate a variable with an expression in parentheses. However, it notices that you used a function name and not a variable name, and reports an error. - When a function is called, it is given a _copy_ of the values of its +When a function is called, it is given a _copy_ of the values of its arguments. This is known as "call by value". The caller may use a variable as the expression for the argument, but the called function does not know this--it only knows what value the argument had. For @@ -10561,31 +10693,31 @@ outside of `myfunc', the function body cannot alter this outer value, because it is shadowed during the execution of `myfunc' and cannot be seen or changed from there. - However, when arrays are the parameters to functions, they are _not_ +However, when arrays are the parameters to functions, they are _not_ copied. Instead, the array itself is made available for direct manipulation by the function. This is usually called "call by reference". Changes made to an array parameter inside the body of a function _are_ visible outside that function. - *Note:* Changing an array parameter inside a function can be very -dangerous if you do not watch what you are doing. For example: + NOTE: Changing an array parameter inside a function can be very + dangerous if you do not watch what you are doing. For example: - function changeit(array, ind, nvalue) - { - array[ind] = nvalue - } - - BEGIN { - a[1] = 1; a[2] = 2; a[3] = 3 - changeit(a, 2, "two") - printf "a[1] = %s, a[2] = %s, a[3] = %s\n", - a[1], a[2], a[3] - } + function changeit(array, ind, nvalue) + { + array[ind] = nvalue + } -prints `a[1] = 1, a[2] = two, a[3] = 3', because `changeit' stores -`"two"' in the second element of `a'. + BEGIN { + a[1] = 1; a[2] = 2; a[3] = 3 + changeit(a, 2, "two") + printf "a[1] = %s, a[2] = %s, a[3] = %s\n", + a[1], a[2], a[3] + } - Some `awk' implementations allow you to call a function that has not + prints `a[1] = 1, a[2] = two, a[3] = 3', because `changeit' stores + `"two"' in the second element of `a'. + +Some `awk' implementations allow you to call a function that has not been defined. They only report a problem at runtime when the program actually tries to call the function. For example: @@ -10602,42 +10734,42 @@ Because the `if' statement will never be true, it is not really a problem that `foo' has not been defined. Usually, though, it is a problem if a program calls an undefined function. - If `--lint' is specified (*note Options::), `gawk' reports calls to +If `--lint' is specified (*note Options::), `gawk' reports calls to undefined functions. - Some `awk' implementations generate a runtime error if you use the +Some `awk' implementations generate a runtime error if you use the `next' statement (*note Next Statement::) inside a user-defined function. `gawk' does not have this limitation. File: gawk.info, Node: Return Statement, Next: Dynamic Typing, Prev: Function Caveats, Up: User-defined -The `return' Statement ----------------------- +8.2.4 The `return' Statement +---------------------------- - The body of a user-defined function can contain a `return' statement. +The body of a user-defined function can contain a `return' statement. This statement returns control to the calling part of the `awk' program. It can also be used to return a value for use in the rest of the `awk' program. It looks like this: return [EXPRESSION] - The EXPRESSION part is optional. If it is omitted, then the returned +The EXPRESSION part is optional. If it is omitted, then the returned value is undefined, and therefore, unpredictable. - A `return' statement with no value expression is assumed at the end -of every function definition. So if control reaches the end of the +A `return' statement with no value expression is assumed at the end of +every function definition. So if control reaches the end of the function body, then the function returns an unpredictable value. `awk' does _not_ warn you if you use the return value of such a function. - Sometimes, you want to write a function for what it does, not for -what it returns. Such a function corresponds to a `void' function in C -or to a `procedure' in Pascal. Thus, it may be appropriate to not -return any value; simply bear in mind that if you use the return value -of such a function, you do so at your own risk. +Sometimes, you want to write a function for what it does, not for what +it returns. Such a function corresponds to a `void' function in C or +to a `procedure' in Pascal. Thus, it may be appropriate to not return +any value; simply bear in mind that if you use the return value of such +a function, you do so at your own risk. - The following is an example of a user-defined function that returns -a value for the largest number among the elements of an array: +The following is an example of a user-defined function that returns a +value for the largest number among the elements of an array: function maxelt(vec, i, ret) { @@ -10656,9 +10788,8 @@ function parameter list indicates that `i' and `ret' are not supposed to be arguments. You should follow this convention when defining functions. - The following program uses the `maxelt' function. It loads an -array, calls `maxelt', and then reports the maximum number in that -array: +The following program uses the `maxelt' function. It loads an array, +calls `maxelt', and then reports the maximum number in that array: function maxelt(vec, i, ret) { @@ -10668,18 +10799,18 @@ array: } return ret } - + # Load all fields of each record into nums. { for(i = 1; i <= NF; i++) nums[NR, i] = $i } - + END { print maxelt(nums) } - Given the following input: +Given the following input: 1 5 23 8 16 44 3 5 2 8 26 @@ -10693,50 +10824,49 @@ the array. File: gawk.info, Node: Dynamic Typing, Prev: Return Statement, Up: User-defined -Functions and Their Effects on Variable Typing ----------------------------------------------- +8.2.5 Functions and Their Effects on Variable Typing +---------------------------------------------------- - `awk' is a very fluid language. It is possible that `awk' can't -tell if an identifier represents a regular variable or an array until +`awk' is a very fluid language. It is possible that `awk' can't tell +if an identifier represents a regular variable or an array until runtime. Here is an annotated sample program: function foo(a) { a[1] = 1 # parameter is an array } - + BEGIN { b = 1 foo(b) # invalid: fatal type mismatch - + foo(x) # x uninitialized, becomes an array dynamically x = 1 # now not allowed, runtime error } - Usually, such things aren't a big issue, but it's worth being aware -of them. +Usually, such things aren't a big issue, but it's worth being aware of +them. File: gawk.info, Node: Internationalization, Next: Advanced Features, Prev: Functions, Up: Top -Internationalization with `gawk' -******************************** +9 Internationalization with `gawk' +********************************** - Once upon a time, computer makers wrote software that worked only in +Once upon a time, computer makers wrote software that worked only in English. Eventually, hardware and software vendors noticed that if their systems worked in the native languages of non-English-speaking countries, they were able to sell more systems. As a result, internationalization and localization of programs and software systems became a common practice. - Until recently, the ability to provide internationalization was -largely restricted to programs written in C and C++. This major node -describes the underlying library `gawk' uses for internationalization, -as well as how `gawk' makes internationalization features available at -the `awk' program level. Having internationalization available at the -`awk' level gives software developers additional flexibility--they are -no longer required to write in C when internationalization is a -requirement. +Until recently, the ability to provide internationalization was largely +restricted to programs written in C and C++. This major node describes +the underlying library `gawk' uses for internationalization, as well as +how `gawk' makes internationalization features available at the `awk' +program level. Having internationalization available at the `awk' level +gives software developers additional flexibility--they are no longer +required to write in C when internationalization is a requirement. * Menu: @@ -10750,35 +10880,35 @@ requirement. File: gawk.info, Node: I18N and L10N, Next: Explaining gettext, Up: Internationalization -Internationalization and Localization -===================================== +9.1 Internationalization and Localization +========================================= - "Internationalization" means writing (or modifying) a program once, -in such a way that it can use multiple languages without requiring -further source-code changes. "Localization" means providing the data -necessary for an internationalized program to work in a particular -language. Most typically, these terms refer to features such as the -language used for printing error messages, the language used to read -responses, and information related to how numerical and monetary values -are printed and read. +"Internationalization" means writing (or modifying) a program once, in +such a way that it can use multiple languages without requiring further +source-code changes. "Localization" means providing the data necessary +for an internationalized program to work in a particular language. +Most typically, these terms refer to features such as the language used +for printing error messages, the language used to read responses, and +information related to how numerical and monetary values are printed +and read. File: gawk.info, Node: Explaining gettext, Next: Programmer i18n, Prev: I18N and L10N, Up: Internationalization -GNU `gettext' -============= +9.2 GNU `gettext' +================= - The facilities in GNU `gettext' focus on messages; strings printed -by a program, either directly or via formatting with `printf' or +The facilities in GNU `gettext' focus on messages; strings printed by a +program, either directly or via formatting with `printf' or `sprintf'.(1) - When using GNU `gettext', each application has its own "text -domain". This is a unique name, such as `kpilot' or `gawk', that -identifies the application. A complete application may have multiple +When using GNU `gettext', each application has its own "text domain". +This is a unique name, such as `kpilot' or `gawk', that identifies the +application. A complete application may have multiple components--programs written in C or C++, as well as scripts written in `sh' or `awk'. All of the components use the same text domain. - To make the discussion concrete, assume we're writing an application +To make the discussion concrete, assume we're writing an application named `guide'. Internationalization consists of the following steps, in this order: @@ -10822,21 +10952,21 @@ in this order: having to switch the application's default text domain back and forth. - In C (or C++), the string marking and dynamic translation lookup are +In C (or C++), the string marking and dynamic translation lookup are accomplished by wrapping each string in a call to `gettext': printf(gettext("Don't Panic!\n")); - The tools that extract messages from source code pull out all -strings enclosed in calls to `gettext'. +The tools that extract messages from source code pull out all strings +enclosed in calls to `gettext'. - The GNU `gettext' developers, recognizing that typing `gettext' over +The GNU `gettext' developers, recognizing that typing `gettext' over and over again is both painful and ugly to look at, use the macro `_' (an underscore) to make things easier: /* In the standard header file: */ #define _(str) gettext(str) - + /* In the program text: */ printf(_("Don't Panic!\n")); @@ -10881,24 +11011,24 @@ defined locale categories that `gettext' knows about are: `LC_ALL' All of the above. (Not too useful in the context of `gettext'.) - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) For some operating systems, the `gawk' port doesn't support GNU +(1) For some operating systems, the `gawk' port doesn't support GNU `gettext'. This applies most notably to the PC operating systems. As such, these features are not available if you are using one of those operating systems. Sorry. - (2) Americans use a comma every three decimal places and a period -for the decimal point, while many Europeans do exactly the opposite: +(2) Americans use a comma every three decimal places and a period for +the decimal point, while many Europeans do exactly the opposite: `1,234.56' versus `1.234,56'. File: gawk.info, Node: Programmer i18n, Next: Translator i18n, Prev: Explaining gettext, Up: Internationalization -Internationalizing `awk' Programs -================================= +9.3 Internationalizing `awk' Programs +===================================== - `gawk' provides the following variables and functions for +`gawk' provides the following variables and functions for internationalization: `TEXTDOMAIN' @@ -10947,7 +11077,7 @@ internationalization: the null string (`""'), then `bindtextdomain' returns the current binding for the given DOMAIN. - To use these facilities in your `awk' program, follow the steps +To use these facilities in your `awk' program, follow the steps outlined in *Note Explaining gettext::, like so: 1. Set the variable `TEXTDOMAIN' to the text domain of your program. @@ -10994,21 +11124,21 @@ outlined in *Note Explaining gettext::, like so: } - *Note I18N Example::, for an example program showing the steps to -create and use translations from `awk'. +*Note I18N Example::, for an example program showing the steps to create +and use translations from `awk'. File: gawk.info, Node: Translator i18n, Next: I18N Example, Prev: Programmer i18n, Up: Internationalization -Translating `awk' Programs -========================== +9.4 Translating `awk' Programs +============================== - Once a program's translatable strings have been marked, they must be +Once a program's translatable strings have been marked, they must be extracted to create the initial `.po' file. As part of translation, it is often helpful to rearrange the order in which arguments to `printf' are output. - `gawk''s `--gen-po' command-line option extracts the messages and is +`gawk''s `--gen-po' command-line option extracts the messages and is discussed next. After that, `printf''s ability to rearrange the order for `printf' arguments at runtime is covered. @@ -11021,17 +11151,17 @@ for `printf' arguments at runtime is covered. File: gawk.info, Node: String Extraction, Next: Printf Ordering, Up: Translator i18n -Extracting Marked Strings -------------------------- +9.4.1 Extracting Marked Strings +------------------------------- - Once your `awk' program is working, and all the strings have been +Once your `awk' program is working, and all the strings have been marked and you've set (and perhaps bound) the text domain, it is time to produce translations. First, use the `--gen-po' command-line option to create the initial `.po' file: $ gawk --gen-po -f guide.awk > guide.po - When run with `--gen-po', `gawk' does not execute your program. +When run with `--gen-po', `gawk' does not execute your program. Instead, it parses it as usual and prints all marked strings to standard output in the format of a GNU `gettext' Portable Object file. Also included in the output are any constant strings that appear as the @@ -11039,39 +11169,39 @@ first argument to `dcgettext' or as the first and second argument to `dcngettext'.(1) *Note I18N Example::, for the full list of steps to go through to create and test translations for `guide'. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Starting with `gettext' version 0.11.5, the `xgettext' utility -that comes with GNU `gettext' can handle `.awk' files. +(1) Starting with `gettext' version 0.11.5, the `xgettext' utility that +comes with GNU `gettext' can handle `.awk' files. File: gawk.info, Node: Printf Ordering, Next: I18N Portability, Prev: String Extraction, Up: Translator i18n -Rearranging `printf' Arguments ------------------------------- +9.4.2 Rearranging `printf' Arguments +------------------------------------ - Format strings for `printf' and `sprintf' (*note Printf::) present a +Format strings for `printf' and `sprintf' (*note Printf::) present a special problem for translation. Consider the following:(1) printf(_"String `%s' has %d characters\n", string, length(string))) - A possible German translation for this might be: +A possible German translation for this might be: "%d Zeichen lang ist die Zeichenkette `%s'\n" - The problem should be obvious: the order of the format -specifications is different from the original! Even though `gettext' -can return the translated string at runtime, it cannot change the -argument order in the call to `printf'. +The problem should be obvious: the order of the format specifications +is different from the original! Even though `gettext' can return the +translated string at runtime, it cannot change the argument order in +the call to `printf'. - To solve this problem, `printf' format specificiers may have an +To solve this problem, `printf' format specificiers may have an additional optional element, which we call a "positional specifier". For example: "%2$d Zeichen lang ist die Zeichenkette `%1$s'\n" - Here, the positional specifier consists of an integer count, which +Here, the positional specifier consists of an integer count, which indicates which argument to use, and a `$'. Counts are one-based, and the format string itself is _not_ included. Thus, in the following example, `string' is the first argument and `length(string)' is the @@ -11084,10 +11214,10 @@ second: > }' -| 10 characters live in "Dont Panic" - If present, positional specifiers come first in the format +If present, positional specifiers come first in the format specification, before the flags, the field width, and/or the precision. - Positional specifiers can be used with the dynamic field width and +Positional specifiers can be used with the dynamic field width and precision capability: $ gawk 'BEGIN { @@ -11097,38 +11227,39 @@ precision capability: -| hello -| hello -*Note:* When using `*' with a positional specifier, the `*' comes -first, then the integer position, and then the `$'. This is somewhat -counterintutive. + NOTE: When using `*' with a positional specifier, the `*' comes + first, then the integer position, and then the `$'. This is + somewhat counterintutive. - `gawk' does not allow you to mix regular format specifiers and those +`gawk' does not allow you to mix regular format specifiers and those with positional specifiers in the same string: $ gawk 'BEGIN { printf _"%d %3$s\n", 1, 2, "hi" }' error--> gawk: cmd. line:1: fatal: must use `count$' on all formats or none - *Note:* There are some pathological cases that `gawk' may fail to -diagnose. In such cases, the output may not be what you expect. It's -still a bad idea to try mixing them, even if `gawk' doesn't detect it. + NOTE: There are some pathological cases that `gawk' may fail to + diagnose. In such cases, the output may not be what you expect. + It's still a bad idea to try mixing them, even if `gawk' doesn't + detect it. - Although positional specifiers can be used directly in `awk' -programs, their primary purpose is to help in producing correct -translations of format strings into languages different from the one in -which the program is first written. +Although positional specifiers can be used directly in `awk' programs, +their primary purpose is to help in producing correct translations of +format strings into languages different from the one in which the +program is first written. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) This example is borrowed from the GNU `gettext' manual. +(1) This example is borrowed from the GNU `gettext' manual. File: gawk.info, Node: I18N Portability, Prev: Printf Ordering, Up: Translator i18n -`awk' Portability Issues ------------------------- +9.4.3 `awk' Portability Issues +------------------------------ - `gawk''s internationalization features were purposely chosen to have -as little impact as possible on the portability of `awk' programs that -use them to other versions of `awk'. Consider this program: +`gawk''s internationalization features were purposely chosen to have as +little impact as possible on the portability of `awk' programs that use +them to other versions of `awk'. Consider this program: BEGIN { TEXTDOMAIN = "guide" @@ -11156,12 +11287,12 @@ actually almost portable, requiring very little change: { return dir } - + function dcgettext(string, domain, category) { return string } - + function dcngettext(string1, string2, number, domain, category) { return (number == 1 ? string1 : string2) @@ -11180,18 +11311,18 @@ actually almost portable, requiring very little change: retrieve the translated string, this should not be a problem in practice. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) This is good fodder for an "Obfuscated `awk'" contest. +(1) This is good fodder for an "Obfuscated `awk'" contest. File: gawk.info, Node: I18N Example, Next: Gawk I18N, Prev: Translator i18n, Up: Internationalization -A Simple Internationalization Example -===================================== +9.5 A Simple Internationalization Example +========================================= - Now let's look at a step-by-step example of how to internationalize -and localize a simple `awk' program, using `guide.awk' as our original +Now let's look at a step-by-step example of how to internationalize and +localize a simple `awk' program, using `guide.awk' as our original source: BEGIN { @@ -11211,19 +11342,19 @@ This produces: #: guide.awk:4 msgid "Don't Panic" msgstr "" - + #: guide.awk:5 msgid "The Answer Is" msgstr "" - This original portable object file is saved and reused for each -language into which the application is translated. The `msgid' is the -original string and the `msgstr' is the translation. +This original portable object file is saved and reused for each language +into which the application is translated. The `msgid' is the original +string and the `msgstr' is the translation. - *Note:* Strings not marked with a leading underscore do not appear -in the `guide.po' file. + NOTE: Strings not marked with a leading underscore do not appear + in the `guide.po' file. - Next, the messages must be translated. Here is a translation to a +Next, the messages must be translated. Here is a translation to a hypothetical dialect of English, called "Mellow":(1) $ cp guide.po guide-mellow.po @@ -11234,34 +11365,34 @@ Following are the translations: #: guide.awk:4 msgid "Don't Panic" msgstr "Hey man, relax!" - + #: guide.awk:5 msgid "The Answer Is" msgstr "Like, the scoop is" - The next step is to make the directory to hold the binary message -object file and then to create the `guide.mo' file. The directory -layout shown here is standard for GNU `gettext' on GNU/Linux systems. -Other versions of `gettext' may use a different layout: +The next step is to make the directory to hold the binary message object +file and then to create the `guide.mo' file. The directory layout +shown here is standard for GNU `gettext' on GNU/Linux systems. Other +versions of `gettext' may use a different layout: $ mkdir en_US en_US/LC_MESSAGES - The `msgfmt' utility does the conversion from human-readable `.po' -file to machine-readable `.mo' file. By default, `msgfmt' creates a -file named `messages'. This file must be renamed and placed in the -proper directory so that `gawk' can find it: +The `msgfmt' utility does the conversion from human-readable `.po' file +to machine-readable `.mo' file. By default, `msgfmt' creates a file +named `messages'. This file must be renamed and placed in the proper +directory so that `gawk' can find it: $ msgfmt guide-mellow.po $ mv messages en_US/LC_MESSAGES/guide.mo - Finally, we run the program to test it: +Finally, we run the program to test it: $ gawk -f guide.awk -| Hey man, relax! -| Like, the scoop is 42 -| Pardon me, Zaphod who? - If the three replacement functions for `dcgettext', `dcngettext' and +If the three replacement functions for `dcgettext', `dcngettext' and `bindtextdomain' (*note I18N Portability::) are in a file named `libintl.awk', then we can run `guide.awk' unchanged as follows: @@ -11270,50 +11401,50 @@ proper directory so that `gawk' can find it: -| The Answer Is 42 -| Pardon me, Zaphod who? - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Perhaps it would be better if it were called "Hippy." Ah, well. +(1) Perhaps it would be better if it were called "Hippy." Ah, well. File: gawk.info, Node: Gawk I18N, Prev: I18N Example, Up: Internationalization -`gawk' Can Speak Your Language -============================== +9.6 `gawk' Can Speak Your Language +================================== - As of version 3.1, `gawk' itself has been internationalized using -the GNU `gettext' package. (GNU `gettext' is described in complete -detail in *Note Top::.) As of this writing, the latest version of GNU +As of version 3.1, `gawk' itself has been internationalized using the +GNU `gettext' package. (GNU `gettext' is described in complete detail +in *Note Top::.) As of this writing, the latest version of GNU `gettext' is version 0.11.5 (ftp://ftp.gnu.org/gnu/gettext/gettext-0.11.5.tar.gz). - If a translation of `gawk''s messages exists, then `gawk' produces +If a translation of `gawk''s messages exists, then `gawk' produces usage messages, warnings, and fatal errors in the local language. - On systems that do not use version 2 (or later) of the GNU C -library, you should configure `gawk' with the `--with-included-gettext' -option before compiling and installing it. *Note Additional -Configuration Options::, for more information. +On systems that do not use version 2 (or later) of the GNU C library, +you should configure `gawk' with the `--with-included-gettext' option +before compiling and installing it. *Note Additional Configuration +Options::, for more information. File: gawk.info, Node: Advanced Features, Next: Invoking Gawk, Prev: Internationalization, Up: Top -Advanced Features of `gawk' -*************************** +10 Advanced Features of `gawk' +****************************** Write documentation as if whoever reads it is a violent psychopath who knows where you live. Steve English, as quoted by Peter Langston - This major node discusses advanced features in `gawk'. It's a bit -of a "grab bag" of items that are otherwise unrelated to each other. -First, a command-line option allows `gawk' to recognize nondecimal -numbers in input data, not just in `awk' programs. Next, two-way I/O, -discussed briefly in earlier parts of this Info file, is described in -full detail, along with the basics of TCP/IP networking and BSD portal +This major node discusses advanced features in `gawk'. It's a bit of a +"grab bag" of items that are otherwise unrelated to each other. First, +a command-line option allows `gawk' to recognize nondecimal numbers in +input data, not just in `awk' programs. Next, two-way I/O, discussed +briefly in earlier parts of this Info file, is described in full +detail, along with the basics of TCP/IP networking and BSD portal files. Finally, `gawk' can "profile" an `awk' program, making it possible to tune it for performance. - *Note Dynamic Extensions::, discusses the ability to dynamically add +*Note Dynamic Extensions::, discusses the ability to dynamically add new built-in functions to `gawk'. As this feature is still immature and likely to change, its description is relegated to an appendix. @@ -11328,10 +11459,10 @@ and likely to change, its description is relegated to an appendix. File: gawk.info, Node: Nondecimal Data, Next: Two-way I/O, Up: Advanced Features -Allowing Nondecimal Input Data -============================== +10.1 Allowing Nondecimal Input Data +=================================== - If you run `gawk' with the `--non-decimal-data' option, you can have +If you run `gawk' with the `--non-decimal-data' option, you can have nondecimal constants in your input data: $ echo 0123 123 0x123 | @@ -11339,8 +11470,8 @@ nondecimal constants in your input data: > $1, $2, $3 }' -| 83, 123, 291 - For this feature to work, write your program so that `gawk' treats -your data as numeric: +For this feature to work, write your program so that `gawk' treats your +data as numeric: $ echo 0123 123 0x123 | gawk '{ print $1, $2, $3 }' -| 0123 123 0x123 @@ -11356,12 +11487,12 @@ zero to a field to force it to be treated as a number. For example: -| 0123 123 0x123 -| 83 123 291 - Because it is common to have decimal data with leading zeros, and +Because it is common to have decimal data with leading zeros, and because using it could lead to surprising results, the default is to leave this facility disabled. If you want it, you must explicitly request it. - *Caution:* _Use of this option is not recommended._ It can break old +*Caution:* _Use of this option is not recommended._ It can break old programs very badly. Instead, use the `strtonum' function to convert your data (*note Nondecimal-numbers::). This makes your programs easier to write and easier to read, and leads to less surprising @@ -11370,27 +11501,27 @@ results. File: gawk.info, Node: Two-way I/O, Next: TCP/IP Networking, Prev: Nondecimal Data, Up: Advanced Features -Two-Way Communications with Another Process -=========================================== +10.2 Two-Way Communications with Another Process +================================================ From: brennan@whidbey.com (Mike Brennan) Newsgroups: comp.lang.awk Subject: Re: Learn the SECRET to Attract Women Easily Date: 4 Aug 1997 17:34:46 GMT Message-ID: <5s53rm$eca@news.whidbey.com> - + On 3 Aug 1997 13:17:43 GMT, Want More Dates??? <tracy78@kilgrona.com> wrote: >Learn the SECRET to Attract Women Easily > >The SCENT(tm) Pheromone Sex Attractant For Men to Attract Women - + The scent of awk programmers is a lot more attractive to women than the scent of perl programmers. -- Mike Brennan - It is often useful to be able to send data to a separate program for +It is often useful to be able to send data to a separate program for processing and then read the result. This can always be done with temporary files: @@ -11399,7 +11530,7 @@ temporary files: while (NOT DONE WITH DATA) print DATA | ("subprogram > " tempfile) close("subprogram > " tempfile) - + # read the results, remove tempfile when done while ((getline newdata < tempfile) > 0) PROCESS newdata APPROPRIATELY @@ -11411,11 +11542,11 @@ the program be run in a directory that cannot be shared among users; for example, `/tmp' will not do, as another user might happen to be using a temporary file with the same name. - Starting with version 3.1 of `gawk', it is possible to open a -_two-way_ pipe to another process. The second process is termed a -"coprocess", since it runs in parallel with `gawk'. The two-way -connection is created using the new `|&' operator (borrowed from the -Korn shell, `ksh'):(1) +Starting with version 3.1 of `gawk', it is possible to open a _two-way_ +pipe to another process. The second process is termed a "coprocess", +since it runs in parallel with `gawk'. The two-way connection is +created using the new `|&' operator (borrowed from the Korn shell, +`ksh'):(1) do { print DATA |& "subprogram" @@ -11423,7 +11554,7 @@ Korn shell, `ksh'):(1) } while (DATA LEFT TO PROCESS) close("subprogram") - The first time an I/O operation is executed using the `|&' operator, +The first time an I/O operation is executed using the `|&' operator, `gawk' creates a two-way pipeline to a child process that runs the other program. Output created with `print' or `printf' is written to the program's standard input, and output from the program's standard @@ -11431,7 +11562,7 @@ output can be read by the `gawk' program using `getline'. As is the case with processes started by `|', the subprogram can be any program, or pipeline of programs, that can be started by the shell. - There are some cautionary items to be aware of: +There are some cautionary items to be aware of: * As the code inside `gawk' currently stands, the coprocess's standard error goes to the same place that the parent `gawk''s @@ -11445,49 +11576,49 @@ or pipeline of programs, that can be started by the shell. lead to a situation known as "deadlock", where each process is waiting for the other one to do something. - It is possible to close just one end of the two-way pipe to a +It is possible to close just one end of the two-way pipe to a coprocess, by supplying a second argument to the `close' function of either `"to"' or `"from"' (*note Close Files And Pipes::). These strings tell `gawk' to close the end of the pipe that sends data to the process or the end that reads from it, respectively. - This is particularly necessary in order to use the system `sort' +This is particularly necessary in order to use the system `sort' utility as part of a coprocess; `sort' must read _all_ of its input data before it can produce any output. The `sort' program does not receive an end-of-file indication until `gawk' closes the write end of the pipe. - When you have finished writing data to the `sort' utility, you can +When you have finished writing data to the `sort' utility, you can close the `"to"' end of the pipe, and then start reading sorted data via `getline'. For example: BEGIN { command = "LC_ALL=C sort" n = split("abcdefghijklmnopqrstuvwxyz", a, "") - + for (i = n; i > 0; i--) print a[i] |& command close(command, "to") - + while ((command |& getline line) > 0) print "got", line close(command) } - This program writes the letters of the alphabet in reverse order, one +This program writes the letters of the alphabet in reverse order, one per line, down the two-way pipe to `sort'. It then closes the write end of the pipe, so that `sort' receives an end-of-file indication. This causes `sort' to sort the data and write the sorted data back to the `gawk' program. Once all of the data has been read, `gawk' terminates the coprocess and exits. - As a side note, the assignment `LC_ALL=C' in the `sort' command -ensures traditional Unix (ASCII) sorting from `sort'. +As a side note, the assignment `LC_ALL=C' in the `sort' command ensures +traditional Unix (ASCII) sorting from `sort'. - Beginning with `gawk' 3.1.2, you may use Pseudo-ttys (ptys) for -two-way communication instead of pipes, if your system supports them. -This is done on a per-command basis, by setting a special element in -the `PROCINFO' array (*note Auto-set::), like so: +Beginning with `gawk' 3.1.2, you may use Pseudo-ttys (ptys) for two-way +communication instead of pipes, if your system supports them. This is +done on a per-command basis, by setting a special element in the +`PROCINFO' array (*note Auto-set::), like so: command = "sort -nr" # command, saved in variable for convenience PROCINFO[command, "pty"] = 1 # update PROCINFO @@ -11499,33 +11630,32 @@ loss in performance. If your system does not have ptys, or if all the system's ptys are in use, `gawk' automatically falls back to using regular pipes. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) This is very different from the same operator in the C shell, -`csh'. +(1) This is very different from the same operator in the C shell, `csh'. File: gawk.info, Node: TCP/IP Networking, Next: Portal Files, Prev: Two-way I/O, Up: Advanced Features -Using `gawk' for Network Programming -==================================== +10.3 Using `gawk' for Network Programming +========================================= `EMISTERED': A host is a host from coast to coast, and no-one can talk to host that's close, unless the host that isn't close is busy hung or dead. - In addition to being able to open a two-way pipeline to a coprocess -on the same system (*note Two-way I/O::), it is possible to make a -two-way connection to another process on another system across an IP -networking connection. +In addition to being able to open a two-way pipeline to a coprocess on +the same system (*note Two-way I/O::), it is possible to make a two-way +connection to another process on another system across an IP networking +connection. - You can think of this as just a _very long_ two-way pipeline to a +You can think of this as just a _very long_ two-way pipeline to a coprocess. The way `gawk' decides that you want to use TCP/IP networking is by recognizing special file names that begin with `/inet/'. - The full syntax of the special file name is +The full syntax of the special file name is `/inet/PROTOCOL/LOCAL-PORT/REMOTE-HOST/REMOTE-PORT'. The components are: @@ -11554,7 +11684,7 @@ REMOTE-PORT Again, use `0' if you don't care, or else a well-known service name. - Consider the following very simple example: +Consider the following very simple example: BEGIN { Service = "/inet/tcp/0/localhost/daytime" @@ -11563,25 +11693,25 @@ REMOTE-PORT close(Service) } - This program reads the current date and time from the local system's +This program reads the current date and time from the local system's TCP `daytime' server. It then prints the results and closes the connection. - Because this topic is extensive, the use of `gawk' for TCP/IP +Because this topic is extensive, the use of `gawk' for TCP/IP programming is documented separately. *Note Top::, for a much more complete introduction and discussion, as well as extensive examples. File: gawk.info, Node: Portal Files, Next: Profiling, Prev: TCP/IP Networking, Up: Advanced Features -Using `gawk' with BSD Portals -============================= +10.4 Using `gawk' with BSD Portals +================================== - Similar to the `/inet' special files, if `gawk' is configured with -the `--enable-portals' option (*note Quick Installation::), then `gawk' +Similar to the `/inet' special files, if `gawk' is configured with the +`--enable-portals' option (*note Quick Installation::), then `gawk' treats files whose pathnames begin with `/p' as 4.4 BSD-style portals. - When used with the `|&' operator, `gawk' opens the file for two-way +When used with the `|&' operator, `gawk' opens the file for two-way communications. The operating system's portal mechanism then manages creating the process associated with the portal and the corresponding communications with the portal's process. @@ -11589,28 +11719,27 @@ communications with the portal's process. File: gawk.info, Node: Profiling, Prev: Portal Files, Up: Advanced Features -Profiling Your `awk' Programs -============================= +10.5 Profiling Your `awk' Programs +================================== - Beginning with version 3.1 of `gawk', you may produce execution -traces of your `awk' programs. This is done with a specially compiled -version of `gawk', called `pgawk' ("profiling `gawk'"). +Beginning with version 3.1 of `gawk', you may produce execution traces +of your `awk' programs. This is done with a specially compiled version +of `gawk', called `pgawk' ("profiling `gawk'"). - `pgawk' is identical in every way to `gawk', except that when it has +`pgawk' is identical in every way to `gawk', except that when it has finished running, it creates a profile of your program in a file named `awkprof.out'. Because it is profiling, it also executes up to 45% slower than `gawk' normally does. - As shown in the following example, the `--profile' option can be -used to change the name of the file where `pgawk' will write the -profile: +As shown in the following example, the `--profile' option can be used +to change the name of the file where `pgawk' will write the profile: $ pgawk --profile=myprog.prof -f myprog.awk data1 data2 In the above example, `pgawk' places the profile in `myprog.prof' instead of in `awkprof.out'. - Regular `gawk' also accepts this option. When called with just +Regular `gawk' also accepts this option. When called with just `--profile', `gawk' "pretty prints" the program into `awkprof.out', without any execution counts. You may supply an option to `--profile' to change the file name. Here is a sample session showing a simple @@ -11618,32 +11747,32 @@ to change the file name. Here is a sample session showing a simple First, the `awk' program: BEGIN { print "First BEGIN rule" } - + END { print "First END rule" } - + /foo/ { print "matched /foo/, gosh" for (i = 1; i <= 3; i++) sing() } - + { if (/foo/) print "if is true" else print "else is true" } - + BEGIN { print "Second BEGIN rule" } - + END { print "Second END rule" } - + function sing( dummy) { print "I gotta be me!" } - Following is the input data: +Following is the input data: foo bar @@ -11651,28 +11780,28 @@ First, the `awk' program: foo junk - Here is the `awkprof.out' that results from running `pgawk' on this +Here is the `awkprof.out' that results from running `pgawk' on this program and data (this example also illustrates that `awk' programmers sometimes have to work late): # gawk profile, created Sun Aug 13 00:00:15 2000 - + # BEGIN block(s) - + BEGIN { 1 print "First BEGIN rule" 1 print "Second BEGIN rule" } - + # Rule(s) - + 5 /foo/ { # 2 2 print "matched /foo/, gosh" 6 for (i = 1; i <= 3; i++) { 6 sing() } } - + 5 { 5 if (/foo/) { # 2 2 print "if is true" @@ -11680,23 +11809,23 @@ sometimes have to work late): 3 print "else is true" } } - + # END block(s) - + END { 1 print "First END rule" 1 print "Second END rule" } - + # Functions, listed alphabetically - + 6 function sing(dummy) { 6 print "I gotta be me!" } - This example illustrates many of the basic rules for profiling -output. The rules are as follows: +This example illustrates many of the basic rules for profiling output. +The rules are as follows: * The program is printed in the order `BEGIN' rule, pattern/action rules, `END' rule and functions, listed alphabetically. Multiple @@ -11748,13 +11877,13 @@ output. The rules are as follows: `END' rules, the pattern/action rules, and the functions. - The profiled version of your program may not look exactly like what -you typed when you wrote it. This is because `pgawk' creates the -profiled version by "pretty printing" its internal representation of -the program. The advantage to this is that `pgawk' can produce a -standard representation. The disadvantage is that all source-code -comments are lost, as are the distinctions among multiple `BEGIN' and -`END' rules. Also, things such as: +The profiled version of your program may not look exactly like what you +typed when you wrote it. This is because `pgawk' creates the profiled +version by "pretty printing" its internal representation of the +program. The advantage to this is that `pgawk' can produce a standard +representation. The disadvantage is that all source-code comments are +lost, as are the distinctions among multiple `BEGIN' and `END' rules. +Also, things such as: /foo/ @@ -11766,7 +11895,7 @@ come out as: which is correct, but possibly surprising. - Besides creating profiles when a program has completed, `pgawk' can +Besides creating profiles when a program has completed, `pgawk' can produce a profile while it is running. This is useful if your `awk' program goes into an infinite loop and you want to see what has been executed. To use this feature, run `pgawk' in the background: @@ -11782,45 +11911,45 @@ The shell prints a job number and process ID number; in this case, As usual, the profiled version of the program is written to `awkprof.out', or to a different file if you use the `--profile' option. - Along with the regular profile, as shown earlier, the profile -includes a trace of any active functions: +Along with the regular profile, as shown earlier, the profile includes +a trace of any active functions: # Function Call Stack: - + # 3. baz # 2. bar # 1. foo # -- main -- - You may send `pgawk' the `USR1' signal as many times as you like. -Each time, the profile and function call trace are appended to the -output profile file. +You may send `pgawk' the `USR1' signal as many times as you like. Each +time, the profile and function call trace are appended to the output +profile file. - If you use the `HUP' signal instead of the `USR1' signal, `pgawk' +If you use the `HUP' signal instead of the `USR1' signal, `pgawk' produces the profile and the function call trace and then exits. - When `pgawk' runs on MS-DOS or MS-Windows, it uses the `INT' and -`QUIT' signals for producing the profile and, in the case of the `INT' -signal, `pgawk' exits. This is because these systems don't support the -`kill' command, so the only signals you can deliver to a program are -those generated by the keyboard. The `INT' signal is generated by the +When `pgawk' runs on MS-DOS or MS-Windows, it uses the `INT' and `QUIT' +signals for producing the profile and, in the case of the `INT' signal, +`pgawk' exits. This is because these systems don't support the `kill' +command, so the only signals you can deliver to a program are those +generated by the keyboard. The `INT' signal is generated by the `Ctrl-<C>' or `Ctrl-<BREAK>' key, while the `QUIT' signal is generated by the `Ctrl-<\>' key. File: gawk.info, Node: Invoking Gawk, Next: Library Functions, Prev: Advanced Features, Up: Top -Running `awk' and `gawk' -************************ +11 Running `awk' and `gawk' +*************************** - This major node covers how to run awk, both POSIX-standard and +This major node covers how to run awk, both POSIX-standard and `gawk'-specific command-line options, and what `awk' and `gawk' do with non-option arguments. It then proceeds to cover how `gawk' searches for source files, obsolete options and/or features, and known bugs in `gawk'. This major node rounds out the discussion of `awk' as a program and as a language. - While a number of the options and features described here were +While a number of the options and features described here were discussed in passing earlier in the book, this major node provides the full details. @@ -11838,20 +11967,20 @@ full details. File: gawk.info, Node: Command Line, Next: Options, Up: Invoking Gawk -Invoking `awk' -============== +11.1 Invoking `awk' +=================== - There are two ways to run `awk'--with an explicit program or with -one or more program files. Here are templates for both of them; items +There are two ways to run `awk'--with an explicit program or with one +or more program files. Here are templates for both of them; items enclosed in [...] in these templates are optional: awk [OPTIONS] -f progfile [`--'] FILE ... awk [OPTIONS] [`--'] 'PROGRAM' FILE ... - Besides traditional one-letter POSIX-style options, `gawk' also +Besides traditional one-letter POSIX-style options, `gawk' also supports GNU long options. - It is possible to invoke `awk' with an empty program: +It is possible to invoke `awk' with an empty program: awk '' datafile1 datafile2 @@ -11862,19 +11991,19 @@ line, `gawk' issues a warning that the program is empty. File: gawk.info, Node: Options, Next: Other Arguments, Prev: Command Line, Up: Invoking Gawk -Command-Line Options -==================== +11.2 Command-Line Options +========================= - Options begin with a dash and consist of a single character. -GNU-style long options consist of two dashes and a keyword. The -keyword can be abbreviated, as long as the abbreviation allows the -option to be uniquely identified. If the option takes an argument, -then the keyword is either immediately followed by an equals sign (`=') -and the argument's value, or the keyword and the argument's value are -separated by whitespace. If a particular option with a value is given -more than once, it is the last value that counts. +Options begin with a dash and consist of a single character. GNU-style +long options consist of two dashes and a keyword. The keyword can be +abbreviated, as long as the abbreviation allows the option to be +uniquely identified. If the option takes an argument, then the keyword +is either immediately followed by an equals sign (`=') and the +argument's value, or the keyword and the argument's value are separated +by whitespace. If a particular option with a value is given more than +once, it is the last value that counts. - Each long option for `gawk' has a corresponding POSIX-style option. +Each long option for `gawk' has a corresponding POSIX-style option. The long and short options are interchangeable in all contexts. The options and their meanings are as follows: @@ -11930,8 +12059,8 @@ options and their meanings are as follows: shell scripts, if you have file names that will be specified by the user that could start with `-'. - The previous list described options mandated by the POSIX standard, -as well as options available in the Bell Laboratories version of `awk'. +The previous list described options mandated by the POSIX standard, as +well as options available in the Bell Laboratories version of `awk'. The following list describes `gawk'-specific options: `-W compat' @@ -12074,40 +12203,40 @@ The following list describes `gawk'-specific options: with respect to whatever the Free Software Foundation is currently distributing. It is also useful for bug reports (*note Bugs::). - As long as program text has been supplied, any other options are +As long as program text has been supplied, any other options are flagged as invalid with a warning message but are otherwise ignored. - In compatibility mode, as a special case, if the value of FS supplied +In compatibility mode, as a special case, if the value of FS supplied to the `-F' option is `t', then `FS' is set to the TAB character (`"\t"'). This is true only for `--traditional' and not for `--posix' (*note Field Separators::). - The `-f' option may be used more than once on the command line. If -it is, `awk' reads its program source from all of the named files, as -if they had been concatenated together into one big file. This is -useful for creating libraries of `awk' functions. These functions can -be written once and then retrieved from a standard place, instead of +The `-f' option may be used more than once on the command line. If it +is, `awk' reads its program source from all of the named files, as if +they had been concatenated together into one big file. This is useful +for creating libraries of `awk' functions. These functions can be +written once and then retrieved from a standard place, instead of having to be included into each individual program. (As mentioned in *Note Definition Syntax::, function names must be unique.) - Library functions can still be used, even if the program is entered -at the terminal, by specifying `-f /dev/tty'. After typing your -program, type `Ctrl-d' (the end-of-file character) to terminate it. -(You may also use `-f -' to read program source from the standard input -but then you will not be able to also use the standard input as a -source of data.) +Library functions can still be used, even if the program is entered at +the terminal, by specifying `-f /dev/tty'. After typing your program, +type `Ctrl-d' (the end-of-file character) to terminate it. (You may +also use `-f -' to read program source from the standard input but then +you will not be able to also use the standard input as a source of +data.) - Because it is clumsy using the standard `awk' mechanisms to mix -source file and command-line `awk' programs, `gawk' provides the -`--source' option. This does not require you to pre-empt the standard -input for your source code; it allows you to easily mix command-line -and library source code (*note AWKPATH Variable::). +Because it is clumsy using the standard `awk' mechanisms to mix source +file and command-line `awk' programs, `gawk' provides the `--source' +option. This does not require you to pre-empt the standard input for +your source code; it allows you to easily mix command-line and library +source code (*note AWKPATH Variable::). - If no `-f' or `--source' option is specified, then `gawk' uses the +If no `-f' or `--source' option is specified, then `gawk' uses the first non-option command-line argument as the text of the program source code. - If the environment variable `POSIXLY_CORRECT' exists, then `gawk' +If the environment variable `POSIXLY_CORRECT' exists, then `gawk' behaves in strict POSIX mode, exactly as if you had supplied the `--posix' command-line option. Many GNU programs look for this environment variable to turn on strict POSIX mode. If `--lint' is @@ -12120,54 +12249,54 @@ you would add these lines to the `.profile' file in your home directory: POSIXLY_CORRECT=true export POSIXLY_CORRECT - For a `csh'-compatible shell,(1) you would add this line to the +For a `csh'-compatible shell,(1) you would add this line to the `.login' file in your home directory: setenv POSIXLY_CORRECT true - Having `POSIXLY_CORRECT' set is not recommended for daily use, but -it is good for testing the portability of your programs to other +Having `POSIXLY_CORRECT' set is not recommended for daily use, but it +is good for testing the portability of your programs to other environments. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Not recommended. +(1) Not recommended. File: gawk.info, Node: Other Arguments, Next: AWKPATH Variable, Prev: Options, Up: Invoking Gawk -Other Command-Line Arguments -============================ +11.3 Other Command-Line Arguments +================================= - Any additional arguments on the command line are normally treated as +Any additional arguments on the command line are normally treated as input files to be processed in the order specified. However, an argument that has the form `VAR=VALUE', assigns the value VALUE to the variable VAR--it does not specify a file at all. (This was discussed earlier in *Note Assignment Options::.) - All these arguments are made available to your `awk' program in the +All these arguments are made available to your `awk' program in the `ARGV' array (*note Built-in Variables::). Command-line options and the program text (if present) are omitted from `ARGV'. All other arguments, including variable assignments, are included. As each element of `ARGV' is processed, `gawk' sets the variable `ARGIND' to the index in `ARGV' of the current element. - The distinction between file name arguments and variable-assignment +The distinction between file name arguments and variable-assignment arguments is made when `awk' is about to open the next input file. At that point in execution, it checks the file name to see whether it is really a variable assignment; if so, `awk' sets the variable instead of reading a file. - Therefore, the variables actually receive the given values after all +Therefore, the variables actually receive the given values after all previously specified files have been read. In particular, the values of variables assigned in this fashion are _not_ available inside a `BEGIN' rule (*note BEGIN/END::), because such rules are run before `awk' begins scanning the argument list. - The variable values given on the command line are processed for -escape sequences (*note Escape Sequences::). (d.c.) +The variable values given on the command line are processed for escape +sequences (*note Escape Sequences::). (d.c.) - In some earlier implementations of `awk', when a variable assignment +In some earlier implementations of `awk', when a variable assignment occurred before any file names, the assignment would happen _before_ the `BEGIN' rule was executed. `awk''s behavior was thus inconsistent; some command-line assignments were available inside the `BEGIN' rule, @@ -12176,7 +12305,7 @@ upon this "feature." When `awk' was changed to be more consistent, the `-v' option was added to accommodate applications that depended upon the old behavior. - The variable assignment feature is most useful for assigning to +The variable assignment feature is most useful for assigning to variables such as `RS', `OFS', and `ORS', which control input and output formats before scanning the data files. It is also useful for controlling state if multiple passes are needed over a data file. For @@ -12185,66 +12314,66 @@ example: awk 'pass == 1 { PASS 1 STUFF } pass == 2 { PASS 2 STUFF }' pass=1 mydata pass=2 mydata - Given the variable assignment feature, the `-F' option for setting -the value of `FS' is not strictly necessary. It remains for historical +Given the variable assignment feature, the `-F' option for setting the +value of `FS' is not strictly necessary. It remains for historical compatibility. File: gawk.info, Node: AWKPATH Variable, Next: Obsolete, Prev: Other Arguments, Up: Invoking Gawk -The `AWKPATH' Environment Variable -================================== +11.4 The `AWKPATH' Environment Variable +======================================= - The previous minor node described how `awk' program files can be -named on the command-line with the `-f' option. In most `awk' +The previous minor node described how `awk' program files can be named +on the command-line with the `-f' option. In most `awk' implementations, you must supply a precise path name for each program file, unless the file is in the current directory. But in `gawk', if the file name supplied to the `-f' option does not contain a `/', then `gawk' searches a list of directories (called the "search path"), one by one, looking for a file with the specified name. - The search path is a string consisting of directory names separated -by colons. `gawk' gets its search path from the `AWKPATH' environment +The search path is a string consisting of directory names separated by +colons. `gawk' gets its search path from the `AWKPATH' environment variable. If that variable does not exist, `gawk' uses a default path, `.:/usr/local/share/awk'.(1) (Programs written for use by system administrators should use an `AWKPATH' variable that does not include the current directory, `.'.) - The search path feature is particularly useful for building libraries +The search path feature is particularly useful for building libraries of useful `awk' functions. The library files can be placed in a standard directory in the default path and then specified on the command line with a short file name. Otherwise, the full file name would have to be typed for each file. - By using both the `--source' and `-f' options, your command-line -`awk' programs can use facilities in `awk' library files (*note Library +By using both the `--source' and `-f' options, your command-line `awk' +programs can use facilities in `awk' library files (*note Library Functions::). Path searching is not done if `gawk' is in compatibility mode. This is true for both `--traditional' and `--posix'. *Note Options::. - *Note:* If you want files in the current directory to be found, you -must include the current directory in the path, either by including `.' -explicitly in the path or by writing a null entry in the path. (A null -entry is indicated by starting or ending the path with a colon or by -placing two colons next to each other (`::').) If the current -directory is not included in the path, then files cannot be found in -the current directory. This path search mechanism is identical to the -shell's. + NOTE: If you want files in the current directory to be found, you + must include the current directory in the path, either by including + `.' explicitly in the path or by writing a null entry in the path. + (A null entry is indicated by starting or ending the path with a + colon or by placing two colons next to each other (`::').) If the + current directory is not included in the path, then files cannot be + found in the current directory. This path search mechanism is + identical to the shell's. - Starting with version 3.0, if `AWKPATH' is not defined in the +Starting with version 3.0, if `AWKPATH' is not defined in the environment, `gawk' places its default search path into `ENVIRON["AWKPATH"]'. This makes it easy to determine the actual search path that `gawk' will use from within an `awk' program. - While you can change `ENVIRON["AWKPATH"]' within your `awk' program, +While you can change `ENVIRON["AWKPATH"]' within your `awk' program, this has no effect on the running program's behavior. This makes sense: the `AWKPATH' environment variable is used to find the program source files. Once your program is running, all the files have been found, and `gawk' no longer needs to use `AWKPATH'. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Your version of `gawk' may use a different directory; it will +(1) Your version of `gawk' may use a different directory; it will depend upon how `gawk' was built and installed. The actual directory is the value of `$(datadir)' generated when `gawk' was configured. You probably don't need to worry about this, though. @@ -12252,42 +12381,41 @@ probably don't need to worry about this, though. File: gawk.info, Node: Obsolete, Next: Undocumented, Prev: AWKPATH Variable, Up: Invoking Gawk -Obsolete Options and/or Features -================================ +11.5 Obsolete Options and/or Features +===================================== - This minor node describes features and/or command-line options from +This minor node describes features and/or command-line options from previous releases of `gawk' that are either not available in the current version or that are still supported but deprecated (meaning that they will _not_ be in the next release). - For version 3.1 of `gawk', there are no deprecated command-line -options from the previous version of `gawk'. The use of `next file' -(two words) for `nextfile' was deprecated in `gawk' 3.0 but still -worked. Starting with version 3.1, the two-word usage is no longer -accepted. +For version 3.1 of `gawk', there are no deprecated command-line options +from the previous version of `gawk'. The use of `next file' (two +words) for `nextfile' was deprecated in `gawk' 3.0 but still worked. +Starting with version 3.1, the two-word usage is no longer accepted. - The process-related special files described in *Note Special -Process::, work as described, but are now considered deprecated. -`gawk' prints a warning message every time they are used. (Use -`PROCINFO' instead; see *Note Auto-set::.) They will be removed from -the next release of `gawk'. +The process-related special files described in *Note Special Process::, +work as described, but are now considered deprecated. `gawk' prints a +warning message every time they are used. (Use `PROCINFO' instead; see +*Note Auto-set::.) They will be removed from the next release of +`gawk'. File: gawk.info, Node: Undocumented, Next: Known Bugs, Prev: Obsolete, Up: Invoking Gawk -Undocumented Options and Features -================================= +11.6 Undocumented Options and Features +====================================== Use the Source, Luke! Obi-Wan - This minor node intentionally left blank. +This minor node intentionally left blank. File: gawk.info, Node: Known Bugs, Prev: Undocumented, Up: Invoking Gawk -Known Bugs in `gawk' -==================== +11.7 Known Bugs in `gawk' +========================= * The `-F' option for changing the value of `FS' (*note Options::) is not necessary given the command-line variable assignment @@ -12301,47 +12429,47 @@ Known Bugs in `gawk' File: gawk.info, Node: Library Functions, Next: Sample Programs, Prev: Invoking Gawk, Up: Top -A Library of `awk' Functions -**************************** +12 A Library of `awk' Functions +******************************* - *Note User-defined::, describes how to write your own `awk' -functions. Writing functions is important, because it allows you to -encapsulate algorithms and program tasks in a single place. It -simplifies programming, making program development more manageable, and -making programs more readable. +*Note User-defined::, describes how to write your own `awk' functions. +Writing functions is important, because it allows you to encapsulate +algorithms and program tasks in a single place. It simplifies +programming, making program development more manageable, and making +programs more readable. - One valuable way to learn a new programming language is to _read_ +One valuable way to learn a new programming language is to _read_ programs in that language. To that end, this major node and *Note Sample Programs::, provide a good-sized body of code for you to read, and hopefully, to learn from. - This major node presents a library of useful `awk' functions. Many -of the sample programs presented later in this Info file use these +This major node presents a library of useful `awk' functions. Many of +the sample programs presented later in this Info file use these functions. The functions are presented here in a progression from simple to complex. - *Note Extract Program::, presents a program that you can use to -extract the source code for these example library functions and -programs from the Texinfo source for this Info file. (This has already -been done as part of the `gawk' distribution.) +*Note Extract Program::, presents a program that you can use to extract +the source code for these example library functions and programs from +the Texinfo source for this Info file. (This has already been done as +part of the `gawk' distribution.) - If you have written one or more useful, general-purpose `awk' -functions and would like to contribute them to the author's collection -of `awk' programs, see *Note How To Contribute::, for more information. +If you have written one or more useful, general-purpose `awk' functions +and would like to contribute them to the author's collection of `awk' +programs, see *Note How To Contribute::, for more information. - The programs in this major node and in *Note Sample Programs::, -freely use features that are `gawk'-specific. Rewriting these programs -for different implementations of awk is pretty straightforward. +The programs in this major node and in *Note Sample Programs::, freely +use features that are `gawk'-specific. Rewriting these programs for +different implementations of awk is pretty straightforward. - Diagnostic error messages are sent to `/dev/stderr'. Use `| "cat +Diagnostic error messages are sent to `/dev/stderr'. Use `| "cat 1>&2"' instead of `> "/dev/stderr"' if your system does not have a `/dev/stderr', or if you cannot use `gawk'. - A number of programs use `nextfile' (*note Nextfile Statement::) to +A number of programs use `nextfile' (*note Nextfile Statement::) to skip any remaining input in the input file. *Note Nextfile Function::, shows you how to write a function that does the same thing. - Finally, some of the programs choose to ignore upper- and lowercase +Finally, some of the programs choose to ignore upper- and lowercase distinctions in their input. They do so by assigning one to `IGNORECASE'. You can achieve almost the same effect(1) by adding the following rule to the beginning of the program: @@ -12364,42 +12492,42 @@ use only lowercase letters. * Passwd Functions:: Functions for getting user information. * Group Functions:: Functions for getting group information. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) The effects are not identical. Output of the transformed record +(1) The effects are not identical. Output of the transformed record will be in all lowercase, while `IGNORECASE' preserves the original contents of the input record. File: gawk.info, Node: Library Names, Next: General Functions, Up: Library Functions -Naming Library Function Global Variables -======================================== +12.1 Naming Library Function Global Variables +============================================= - Due to the way the `awk' language evolved, variables are either +Due to the way the `awk' language evolved, variables are either "global" (usable by the entire program) or "local" (usable just by a specific function). There is no intermediate state analogous to `static' variables in C. - Library functions often need to have global variables that they can -use to preserve state information between calls to the function--for +Library functions often need to have global variables that they can use +to preserve state information between calls to the function--for example, `getopt''s variable `_opti' (*note Getopt Function::). Such variables are called "private", since the only functions that need to use them are the ones in the library. - When writing a library function, you should try to choose names for -your private variables that will not conflict with any variables used by +When writing a library function, you should try to choose names for your +private variables that will not conflict with any variables used by either another library function or a user's main program. For example, a name like `i' or `j' is not a good choice, because user programs often use variable names like these for their own purposes. - The example programs shown in this major node all start the names of +The example programs shown in this major node all start the names of their private variables with an underscore (`_'). Users generally don't use leading underscores in their variable names, so this convention immediately decreases the chances that the variable name will be accidentally shared with the user's program. - In addition, several of the library functions use a prefix that helps +In addition, several of the library functions use a prefix that helps indicate what function or set of functions use the variables--for example, `_pw_byname' in the user database routines (*note Passwd Functions::). This convention is recommended, since it even further @@ -12407,18 +12535,18 @@ decreases the chance of inadvertent conflict among variable names. Note that this convention is used equally well for variable names and for private function names as well.(1) - As a final note on variable naming, if a function makes global -variables available for use by a main program, it is a good convention -to start that variable's name with a capital letter--for example, -`getopt''s `Opterr' and `Optind' variables (*note Getopt Function::). -The leading capital letter indicates that it is global, while the fact -that the variable name is not all capital letters indicates that the -variable is not one of `awk''s built-in variables, such as `FS'. +As a final note on variable naming, if a function makes global variables +available for use by a main program, it is a good convention to start +that variable's name with a capital letter--for example, `getopt''s +`Opterr' and `Optind' variables (*note Getopt Function::). The leading +capital letter indicates that it is global, while the fact that the +variable name is not all capital letters indicates that the variable is +not one of `awk''s built-in variables, such as `FS'. - It is also important that _all_ variables in library functions that -do not need to save state are, in fact, declared local.(2) If this is -not done, the variable could accidentally be used in the user's -program, leading to bugs that are very difficult to track down: +It is also important that _all_ variables in library functions that do +not need to save state are, in fact, declared local.(2) If this is not +done, the variable could accidentally be used in the user's program, +leading to bugs that are very difficult to track down: function lib_func(x, y, l1, l2) { @@ -12427,42 +12555,43 @@ program, leading to bugs that are very difficult to track down: ... # but is not by oversight } - A different convention, common in the Tcl community, is to use a -single associative array to hold the values needed by the library -function(s), or "package." This significantly decreases the number of -actual global names in use. For example, the functions described in -*Note Passwd Functions::, might have used array elements -`PW_data["inited"]', `PW_data["total"]', `PW_data["count"]', and -`PW_data["awklib"]', instead of `_pw_inited', `_pw_awklib', `_pw_total', -and `_pw_count'. +A different convention, common in the Tcl community, is to use a single +associative array to hold the values needed by the library function(s), +or "package." This significantly decreases the number of actual global +names in use. For example, the functions described in *Note Passwd +Functions::, might have used array elements `PW_data["inited"]', +`PW_data["total"]', `PW_data["count"]', and `PW_data["awklib"]', +instead of `_pw_inited', `_pw_awklib', `_pw_total', and `_pw_count'. - The conventions presented in this minor node are exactly that: +The conventions presented in this minor node are exactly that: conventions. You are not required to write your programs this way--we merely recommend that you do so. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) While all the library routines could have been rewritten to use +(1) While all the library routines could have been rewritten to use this convention, this was not done, in order to show how my own `awk' programming style has evolved and to provide some basis for this discussion. - (2) `gawk''s `--dump-variables' command-line option is useful for +(2) `gawk''s `--dump-variables' command-line option is useful for verifying this. File: gawk.info, Node: General Functions, Next: Data File Management, Prev: Library Names, Up: Library Functions -General Programming -=================== +12.2 General Programming +======================== - This minor node presents a number of functions that are of general +This minor node presents a number of functions that are of general programming use. * Menu: * Nextfile Function:: Two implementations of a `nextfile' function. +* Strtonum Function:: A replacement for the built-in `strtonum' + function. * Assert Function:: A function for assertions in `awk' programs. * Round Function:: A function for rounding if `sprintf' does @@ -12474,44 +12603,44 @@ programming use. * Gettimeofday Function:: A function to get formatted times. -File: gawk.info, Node: Nextfile Function, Next: Assert Function, Up: General Functions +File: gawk.info, Node: Nextfile Function, Next: Strtonum Function, Up: General Functions -Implementing `nextfile' as a Function -------------------------------------- +12.2.1 Implementing `nextfile' as a Function +-------------------------------------------- - The `nextfile' statement, presented in *Note Nextfile Statement::, -is a `gawk'-specific extension--it is not available in most other +The `nextfile' statement, presented in *Note Nextfile Statement::, is a +`gawk'-specific extension--it is not available in most other implementations of `awk'. This minor node shows two versions of a `nextfile' function that you can use to simulate `gawk''s `nextfile' statement if you cannot use `gawk'. - A first attempt at writing a `nextfile' function is as follows: +A first attempt at writing a `nextfile' function is as follows: # nextfile --- skip remaining records in current file # this should be read in before the "main" awk program - + function nextfile() { _abandon_ = FILENAME; next } _abandon_ == FILENAME { next } - Because it supplies a rule that must be executed first, this file -should be included before the main program. This rule compares the -current data file's name (which is always in the `FILENAME' variable) to -a private variable named `_abandon_'. If the file name matches, then -the action part of the rule executes a `next' statement to go on to the +Because it supplies a rule that must be executed first, this file should +be included before the main program. This rule compares the current +data file's name (which is always in the `FILENAME' variable) to a +private variable named `_abandon_'. If the file name matches, then the +action part of the rule executes a `next' statement to go on to the next record. (The use of `_' in the variable name is a convention. It is discussed more fully in *Note Library Names::.) - The use of the `next' statement effectively creates a loop that reads +The use of the `next' statement effectively creates a loop that reads all the records from the current data file. The end of the file is eventually reached and a new data file is opened, changing the value of `FILENAME'. Once this happens, the comparison of `_abandon_' to `FILENAME' fails, and execution continues with the first rule of the "real" program. - The `nextfile' function itself simply sets the value of `_abandon_' -and then executes a `next' statement to start the loop. +The `nextfile' function itself simply sets the value of `_abandon_' and +then executes a `next' statement to start the loop. - This initial version has a subtle problem. If the same data file is +This initial version has a subtle problem. If the same data file is listed _twice_ on the commandline, one right after the other or even with just a variable assignment between them, this code skips right through the file a second time, even though it should stop when it gets @@ -12521,9 +12650,9 @@ that remedies this problem is shown here: # nextfile --- skip remaining records in current file # correctly handle successive occurrences of the same file # this should be read in before the "main" awk program - + function nextfile() { _abandon_ = FILENAME; next } - + _abandon_ == FILENAME { if (FNR == 1) _abandon_ = "" @@ -12531,24 +12660,24 @@ that remedies this problem is shown here: next } - The `nextfile' function has not changed. It makes `_abandon_' equal -to the current file name and then executes a `next' statement. The -`next' statement reads the next record and increments `FNR' so that -`FNR' is guaranteed to have a value of at least two. However, if -`nextfile' is called for the last record in the file, then `awk' closes -the current data file and moves on to the next one. Upon doing so, -`FILENAME' is set to the name of the new file and `FNR' is reset to -one. If this next file is the same as the previous one, `_abandon_' is -still equal to `FILENAME'. However, `FNR' is equal to one, telling us -that this is a new occurrence of the file and not the one we were -reading when the `nextfile' function was executed. In that case, -`_abandon_' is reset to the empty string, so that further executions of -this rule fail (until the next time that `nextfile' is called). - - If `FNR' is not one, then we are still in the original data file and +The `nextfile' function has not changed. It makes `_abandon_' equal to +the current file name and then executes a `next' statement. The `next' +statement reads the next record and increments `FNR' so that `FNR' is +guaranteed to have a value of at least two. However, if `nextfile' is +called for the last record in the file, then `awk' closes the current +data file and moves on to the next one. Upon doing so, `FILENAME' is +set to the name of the new file and `FNR' is reset to one. If this +next file is the same as the previous one, `_abandon_' is still equal +to `FILENAME'. However, `FNR' is equal to one, telling us that this is +a new occurrence of the file and not the one we were reading when the +`nextfile' function was executed. In that case, `_abandon_' is reset +to the empty string, so that further executions of this rule fail +(until the next time that `nextfile' is called). + +If `FNR' is not one, then we are still in the original data file and the program executes a `next' statement to skip through it. - An important question to ask at this point is: given that the +An important question to ask at this point is: given that the functionality of `nextfile' can be provided with a library file, why is it built into `gawk'? Adding features for little reason leads to larger, slower programs that are harder to maintain. The answer is @@ -12562,12 +12691,94 @@ saves a lot of time. This is particularly important in `awk', because time doing input and output, instead of performing computations). -File: gawk.info, Node: Assert Function, Next: Round Function, Prev: Nextfile Function, Up: General Functions +File: gawk.info, Node: Strtonum Function, Next: Assert Function, Prev: Nextfile Function, Up: General Functions + +12.2.2 Converting Strings To Numbers +------------------------------------ + +The `strtonum' function (*note String Functions::) is a `gawk' +extension. The following function provides an implementation for other +versions of `awk': -Assertions ----------- + # strtonum --- convert string to number + function mystrtonum(str, ret, chars, n, i, k, c) + { + if (str ~ /^0[0-7]*$/) { + # octal + n = length(str) + ret = 0 + for (i = 1; i <= n; i++) { + c = substr(str, i, 1) + if ((k = index("01234567", c)) > 0) + k-- # adjust for 1-basing in awk + + ret = ret * 8 + k + } + } else if (str ~ /^0[xX][0-9a-fA-f]+/) { + # hexadecimal + str = substr(str, 3) # lop off leading 0x + n = length(str) + ret = 0 + for (i = 1; i <= n; i++) { + c = substr(str, i, 1) + c = tolower(c) + if ((k = index("0123456789", c)) > 0) + k-- # adjust for 1-basing in awk + else if ((k = index("abcdef", c)) > 0) + k += 9 + + ret = ret * 16 + k + } + } else if (str ~ /^[-+]?([0-9]+([.][0-9]*([Ee][0-9]+)?)?|([.][0-9]+([Ee][-+]?[0-9]+)?))$/) { + # decimal number, possibly floating point + ret = str + 0 + } else + ret = "NOT-A-NUMBER" + + return ret + } - When writing large programs, it is often useful to know that a + # BEGIN { # gawk test harness + # a[1] = "25" + # a[2] = ".31" + # a[3] = "0123" + # a[4] = "0xdeadBEEF" + # a[5] = "123.45" + # a[6] = "1.e3" + # a[7] = "1.32" + # a[7] = "1.32E2" + # + # for (i = 1; i in a; i++) + # print a[i], strtonum(a[i]), mystrtonum(a[i]) + # } + +The function first looks for C-style octal numbers (base 8). If the +input string matches a regular expression describing octal numbers, +then `mystrtonum' loops through each character in the string. It sets +`k' to the index in `"01234567"' of the current octal digit. Since the +return value is one-based, the `k--' adjusts `k' so it can be used in +computing the return value. + +Similar logic applies to the code that checks for and converts a +hexadecimal value, which starts with `0x' or `0X'. The use of +`tolower' simplifies the computation for finding the correct numeric +value for each hexadecimal digit. + +Finally, if the string matches the (rather complicated) regex for a +regular decimal integer or floating-point numer, the computation `ret = +str + 0' lets `awk' convert the value to a number. + +A commented-out test program is included, so that the function can be +tested with `gawk' and the results compared to the built-in `strtonum' +function. + + +File: gawk.info, Node: Assert Function, Next: Round Function, Prev: Strtonum Function, Up: General Functions + +12.2.3 Assertions +----------------- + +When writing large programs, it is often useful to know that a condition or set of conditions is true. Before proceeding with a particular computation, you make a statement about what you believe to be the case. Such a statement is known as an "assertion". The C @@ -12578,18 +12789,18 @@ message describing the condition that should have been true but was not, and then it kills the program. In C, using `assert' looks this: #include <assert.h> - + int myfunc(int a, double b) { assert(a <= 5 && b >= 17.1); ... } - If the assertion fails, the program prints a message similar to this: +If the assertion fails, the program prints a message similar to this: prog.c:5: assertion failed: a <= 5 && b >= 17.1 - The C language makes it possible to turn the condition into a string +The C language makes it possible to turn the condition into a string for use in printing the diagnostic message. This is not possible in `awk', so this `assert' function also requires a string version of the condition that is being tested. Following is the function: @@ -12604,20 +12815,20 @@ condition that is being tested. Following is the function: exit 1 } } - + END { if (_assert_exit) exit 1 } - The `assert' function tests the `condition' parameter. If it is -false, it prints a message to standard error, using the `string' -parameter to describe the failed condition. It then sets the variable +The `assert' function tests the `condition' parameter. If it is false, +it prints a message to standard error, using the `string' parameter to +describe the failed condition. It then sets the variable `_assert_exit' to one and executes the `exit' statement. The `exit' statement jumps to the `END' rule. If the `END' rules finds `_assert_exit' to be true, it exits immediately. - The purpose of the test in the `END' rule is to keep any other `END' +The purpose of the test in the `END' rule is to keep any other `END' rules from running. When an assertion fails, the program should exit immediately. If no assertions fail, then `_assert_exit' is still false when the `END' rule is run normally, and the rest of the program's @@ -12635,42 +12846,42 @@ If the assertion fails, you see a message similar to the following: mydata:1357: assertion failed: a <= 5 && b >= 17.1 - There is a small problem with this version of `assert'. An `END' -rule is automatically added to the program calling `assert'. Normally, -if a program consists of just a `BEGIN' rule, the input files and/or +There is a small problem with this version of `assert'. An `END' rule +is automatically added to the program calling `assert'. Normally, if a +program consists of just a `BEGIN' rule, the input files and/or standard input are not read. However, now that the program has an `END' rule, `awk' attempts to read the input data files or standard input (*note Using BEGIN/END::), most likely causing the program to hang as it waits for input. - There is a simple workaround to this: make sure the `BEGIN' rule -always ends with an `exit' statement. +There is a simple workaround to this: make sure the `BEGIN' rule always +ends with an `exit' statement. File: gawk.info, Node: Round Function, Next: Cliff Random Function, Prev: Assert Function, Up: General Functions -Rounding Numbers ----------------- +12.2.4 Rounding Numbers +----------------------- - The way `printf' and `sprintf' (*note Printf::) perform rounding -often depends upon the system's C `sprintf' subroutine. On many -machines, `sprintf' rounding is "unbiased," which means it doesn't -always round a trailing `.5' up, contrary to naive expectations. In -unbiased rounding, `.5' rounds to even, rather than always up, so 1.5 -rounds to 2 but 4.5 rounds to 4. This means that if you are using a -format that does rounding (e.g., `"%.0f"'), you should check what your -system does. The following function does traditional rounding; it -might be useful if your awk's `printf' does unbiased rounding: +The way `printf' and `sprintf' (*note Printf::) perform rounding often +depends upon the system's C `sprintf' subroutine. On many machines, +`sprintf' rounding is "unbiased," which means it doesn't always round a +trailing `.5' up, contrary to naive expectations. In unbiased +rounding, `.5' rounds to even, rather than always up, so 1.5 rounds to +2 but 4.5 rounds to 4. This means that if you are using a format that +does rounding (e.g., `"%.0f"'), you should check what your system does. +The following function does traditional rounding; it might be useful +if your awk's `printf' does unbiased rounding: # round.awk --- do normal rounding function round(x, ival, aval, fraction) { ival = int(x) # integer part, int() truncates - + # see if fractional part if (ival == x) # no fraction return x - + if (x < 0) { aval = -x # absolute value ival = int(aval) @@ -12687,24 +12898,24 @@ might be useful if your awk's `printf' does unbiased rounding: return ival } } - + # test harness { print $0, round($0) } File: gawk.info, Node: Cliff Random Function, Next: Ordinal Functions, Prev: Round Function, Up: General Functions -The Cliff Random Number Generator ---------------------------------- +12.2.5 The Cliff Random Number Generator +---------------------------------------- - The Cliff random number generator(1) is a very simple random number +The Cliff random number generator(1) is a very simple random number generator that "passes the noise sphere test for randomness by showing no structure." It is easily programmed, in less than 10 lines of `awk' code: # cliff_rand.awk --- generate Cliff random numbers BEGIN { _cliff_seed = 0.1 } - + function cliff_rand() { _cliff_seed = (100 * log(_cliff_seed)) % 1 @@ -12713,38 +12924,38 @@ code: return _cliff_seed } - This algorithm requires an initial "seed" of 0.1. Each new value -uses the current seed as input for the calculation. If the built-in -`rand' function (*note Numeric Functions::) isn't random enough, you -might try using this function instead. +This algorithm requires an initial "seed" of 0.1. Each new value uses +the current seed as input for the calculation. If the built-in `rand' +function (*note Numeric Functions::) isn't random enough, you might try +using this function instead. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) `http://mathworld.wolfram.com/CliffRandomNumberGenerator.hmtl' +(1) `http://mathworld.wolfram.com/CliffRandomNumberGenerator.hmtl' File: gawk.info, Node: Ordinal Functions, Next: Join Function, Prev: Cliff Random Function, Up: General Functions -Translating Between Characters and Numbers ------------------------------------------- +12.2.6 Translating Between Characters and Numbers +------------------------------------------------- - One commercial implementation of `awk' supplies a built-in function, +One commercial implementation of `awk' supplies a built-in function, `ord', which takes a character and returns the numeric value for that character in the machine's character set. If the string passed to `ord' has more than one character, only the first one is used. - The inverse of this function is `chr' (from the function of the same +The inverse of this function is `chr' (from the function of the same name in Pascal), which takes a number and returns the corresponding character. Both functions are written very nicely in `awk'; there is no real reason to build them into the `awk' interpreter: # ord.awk --- do ord and chr - + # Global identifiers: # _ord_: numerical values indexed by characters # _ord_init: function to initialize _ord_ BEGIN { _ord_init() } - + function _ord_init( low, high, i, t) { low = sprintf("%c", 7) # BEL is ascii 7 @@ -12759,16 +12970,16 @@ no real reason to build them into the `awk' interpreter: low = 0 high = 255 } - + for (i = low; i <= high; i++) { t = sprintf("%c", i) _ord_[t] = i } } - Some explanation of the numbers used by `chr' is worthwhile. The -most prominent character set in use today is ASCII. Although an 8-bit -byte can hold 256 distinct values (from 0 to 255), ASCII only defines +Some explanation of the numbers used by `chr' is worthwhile. The most +prominent character set in use today is ASCII. Although an 8-bit byte +can hold 256 distinct values (from 0 to 255), ASCII only defines characters that use the values from 0 to 127.(1) In the now distant past, at least one minicomputer manufacturer used ASCII, but with mark parity, meaning that the leftmost bit in the byte is always 1. This @@ -12783,13 +12994,13 @@ on some older systems, they are not really worth worrying about: c = substr(str, 1, 1) return _ord_[c] } - + function chr(c) { # force c to be numeric by adding 0 return sprintf("%c", c + 0) } - + #### test code #### # BEGIN \ # { @@ -12801,30 +13012,30 @@ on some older systems, they are not really worth worrying about: # } # } - An obvious improvement to these functions is to move the code for the +An obvious improvement to these functions is to move the code for the `_ord_init' function into the body of the `BEGIN' rule. It was written this way initially for ease of development. There is a "test program" in a `BEGIN' rule, to test the function. It is commented out for production use. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) ASCII has been extended in many countries to use the values from +(1) ASCII has been extended in many countries to use the values from 128 to 255 for country-specific characters. If your system uses these extensions, you can simplify `_ord_init' to simply loop from 0 to 255. File: gawk.info, Node: Join Function, Next: Gettimeofday Function, Prev: Ordinal Functions, Up: General Functions -Merging an Array into a String ------------------------------- +12.2.7 Merging an Array into a String +------------------------------------- - When doing string processing, it is often useful to be able to join -all the strings in an array into one long string. The following -function, `join', accomplishes this task. It is used later in several -of the application programs (*note Sample Programs::). +When doing string processing, it is often useful to be able to join all +the strings in an array into one long string. The following function, +`join', accomplishes this task. It is used later in several of the +application programs (*note Sample Programs::). - Good function design is important; this function needs to be general +Good function design is important; this function needs to be general but it should also have a reasonable default behavior. It is called with an array as well as the beginning and ending indices of the elements in the array to be merged. This assumes that the array @@ -12844,39 +13055,38 @@ created with `split' (*note String Functions::): return result } - An optional additional argument is the separator to use when joining -the strings back together. If the caller supplies a nonempty value, -`join' uses it; if it is not supplied, it has a null value. In this -case, `join' uses a single blank as a default separator for the -strings. If the value is equal to `SUBSEP', then `join' joins the -strings with no separator between them. `SUBSEP' serves as a "magic" -value to indicate that there should be no separation between the -component strings.(1) +An optional additional argument is the separator to use when joining the +strings back together. If the caller supplies a nonempty value, `join' +uses it; if it is not supplied, it has a null value. In this case, +`join' uses a single blank as a default separator for the strings. If +the value is equal to `SUBSEP', then `join' joins the strings with no +separator between them. `SUBSEP' serves as a "magic" value to indicate +that there should be no separation between the component strings.(1) - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) It would be nice if `awk' had an assignment operator for +(1) It would be nice if `awk' had an assignment operator for concatenation. The lack of an explicit operator for concatenation makes string operations more difficult than they really need to be. File: gawk.info, Node: Gettimeofday Function, Prev: Join Function, Up: General Functions -Managing the Time of Day ------------------------- +12.2.8 Managing the Time of Day +------------------------------- - The `systime' and `strftime' functions described in *Note Time +The `systime' and `strftime' functions described in *Note Time Functions::, provide the minimum functionality necessary for dealing with the time of day in human readable form. While `strftime' is extensive, the control formats are not necessarily easy to remember or intuitively obvious when reading a program. - The following function, `gettimeofday', populates a user-supplied -array with preformatted time information. It returns a string with the +The following function, `gettimeofday', populates a user-supplied array +with preformatted time information. It returns a string with the current time formatted in the same way as the `date' utility: # gettimeofday.awk --- get the time of day in a usable format - + # Returns a string in the format of output of date(1) # Populates the array argument time with individual values: # time["second"] -- seconds (0 - 59) @@ -12898,18 +13108,18 @@ current time formatted in the same way as the `date' utility: # time["ampm"] -- AM or PM designation # time["weeknum"] -- week number, Sunday first day # time["altweeknum"] -- week number, Monday first day - + function gettimeofday(time, ret, now, i) { # get time once, avoids unnecessary system calls now = systime() - + # return date(1)-style output ret = strftime("%a %b %d %H:%M:%S %Z %Y", now) - + # clear out target array delete time - + # fill in values, force numeric values to be # numeric by adding 0 time["second"] = strftime("%S", now) + 0 @@ -12931,23 +13141,23 @@ current time formatted in the same way as the `date' utility: time["ampm"] = strftime("%p", now) time["weeknum"] = strftime("%U", now) + 0 time["altweeknum"] = strftime("%W", now) + 0 - + return ret } - The string indices are easier to use and read than the various -formats required by `strftime'. The `alarm' program presented in *Note -Alarm Program::, uses this function. A more general design for the +The string indices are easier to use and read than the various formats +required by `strftime'. The `alarm' program presented in *Note Alarm +Program::, uses this function. A more general design for the `gettimeofday' function would have allowed the user to supply an optional timestamp value to use instead of the current time. File: gawk.info, Node: Data File Management, Next: Getopt Function, Prev: General Functions, Up: Library Functions -Data File Management -==================== +12.3 Data File Management +========================= - This minor node presents functions that are useful for managing +This minor node presents functions that are useful for managing command-line data files. * Menu: @@ -12961,10 +13171,10 @@ command-line data files. File: gawk.info, Node: Filetrans Function, Next: Rewind Function, Up: Data File Management -Noting Data File Boundaries ---------------------------- +12.3.1 Noting Data File Boundaries +---------------------------------- - The `BEGIN' and `END' rules are each executed exactly once at the +The `BEGIN' and `END' rules are each executed exactly once at the beginning and end of your `awk' program, respectively (*note BEGIN/END::). We (the `gawk' authors) once had a user who mistakenly thought that the `BEGIN' rule is executed at the beginning of each data @@ -12973,8 +13183,8 @@ informed that this was not the case, the user requested that we add new special patterns to `gawk', named `BEGIN_FILE' and `END_FILE', that would have the desired behavior. He even supplied us the code to do so. - Adding these special patterns to `gawk' wasn't necessary; the job -can be done cleanly in `awk' itself, as illustrated by the following +Adding these special patterns to `gawk' wasn't necessary; the job can +be done cleanly in `awk' itself, as illustrated by the following library program. It arranges to call two user-supplied functions, `beginfile' and `endfile', at the beginning and end of each data file. Besides solving the problem in only nine(!) lines of code, it does so @@ -12987,7 +13197,7 @@ _portably_; this works with any implementation of `awk': # The user must supply functions beginfile() and endfile() # that each take the name of the file being started or # finished, respectively. - + FILENAME != _oldfilename \ { if (_oldfilename != "") @@ -12995,13 +13205,13 @@ _portably_; this works with any implementation of `awk': _oldfilename = FILENAME beginfile(FILENAME) } - + END { endfile(FILENAME) } - This file must be loaded before the user's "main" program, so that -the rule it supplies is executed first. +This file must be loaded before the user's "main" program, so that the +rule it supplies is executed first. - This rule relies on `awk''s `FILENAME' variable that automatically +This rule relies on `awk''s `FILENAME' variable that automatically changes for each new data file. The current file name is saved in a private variable, `_oldfilename'. If `FILENAME' does not equal `_oldfilename', then a new data file is being processed and it is @@ -13013,16 +13223,16 @@ then assigns the current file name to `_oldfilename' and calls `_oldfilename' is initialized to the null string, this rule executes correctly even for the first data file. - The program also supplies an `END' rule to do the final processing -for the last file. Because this `END' rule comes before any `END' rules +The program also supplies an `END' rule to do the final processing for +the last file. Because this `END' rule comes before any `END' rules supplied in the "main" program, `endfile' is called first. Once again the value of multiple `BEGIN' and `END' rules should be clear. - This version has same problem as the first version of `nextfile' -(*note Nextfile Function::). If the same data file occurs twice in a -row on the command line, then `endfile' and `beginfile' are not -executed at the end of the first pass and at the beginning of the -second pass. The following version solves the problem: +This version has same problem as the first version of `nextfile' (*note +Nextfile Function::). If the same data file occurs twice in a row on +the command line, then `endfile' and `beginfile' are not executed at +the end of the first pass and at the beginning of the second pass. The +following version solves the problem: # ftrans.awk --- handle data file transitions # @@ -13033,26 +13243,26 @@ second pass. The following version solves the problem: _filename_ = FILENAME beginfile(FILENAME) } - + END { endfile(_filename_) } - *Note Wc Program::, shows how this library function can be used and -how it simplifies writing the main program. +*Note Wc Program::, shows how this library function can be used and how +it simplifies writing the main program. File: gawk.info, Node: Rewind Function, Next: File Checking, Prev: Filetrans Function, Up: Data File Management -Rereading the Current File --------------------------- +12.3.2 Rereading the Current File +--------------------------------- - Another request for a new built-in function was for a `rewind' -function that would make it possible to reread the current file. The -requesting user didn't want to have to use `getline' (*note Getline::) -inside a loop. +Another request for a new built-in function was for a `rewind' function +that would make it possible to reread the current file. The requesting +user didn't want to have to use `getline' (*note Getline::) inside a +loop. - However, as long as you are not in the `END' rule, it is quite easy -to arrange to immediately close the current input file and then start -over with it from the top. For lack of a better name, we'll call it +However, as long as you are not in the `END' rule, it is quite easy to +arrange to immediately close the current input file and then start over +with it from the top. For lack of a better name, we'll call it `rewind': # rewind.awk --- rewind the current file and start over @@ -13061,36 +13271,36 @@ over with it from the top. For lack of a better name, we'll call it # shift remaining arguments up for (i = ARGC; i > ARGIND; i--) ARGV[i] = ARGV[i-1] - + # make sure gawk knows to keep going ARGC++ - + # make current file next to get done ARGV[ARGIND+1] = FILENAME - + # do it nextfile } - This code relies on the `ARGIND' variable (*note Auto-set::), which -is specific to `gawk'. If you are not using `gawk', you can use ideas +This code relies on the `ARGIND' variable (*note Auto-set::), which is +specific to `gawk'. If you are not using `gawk', you can use ideas presented in *Note Filetrans Function::, to either update `ARGIND' on your own or modify this code as appropriate. - The `rewind' function also relies on the `nextfile' keyword (*note +The `rewind' function also relies on the `nextfile' keyword (*note Nextfile Statement::). *Note Nextfile Function::, for a function version of `nextfile'. File: gawk.info, Node: File Checking, Next: Empty Files, Prev: Rewind Function, Up: Data File Management -Checking for Readable Data Files --------------------------------- +12.3.3 Checking for Readable Data Files +--------------------------------------- - Normally, if you give `awk' a data file that isn't readable, it -stops with a fatal error. There are times when you might want to just -ignore such files and keep going. You can do this by prepending the -following program to your `awk' program: +Normally, if you give `awk' a data file that isn't readable, it stops +with a fatal error. There are times when you might want to just ignore +such files and keep going. You can do this by prepending the following +program to your `awk' program: # readable.awk --- library file to skip over unreadable files BEGIN { @@ -13105,17 +13315,17 @@ following program to your `awk' program: } } - In `gawk', the `getline' won't be fatal (unless `--posix' is in -force). Removing the element from `ARGV' with `delete' skips the file -(since it's no longer in the list). +In `gawk', the `getline' won't be fatal (unless `--posix' is in force). +Removing the element from `ARGV' with `delete' skips the file (since +it's no longer in the list). File: gawk.info, Node: Empty Files, Next: Ignoring Assigns, Prev: File Checking, Up: Data File Management -Checking For Zero-length Files ------------------------------- +12.3.4 Checking For Zero-length Files +------------------------------------- - All known `awk' implementations silently skip over zero-length files. +All known `awk' implementations silently skip over zero-length files. This is a by-product of `awk''s implicit read-a-record-and-match-against-the-rules loop: when `awk' tries to read a record from an empty file, it immediately receives an end of @@ -13123,7 +13333,7 @@ file indication, closes the file, and proceeds on to the next command-line data file, _without_ executing any user-level `awk' program code. - Using `gawk''s `ARGIND' variable (*note Built-in Variables::), it is +Using `gawk''s `ARGIND' variable (*note Built-in Variables::), it is possible to detect when an empty data file has been skipped. Similar to the library file presented in *Note Filetrans Function::, the following library file calls a function named `zerofile' that the user @@ -13132,53 +13342,53 @@ in `ARGV' where it was found: # zerofile.awk --- library file to process empty input files BEGIN { Argind = 0 } - + ARGIND > Argind + 1 { for (Argind++; Argind < ARGIND; Argind++) zerofile(ARGV[Argind], Argind) } - + ARGIND != Argind { Argind = ARGIND } - + END { if (ARGIND > Argind) for (Argind++; Argind <= ARGIND; Argind++) zerofile(ARGV[Argind], Argind) } - The user-level variable `Argind' allows the `awk' program to track -its progress through `ARGV'. Whenever the program detects that -`ARGIND' is greater than `Argind + 1', it means that one or more empty -files were skipped. The action then calls `zerofile' for each such -file, incrementing `Argind' along the way. +The user-level variable `Argind' allows the `awk' program to track its +progress through `ARGV'. Whenever the program detects that `ARGIND' is +greater than `Argind + 1', it means that one or more empty files were +skipped. The action then calls `zerofile' for each such file, +incrementing `Argind' along the way. - The `Argind != ARGIND' rule simply keeps `Argind' up to date in the +The `Argind != ARGIND' rule simply keeps `Argind' up to date in the normal case. - Finally, the `END' rule catches the case of any empty files at the -end of the command-line arguments. Note that the test in the condition -of the `for' loop uses the `<=' operator, not `<'. +Finally, the `END' rule catches the case of any empty files at the end +of the command-line arguments. Note that the test in the condition of +the `for' loop uses the `<=' operator, not `<'. - As an exercise, you might consider whether this same problem can be +As an exercise, you might consider whether this same problem can be solved without relying on `gawk''s `ARGIND' variable. - As a second exercise, revise this code to handle the case where an +As a second exercise, revise this code to handle the case where an intervening value in `ARGV' is a variable assignment. File: gawk.info, Node: Ignoring Assigns, Prev: Empty Files, Up: Data File Management -Treating Assignments as File Names ----------------------------------- +12.3.5 Treating Assignments as File Names +----------------------------------------- - Occasionally, you might not want `awk' to process command-line -variable assignments (*note Assignment Options::). In particular, if -you have file names that contain an `=' character, `awk' treats the -file name as an assignment, and does not process it. +Occasionally, you might not want `awk' to process command-line variable +assignments (*note Assignment Options::). In particular, if you have +file names that contain an `=' character, `awk' treats the file name as +an assignment, and does not process it. - Some users have suggested an additional command-line option for -`gawk' to disable command-line assignments. However, some simple -programming with a library file does the trick: +Some users have suggested an additional command-line option for `gawk' +to disable command-line assignments. However, some simple programming +with a library file does the trick: # noassign.awk --- library file to avoid the need for a # special option that disables command-line assignments @@ -13188,21 +13398,21 @@ programming with a library file does the trick: if (argv[i] ~ /^[A-Za-z_][A-Za-z_0-9]*=.*/) argv[i] = ("./" argv[i]) } - + BEGIN { if (No_command_assign) disable_assigns(ARGC, ARGV) } - You then run your program this way: +You then run your program this way: awk -v No_command_assign=1 -f noassign.awk -f yourprog.awk * - The function works by looping through the arguments. It prepends -`./' to any argument that matches the form of a variable assignment, -turning that argument into a file name. +The function works by looping through the arguments. It prepends `./' +to any argument that matches the form of a variable assignment, turning +that argument into a file name. - The use of `No_command_assign' allows you to disable command-line +The use of `No_command_assign' allows you to disable command-line assignments at invocation time, by giving the variable a true value. When not set, it is initially zero (i.e., false), so the command-line arguments are left alone. @@ -13210,34 +13420,34 @@ arguments are left alone. File: gawk.info, Node: Getopt Function, Next: Passwd Functions, Prev: Data File Management, Up: Library Functions -Processing Command-Line Options -=============================== +12.4 Processing Command-Line Options +==================================== - Most utilities on POSIX compatible systems take options, or -"switches," on the command line that can be used to change the way a -program behaves. `awk' is an example of such a program (*note -Options::). Often, options take "arguments"; i.e., data that the -program needs to correctly obey the command-line option. For example, -`awk''s `-F' option requires a string to use as the field separator. -The first occurrence on the command line of either `--' or a string -that does not begin with `-' ends the options. - - Modern Unix systems provide a C function named `getopt' for -processing command-line arguments. The programmer provides a string -describing the one-letter options. If an option requires an argument, -it is followed in the string with a colon. `getopt' is also passed the -count and values of the command-line arguments and is called in a loop. -`getopt' processes the command-line arguments for option letters. Each -time around the loop, it returns a single character representing the -next option letter that it finds, or `?' if it finds an invalid option. +Most utilities on POSIX compatible systems take options, or "switches," +on the command line that can be used to change the way a program +behaves. `awk' is an example of such a program (*note Options::). +Often, options take "arguments"; i.e., data that the program needs to +correctly obey the command-line option. For example, `awk''s `-F' +option requires a string to use as the field separator. The first +occurrence on the command line of either `--' or a string that does not +begin with `-' ends the options. + +Modern Unix systems provide a C function named `getopt' for processing +command-line arguments. The programmer provides a string describing the +one-letter options. If an option requires an argument, it is followed +in the string with a colon. `getopt' is also passed the count and +values of the command-line arguments and is called in a loop. `getopt' +processes the command-line arguments for option letters. Each time +around the loop, it returns a single character representing the next +option letter that it finds, or `?' if it finds an invalid option. When it returns -1, there are no options left on the command line. - When using `getopt', options that do not take arguments can be -grouped together. Furthermore, options that take arguments require -that the argument is present. The argument can immediately follow the -option letter, or it can be a separate command-line argument. +When using `getopt', options that do not take arguments can be grouped +together. Furthermore, options that take arguments require that the +argument is present. The argument can immediately follow the option +letter, or it can be a separate command-line argument. - Given a hypothetical program that takes three command-line options, +Given a hypothetical program that takes three command-line options, `-a', `-b', and `-c', where `-b' requires an argument, all of the following are valid ways of invoking the program: @@ -13245,14 +13455,13 @@ following are valid ways of invoking the program: prog -ac -bfoo -- data1 data2 data3 prog -acbfoo data1 data2 data3 - Notice that when the argument is grouped with its option, the rest of +Notice that when the argument is grouped with its option, the rest of the argument is considered to be the option's argument. In this example, `-acbfoo' indicates that all of the `-a', `-b', and `-c' options were supplied, and that `foo' is the argument to the `-b' option. - `getopt' provides four external variables that the programmer can -use: +`getopt' provides four external variables that the programmer can use: `optind' The index in the argument value array (`argv') where the first @@ -13269,8 +13478,8 @@ use: `optopt' The letter representing the command-line option. - The following C fragment shows how `getopt' might process -command-line arguments for `awk': +The following C fragment shows how `getopt' might process command-line +arguments for `awk': int main(int argc, char *argv[]) @@ -13301,17 +13510,17 @@ command-line arguments for `awk': ... } - As a side point, `gawk' actually uses the GNU `getopt_long' function -to process both normal and GNU-style long options (*note Options::). +As a side point, `gawk' actually uses the GNU `getopt_long' function to +process both normal and GNU-style long options (*note Options::). - The abstraction provided by `getopt' is very useful and is quite -handy in `awk' programs as well. Following is an `awk' version of -`getopt'. This function highlights one of the greatest weaknesses in -`awk', which is that it is very poor at manipulating single characters. -Repeated calls to `substr' are necessary for accessing individual -characters (*note String Functions::).(1) +The abstraction provided by `getopt' is very useful and is quite handy +in `awk' programs as well. Following is an `awk' version of `getopt'. +This function highlights one of the greatest weaknesses in `awk', which +is that it is very poor at manipulating single characters. Repeated +calls to `substr' are necessary for accessing individual characters +(*note String Functions::).(1) - The discussion that follows walks through the code a bit at a time: +The discussion that follows walks through the code a bit at a time: # getopt.awk --- do C library getopt(3) function in awk # External variables: @@ -13319,21 +13528,21 @@ characters (*note String Functions::).(1) # Optarg -- string value of argument to current option # Opterr -- if nonzero, print our own diagnostic # Optopt -- current option letter - + # Returns: # -1 at end of options # ? for unrecognized option # <c> a character representing the current option - + # Private Data: # _opti -- index in multi-flag option, e.g., -abc - The function starts out with a list of the global variables it uses, +The function starts out with a list of the global variables it uses, what the return values are, what they mean, and any global variables that are "private" to this library function. Such documentation is essential for any program, and particularly for library functions. - The `getopt' function first checks that it was indeed called with a +The `getopt' function first checks that it was indeed called with a string of options (the `options' parameter). If `options' has a zero length, `getopt' immediately returns -1: @@ -13341,7 +13550,7 @@ length, `getopt' immediately returns -1: { if (length(options) == 0) # no options given return -1 - + if (argv[Optind] == "--") { # all done Optind++ _opti = 0 @@ -13351,13 +13560,13 @@ length, `getopt' immediately returns -1: return -1 } - The next thing to check for is the end of the options. A `--' ends -the command-line options, as does any command-line argument that does -not begin with a `-'. `Optind' is used to step through the array of +The next thing to check for is the end of the options. A `--' ends the +command-line options, as does any command-line argument that does not +begin with a `-'. `Optind' is used to step through the array of command-line arguments; it retains its value across calls to `getopt', because it is a global variable. - The regular expression that is used, `/^-[^: \t\n\f\r\v\b]/', is +The regular expression that is used, `/^-[^: \t\n\f\r\v\b]/', is perhaps a bit of overkill; it checks for a `-' followed by anything that is not whitespace and not a colon. If the current command-line argument does not match this pattern, it is not an option, and it ends @@ -13380,31 +13589,31 @@ option processing: return "?" } - The `_opti' variable tracks the position in the current command-line +The `_opti' variable tracks the position in the current command-line argument (`argv[Optind]'). If multiple options are grouped together with one `-' (e.g., `-abx'), it is necessary to return them to the user one at a time. - If `_opti' is equal to zero, it is set to two, which is the index in +If `_opti' is equal to zero, it is set to two, which is the index in the string of the next character to look at (we skip the `-', which is at position one). The variable `thisopt' holds the character, obtained with `substr'. It is saved in `Optopt' for the main program to use. - If `thisopt' is not in the `options' string, then it is an invalid +If `thisopt' is not in the `options' string, then it is an invalid option. If `Opterr' is nonzero, `getopt' prints an error message on the standard error that is similar to the message from the C version of `getopt'. - Because the option is invalid, it is necessary to skip it and move -on to the next option character. If `_opti' is greater than or equal -to the length of the current command-line argument, it is necessary to +Because the option is invalid, it is necessary to skip it and move on +to the next option character. If `_opti' is greater than or equal to +the length of the current command-line argument, it is necessary to move on to the next argument, so `Optind' is incremented and `_opti' is reset to zero. Otherwise, `Optind' is left alone and `_opti' is merely incremented. - In any case, because the option is invalid, `getopt' returns `?'. -The main program can examine `Optopt' if it needs to know what the -invalid option letter actually is. Continuing on: +In any case, because the option is invalid, `getopt' returns `?'. The +main program can examine `Optopt' if it needs to know what the invalid +option letter actually is. Continuing on: if (substr(options, i + 1, 1) == ":") { # get option argument @@ -13416,10 +13625,10 @@ invalid option letter actually is. Continuing on: } else Optarg = "" - If the option requires an argument, the option letter is followed by -a colon in the `options' string. If there are remaining characters in -the current command-line argument (`argv[Optind]'), then the rest of -that string is assigned to `Optarg'. Otherwise, the next command-line +If the option requires an argument, the option letter is followed by a +colon in the `options' string. If there are remaining characters in the +current command-line argument (`argv[Optind]'), then the rest of that +string is assigned to `Optarg'. Otherwise, the next command-line argument is used (`-xFOO' versus `-x FOO'). In either case, `_opti' is reset to zero, because there are no more characters left to examine in the current command-line argument. Continuing: @@ -13432,14 +13641,14 @@ the current command-line argument. Continuing: return thisopt } - Finally, if `_opti' is either zero or greater than the length of the +Finally, if `_opti' is either zero or greater than the length of the current command-line argument, it means this element in `argv' is through being processed, so `Optind' is incremented to point to the next element in `argv'. If neither condition is true, then only `_opti' is incremented, so that the next option letter can be processed on the next call to `getopt'. - The `BEGIN' rule initializes both `Opterr' and `Optind' to one. +The `BEGIN' rule initializes both `Opterr' and `Optind' to one. `Opterr' is set to one, since the default behavior is for `getopt' to print a diagnostic message upon seeing an invalid option. `Optind' is set to one, since there's no reason to look at the program name, which @@ -13448,7 +13657,7 @@ is in `ARGV[0]': BEGIN { Opterr = 1 # default is to diagnose Optind = 1 # skip ARGV[0] - + # test program if (_getopt_test) { while ((_go_c = getopt(ARGC, ARGV, "ab:cd")) != -1) @@ -13461,7 +13670,7 @@ is in `ARGV[0]': } } - The rest of the `BEGIN' rule is a simple test program. Here is the +The rest of the `BEGIN' rule is a simple test program. Here is the result of two sample runs of the test program: $ awk -f getopt.awk -v _getopt_test=1 -- -a -cbARG bax -x @@ -13471,7 +13680,7 @@ result of two sample runs of the test program: -| non-option arguments: -| ARGV[3] = <bax> -| ARGV[4] = <-x> - + $ awk -f getopt.awk -v _getopt_test=1 -- -a -x -- xyz abc -| c = <a>, optarg = <> error--> x -- invalid option @@ -13480,24 +13689,24 @@ result of two sample runs of the test program: -| ARGV[4] = <xyz> -| ARGV[5] = <abc> - In both runs, the first `--' terminates the arguments to `awk', so -that it does not try to interpret the `-a', etc., as its own options. +In both runs, the first `--' terminates the arguments to `awk', so that +it does not try to interpret the `-a', etc., as its own options. Several of the sample programs presented in *Note Sample Programs::, use `getopt' to process their arguments. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) This function was written before `gawk' acquired the ability to +(1) This function was written before `gawk' acquired the ability to split strings into single characters using `""' as the separator. We have left it alone, since using `substr' is more portable. File: gawk.info, Node: Passwd Functions, Next: Group Functions, Prev: Getopt Function, Up: Library Functions -Reading the User Database -========================= +12.5 Reading the User Database +============================== - The `PROCINFO' array (*note Built-in Variables::) provides access to +The `PROCINFO' array (*note Built-in Variables::) provides access to the current user's real and effective user and group ID numbers, and if available, the user's supplementary group set. However, because these are numbers, they do not provide very useful information to the average @@ -13507,16 +13716,16 @@ presents a suite of functions for retrieving information from the user database. *Note Group Functions::, for a similar suite that retrieves information from the group database. - The POSIX standard does not define the file where user information is +The POSIX standard does not define the file where user information is kept. Instead, it provides the `<pwd.h>' header file and several C language subroutines for obtaining user information. The primary function is `getpwent', for "get password entry." The "password" comes from the original user database file, `/etc/passwd', which stores user information, along with the encrypted passwords (hence the name). - While an `awk' program could simply read `/etc/passwd' directly, -this file may not contain complete information about the system's set -of users.(1) To be sure you are able to produce a readable and complete +While an `awk' program could simply read `/etc/passwd' directly, this +file may not contain complete information about the system's set of +users.(1) To be sure you are able to produce a readable and complete version of the user database, it is necessary to write a small C program that calls `getpwent'. `getpwent' is defined as returning a pointer to a `struct passwd'. Each time it is called, it returns the @@ -13532,24 +13741,24 @@ that "cats" the password database: */ #include <stdio.h> #include <pwd.h> - + int main(argc, argv) int argc; char **argv; { struct passwd *p; - + while ((p = getpwent()) != NULL) printf("%s:%s:%ld:%ld:%s:%s:%s\n", p->pw_name, p->pw_passwd, (long) p->pw_uid, (long) p->pw_gid, p->pw_gecos, p->pw_dir, p->pw_shell); - + endpwent(); return 0; } - If you don't understand C, don't worry about it. The output from +If you don't understand C, don't worry about it. The output from `pwcat' is the user database, in the traditional `/etc/passwd' format of colon-separated fields. The fields are: @@ -13565,7 +13774,7 @@ Home directory The user's login (or "home") directory Login shell The program that is run when the user logs in. This is usually a shell, such as `bash'. - A few lines representative of `pwcat''s output are as follows: +A few lines representative of `pwcat''s output are as follows: $ pwcat -| root:3Ov02d5VaUPB6:0:1:Operator:/:/bin/sh @@ -13578,28 +13787,28 @@ Login shell The program that is run when the user logs in. -| andy:abcca2:113:10:Andy Jacobs:/home/andy:/bin/sh ... - With that introduction, following is a group of functions for -getting user information. There are several functions here, -corresponding to the C functions of the same names: +With that introduction, following is a group of functions for getting +user information. There are several functions here, corresponding to +the C functions of the same names: # passwd.awk --- access password file information BEGIN { # tailor this to suit your system _pw_awklib = "/usr/local/libexec/awk/" } - + function _pw_init( oldfs, oldrs, olddol0, pwcat, using_fw) { if (_pw_inited) return - + oldfs = FS oldrs = RS olddol0 = $0 using_fw = (PROCINFO["FS"] == "FIELDWIDTHS") FS = ":" RS = "\n" - + pwcat = _pw_awklib "pwcat" while ((pwcat | getline) > 0) { _pw_byname[$1] = $0 @@ -13616,40 +13825,40 @@ corresponding to the C functions of the same names: $0 = olddol0 } - The `BEGIN' rule sets a private variable to the directory where -`pwcat' is stored. Because it is used to help out an `awk' library -routine, we have chosen to put it in `/usr/local/libexec/awk'; however, -you might want it to be in a different directory on your system. +The `BEGIN' rule sets a private variable to the directory where `pwcat' +is stored. Because it is used to help out an `awk' library routine, we +have chosen to put it in `/usr/local/libexec/awk'; however, you might +want it to be in a different directory on your system. - The function `_pw_init' keeps three copies of the user information -in three associative arrays. The arrays are indexed by username +The function `_pw_init' keeps three copies of the user information in +three associative arrays. The arrays are indexed by username (`_pw_byname'), by user ID number (`_pw_byuid'), and by order of occurrence (`_pw_bycount'). The variable `_pw_inited' is used for efficiency; `_pw_init' needs only to be called once. - Because this function uses `getline' to read information from -`pwcat', it first saves the values of `FS', `RS', and `$0'. It notes -in the variable `using_fw' whether field splitting with `FIELDWIDTHS' -is in effect or not. Doing so is necessary, since these functions -could be called from anywhere within a user's program, and the user may -have his or her own way of splitting records and fields. +Because this function uses `getline' to read information from `pwcat', +it first saves the values of `FS', `RS', and `$0'. It notes in the +variable `using_fw' whether field splitting with `FIELDWIDTHS' is in +effect or not. Doing so is necessary, since these functions could be +called from anywhere within a user's program, and the user may have his +or her own way of splitting records and fields. - The `using_fw' variable checks `PROCINFO["FS"]', which is +The `using_fw' variable checks `PROCINFO["FS"]', which is `"FIELDWIDTHS"' if field splitting is being done with `FIELDWIDTHS'. This makes it possible to restore the correct field-splitting mechanism later. The test can only be true for `gawk'. It is false if using `FS' or on some other `awk' implementation. - The main part of the function uses a loop to read database lines, -split the line into fields, and then store the line into each array as +The main part of the function uses a loop to read database lines, split +the line into fields, and then store the line into each array as necessary. When the loop is done, `_pw_init' cleans up by closing the pipeline, setting `_pw_inited' to one, and restoring `FS' (and `FIELDWIDTHS' if necessary), `RS', and `$0'. The use of `_pw_count' is explained shortly. - The `getpwnam' function takes a username as a string argument. If -that user is in the database, it returns the appropriate line. -Otherwise, it returns the null string: +The `getpwnam' function takes a username as a string argument. If that +user is in the database, it returns the appropriate line. Otherwise, it +returns the null string: function getpwnam(name) { @@ -13659,9 +13868,9 @@ Otherwise, it returns the null string: return "" } - Similarly, the `getpwuid' function takes a user ID number argument. -If that user number is in the database, it returns the appropriate -line. Otherwise, it returns the null string: +Similarly, the `getpwuid' function takes a user ID number argument. If +that user number is in the database, it returns the appropriate line. +Otherwise, it returns the null string: function getpwuid(uid) { @@ -13671,8 +13880,8 @@ line. Otherwise, it returns the null string: return "" } - The `getpwent' function simply steps through the database, one entry -at a time. It uses `_pw_count' to track its current position in the +The `getpwent' function simply steps through the database, one entry at +a time. It uses `_pw_count' to track its current position in the `_pw_bycount' array: function getpwent() @@ -13683,26 +13892,25 @@ at a time. It uses `_pw_count' to track its current position in the return "" } - The `endpwent' function resets `_pw_count' to zero, so that -subsequent calls to `getpwent' start over again: +The `endpwent' function resets `_pw_count' to zero, so that subsequent +calls to `getpwent' start over again: function endpwent() { _pw_count = 0 } - A conscious design decision in this suite was made that each -subroutine calls `_pw_init' to initialize the database arrays. The -overhead of running a separate process to generate the user database, -and the I/O to scan it, are only incurred if the user's main program -actually calls one of these functions. If this library file is loaded -along with a user's program, but none of the routines are ever called, -then there is no extra runtime overhead. (The alternative is move the -body of `_pw_init' into a `BEGIN' rule, which always runs `pwcat'. -This simplifies the code but runs an extra process that may never be -needed.) - - In turn, calling `_pw_init' is not too expensive, because the +A conscious design decision in this suite was made that each subroutine +calls `_pw_init' to initialize the database arrays. The overhead of +running a separate process to generate the user database, and the I/O +to scan it, are only incurred if the user's main program actually calls +one of these functions. If this library file is loaded along with a +user's program, but none of the routines are ever called, then there is +no extra runtime overhead. (The alternative is move the body of +`_pw_init' into a `BEGIN' rule, which always runs `pwcat'. This +simplifies the code but runs an extra process that may never be needed.) + +In turn, calling `_pw_init' is not too expensive, because the `_pw_inited' variable keeps the program from reading the data more than once. If you are worried about squeezing every last cycle out of your `awk' program, the check of `_pw_inited' could be moved out of @@ -13710,29 +13918,29 @@ once. If you are worried about squeezing every last cycle out of your this is not necessary, since most `awk' programs are I/O-bound, and it clutters up the code. - The `id' program in *Note Id Program::, uses these functions. +The `id' program in *Note Id Program::, uses these functions. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) It is often the case that password information is stored in a +(1) It is often the case that password information is stored in a network database. File: gawk.info, Node: Group Functions, Prev: Passwd Functions, Up: Library Functions -Reading the Group Database -========================== +12.6 Reading the Group Database +=============================== - Much of the discussion presented in *Note Passwd Functions::, -applies to the group database as well. Although there has traditionally -been a well-known file (`/etc/group') in a well-known format, the POSIX +Much of the discussion presented in *Note Passwd Functions::, applies +to the group database as well. Although there has traditionally been a +well-known file (`/etc/group') in a well-known format, the POSIX standard only provides a set of C library routines (`<grp.h>' and `getgrent') for accessing the information. Even though this file may exist, it likely does not have complete information. Therefore, as with the user database, it is necessary to have a small C program that generates the group database as its output. - `grcat', a C program that "cats" the group database, is as follows: +`grcat', a C program that "cats" the group database, is as follows: /* * grcat.c @@ -13741,7 +13949,7 @@ generates the group database as its output. */ #include <stdio.h> #include <grp.h> - + int main(argc, argv) int argc; @@ -13749,7 +13957,7 @@ generates the group database as its output. { struct group *g; int i; - + while ((g = getgrent()) != NULL) { printf("%s:%s:%ld:", g->gr_name, g->gr_passwd, (long) g->gr_gid); @@ -13764,7 +13972,7 @@ generates the group database as its output. return 0; } - Each line in the group database represents one group. The fields are +Each line in the group database represents one group. The fields are separated with colons and represent the following information: Group name The group's name. @@ -13782,7 +13990,7 @@ Group member list A comma-separated list of usernames. These numbers. (Note that `PROCINFO' is a `gawk' extension; *note Built-in Variables::.) - Here is what running `grcat' might produce: +Here is what running `grcat' might produce: $ grcat -| wheel:*:0:arnold @@ -13793,7 +14001,7 @@ Group member list A comma-separated list of usernames. These -| other:*:20: ... - Here are the functions for obtaining information from the group +Here are the functions for obtaining information from the group database. There are several, modeled after the C library functions of the same names: @@ -13803,20 +14011,20 @@ the same names: # Change to suit your system _gr_awklib = "/usr/local/libexec/awk/" } - + function _gr_init( oldfs, oldrs, olddol0, grcat, using_fw, n, a, i) { if (_gr_inited) return - + oldfs = FS oldrs = RS olddol0 = $0 using_fw = (PROCINFO["FS"] == "FIELDWIDTHS") FS = ":" RS = "\n" - + grcat = _gr_awklib "grcat" while ((grcat | getline) > 0) { if ($1 in _gr_byname) @@ -13827,7 +14035,7 @@ the same names: _gr_bygid[$3] = _gr_bygid[$3] "," $4 else _gr_bygid[$3] = $0 - + n = split($4, a, "[ \t]*,[ \t]*") for (i = 1; i <= n; i++) if (a[i] in _gr_groupsbyuser) @@ -13835,7 +14043,7 @@ the same names: _gr_groupsbyuser[a[i]] " " $1 else _gr_groupsbyuser[a[i]] = $1 - + _gr_bycount[++_gr_count] = $0 } close(grcat) @@ -13848,46 +14056,46 @@ the same names: $0 = olddol0 } - The `BEGIN' rule sets a private variable to the directory where -`grcat' is stored. Because it is used to help out an `awk' library -routine, we have chosen to put it in `/usr/local/libexec/awk'. You -might want it to be in a different directory on your system. +The `BEGIN' rule sets a private variable to the directory where `grcat' +is stored. Because it is used to help out an `awk' library routine, we +have chosen to put it in `/usr/local/libexec/awk'. You might want it +to be in a different directory on your system. - These routines follow the same general outline as the user database +These routines follow the same general outline as the user database routines (*note Passwd Functions::). The `_gr_inited' variable is used to ensure that the database is scanned no more than once. The `_gr_init' function first saves `FS', `FIELDWIDTHS', `RS', and `$0', and then sets `FS' and `RS' to the correct values for scanning the group information. - The group information is stored is several associative arrays. The +The group information is stored is several associative arrays. The arrays are indexed by group name (`_gr_byname'), by group ID number (`_gr_bygid'), and by position in the database (`_gr_bycount'). There is an additional array indexed by username (`_gr_groupsbyuser'), which is a space-separated list of groups to which each user belongs. - Unlike the user database, it is possible to have multiple records in -the database for the same group. This is common when a group has a -large number of members. A pair of such entries might look like the +Unlike the user database, it is possible to have multiple records in the +database for the same group. This is common when a group has a large +number of members. A pair of such entries might look like the following: tvpeople:*:101:johnny,jay,arsenio tvpeople:*:101:david,conan,tom,joan - For this reason, `_gr_init' looks to see if a group name or group ID +For this reason, `_gr_init' looks to see if a group name or group ID number is already seen. If it is, then the usernames are simply concatenated onto the previous list of users. (There is actually a subtle problem with the code just presented. Suppose that the first time there were no names. This code adds the names with a leading comma. It also doesn't check that there is a `$4'.) - Finally, `_gr_init' closes the pipeline to `grcat', restores `FS' -(and `FIELDWIDTHS' if necessary), `RS', and `$0', initializes -`_gr_count' to zero (it is used later), and makes `_gr_inited' nonzero. +Finally, `_gr_init' closes the pipeline to `grcat', restores `FS' (and +`FIELDWIDTHS' if necessary), `RS', and `$0', initializes `_gr_count' to +zero (it is used later), and makes `_gr_inited' nonzero. - The `getgrnam' function takes a group name as its argument, and if -that group exists, it is returned. Otherwise, `getgrnam' returns the -null string: +The `getgrnam' function takes a group name as its argument, and if that +group exists, it is returned. Otherwise, `getgrnam' returns the null +string: function getgrnam(group) { @@ -13897,7 +14105,7 @@ null string: return "" } - The `getgrgid' function is similar, it takes a numeric group ID and +The `getgrgid' function is similar, it takes a numeric group ID and looks up the information associated with that group ID: function getgrgid(gid) @@ -13908,7 +14116,7 @@ looks up the information associated with that group ID: return "" } - The `getgruser' function does not have a C counterpart. It takes a +The `getgruser' function does not have a C counterpart. It takes a username and returns the list of groups that have the user as a member: function getgruser(user) @@ -13919,8 +14127,8 @@ username and returns the list of groups that have the user as a member: return "" } - The `getgrent' function steps through the database one entry at a -time. It uses `_gr_count' to track its position in the list: +The `getgrent' function steps through the database one entry at a time. +It uses `_gr_count' to track its position in the list: function getgrent() { @@ -13930,37 +14138,37 @@ time. It uses `_gr_count' to track its position in the list: return "" } - The `endgrent' function resets `_gr_count' to zero so that -`getgrent' can start over again: +The `endgrent' function resets `_gr_count' to zero so that `getgrent' +can start over again: function endgrent() { _gr_count = 0 } - As with the user database routines, each function calls `_gr_init' to +As with the user database routines, each function calls `_gr_init' to initialize the arrays. Doing so only incurs the extra overhead of running `grcat' if these functions are used (as opposed to moving the body of `_gr_init' into a `BEGIN' rule). - Most of the work is in scanning the database and building the various +Most of the work is in scanning the database and building the various associative arrays. The functions that the user calls are themselves very simple, relying on `awk''s associative arrays to do work. - The `id' program in *Note Id Program::, uses these functions. +The `id' program in *Note Id Program::, uses these functions. File: gawk.info, Node: Sample Programs, Next: Language History, Prev: Library Functions, Up: Top -Practical `awk' Programs -************************ +13 Practical `awk' Programs +*************************** - *Note Library Functions::, presents the idea that reading programs -in a language contributes to learning that language. This major node +*Note Library Functions::, presents the idea that reading programs in a +language contributes to learning that language. This major node continues that theme, presenting a potpourri of `awk' programs for your reading enjoyment. - Many of these programs use the library functions presented in *Note +Many of these programs use the library functions presented in *Note Library Functions::. * Menu: @@ -13972,10 +14180,10 @@ Library Functions::. File: gawk.info, Node: Running Examples, Next: Clones, Up: Sample Programs -Running the Example Programs -============================ +13.1 Running the Example Programs +================================= - To run a given program, you would typically do something like this: +To run a given program, you would typically do something like this: awk -f PROGRAM -- OPTIONS FILES @@ -13983,33 +14191,32 @@ Here, PROGRAM is the name of the `awk' program (such as `cut.awk'), OPTIONS are any command-line options for the program that start with a `-', and FILES are the actual data files. - If your system supports the `#!' executable interpreter mechanism +If your system supports the `#!' executable interpreter mechanism (*note Executable Scripts::), you can instead run your program directly: cut.awk -c1-8 myfiles > results - If your `awk' is not `gawk', you may instead need to use this: +If your `awk' is not `gawk', you may instead need to use this: cut.awk -- -c1-8 myfiles > results File: gawk.info, Node: Clones, Next: Miscellaneous Programs, Prev: Running Examples, Up: Sample Programs -Reinventing Wheels for Fun and Profit -===================================== +13.2 Reinventing Wheels for Fun and Profit +========================================== - This minor node presents a number of POSIX utilities that are +This minor node presents a number of POSIX utilities that are implemented in `awk'. Reinventing these programs in `awk' is often enjoyable, because the algorithms can be very clearly expressed, and the code is usually very concise and simple. This is true because `awk' does so much for you. - It should be noted that these programs are not necessarily intended -to replace the installed versions on your system. Instead, their -purpose is to illustrate `awk' language programming for "real world" -tasks. +It should be noted that these programs are not necessarily intended to +replace the installed versions on your system. Instead, their purpose +is to illustrate `awk' language programming for "real world" tasks. - The programs are presented in alphabetical order. +The programs are presented in alphabetical order. * Menu: @@ -14024,22 +14231,22 @@ tasks. File: gawk.info, Node: Cut Program, Next: Egrep Program, Up: Clones -Cutting out Fields and Columns ------------------------------- +13.2.1 Cutting out Fields and Columns +------------------------------------- - The `cut' utility selects, or "cuts," characters or fields from its +The `cut' utility selects, or "cuts," characters or fields from its standard input and sends them to its standard output. Fields are separated by tabs by default, but you may supply a command-line option to change the field "delimiter" (i.e., the field-separator character). `cut''s definition of fields is less general than `awk''s. - A common use of `cut' might be to pull out just the login name of +A common use of `cut' might be to pull out just the login name of logged-on users from the output of `who'. For example, the following pipeline generates a sorted, unique list of the logged-on users: who | cut -c1-8 | sort | uniq - The options for `cut' are: +The options for `cut' are: `-c LIST' Use LIST as the list of characters to cut out. Items within the @@ -14057,11 +14264,11 @@ pipeline generates a sorted, unique list of the logged-on users: `-s' Suppress printing of lines that do not contain the field delimiter. - The `awk' implementation of `cut' uses the `getopt' library function +The `awk' implementation of `cut' uses the `getopt' library function (*note Getopt Function::) and the `join' library function (*note Join Function::). - The program begins with a comment describing the options, the library +The program begins with a comment describing the options, the library functions needed, and a `usage' function that prints out a usage message and exits. `usage' is called if invalid arguments are supplied: @@ -14074,7 +14281,7 @@ message and exits. `usage' is called if invalid arguments are supplied: # -s Suppress lines without the delimiter # # Requires getopt and join library functions - + function usage( e1, e2) { e1 = "usage: cut [-f list] [-d c] [-s] [files...]" @@ -14087,7 +14294,7 @@ message and exits. `usage' is called if invalid arguments are supplied: The variables `e1' and `e2' are used so that the function fits nicely on the screen. - Next comes a `BEGIN' rule that parses the command-line options. It +Next comes a `BEGIN' rule that parses the command-line options. It sets `FS' to a single TAB character, because that is `cut''s default field separator. The output field separator is also set to be the same as the input field separator. Then `getopt' is used to step through @@ -14123,11 +14330,11 @@ the output field separator is set to the null string: else usage() } - + for (i = 1; i < Optind; i++) ARGV[i] = "" - Special care is taken when the field delimiter is a space. Using a +Special care is taken when the field delimiter is a space. Using a single space (`" "') for the value of `FS' is incorrect--`awk' would separate fields with runs of spaces, tabs, and/or newlines, and we want them to be separated with individual spaces. Also, note that after @@ -14135,30 +14342,30 @@ them to be separated with individual spaces. Also, note that after from 1 to `Optind', so that `awk' does not try to process the command-line options as file names. - After dealing with the command-line options, the program verifies -that the options make sense. Only one or the other of `-c' and `-f' -should be used, and both require a field list. Then the program calls -either `set_fieldlist' or `set_charlist' to pull apart the list of -fields or characters: +After dealing with the command-line options, the program verifies that +the options make sense. Only one or the other of `-c' and `-f' should +be used, and both require a field list. Then the program calls either +`set_fieldlist' or `set_charlist' to pull apart the list of fields or +characters: if (by_fields && by_chars) usage() - + if (by_fields == 0 && by_chars == 0) by_fields = 1 # default - + if (fieldlist == "") { print "cut: needs list for -c or -f" > "/dev/stderr" exit 1 } - + if (by_fields) set_fieldlist() else set_charlist() } - `set_fieldlist' is used to split the field list apart at the commas +`set_fieldlist' is used to split the field list apart at the commas and into an array. Then, for each element of the array, it looks to see if it is actually a range, and if so, splits it apart. The range is verified to make sure the first number is smaller than the second. @@ -14186,12 +14393,12 @@ The program lets `awk' handle the job of doing the field splitting: nfields = j - 1 } - The `set_charlist' function is more complicated than `set_fieldlist'. +The `set_charlist' function is more complicated than `set_fieldlist'. The idea here is to use `gawk''s `FIELDWIDTHS' variable (*note Constant Size::), which describes constant-width input. When using a character list, that is exactly what we have. - Setting up `FIELDWIDTHS' is more complicated than simply listing the +Setting up `FIELDWIDTHS' is more complicated than simply listing the fields that need to be printed. We have to keep track of the fields to print and also the intervening characters that have to be skipped. For example, suppose you wanted characters 1 through 8, 15, and 22 through @@ -14242,13 +14449,13 @@ filler fields: nfields = j - 1 } - Next is the rule that actually processes the data. If the `-s' -option is given, then `suppress' is true. The first `if' statement -makes sure that the input record does have the field separator. If -`cut' is processing fields, `suppress' is true, and the field separator +Next is the rule that actually processes the data. If the `-s' option +is given, then `suppress' is true. The first `if' statement makes sure +that the input record does have the field separator. If `cut' is +processing fields, `suppress' is true, and the field separator character is not in the record, then the record is skipped. - If the record is valid, then `gawk' has split the data into fields, +If the record is valid, then `gawk' has split the data into fields, either using the character in `FS' or using fixed-length fields and `FIELDWIDTHS'. The loop goes through the list of fields that should be printed. The corresponding field is printed if it contains data. If @@ -14258,7 +14465,7 @@ out between the fields: { if (by_fields && suppress && index($0, FS) != 0) next - + for (i = 1; i <= nfields; i++) { if ($flist[i] != "") { printf "%s", $flist[i] @@ -14269,8 +14476,8 @@ out between the fields: print "" } - This version of `cut' relies on `gawk''s `FIELDWIDTHS' variable to -do the character-based cutting. While it is possible in other `awk' +This version of `cut' relies on `gawk''s `FIELDWIDTHS' variable to do +the character-based cutting. While it is possible in other `awk' implementations to use `substr' (*note String Functions::), it is also extremely painful. The `FIELDWIDTHS' variable supplies an elegant solution to the problem of picking the input line apart by characters. @@ -14278,23 +14485,23 @@ solution to the problem of picking the input line apart by characters. File: gawk.info, Node: Egrep Program, Next: Id Program, Prev: Cut Program, Up: Clones -Searching for Regular Expressions in Files ------------------------------------------- +13.2.2 Searching for Regular Expressions in Files +------------------------------------------------- - The `egrep' utility searches files for patterns. It uses regular +The `egrep' utility searches files for patterns. It uses regular expressions that are almost identical to those available in `awk' (*note Regexp::). It is used in the following manner: egrep [ OPTIONS ] 'PATTERN' FILES ... - The PATTERN is a regular expression. In typical usage, the regular +The PATTERN is a regular expression. In typical usage, the regular expression is quoted to prevent the shell from expanding any of the special characters as file name wildcards. Normally, `egrep' prints the lines that matched. If multiple file names are provided on the command line, each output line is preceded by the name of the file and a colon. - The options to `egrep' are as follows: +The options to `egrep' are as follows: `-c' Print out a count of the lines that matched the pattern, instead @@ -14320,11 +14527,11 @@ a colon. Use PATTERN as the regexp to match. The purpose of the `-e' option is to allow patterns that start with a `-'. - This version uses the `getopt' library function (*note Getopt +This version uses the `getopt' library function (*note Getopt Function::) and the file transition library program (*note Filetrans Function::). - The program begins with a descriptive comment and then a `BEGIN' rule +The program begins with a descriptive comment and then a `BEGIN' rule that processes the command-line arguments with `getopt'. The `-i' (ignore case) option is particularly easy with `gawk'; we just use the `IGNORECASE' built-in variable (*note Built-in Variables::): @@ -14339,7 +14546,7 @@ that processes the command-line arguments with `getopt'. The `-i' # -e argument is pattern # # Requires getopt and file transition library functions - + BEGIN { while ((c = getopt(ARGC, ARGV, "ce:svil")) != -1) { if (c == "c") @@ -14358,7 +14565,7 @@ that processes the command-line arguments with `getopt'. The `-i' usage() } - Next comes the code that handles the `egrep'-specific behavior. If no +Next comes the code that handles the `egrep'-specific behavior. If no pattern is supplied with `-e', the first nonoption on the command line is used. The `awk' command-line arguments up to `ARGV[Optind]' are cleared, so that `awk' won't try to process them as files. If no files @@ -14368,7 +14575,7 @@ the matched lines in the output: if (pattern == "") pattern = ARGV[Optind++] - + for (i = 1; i < Optind; i++) ARGV[i] = "" if (Optind >= ARGC) { @@ -14376,16 +14583,16 @@ the matched lines in the output: ARGC = 2 } else if (ARGC - Optind > 1) do_filenames++ - + # if (IGNORECASE) # pattern = tolower(pattern) } - The last two lines are commented out, since they are not needed in +The last two lines are commented out, since they are not needed in `gawk'. They should be uncommented if you have to use another version of `awk'. - The next set of lines should be uncommented if you are not using +The next set of lines should be uncommented if you are not using `gawk'. This rule translates all the characters in the input line into lowercase if the `-i' option is specified.(1) The rule is commented out since it is not necessary with `gawk': @@ -14395,7 +14602,7 @@ since it is not necessary with `gawk': # $0 = tolower($0) #} - The `beginfile' function is called by the rule in `ftrans.awk' when +The `beginfile' function is called by the rule in `ftrans.awk' when each new file is processed. In this case, it is very simple; all it does is initialize a variable `fcount' to zero. `fcount' tracks how many lines in the current file matched the pattern (naming the @@ -14407,7 +14614,7 @@ parameter, but that we're not interested in its value): fcount = 0 } - The `endfile' function is called after each file has been processed. +The `endfile' function is called after each file has been processed. It affects the output only when the user wants a count of the number of lines that matched. `no_print' is true only if the exit status is desired. `count_only' is true if line counts are desired. `egrep' @@ -14423,20 +14630,20 @@ total number of lines that matched the pattern: print file ":" fcount else print fcount - + total += fcount } - The following rule does most of the work of matching lines. The -variable `matches' is true if the line matched the pattern. If the user -wants lines that did not match, the sense of `matches' is inverted -using the `!' operator. `fcount' is incremented with the value of -`matches', which is either one or zero, depending upon a successful or +The following rule does most of the work of matching lines. The variable +`matches' is true if the line matched the pattern. If the user wants +lines that did not match, the sense of `matches' is inverted using the +`!' operator. `fcount' is incremented with the value of `matches', +which is either one or zero, depending upon a successful or unsuccessful match. If the line does not match, the `next' statement just moves on to the next record. - A number of additional tests are made, but they are only done if we -are not counting lines. First, if the user only wants exit status +A number of additional tests are made, but they are only done if we are +not counting lines. First, if the user only wants exit status (`no_print' is true), then it is enough to know that _one_ line in this file matched, and we can skip on to the next file with `nextfile'. Similarly, if we are only printing file names, we can print the file @@ -14447,21 +14654,21 @@ line is printed, with a leading file name and colon if necessary: matches = ($0 ~ pattern) if (invert) matches = ! matches - + fcount += matches # 1 or 0 - + if (! matches) next - + if (! count_only) { if (no_print) nextfile - + if (filenames_only) { print FILENAME nextfile } - + if (do_filenames) print FILENAME ":" $0 else @@ -14469,7 +14676,7 @@ line is printed, with a leading file name and colon if necessary: } } - The `END' rule takes care of producing the correct exit status. If +The `END' rule takes care of producing the correct exit status. If there are no matches, the exit status is one; otherwise it is zero: END \ @@ -14479,8 +14686,8 @@ there are no matches, the exit status is one; otherwise it is zero: exit 0 } - The `usage' function prints a usage message in case of invalid -options, and then exits: +The `usage' function prints a usage message in case of invalid options, +and then exits: function usage( e) { @@ -14490,28 +14697,28 @@ options, and then exits: exit 1 } - The variable `e' is used so that the function fits nicely on the +The variable `e' is used so that the function fits nicely on the printed page. - Just a note on programming style: you may have noticed that the `END' +Just a note on programming style: you may have noticed that the `END' rule uses backslash continuation, with the open brace on a line by itself. This is so that it more closely resembles the way functions are written. Many of the examples in this major node use this style. You can decide for yourself if you like writing your `BEGIN' and `END' rules this way or not. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) It also introduces a subtle bug; if a match happens, we output -the translated line, not the original. +(1) It also introduces a subtle bug; if a match happens, we output the +translated line, not the original. File: gawk.info, Node: Id Program, Next: Split Program, Prev: Egrep Program, Up: Clones -Printing out User Information ------------------------------ +13.2.3 Printing out User Information +------------------------------------ - The `id' utility lists a user's real and effective user ID numbers, +The `id' utility lists a user's real and effective user ID numbers, real and effective group ID numbers, and the user's group set, if any. `id' only prints the effective user ID and group ID if they are different from the real ones. If possible, `id' also supplies the @@ -14520,15 +14727,15 @@ corresponding user and group names. The output might look like this: $ id -| uid=2076(arnold) gid=10(staff) groups=10(staff),4(tty) - This information is part of what is provided by `gawk''s `PROCINFO' +This information is part of what is provided by `gawk''s `PROCINFO' array (*note Built-in Variables::). However, the `id' utility provides a more palatable output than just individual numbers. - Here is a simple version of `id' written in `awk'. It uses the user +Here is a simple version of `id' written in `awk'. It uses the user database library functions (*note Passwd Functions::) and the group database library functions (*note Group Functions::): - The program is fairly straightforward. All the work is done in the +The program is fairly straightforward. All the work is done in the `BEGIN' rule. The user and group ID numbers are obtained from `PROCINFO'. The code is repetitive. The entry in the user database for the real user ID number is split into parts at the `:'. The name is @@ -14541,21 +14748,21 @@ and the group numbers: # output is: # uid=12(foo) euid=34(bar) gid=3(baz) \ # egid=5(blat) groups=9(nine),2(two),1(one) - + BEGIN \ { uid = PROCINFO["uid"] euid = PROCINFO["euid"] gid = PROCINFO["gid"] egid = PROCINFO["egid"] - + printf("uid=%d", uid) pw = getpwuid(uid) if (pw != "") { split(pw, a, ":") printf("(%s)", a[1]) } - + if (euid != uid) { printf(" euid=%d", euid) pw = getpwuid(euid) @@ -14564,14 +14771,14 @@ and the group numbers: printf("(%s)", a[1]) } } - + printf(" gid=%d", gid) pw = getgrgid(gid) if (pw != "") { split(pw, a, ":") printf("(%s)", a[1]) } - + if (egid != gid) { printf(" egid=%d", egid) pw = getgrgid(egid) @@ -14580,7 +14787,7 @@ and the group numbers: printf("(%s)", a[1]) } } - + for (i = 1; ("group" i) in PROCINFO; i++) { if (i == 1) printf(" groups=") @@ -14594,36 +14801,36 @@ and the group numbers: if (("group" (i+1)) in PROCINFO) printf(",") } - + print "" } - The test in the `for' loop is worth noting. Any supplementary -groups in the `PROCINFO' array have the indices `"group1"' through -`"groupN"' for some N, i.e., the total number of supplementary groups. -However, we don't know in advance how many of these groups there are. +The test in the `for' loop is worth noting. Any supplementary groups +in the `PROCINFO' array have the indices `"group1"' through `"groupN"' +for some N, i.e., the total number of supplementary groups. However, +we don't know in advance how many of these groups there are. - This loop works by starting at one, concatenating the value with +This loop works by starting at one, concatenating the value with `"group"', and then using `in' to see if that value is in the array. Eventually, `i' is incremented past the last group in the array and the loop exits. - The loop is also correct if there are _no_ supplementary groups; -then the condition is false the first time it's tested, and the loop -body never executes. +The loop is also correct if there are _no_ supplementary groups; then +the condition is false the first time it's tested, and the loop body +never executes. File: gawk.info, Node: Split Program, Next: Tee Program, Prev: Id Program, Up: Clones -Splitting a Large File into Pieces ----------------------------------- +13.2.4 Splitting a Large File into Pieces +----------------------------------------- - The `split' program splits large text files into smaller pieces. -Usage is as follows: +The `split' program splits large text files into smaller pieces. Usage +is as follows: split [-COUNT] file [ PREFIX ] - By default, the output files are named `xaa', `xab', and so on. Each +By default, the output files are named `xaa', `xab', and so on. Each file has 1000 lines in it, with the likely exception of the last file. To change the number of lines in each file, supply a number on the command line preceded with a minus; e.g., `-500' for files with 500 @@ -14631,13 +14838,13 @@ lines in them instead of 1000. To change the name of the output files to something like `myfileaa', `myfileab', and so on, supply an additional argument that specifies the file name prefix. - Here is a version of `split' in `awk'. It uses the `ord' and `chr' +Here is a version of `split' in `awk'. It uses the `ord' and `chr' functions presented in *Note Ordinal Functions::. - The program first sets its defaults, and then tests to make sure -there are not too many arguments. It then looks at each argument in -turn. The first argument could be a minus sign followed by a number. -If it is, this happens to look like a negative number, so it is made +The program first sets its defaults, and then tests to make sure there +are not too many arguments. It then looks at each argument in turn. +The first argument could be a minus sign followed by a number. If it +is, this happens to look like a negative number, so it is made positive, and that is the count of lines. The data file name is skipped over and the final argument is used as the prefix for the output file names: @@ -14646,13 +14853,13 @@ output file names: # # Requires ord and chr library functions # usage: split [-num] [file] [outname] - + BEGIN { outfile = "x" # default count = 1000 if (ARGC > 4) usage() - + i = 1 if (ARGV[i] ~ /^-[0-9]+$/) { count = -ARGV[i] @@ -14666,18 +14873,17 @@ output file names: outfile = ARGV[i] ARGV[i] = "" } - + s1 = s2 = "a" out = (outfile s1 s2) } - The next rule does most of the work. `tcount' (temporary count) -tracks how many lines have been printed to the output file so far. If -it is greater than `count', it is time to close the current file and -start a new one. `s1' and `s2' track the current suffixes for the file -name. If they are both `z', the file is just too big. Otherwise, `s1' -moves to the next letter in the alphabet and `s2' starts over again at -`a': +The next rule does most of the work. `tcount' (temporary count) tracks +how many lines have been printed to the output file so far. If it is +greater than `count', it is time to close the current file and start a +new one. `s1' and `s2' track the current suffixes for the file name. If +they are both `z', the file is just too big. Otherwise, `s1' moves to +the next letter in the alphabet and `s2' starts over again at `a': { if (++tcount > count) { @@ -14710,33 +14916,33 @@ The `usage' function simply prints an error message and exits: The variable `e' is used so that the function fits nicely on the screen. - This program is a bit sloppy; it relies on `awk' to automatically -close the last file instead of doing it in an `END' rule. It also -assumes that letters are contiguous in the character set, which isn't -true for EBCDIC systems. +This program is a bit sloppy; it relies on `awk' to automatically close +the last file instead of doing it in an `END' rule. It also assumes +that letters are contiguous in the character set, which isn't true for +EBCDIC systems. File: gawk.info, Node: Tee Program, Next: Uniq Program, Prev: Split Program, Up: Clones -Duplicating Output into Multiple Files --------------------------------------- +13.2.5 Duplicating Output into Multiple Files +--------------------------------------------- - The `tee' program is known as a "pipe fitting." `tee' copies its +The `tee' program is known as a "pipe fitting." `tee' copies its standard input to its standard output and also duplicates it to the files named on the command line. Its usage is as follows: tee [-a] file ... - The `-a' option tells `tee' to append to the named files, instead of +The `-a' option tells `tee' to append to the named files, instead of truncating them and starting over. - The `BEGIN' rule first makes a copy of all the command-line arguments +The `BEGIN' rule first makes a copy of all the command-line arguments into an array named `copy'. `ARGV[0]' is not copied, since it is not needed. `tee' cannot use `ARGV' directly, since `awk' attempts to process each file name in `ARGV' as input data. - If the first argument is `-a', then the flag variable `append' is -set to true, and both `ARGV[1]' and `copy[1]' are deleted. If `ARGC' is +If the first argument is `-a', then the flag variable `append' is set +to true, and both `ARGV[1]' and `copy[1]' are deleted. If `ARGC' is less than two, then no file names were supplied and `tee' prints a usage message and exits. Finally, `awk' is forced to read the standard input by setting `ARGV[1]' to `"-"' and `ARGC' to two: @@ -14746,7 +14952,7 @@ input by setting `ARGV[1]' to `"-"' and `ARGC' to two: { for (i = 1; i < ARGC; i++) copy[i] = ARGV[i] - + if (ARGV[1] == "-a") { append = 1 delete ARGV[1] @@ -14761,7 +14967,7 @@ input by setting `ARGV[1]' to `"-"' and `ARGC' to two: ARGC = 2 } - The single rule does all the work. Since there is no pattern, it is +The single rule does all the work. Since there is no pattern, it is executed for each line of input. The body of the rule simply prints the line into each file on the command line, and then to the standard output: @@ -14791,7 +14997,7 @@ body, the `if' is only tested once for each input record. If there are N input records and M output files, the first method only executes N `if' statements, while the second executes N`*'M `if' statements. - Finally, the `END' rule cleans up by closing all the output files: +Finally, the `END' rule cleans up by closing all the output files: END \ { @@ -14802,17 +15008,17 @@ N input records and M output files, the first method only executes N File: gawk.info, Node: Uniq Program, Next: Wc Program, Prev: Tee Program, Up: Clones -Printing Nonduplicated Lines of Text ------------------------------------- +13.2.6 Printing Nonduplicated Lines of Text +------------------------------------------- - The `uniq' utility reads sorted lines of data on its standard input, +The `uniq' utility reads sorted lines of data on its standard input, and by default removes duplicate lines. In other words, it only prints unique lines--hence the name. `uniq' has a number of options. The usage is as follows: uniq [-udc [-N]] [+N] [ INPUT FILE [ OUTPUT FILE ]] - The options for `uniq' are: +The options for `uniq' are: `-d' Pnly print only repeated lines. @@ -14841,14 +15047,14 @@ usage is as follows: The generated output is sent to the named output file, instead of to the standard output. - Normally `uniq' behaves as if both the `-d' and `-u' options are +Normally `uniq' behaves as if both the `-d' and `-u' options are provided. - `uniq' uses the `getopt' library function (*note Getopt Function::) -and the `join' library function (*note Join Function::). +`uniq' uses the `getopt' library function (*note Getopt Function::) and +the `join' library function (*note Join Function::). - The program begins with a `usage' function and then a brief outline -of the options and their meanings in a comment. The `BEGIN' rule deals +The program begins with a `usage' function and then a brief outline of +the options and their meanings in a comment. The `BEGIN' rule deals with the command-line arguments and options. It uses a trick to get `getopt' to handle options of the form `-25', treating such an option as the option letter `2' with an argument of `5'. If indeed two or more @@ -14859,7 +15065,7 @@ then `Optarg' is not needed. In this case, `Optind' must be decremented so that `getopt' processes it next time. This code is admittedly a bit tricky. - If no options are supplied, then the default is taken, to print both +If no options are supplied, then the default is taken, to print both repeated and nonrepeated lines. The output file, if provided, is assigned to `outputfile'. Early on, `outputfile' is initialized to the standard output, `/dev/stdout': @@ -14873,13 +15079,13 @@ standard output, `/dev/stdout': print e > "/dev/stderr" exit 1 } - + # -c count lines. overrides -d and -u # -d only repeated lines # -u only non-repeated lines # -n skip n fields # +n skip n characters, skip fields first - + BEGIN \ { count = 1 @@ -14904,26 +15110,26 @@ standard output, `/dev/stdout': } else usage() } - + if (ARGV[Optind] ~ /^\+[0-9]+$/) { charcount = substr(ARGV[Optind], 2) + 0 Optind++ } - + for (i = 1; i < Optind; i++) ARGV[i] = "" - + if (repeated_only == 0 && non_repeated_only == 0) repeated_only = non_repeated_only = 1 - + if (ARGC - Optind == 2) { outputfile = ARGV[ARGC - 1] ARGV[ARGC - 1] = "" } } - The following function, `are_equal', compares the current line, -`$0', to the previous line, `last'. It handles skipping fields and +The following function, `are_equal', compares the current line, `$0', +to the previous line, `last'. It handles skipping fields and characters. If no field count and no character count are specified, `are_equal' simply returns one or zero depending upon the result of a simple string comparison of `last' and `$0'. Otherwise, things get more @@ -14940,7 +15146,7 @@ and `are_equal' returns the result: { if (fcount == 0 && charcount == 0) return (last == $0) - + if (fcount > 0) { n = split(last, alast) m = split($0, aline) @@ -14954,38 +15160,37 @@ and `are_equal' returns the result: clast = substr(clast, charcount + 1) cline = substr(cline, charcount + 1) } - + return (clast == cline) } - The following two rules are the body of the program. The first one -is executed only for the very first line of data. It sets `last' equal -to `$0', so that subsequent lines of text have something to be compared -to. +The following two rules are the body of the program. The first one is +executed only for the very first line of data. It sets `last' equal to +`$0', so that subsequent lines of text have something to be compared to. - The second rule does the work. The variable `equal' is one or zero, +The second rule does the work. The variable `equal' is one or zero, depending upon the results of `are_equal''s comparison. If `uniq' is counting repeated lines, and the lines are equal, then it increments the `count' variable. Otherwise, it prints the line and resets `count', since the two lines are not equal. - If `uniq' is not counting, and if the lines are equal, `count' is +If `uniq' is not counting, and if the lines are equal, `count' is incremented. Nothing is printed, since the point is to remove duplicates. Otherwise, if `uniq' is counting repeated lines and more than one line is seen, or if `uniq' is counting nonrepeated lines and only one line is seen, then the line is printed, and `count' is reset. - Finally, similar logic is used in the `END' rule to print the final +Finally, similar logic is used in the `END' rule to print the final line of input data: NR == 1 { last = $0 next } - + { equal = are_equal() - + if (do_count) { # overrides -d and -u if (equal) count++ @@ -14996,7 +15201,7 @@ line of input data: } next } - + if (equal) count++ else { @@ -15007,7 +15212,7 @@ line of input data: count = 1 } } - + END { if (do_count) printf("%4d %s\n", count, last) > outputfile @@ -15019,18 +15224,18 @@ line of input data: File: gawk.info, Node: Wc Program, Prev: Uniq Program, Up: Clones -Counting Things ---------------- +13.2.7 Counting Things +---------------------- - The `wc' (word count) utility counts lines, words, and characters in +The `wc' (word count) utility counts lines, words, and characters in one or more input files. Its usage is as follows: wc [-lwc] [ FILES ... ] - If no files are specified on the command line, `wc' reads its -standard input. If there are multiple files, it also prints total -counts for all the files. The options and their meanings are shown in -the following list: +If no files are specified on the command line, `wc' reads its standard +input. If there are multiple files, it also prints total counts for all +the files. The options and their meanings are shown in the following +list: `-l' Count only lines. @@ -15044,25 +15249,25 @@ the following list: `-c' Count only characters. - Implementing `wc' in `awk' is particularly elegant, since `awk' does -a lot of the work for us; it splits lines into words (i.e., fields) and +Implementing `wc' in `awk' is particularly elegant, since `awk' does a +lot of the work for us; it splits lines into words (i.e., fields) and counts them, it counts lines (i.e., records), and it can easily tell us how long a line is. - This uses the `getopt' library function (*note Getopt Function::) -and the file-transition functions (*note Filetrans Function::). +This uses the `getopt' library function (*note Getopt Function::) and +the file-transition functions (*note Filetrans Function::). - This version has one notable difference from traditional versions of +This version has one notable difference from traditional versions of `wc': it always prints the counts in the order lines, words, and characters. Traditional versions note the order of the `-l', `-w', and `-c' options on the command line, and print the counts in that order. - The `BEGIN' rule does the argument processing. The variable +The `BEGIN' rule does the argument processing. The variable `print_total' is true if more than one file is named on the command line: # wc.awk --- count lines, words, characters - + # Options: # -l only count lines # -w only count words @@ -15071,7 +15276,7 @@ line: # Default is to count lines, words, characters # # Requires getopt and file transition library functions - + BEGIN { # let getopt print a message about # invalid options. we ignore them @@ -15085,16 +15290,16 @@ line: } for (i = 1; i < Optind; i++) ARGV[i] = "" - + # if no options, do all if (! do_lines && ! do_words && ! do_chars) do_lines = do_words = do_chars = 1 - + print_total = (ARGC - i > 2) } - The `beginfile' function is simple; it just resets the counts of -lines, words, and characters to zero, and saves the current file name in +The `beginfile' function is simple; it just resets the counts of lines, +words, and characters to zero, and saves the current file name in `fname': function beginfile(file) @@ -15103,7 +15308,7 @@ lines, words, and characters to zero, and saves the current file name in fname = FILENAME } - The `endfile' function adds the current file's numbers to the running +The `endfile' function adds the current file's numbers to the running totals of lines, words, and characters.(1) It then prints out those numbers for the file that was just read. It relies on `beginfile' to reset the numbers for the following data file: @@ -15122,10 +15327,10 @@ reset the numbers for the following data file: printf "\t%s\n", fname } - There is one rule that is executed for each line. It adds the length -of the record, plus one, to `chars'. Adding one plus the record length -is needed because the newline character separating records (the value -of `RS') is not part of the record itself, and thus not included in its +There is one rule that is executed for each line. It adds the length of +the record, plus one, to `chars'. Adding one plus the record length is +needed because the newline character separating records (the value of +`RS') is not part of the record itself, and thus not included in its length. Next, `lines' is incremented for each line read, and `words' is incremented by the value of `NF', which is the number of "words" on this line: @@ -15137,7 +15342,7 @@ this line: words += NF } - Finally, the `END' rule simply prints the totals for all the files: +Finally, the `END' rule simply prints the totals for all the files: END { if (print_total) { @@ -15151,19 +15356,19 @@ this line: } } - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) `wc' can't just use the value of `FNR' in `endfile'. If you -examine the code in *Note Filetrans Function:: you will see that `FNR' -has already been reset by the time `endfile' is called. +(1) `wc' can't just use the value of `FNR' in `endfile'. If you examine +the code in *Note Filetrans Function::, you will see that `FNR' has +already been reset by the time `endfile' is called. File: gawk.info, Node: Miscellaneous Programs, Prev: Clones, Up: Sample Programs -A Grab Bag of `awk' Programs -============================ +13.3 A Grab Bag of `awk' Programs +================================= - This minor node is a large "grab bag" of miscellaneous programs. We +This minor node is a large "grab bag" of miscellaneous programs. We hope you find them both interesting and enjoyable. * Menu: @@ -15184,22 +15389,22 @@ hope you find them both interesting and enjoyable. File: gawk.info, Node: Dupword Program, Next: Alarm Program, Up: Miscellaneous Programs -Finding Duplicated Words in a Document --------------------------------------- +13.3.1 Finding Duplicated Words in a Document +--------------------------------------------- - A common error when writing large amounts of prose is to accidentally +A common error when writing large amounts of prose is to accidentally duplicate words. Typically you will see this in text as something like "the the program does the following..." When the text is online, often the duplicated words occur at the end of one line and the beginning of another, making them very difficult to spot. - This program, `dupword.awk', scans through a file one line at a time +This program, `dupword.awk', scans through a file one line at a time and looks for adjacent occurrences of the same word. It also saves the last word on a line (in the variable `prev') for comparison with the first word on the next line. - The first two statements make sure that the line is all lowercase, -so that, for example, "The" and "the" compare equal to each other. The +The first two statements make sure that the line is all lowercase, so +that, for example, "The" and "the" compare equal to each other. The next statement replaces nonalphanumeric and nonwhitespace characters with spaces, so that punctuation does not affect the comparison either. The characters are replaced with spaces so that formatting controls @@ -15208,7 +15413,7 @@ don't create nonsense words (e.g., the Texinfo `@code{NF}' becomes into fields, yielding just the actual words on the line, and ensuring that there are no empty fields. - If there are no fields left after removing all the punctuation, the +If there are no fields left after removing all the punctuation, the current record is skipped. Otherwise, the program loops through each word, comparing it to the previous one: @@ -15232,22 +15437,22 @@ word, comparing it to the previous one: File: gawk.info, Node: Alarm Program, Next: Translate Program, Prev: Dupword Program, Up: Miscellaneous Programs -An Alarm Clock Program ----------------------- +13.3.2 An Alarm Clock Program +----------------------------- Nothing cures insomnia like a ringing alarm clock. Arnold Robbins - The following program is a simple "alarm clock" program. You give -it a time of day and an optional message. At the specified time, it -prints the message on the standard output. In addition, you can give it -the number of times to repeat the message as well as a delay between +The following program is a simple "alarm clock" program. You give it a +time of day and an optional message. At the specified time, it prints +the message on the standard output. In addition, you can give it the +number of times to repeat the message as well as a delay between repetitions. - This program uses the `gettimeofday' function from *Note -Gettimeofday Function::. +This program uses the `gettimeofday' function from *Note Gettimeofday +Function::. - All the work is done in the `BEGIN' rule. The first part is argument +All the work is done in the `BEGIN' rule. The first part is argument checking and setting of defaults: the delay, the count, and the message to print. If the user supplied a message without the ASCII BEL character (known as the "alert" character, `"\a"'), then it is added to @@ -15260,13 +15465,13 @@ Here is the program: # # Requires gettimeofday library function # usage: alarm time [ "message" [ count [ delay ] ] ] - + BEGIN \ { # Initial argument sanity checking usage1 = "usage: alarm time ['message' [count [delay]]]" usage2 = sprintf("\t(%s) time ::= hh:mm", ARGV[1]) - + if (ARGC < 2) { print usage1 > "/dev/stderr" print usage2 > "/dev/stderr" @@ -15285,7 +15490,7 @@ Here is the program: print usage2 > "/dev/stderr" exit 1 } - + # set defaults for once we reach the desired time if (delay == 0) delay = 180 # 3 minutes @@ -15296,34 +15501,33 @@ Here is the program: else if (index(message, "\a") == 0) message = "\a" message "\a" - The next minor node of code turns the alarm time into hours and -minutes, converts it (if necessary) to a 24-hour clock, and then turns -that time into a count of the seconds since midnight. Next it turns -the current time into a count of seconds since midnight. The -difference between the two is how long to wait before setting off the -alarm: +The next minor node of code turns the alarm time into hours and minutes, +converts it (if necessary) to a 24-hour clock, and then turns that time +into a count of the seconds since midnight. Next it turns the current +time into a count of seconds since midnight. The difference between +the two is how long to wait before setting off the alarm: # split up alarm time split(ARGV[1], atime, ":") hour = atime[1] + 0 # force numeric minute = atime[2] + 0 # force numeric - + # get current broken down time gettimeofday(now) - + # if time given is 12-hour hours and it's after that # hour, e.g., `alarm 5:30' at 9 a.m. means 5:30 p.m., # then add 12 to real hour if (hour < 12 && now["hour"] > hour) hour += 12 - + # set target time in seconds since midnight target = (hour * 60 * 60) + (minute * 60) - + # get current time in seconds since midnight current = (now["hour"] * 60 * 60) + \ (now["minute"] * 60) + now["second"] - + # how long to sleep for naptime = target - current if (naptime <= 0) { @@ -15331,18 +15535,17 @@ alarm: exit 1 } - Finally, the program uses the `system' function (*note I/O -Functions::) to call the `sleep' utility. The `sleep' utility simply -pauses for the given number of seconds. If the exit status is not zero, -the program assumes that `sleep' was interrupted and exits. If `sleep' -exited with an OK status (zero), then the program prints the message in -a loop, again using `sleep' to delay for however many seconds are -necessary: +Finally, the program uses the `system' function (*note I/O Functions::) +to call the `sleep' utility. The `sleep' utility simply pauses for the +given number of seconds. If the exit status is not zero, the program +assumes that `sleep' was interrupted and exits. If `sleep' exited with +an OK status (zero), then the program prints the message in a loop, +again using `sleep' to delay for however many seconds are necessary: # zzzzzz..... go away if interrupted if (system(sprintf("sleep %d", naptime)) != 0) exit 1 - + # time to notify! command = sprintf("sleep %d", delay) for (i = 1; i <= count; i++) { @@ -15351,37 +15554,37 @@ necessary: if (system(command) != 0) break } - + exit 0 } File: gawk.info, Node: Translate Program, Next: Labels Program, Prev: Alarm Program, Up: Miscellaneous Programs -Transliterating Characters --------------------------- +13.3.3 Transliterating Characters +--------------------------------- - The system `tr' utility transliterates characters. For example, it -is often used to map uppercase letters into lowercase for further +The system `tr' utility transliterates characters. For example, it is +often used to map uppercase letters into lowercase for further processing: GENERATE DATA | tr 'A-Z' 'a-z' | PROCESS DATA ... - `tr' requires two lists of characters.(1) When processing the -input, the first character in the first list is replaced with the first +`tr' requires two lists of characters.(1) When processing the input, +the first character in the first list is replaced with the first character in the second list, the second character in the first list is replaced with the second character in the second list, and so on. If there are more characters in the "from" list than in the "to" list, the last character of the "to" list is used for the remaining characters in the "from" list. - Some time ago, a user proposed that a transliteration function should +Some time ago, a user proposed that a transliteration function should be added to `gawk'. The following program was written to prove that character transliteration could be done with a user-level function. This program is not as complete as the system `tr' utility but it does most of the job. - The `translate' program demonstrates one of the few weaknesses of +The `translate' program demonstrates one of the few weaknesses of standard `awk': dealing with individual characters is very painful, requiring repeated use of the `substr', `index', and `gsub' built-in functions (*note String Functions::).(2) There are two functions. The @@ -15396,25 +15599,24 @@ first, `stranslate', takes three arguments: `target' The string on which to do the translation. - Associative arrays make the translation part fairly easy. `t_ar' -holds the "to" characters, indexed by the "from" characters. Then a -simple loop goes through `from', one character at a time. For each -character in `from', if the character appears in `target', `gsub' is -used to change it to the corresponding `to' character. +Associative arrays make the translation part fairly easy. `t_ar' holds +the "to" characters, indexed by the "from" characters. Then a simple +loop goes through `from', one character at a time. For each character +in `from', if the character appears in `target', `gsub' is used to +change it to the corresponding `to' character. - The `translate' function simply calls `stranslate' using `$0' as the +The `translate' function simply calls `stranslate' using `$0' as the target. The main program sets two global variables, `FROM' and `TO', from the command line, and then changes `ARGV' so that `awk' reads from the standard input. - Finally, the processing rule simply calls `translate' for each -record: +Finally, the processing rule simply calls `translate' for each record: # translate.awk --- do tr-like stuff # Bugs: does not handle things like: tr A-Z a-z, it has # to be spelled out. However, if `to' is shorter than `from', # the last character in `to' is used for the rest of `from'. - + function stranslate(from, to, target, lf, lt, t_ar, i, c) { lf = length(from) @@ -15431,12 +15633,12 @@ record: } return target } - + function translate(from, to) { return $0 = stranslate(from, to, $0) } - + # main program BEGIN { if (ARGC < 3) { @@ -15448,13 +15650,13 @@ record: ARGC = 2 ARGV[1] = "-" } - + { translate(FROM, TO) print } - While it is possible to do character transliteration in a user-level +While it is possible to do character transliteration in a user-level function, it is not necessarily efficient, and we (the `gawk' authors) started to consider adding a built-in function. However, shortly after writing this program, we learned that the System V Release 4 `awk' had @@ -15463,52 +15665,52 @@ These functions handle the vast majority of the cases where character transliteration is necessary, and so we chose to simply add those functions to `gawk' as well and then leave well enough alone. - An obvious improvement to this program would be to set up the `t_ar' +An obvious improvement to this program would be to set up the `t_ar' array only once, in a `BEGIN' rule. However, this assumes that the "from" and "to" lists will never change throughout the lifetime of the program. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) On some older System V systems, `tr' may require that the lists -be written as range expressions enclosed in square brackets (`[a-z]') -and quoted, to prevent the shell from attempting a file name expansion. +(1) On some older System V systems, `tr' may require that the lists be +written as range expressions enclosed in square brackets (`[a-z]') and +quoted, to prevent the shell from attempting a file name expansion. This is not a feature. - (2) This program was written before `gawk' acquired the ability to +(2) This program was written before `gawk' acquired the ability to split each character in a string into separate array elements. File: gawk.info, Node: Labels Program, Next: Word Sorting, Prev: Translate Program, Up: Miscellaneous Programs -Printing Mailing Labels ------------------------ +13.3.4 Printing Mailing Labels +------------------------------ - Here is a "real world"(1) program. This script reads lists of names -and addresses and generates mailing labels. Each page of labels has 20 +Here is a "real world"(1) program. This script reads lists of names and +addresses and generates mailing labels. Each page of labels has 20 labels on it, 2 across and 10 down. The addresses are guaranteed to be no more than 5 lines of data. Each address is separated from the next by a blank line. - The basic idea is to read 20 labels worth of data. Each line of -each label is stored in the `line' array. The single rule takes care -of filling the `line' array and printing the page when 20 labels have -been read. +The basic idea is to read 20 labels worth of data. Each line of each +label is stored in the `line' array. The single rule takes care of +filling the `line' array and printing the page when 20 labels have been +read. - The `BEGIN' rule simply sets `RS' to the empty string, so that `awk' +The `BEGIN' rule simply sets `RS' to the empty string, so that `awk' splits records at blank lines (*note Records::). It sets `MAXLINES' to 100, since 100 is the maximum number of lines on the page (20 * 5 = 100). - Most of the work is done in the `printpage' function. The label -lines are stored sequentially in the `line' array. But they have to -print horizontally; `line[1]' next to `line[6]', `line[2]' next to -`line[7]', and so on. Two loops are used to accomplish this. The -outer loop, controlled by `i', steps through every 10 lines of data; -this is each row of labels. The inner loop, controlled by `j', goes -through the lines within the row. As `j' goes from 0 to 4, `i+j' is -the `j'-th line in the row, and `i+j+5' is the entry next to it. The -output ends up looking something like this: +Most of the work is done in the `printpage' function. The label lines +are stored sequentially in the `line' array. But they have to print +horizontally; `line[1]' next to `line[6]', `line[2]' next to `line[7]', +and so on. Two loops are used to accomplish this. The outer loop, +controlled by `i', steps through every 10 lines of data; this is each +row of labels. The inner loop, controlled by `j', goes through the +lines within the row. As `j' goes from 0 to 4, `i+j' is the `j'-th +line in the row, and `i+j+5' is the entry next to it. The output ends +up looking something like this: line 1 line 6 line 2 line 7 @@ -15517,30 +15719,30 @@ output ends up looking something like this: line 5 line 10 ... - As a final note, an extra blank line is printed at lines 21 and 61, -to keep the output lined up on the labels. This is dependent on the +As a final note, an extra blank line is printed at lines 21 and 61, to +keep the output lined up on the labels. This is dependent on the particular brand of labels in use when the program was written. You will also note that there are 2 blank lines at the top and 2 blank lines at the bottom. - The `END' rule arranges to flush the final page of labels; there may +The `END' rule arranges to flush the final page of labels; there may not have been an even multiple of 20 labels in the data: # labels.awk --- print mailing labels - + # Each label is 5 lines of data that may have blank lines. # The label sheets have 2 blank lines at the top and 2 at # the bottom. - + BEGIN { RS = "" ; MAXLINES = 100 } - + function printpage( i, j) { if (Nlines <= 0) return - + printf "\n\n" # header - + for (i = 1; i <= Nlines; i += 10) { if (i == 21 || i == 61) print "" @@ -15551,13 +15753,13 @@ not have been an even multiple of 20 labels in the data: } print "" } - + printf "\n\n" # footer - + for (i in line) line[i] = "" } - + # main rule { if (Count >= 20) { @@ -15572,24 +15774,24 @@ not have been an even multiple of 20 labels in the data: line[++Nlines] = "" Count++ } - + END \ { printpage() } - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) "Real world" is defined as "a program actually used to get +(1) "Real world" is defined as "a program actually used to get something done." File: gawk.info, Node: Word Sorting, Next: History Sorting, Prev: Labels Program, Up: Miscellaneous Programs -Generating Word-Usage Counts ----------------------------- +13.3.5 Generating Word-Usage Counts +----------------------------------- - The following `awk' program prints the number of occurrences of each +The following `awk' program prints the number of occurrences of each word in its input. It illustrates the associative nature of `awk' arrays by using strings as subscripts. It also demonstrates the `for INDEX in ARRAY' mechanism. Finally, it shows how `awk' is used in @@ -15602,13 +15804,13 @@ program listing: for (i = 1; i <= NF; i++) freq[$i]++ } - + END { for (word in freq) printf "%s\t%d\n", word, freq[word] } - This program has two rules. The first rule, because it has an empty +This program has two rules. The first rule, because it has an empty pattern, is executed for every input line. It uses `awk''s field-accessing mechanism (*note Fields::) to pick out the individual words from the line, and the built-in variable `NF' (*note Built-in @@ -15616,7 +15818,7 @@ Variables::) to know how many fields are available. For each input word, it increments an element of the array `freq' to reflect that the word has been seen an additional time. - The second rule, because it has the pattern `END', is not executed +The second rule, because it has the pattern `END', is not executed until the input has been exhausted. It prints out the contents of the `freq' table that has been built up inside the first action. This program has several problems that would prevent it from being useful by @@ -15637,14 +15839,14 @@ itself on real text files: likely to be interested in which words occur most frequently or in having an alphabetized table of how frequently each word occurs. - The way to solve these problems is to use some of `awk''s more -advanced features. First, we use `tolower' to remove case -distinctions. Next, we use `gsub' to remove punctuation characters. -Finally, we use the system `sort' utility to process the output of the -`awk' script. Here is the new version of the program: +The way to solve these problems is to use some of `awk''s more advanced +features. First, we use `tolower' to remove case distinctions. Next, +we use `gsub' to remove punctuation characters. Finally, we use the +system `sort' utility to process the output of the `awk' script. Here +is the new version of the program: # wordfreq.awk --- print list of word frequencies - + { $0 = tolower($0) # remove case distinctions # remove punctuation @@ -15652,14 +15854,14 @@ Finally, we use the system `sort' utility to process the output of the for (i = 1; i <= NF; i++) freq[$i]++ } - + END { for (word in freq) printf "%s\t%d\n", word, freq[word] } - Assuming we have saved this program in a file named `wordfreq.awk', -and that the data is in `file1', the following pipeline: +Assuming we have saved this program in a file named `wordfreq.awk', and +that the data is in `file1', the following pipeline: awk -f wordfreq.awk file1 | sort -k 2nr @@ -15667,15 +15869,15 @@ produces a table of the words appearing in `file1' in order of decreasing frequency. The `awk' program suitably massages the data and produces a word frequency table, which is not ordered. - The `awk' script's output is then sorted by the `sort' utility and +The `awk' script's output is then sorted by the `sort' utility and printed on the terminal. The options given to `sort' specify a sort that uses the second field of each input line (skipping one field), that the sort keys should be treated as numeric quantities (otherwise `15' would come before `5'), and that the sorting should be done in descending (reverse) order. - The `sort' could even be done from within the program, by changing -the `END' action to: +The `sort' could even be done from within the program, by changing the +`END' action to: END { sort = "sort -k 2nr" @@ -15684,29 +15886,29 @@ the `END' action to: close(sort) } - This way of sorting must be used on systems that do not have true -pipes at the command-line (or batch-file) level. See the general -operating system documentation for more information on how to use the -`sort' program. +This way of sorting must be used on systems that do not have true pipes +at the command-line (or batch-file) level. See the general operating +system documentation for more information on how to use the `sort' +program. File: gawk.info, Node: History Sorting, Next: Extract Program, Prev: Word Sorting, Up: Miscellaneous Programs -Removing Duplicates from Unsorted Text --------------------------------------- +13.3.6 Removing Duplicates from Unsorted Text +--------------------------------------------- - The `uniq' program (*note Uniq Program::), removes duplicate lines -from _sorted_ data. +The `uniq' program (*note Uniq Program::), removes duplicate lines from +_sorted_ data. - Suppose, however, you need to remove duplicate lines from a data -file but that you want to preserve the order the lines are in. A good +Suppose, however, you need to remove duplicate lines from a data file +but that you want to preserve the order the lines are in. A good example of this might be a shell history file. The history file keeps a copy of all the commands you have entered, and it is not unusual to repeat a command several times in a row. Occasionally you might want to compact the history by removing duplicate entries. Yet it is desirable to maintain the order of the original commands. - This simple program does the job. It uses two arrays. The `data' +This simple program does the job. It uses two arrays. The `data' array is indexed by the text of each line. For each line, `data[$0]' is incremented. If a particular line has not been seen before, then `data[$0]' is zero. In this case, the text of the line is stored in @@ -15720,40 +15922,39 @@ encountered. The `END' rule simply prints out the lines, in order: if (data[$0]++ == 0) lines[++count] = $0 } - + END { for (i = 1; i <= count; i++) print lines[i] } - This program also provides a foundation for generating other useful +This program also provides a foundation for generating other useful information. For example, using the following `print' statement in the `END' rule indicates how often a particular command is used: print data[lines[i]], lines[i] - This works because `data[$0]' is incremented each time a line is -seen. +This works because `data[$0]' is incremented each time a line is seen. File: gawk.info, Node: Extract Program, Next: Simple Sed, Prev: History Sorting, Up: Miscellaneous Programs -Extracting Programs from Texinfo Source Files ---------------------------------------------- +13.3.7 Extracting Programs from Texinfo Source Files +---------------------------------------------------- - The nodes *Note Library Functions::, and *Note Sample Programs::, -are the top level nodes for a large number of `awk' programs. If you -want to experiment with these programs, it is tedious to have to type -them in by hand. Here we present a program that can extract parts of a +The nodes *Note Library Functions::, and *Note Sample Programs::, are +the top level nodes for a large number of `awk' programs. If you want +to experiment with these programs, it is tedious to have to type them +in by hand. Here we present a program that can extract parts of a Texinfo input file into separate files. - This Info file is written in Texinfo, the GNU project's document +This Info file is written in Texinfo, the GNU project's document formatting language. A single Texinfo source file can be used to produce both printed and online documentation. The Texinfo language is described fully, starting with *Note Top::. - For our purposes, it is enough to know three things about Texinfo -input files: +For our purposes, it is enough to know three things about Texinfo input +files: * The "at" symbol (`@') is special in Texinfo, much as the backslash (`\') is in C or `awk'. Literal `@' symbols are represented in @@ -15768,7 +15969,7 @@ input files: (Unfortunately, TeX isn't always smart enough to do things exactly right, and we have to give it some help.) - The following program, `extract.awk', reads through a Texinfo source +The following program, `extract.awk', reads through a Texinfo source file and does two things, based on the special comments. Upon seeing `@c system ...', it runs a command, by extracting the command text from the control line and passing it on to the `system' function (*note I/O @@ -15779,25 +15980,25 @@ rules in `extract.awk' match either `@c' or `@comment' by letting the are simply removed. `extract.awk' uses the `join' library function (*note Join Function::). - The example programs in the online Texinfo source for `GAWK: -Effective AWK Programming' (`gawk.texi') have all been bracketed inside -`file' and `endfile' lines. The `gawk' distribution uses a copy of -`extract.awk' to extract the sample programs and install many of them -in a standard directory where `gawk' can find them. The Texinfo file -looks something like this: +The example programs in the online Texinfo source for `GAWK: Effective +AWK Programming' (`gawk.texi') have all been bracketed inside `file' and +`endfile' lines. The `gawk' distribution uses a copy of `extract.awk' +to extract the sample programs and install many of them in a standard +directory where `gawk' can find them. The Texinfo file looks something +like this: ... This program has a @code{BEGIN} rule, that prints a nice message: - + @example @c file examples/messages.awk BEGIN @{ print "Don't panic!" @} @c end file @end example - + It also prints some final advice: - + @example @c file examples/messages.awk END @{ print "Always avoid bored archeologists!" @} @@ -15805,17 +16006,17 @@ looks something like this: @end example ... - `extract.awk' begins by setting `IGNORECASE' to one, so that mixed +`extract.awk' begins by setting `IGNORECASE' to one, so that mixed upper- and lowercase letters in the directives won't matter. - The first rule handles calling `system', checking that a command is +The first rule handles calling `system', checking that a command is given (`NF' is at least three) and also checking that the command exits with a zero exit status, signifying OK: # extract.awk --- extract files and run programs # from texinfo files BEGIN { IGNORECASE = 1 } - + /^@c(omment)?[ \t]+system/ \ { if (NF < 3) { @@ -15836,33 +16037,32 @@ with a zero exit status, signifying OK: The variable `e' is used so that the function fits nicely on the screen. - The second rule handles moving data into files. It verifies that a +The second rule handles moving data into files. It verifies that a file name is given in the directive. If the file named is not the current file, then the current file is closed. Keeping the current file open until a new file is encountered allows the use of the `>' redirection for printing the contents, keeping open file management simple. - The `for' loop does the work. It reads lines using `getline' (*note +The `for' loop does the work. It reads lines using `getline' (*note Getline::). For an unexpected end of file, it calls the `unexpected_eof' function. If the line is an "endfile" line, then it breaks out of the loop. If the line is an `@group' or `@end group' line, then it ignores it and goes on to the next line. Similarly, comments within examples are also ignored. - Most of the work is in the following few lines. If the line has no -`@' symbols, the program can print it directly. Otherwise, each -leading `@' must be stripped off. To remove the `@' symbols, the line -is split into separate elements of the array `a', using the `split' -function (*note String Functions::). The `@' symbol is used as the -separator character. Each element of `a' that is empty indicates two -successive `@' symbols in the original line. For each two empty -elements (`@@' in the original file), we have to add a single `@' -symbol back in. +Most of the work is in the following few lines. If the line has no `@' +symbols, the program can print it directly. Otherwise, each leading +`@' must be stripped off. To remove the `@' symbols, the line is split +into separate elements of the array `a', using the `split' function +(*note String Functions::). The `@' symbol is used as the separator +character. Each element of `a' that is empty indicates two successive +`@' symbols in the original line. For each two empty elements (`@@' in +the original file), we have to add a single `@' symbol back in. - When the processing of the array is finished, `join' is called with -the value of `SUBSEP', to rejoin the pieces back into a single line. -That line is then printed to the output file: +When the processing of the array is finished, `join' is called with the +value of `SUBSEP', to rejoin the pieces back into a single line. That +line is then printed to the output file: /^@c(omment)?[ \t]+file/ \ { @@ -15876,7 +16076,7 @@ That line is then printed to the output file: close(curfile) curfile = $3 } - + for (;;) { if ((getline line) <= 0) unexpected_eof() @@ -15904,15 +16104,15 @@ That line is then printed to the output file: } } - An important thing to note is the use of the `>' redirection. -Output done with `>' only opens the file once; it stays open and -subsequent output is appended to the file (*note Redirection::). This -makes it easy to mix program text and explanatory prose for the same -sample source file (as has been done here!) without any hassle. The -file is only closed when a new data file name is encountered or at the -end of the input file. +An important thing to note is the use of the `>' redirection. Output +done with `>' only opens the file once; it stays open and subsequent +output is appended to the file (*note Redirection::). This makes it +easy to mix program text and explanatory prose for the same sample +source file (as has been done here!) without any hassle. The file is +only closed when a new data file name is encountered or at the end of +the input file. - Finally, the function `unexpected_eof' prints an appropriate error +Finally, the function `unexpected_eof' prints an appropriate error message and then exits. The `END' rule handles the final cleanup, closing the open file: @@ -15921,7 +16121,7 @@ closing the open file: FILENAME, FNR) > "/dev/stderr" exit 1 } - + END { if (curfile) close(curfile) @@ -15930,27 +16130,27 @@ closing the open file: File: gawk.info, Node: Simple Sed, Next: Igawk Program, Prev: Extract Program, Up: Miscellaneous Programs -A Simple Stream Editor ----------------------- +13.3.8 A Simple Stream Editor +----------------------------- - The `sed' utility is a stream editor, a program that reads a stream -of data, makes changes to it, and passes it on. It is often used to -make global changes to a large file or to a stream of data generated by -a pipeline of commands. While `sed' is a complicated program in its -own right, its most common use is to perform global substitutions in -the middle of a pipeline: +The `sed' utility is a stream editor, a program that reads a stream of +data, makes changes to it, and passes it on. It is often used to make +global changes to a large file or to a stream of data generated by a +pipeline of commands. While `sed' is a complicated program in its own +right, its most common use is to perform global substitutions in the +middle of a pipeline: command1 < orig.data | sed 's/old/new/g' | command2 > result - Here, `s/old/new/g' tells `sed' to look for the regexp `old' on each +Here, `s/old/new/g' tells `sed' to look for the regexp `old' on each input line and globally replace it with the text `new', i.e., all the occurrences on a line. This is similar to `awk''s `gsub' function (*note String Functions::). - The following program, `awksed.awk', accepts at least two -command-line arguments: the pattern to look for and the text to replace -it with. Any additional arguments are treated as data file names to -process. If none are provided, the standard input is used: +The following program, `awksed.awk', accepts at least two command-line +arguments: the pattern to look for and the text to replace it with. Any +additional arguments are treated as data file names to process. If none +are provided, the standard input is used: # awksed.awk --- do s/foo/bar/g using just print # Thanks to Michael Brennan for the idea @@ -15959,19 +16159,19 @@ process. If none are provided, the standard input is used: print "usage: awksed pat repl [files...]" > "/dev/stderr" exit 1 } - + BEGIN { # validate arguments if (ARGC < 3) usage() - + RS = ARGV[1] ORS = ARGV[2] - + # don't use arguments as files ARGV[1] = ARGV[2] = "" } - + # look ma, no hands! { if (RT == "") @@ -15980,53 +16180,53 @@ process. If none are provided, the standard input is used: print } - The program relies on `gawk''s ability to have `RS' be a regexp, as +The program relies on `gawk''s ability to have `RS' be a regexp, as well as on the setting of `RT' to the actual text that terminates the record (*note Records::). - The idea is to have `RS' be the pattern to look for. `gawk' +The idea is to have `RS' be the pattern to look for. `gawk' automatically sets `$0' to the text between matches of the pattern. This is text that we want to keep, unmodified. Then, by setting `ORS' to the replacement text, a simple `print' statement outputs the text we want to keep, followed by the replacement text. - There is one wrinkle to this scheme, which is what to do if the last +There is one wrinkle to this scheme, which is what to do if the last record doesn't end with text that matches `RS'. Using a `print' statement unconditionally prints the replacement text, which is not correct. However, if the file did not end in text that matches `RS', `RT' is set to the null string. In this case, we can print `$0' using `printf' (*note Printf::). - The `BEGIN' rule handles the setup, checking for the right number of +The `BEGIN' rule handles the setup, checking for the right number of arguments and calling `usage' if there is a problem. Then it sets `RS' and `ORS' from the command-line arguments and sets `ARGV[1]' and `ARGV[2]' to the null string, so that they are not treated as file names (*note ARGC and ARGV::). - The `usage' function prints an error message and exits. Finally, -the single rule handles the printing scheme outlined above, using -`print' or `printf' as appropriate, depending upon the value of `RT'. +The `usage' function prints an error message and exits. Finally, the +single rule handles the printing scheme outlined above, using `print' +or `printf' as appropriate, depending upon the value of `RT'. File: gawk.info, Node: Igawk Program, Prev: Simple Sed, Up: Miscellaneous Programs -An Easy Way to Use Library Functions ------------------------------------- +13.3.9 An Easy Way to Use Library Functions +------------------------------------------- - Using library functions in `awk' can be very beneficial. It -encourages code reuse and the writing of general functions. Programs are -smaller and therefore clearer. However, using library functions is -only easy when writing `awk' programs; it is painful when running them, -requiring multiple `-f' options. If `gawk' is unavailable, then so too -is the `AWKPATH' environment variable and the ability to put `awk' -functions into a library directory (*note Options::). It would be nice -to be able to write programs in the following manner: +Using library functions in `awk' can be very beneficial. It encourages +code reuse and the writing of general functions. Programs are smaller +and therefore clearer. However, using library functions is only easy +when writing `awk' programs; it is painful when running them, requiring +multiple `-f' options. If `gawk' is unavailable, then so too is the +`AWKPATH' environment variable and the ability to put `awk' functions +into a library directory (*note Options::). It would be nice to be +able to write programs in the following manner: # library functions @include getopt.awk @include join.awk ... - + # main program BEGIN { while ((c = getopt(ARGC, ARGV, "a:b:cde")) != -1) @@ -16034,19 +16234,19 @@ to be able to write programs in the following manner: ... } - The following program, `igawk.sh', provides this service. It -simulates `gawk''s searching of the `AWKPATH' variable and also allows -"nested" includes; i.e., a file that is included with `@include' can -contain further `@include' statements. `igawk' makes an effort to only -include files once, so that nested includes don't accidentally include -a library function twice. +The following program, `igawk.sh', provides this service. It simulates +`gawk''s searching of the `AWKPATH' variable and also allows "nested" +includes; i.e., a file that is included with `@include' can contain +further `@include' statements. `igawk' makes an effort to only include +files once, so that nested includes don't accidentally include a +library function twice. - `igawk' should behave just like `gawk' externally. This means it +`igawk' should behave just like `gawk' externally. This means it should accept all of `gawk''s command-line arguments, including the ability to have multiple source files specified via `-f', and the ability to mix command-line and library source files. - The program is written using the POSIX Shell (`sh') command +The program is written using the POSIX Shell (`sh') command language.(1) It works as follows: 1. Loop through the arguments, saving anything that doesn't represent @@ -16072,18 +16272,18 @@ language.(1) It works as follows: command-line arguments that the user supplied (such as the data file names). - This program uses shell variables extensively; for storing command -line arguments, the text of the `awk' program that will expand the -user's program, for the user's original program, and for the expanded -program. Doing so removes some potential problems that might arise -were we to use temporary files instead, at the cost of making the -script somewhat more complicated. +This program uses shell variables extensively; for storing command line +arguments, the text of the `awk' program that will expand the user's +program, for the user's original program, and for the expanded program. +Doing so removes some potential problems that might arise were we to +use temporary files instead, at the cost of making the script somewhat +more complicated. - The initial part of the program turns on shell tracing if the first +The initial part of the program turns on shell tracing if the first argument is `debug'. - The next part loops through all the command-line arguments. There -are several cases of interest: +The next part loops through all the command-line arguments. There are +several cases of interest: `--' This ends the arguments to `igawk'. Anything else should be @@ -16115,7 +16315,7 @@ are several cases of interest: `igawk' prints its version number, runs `gawk --version' to get the `gawk' version information, and then exits. - If none of the `-f', `--file', `-Wfile', `--source', or `-Wsource' +If none of the `-f', `--file', `-Wfile', `--source', or `-Wsource' arguments are supplied, then the first nonoption argument should be the `awk' program. If there are no command-line arguments left, `igawk' prints an error message and exits. Otherwise, the first argument is @@ -16123,7 +16323,7 @@ appended to `program'. In any case, after the arguments have been processed, `program' contains the complete text of the original `awk' program. - The program is as follows: +The program is as follows: #! /bin/sh # igawk --- like gawk but do @include processing @@ -16132,74 +16332,74 @@ program. set -x shift fi - + # A literal newline, so that program text is formmatted correctly n=' ' - + # Initialize variables to empty program= opts= - + while [ $# -ne 0 ] # loop over arguments do case $1 in --) shift; break;; - + -W) shift # The ${x?'message here'} construct prints a # diagnostic if $x is the null string set -- -W"${@?'missing operand'}" continue;; - + -[vF]) opts="$opts $1 '${2?'missing operand'}'" shift;; - + -[vF]*) opts="$opts '$1'" ;; - + -f) program="$program$n@include ${2?'missing operand'}" shift;; - + -f*) f=`expr "$1" : '-f\(.*\)'` program="$program$n@include $f";; - + -[W-]file=*) f=`expr "$1" : '-.file=\(.*\)'` program="$program$n@include $f";; - + -[W-]file) program="$program$n@include ${2?'missing operand'}" shift;; - + -[W-]source=*) t=`expr "$1" : '-.source=\(.*\)'` program="$program$n$t";; - + -[W-]source) program="$program$n${2?'missing operand'}" shift;; - + -[W-]version) echo igawk: version 2.0 1>&2 gawk --version exit 0 ;; - + -[W-]*) opts="$opts '$1'" ;; - + *) break;; esac shift done - + if [ -z "$program" ] then program=${1?'missing program'} shift fi - + # At this point, `program' has the program. - The `awk' program to process `@include' directives is stored in the +The `awk' program to process `@include' directives is stored in the shell variable `expand_prog'. Doing this keeps the shell script readable. The `awk' program reads through the user's program, one line at a time, using `getline' (*note Getline::). The input file names and @@ -16210,8 +16410,8 @@ As each file is finished, the stack is "popped," and the previous input file becomes the current input file again. The process is started by making the original file the first one on the stack. - The `pathto' function does the work of finding the full path to a -file. It simulates `gawk''s behavior when searching the `AWKPATH' +The `pathto' function does the work of finding the full path to a file. +It simulates `gawk''s behavior when searching the `AWKPATH' environment variable (*note AWKPATH Variable::). If a file name has a `/' in it, no path search is done. Otherwise, the file name is concatenated with the name of each directory in the path, and an @@ -16221,12 +16421,12 @@ if a file can be read in `awk' is to go ahead and try to read it with is closed and the file name is returned: expand_prog=' - + function pathto(file, i, t, junk) { if (index(file, "/") != 0) return file - + for (i = 1; i <= ndirs; i++) { t = (pathlist[i] "/" file) if ((getline junk < t) > 0) { @@ -16238,8 +16438,8 @@ is closed and the file name is returned: return "" } - The main program is contained inside one `BEGIN' rule. The first -thing it does is set up the `pathlist' array that `pathto' uses. After +The main program is contained inside one `BEGIN' rule. The first thing +it does is set up the `pathlist' array that `pathto' uses. After splitting the path on `:', null elements are replaced with `"."', which represents the current directory: @@ -16251,26 +16451,26 @@ represents the current directory: pathlist[i] = "." } - The stack is initialized with `ARGV[1]', which will be `/dev/stdin'. +The stack is initialized with `ARGV[1]', which will be `/dev/stdin'. The main loop comes next. Input lines are read in succession. Lines that do not start with `@include' are printed verbatim. If the line does start with `@include', the file name is in `$2'. `pathto' is called to generate the full path. If it cannot, then we print an error message and continue. - The next thing to check is if the file is included already. The +The next thing to check is if the file is included already. The `processed' array is indexed by the full file name of each included file and it tracks this information for us. If the file is seen again, a warning message is printed. Otherwise, the new file name is pushed onto the stack and processing continues. - Finally, when `getline' encounters the end of the input file, the -file is closed and the stack is popped. When `stackptr' is less than -zero, the program is done: +Finally, when `getline' encounters the end of the input file, the file +is closed and the stack is popped. When `stackptr' is less than zero, +the program is done: stackptr = 0 input[stackptr] = ARGV[1] # ARGV[1] is first file - + for (; stackptr >= 0; stackptr--) { while ((getline < input[stackptr]) > 0) { if (tolower($1) != "@include") { @@ -16294,24 +16494,24 @@ zero, the program is done: close(input[stackptr]) } }' # close quote ends `expand_prog' variable - + processed_program=`gawk -- "$expand_prog" /dev/stdin <<EOF $program EOF ` - The shell construct `COMMAND << MARKER' is called a "here document". +The shell construct `COMMAND << MARKER' is called a "here document". Everything in the shell script up to the MARKER is fed to COMMAND as input. The shell processes the contents of the here document for variable and command substitution (and possibly other things as well, depending upon the shell). - The shell construct ``...`' is called "command substitution". The +The shell construct ``...`' is called "command substitution". The output of the command between the two backquotes (grave accents) is substituted into the command line. It is saved as a single string, even if the results contain whitespace. - The expanded program is saved in the variable `processed_program'. +The expanded program is saved in the variable `processed_program'. It's done in these steps: 1. Run `gawk' with the `@include'-processing program (the value of @@ -16324,16 +16524,15 @@ It's done in these steps: 3. The results of this processing are saved in the shell variable `processed_program' by using command substitution. - The last step is to call `gawk' with the expanded program, along -with the original options and command-line arguments that the user -supplied. +The last step is to call `gawk' with the expanded program, along with +the original options and command-line arguments that the user supplied. eval gawk $opts -- '"$processed_program"' '"$@"' - The `eval' command is a shell construct that reruns the shell's -parsing process. This keeps things properly quoted. +The `eval' command is a shell construct that reruns the shell's parsing +process. This keeps things properly quoted. - This version of `igawk' represents my fourth attempt at this program. +This version of `igawk' represents my fourth attempt at this program. There are four key simplifications that make the program work better: * Using `@include' even for the files named with `-f' makes building @@ -16354,19 +16553,19 @@ There are four key simplifications that make the program work better: more features of the `sh' language, making it harder to follow for those who aren't familiar with `sh'. - Also, this program illustrates that it is often worthwhile to combine +Also, this program illustrates that it is often worthwhile to combine `sh' and `awk' programming together. You can usually accomplish quite a lot, without having to resort to low-level programming in C or C++, and it is frequently easier to do certain kinds of string and argument manipulation using the shell than it is in `awk'. - Finally, `igawk' shows that it is not always necessary to add new +Finally, `igawk' shows that it is not always necessary to add new features to a program; they can often be layered on top. With `igawk', there is no real reason to build `@include' processing into `gawk' itself. - As an additional example of this, consider the idea of having two -files in a directory in the search path: +As an additional example of this, consider the idea of having two files +in a directory in the search path: `default.awk' This file contains a set of default library functions, such as @@ -16379,36 +16578,36 @@ files in a directory in the search path: releases, without requiring the system administrator to update it each time by adding the local functions. - One user suggested that `gawk' be modified to automatically read -these files upon startup. Instead, it would be very simple to modify -`igawk' to do this. Since `igawk' can process nested `@include' -directives, `default.awk' could simply contain `@include' statements -for the desired library functions. +One user suggested that `gawk' be modified to automatically read these +files upon startup. Instead, it would be very simple to modify `igawk' +to do this. Since `igawk' can process nested `@include' directives, +`default.awk' could simply contain `@include' statements for the +desired library functions. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Fully explaining the `sh' language is beyond the scope of this +(1) Fully explaining the `sh' language is beyond the scope of this book. We provide some minimal explanations, but see a good shell programming book if you wish to understand things in more depth. - (2) On some very old versions of `awk', the test `getline junk < t' -can loop forever if the file exists but is empty. Caveat emptor. +(2) On some very old versions of `awk', the test `getline junk < t' can +loop forever if the file exists but is empty. Caveat emptor. File: gawk.info, Node: Language History, Next: Installation, Prev: Sample Programs, Up: Top -The Evolution of the `awk' Language -*********************************** +Appendix A The Evolution of the `awk' Language +********************************************** - This Info file describes the GNU implementation of `awk', which -follows the POSIX specification. Many long-time `awk' users learned -`awk' programming with the original `awk' implementation in Version 7 -Unix. (This implementation was the basis for `awk' in Berkeley Unix, -through 4.3-Reno. Subsequent versions of Berkeley Unix, and systems -derived from 4.4BSD-Lite, use various versions of `gawk' for their -`awk'.) This major node briefly describes the evolution of the `awk' -language, with cross-references to other parts of the Info file where -you can find more information. +This Info file describes the GNU implementation of `awk', which follows +the POSIX specification. Many long-time `awk' users learned `awk' +programming with the original `awk' implementation in Version 7 Unix. +(This implementation was the basis for `awk' in Berkeley Unix, through +4.3-Reno. Subsequent versions of Berkeley Unix, and systems derived +from 4.4BSD-Lite, use various versions of `gawk' for their `awk'.) +This major node briefly describes the evolution of the `awk' language, +with cross-references to other parts of the Info file where you can +find more information. * Menu: @@ -16426,11 +16625,11 @@ you can find more information. File: gawk.info, Node: V7/SVR3.1, Next: SVR4, Up: Language History -Major Changes Between V7 and SVR3.1 -=================================== +A.1 Major Changes Between V7 and SVR3.1 +======================================= - The `awk' language evolved considerably between the release of -Version 7 Unix (1978) and the new version that was first made generally +The `awk' language evolved considerably between the release of Version +7 Unix (1978) and the new version that was first made generally available in System V Release 3.1 (1987). This minor node summarizes the changes, with cross-references to further details: @@ -16485,11 +16684,11 @@ the changes, with cross-references to further details: File: gawk.info, Node: SVR4, Next: POSIX, Prev: V7/SVR3.1, Up: Language History -Changes Between SVR3.1 and SVR4 -=============================== +A.2 Changes Between SVR3.1 and SVR4 +=================================== - The System V Release 4 (1989) version of Unix `awk' added these -features (some of which originated in `gawk'): +The System V Release 4 (1989) version of Unix `awk' added these features +(some of which originated in `gawk'): * The `ENVIRON' variable (*note Built-in Variables::). @@ -16526,10 +16725,10 @@ features (some of which originated in `gawk'): File: gawk.info, Node: POSIX, Next: BTL, Prev: SVR4, Up: Language History -Changes Between SVR4 and POSIX `awk' -==================================== +A.3 Changes Between SVR4 and POSIX `awk' +======================================== - The POSIX Command Language and Utilities standard for `awk' (1992) +The POSIX Command Language and Utilities standard for `awk' (1992) introduced the following changes into the language: * The use of `-W' for implementation-specific options (*note @@ -16544,8 +16743,7 @@ introduced the following changes into the language: * More complete documentation of many of the previously undocumented features of the language. - The following common extensions are not permitted by the POSIX -standard: +The following common extensions are not permitted by the POSIX standard: * `\x' escape sequences are not recognized (*note Escape Sequences::). @@ -16571,13 +16769,13 @@ standard: File: gawk.info, Node: BTL, Next: POSIX/GNU, Prev: POSIX, Up: Language History -Extensions in the Bell Laboratories `awk' -========================================= +A.4 Extensions in the Bell Laboratories `awk' +============================================= - Brian Kernighan, one of the original designers of Unix `awk', has -made his version available via his home page (*note Other Versions::). -This minor node describes extensions in his version of `awk' that are -not in POSIX `awk': +Brian Kernighan, one of the original designers of Unix `awk', has made +his version available via his home page (*note Other Versions::). This +minor node describes extensions in his version of `awk' that are not in +POSIX `awk': * The `-mf N' and `-mr N' command-line options to set the maximum number of fields and the maximum record size, respectively (*note @@ -16595,8 +16793,8 @@ not in POSIX `awk': Definition Syntax::). - The Bell Laboratories `awk' also incorporates the following -extensions, originally developed for `gawk': +The Bell Laboratories `awk' also incorporates the following extensions, +originally developed for `gawk': * The `\x' escape sequence (*note Escape Sequences::). @@ -16614,15 +16812,15 @@ extensions, originally developed for `gawk': File: gawk.info, Node: POSIX/GNU, Next: Contributors, Prev: BTL, Up: Language History -Extensions in `gawk' Not in POSIX `awk' -======================================= +A.5 Extensions in `gawk' Not in POSIX `awk' +=========================================== - The GNU implementation, `gawk', adds a large number of features. -This minor node lists them in the order they were added to `gawk'. -They can all be disabled with either the `--traditional' or `--posix' -options (*note Options::). +The GNU implementation, `gawk', adds a large number of features. This +minor node lists them in the order they were added to `gawk'. They can +all be disabled with either the `--traditional' or `--posix' options +(*note Options::). - Version 2.10 of `gawk' introduced the following features: +Version 2.10 of `gawk' introduced the following features: * The `AWKPATH' environment variable for specifying a path search for the `-f' command-line option (*note Options::). @@ -16633,7 +16831,7 @@ options (*note Options::). * The `/dev/stdin', `/dev/stdout', `/dev/stderr' and `/dev/fd/N' special file names (*note Special Files::). - Version 2.13 of `gawk' introduced the following features: +Version 2.13 of `gawk' introduced the following features: * The `FIELDWIDTHS' variable and its effects (*note Constant Size::). @@ -16648,12 +16846,12 @@ options (*note Options::). * The `-W posix' option for full POSIX compliance (*note Options::). - Version 2.14 of `gawk' introduced the following feature: +Version 2.14 of `gawk' introduced the following feature: * The `next file' statement for skipping to the next data file (*note Nextfile Statement::). - Version 2.15 of `gawk' introduced the following features: +Version 2.15 of `gawk' introduced the following features: * The `ARGIND' variable, which tracks the movement of `FILENAME' through `ARGV' (*note Built-in Variables::). @@ -16673,7 +16871,7 @@ options (*note Options::). * The `--source' option for mixing command-line and library-file source code (*note Options::). - Version 3.0 of `gawk' introduced the following features: +Version 3.0 of `gawk' introduced the following features: * `IGNORECASE' changed, now applying to string comparison as well as regexp operations (*note Case-sensitivity::). @@ -16717,7 +16915,7 @@ options (*note Options::). * Amiga support (*note Amiga Installation::). - Version 3.1 of `gawk' introduced the following features: +Version 3.1 of `gawk' introduced the following features: * The `BINMODE' special variable for non-POSIX systems, which allows binary I/O for input and/or output files (*note PC Using::). @@ -16806,17 +17004,19 @@ options (*note Options::). * The `--disable-lint' configuration option to disable lint checking at compile time (*note Additional Configuration Options::). + * POSIX compliance for `sub' and `gsub' (*note Gory Details::). + File: gawk.info, Node: Contributors, Prev: POSIX/GNU, Up: Language History -Major Contributors to `gawk' -============================ +A.6 Major Contributors to `gawk' +================================ Always give credit where credit is due. Anonymous - This minor node names the major contributors to `gawk' and/or this +This minor node names the major contributors to `gawk' and/or this Info file, in approximate chronological order: * Dr. Alfred V. Aho, Dr. Peter J. Weinberger, and Dr. Brian W. @@ -16905,10 +17105,10 @@ Info file, in approximate chronological order: File: gawk.info, Node: Installation, Next: Notes, Prev: Language History, Up: Top -Installing `gawk' -***************** +Appendix B Installing `gawk' +**************************** - This appendix provides instructions for installing `gawk' on the +This appendix provides instructions for installing `gawk' on the various platforms that are supported by the developers. The primary developer supports GNU/Linux (and Unix), whereas the other ports are contributed. *Note Bugs::, for the electronic mail addresses of the @@ -16928,10 +17128,10 @@ people who did the respective ports. File: gawk.info, Node: Gawk Distribution, Next: Unix Installation, Up: Installation -The `gawk' Distribution -======================= +B.1 The `gawk' Distribution +=========================== - This minor node describes how to get the `gawk' distribution, how to +This minor node describes how to get the `gawk' distribution, how to extract it, and then what is in the various files and subdirectories. * Menu: @@ -16943,10 +17143,10 @@ extract it, and then what is in the various files and subdirectories. File: gawk.info, Node: Getting, Next: Extracting, Up: Gawk Distribution -Getting the `gawk' Distribution -------------------------------- +B.1.1 Getting the `gawk' Distribution +------------------------------------- - There are three ways to get GNU software: +There are three ways to get GNU software: * Copy it from someone else who already has it. @@ -16968,8 +17168,8 @@ Getting the `gawk' Distribution * Retrieve `gawk' by using anonymous `ftp' to the Internet host `ftp.gnu.org', in the directory `/gnu/gawk'. - The GNU software archive is mirrored around the world. The -up-to-date list of mirror sites is available from the main FSF web site +The GNU software archive is mirrored around the world. The up-to-date +list of mirror sites is available from the main FSF web site (http://www.gnu.org/order/ftp.html). Try to use one of the mirrors; they will be less busy, and you can usually find one closer to your site. @@ -16977,26 +17177,26 @@ site. File: gawk.info, Node: Extracting, Next: Distribution contents, Prev: Getting, Up: Gawk Distribution -Extracting the Distribution ---------------------------- +B.1.2 Extracting the Distribution +--------------------------------- - `gawk' is distributed as a `tar' file compressed with the GNU Zip +`gawk' is distributed as a `tar' file compressed with the GNU Zip program, `gzip'. - Once you have the distribution (for example, `gawk-3.1.3.tar.gz'), -use `gzip' to expand the file and then use `tar' to extract it. You -can use the following pipeline to produce the `gawk' distribution: +Once you have the distribution (for example, `gawk-3.1.4.tar.gz'), use +`gzip' to expand the file and then use `tar' to extract it. You can +use the following pipeline to produce the `gawk' distribution: # Under System V, add 'o' to the tar options - gzip -d -c gawk-3.1.3.tar.gz | tar -xvpf - + gzip -d -c gawk-3.1.4.tar.gz | tar -xvpf - -This creates a directory named `gawk-3.1.3' in the current directory. +This creates a directory named `gawk-3.1.4' in the current directory. - The distribution file name is of the form `gawk-V.R.P.tar.gz'. The -V represents the major version of `gawk', the R represents the current +The distribution file name is of the form `gawk-V.R.P.tar.gz'. The V +represents the major version of `gawk', the R represents the current release of version V, and the P represents a "patch level", meaning that minor bugs have been fixed in the release. The current patch -level is 3, but when retrieving distributions, you should get the +level is 4, but when retrieving distributions, you should get the version with the highest version, release, and patch level. (Note, however, that patch levels greater than or equal to 80 denote "beta" or nonproduction software; you might not want to retrieve such a version @@ -17007,13 +17207,13 @@ you need to make other arrangements for getting and extracting the File: gawk.info, Node: Distribution contents, Prev: Extracting, Up: Gawk Distribution -Contents of the `gawk' Distribution ------------------------------------ +B.1.3 Contents of the `gawk' Distribution +----------------------------------------- - The `gawk' distribution has a number of C source files, -documentation files, subdirectories, and files related to the -configuration process (*note Unix Installation::), as well as several -subdirectories related to different non-Unix operating systems: +The `gawk' distribution has a number of C source files, documentation +files, subdirectories, and files related to the configuration process +(*note Unix Installation::), as well as several subdirectories related +to different non-Unix operating systems: Various `.c', `.y', and `.h' files The actual `gawk' source code. @@ -17165,10 +17365,10 @@ Various `.c', `.y', and `.h' files File: gawk.info, Node: Unix Installation, Next: Non-Unix Installation, Prev: Gawk Distribution, Up: Installation -Compiling and Installing `gawk' on Unix -======================================= +B.2 Compiling and Installing `gawk' on Unix +=========================================== - Usually, you can compile and install `gawk' by typing only two +Usually, you can compile and install `gawk' by typing only two commands. However, if you use an unusual system, you may need to configure `gawk' for your system yourself. @@ -17181,36 +17381,34 @@ configure `gawk' for your system yourself. File: gawk.info, Node: Quick Installation, Next: Additional Configuration Options, Up: Unix Installation -Compiling `gawk' for Unix -------------------------- +B.2.1 Compiling `gawk' for Unix +------------------------------- - After you have extracted the `gawk' distribution, `cd' to -`gawk-3.1.3'. Like most GNU software, `gawk' is configured +After you have extracted the `gawk' distribution, `cd' to +`gawk-3.1.4'. Like most GNU software, `gawk' is configured automatically for your Unix system by running the `configure' program. This program is a Bourne shell script that is generated automatically using GNU `autoconf'. (The `autoconf' software is described fully starting with *Note Top::.) - To configure `gawk', simply run `configure': +To configure `gawk', simply run `configure': sh ./configure - This produces a `Makefile' and `config.h' tailored to your system. -The `config.h' file describes various facts about your system. You -might want to edit the `Makefile' to change the `CFLAGS' variable, -which controls the command-line options that are passed to the C -compiler (such as optimization levels or compiling for debugging). +This produces a `Makefile' and `config.h' tailored to your system. The +`config.h' file describes various facts about your system. You might +want to edit the `Makefile' to change the `CFLAGS' variable, which +controls the command-line options that are passed to the C compiler +(such as optimization levels or compiling for debugging). - Alternatively, you can add your own values for most `make' variables -on the command line, such as `CC' and `CFLAGS', when running -`configure': +Alternatively, you can add your own values for most `make' variables on +the command line, such as `CC' and `CFLAGS', when running `configure': CC=cc CFLAGS=-g sh ./configure See the file `INSTALL' in the `gawk' distribution for all the details. - After you have run `configure' and possibly edited the `Makefile', -type: +After you have run `configure' and possibly edited the `Makefile', type: make @@ -17225,10 +17423,10 @@ Bugs::.) File: gawk.info, Node: Additional Configuration Options, Next: Configuration Philosophy, Prev: Quick Installation, Up: Unix Installation -Additional Configuration Options --------------------------------- +B.2.2 Additional Configuration Options +-------------------------------------- - There are several additional options you may use on the `configure' +There are several additional options you may use on the `configure' command line when compiling `gawk' from scratch, including: `--enable-portals' @@ -17269,25 +17467,25 @@ command line when compiling `gawk' from scratch, including: File: gawk.info, Node: Configuration Philosophy, Prev: Additional Configuration Options, Up: Unix Installation -The Configuration Process -------------------------- +B.2.3 The Configuration Process +------------------------------- - This minor node is of interest only if you know something about -using the C language and the Unix operating system. +This minor node is of interest only if you know something about using +the C language and the Unix operating system. - The source code for `gawk' generally attempts to adhere to formal +The source code for `gawk' generally attempts to adhere to formal standards wherever possible. This means that `gawk' uses library routines that are specified by the ISO C standard and by the POSIX operating system interface standard. When using an ISO C compiler, function prototypes are used to help improve the compile-time checking. - Many Unix systems do not support all of either the ISO or the POSIX +Many Unix systems do not support all of either the ISO or the POSIX standards. The `missing_d' subdirectory in the `gawk' distribution contains replacement versions of those functions that are most likely to be missing. - The `config.h' file that `configure' creates contains definitions -that describe features of the particular operating system where you are +The `config.h' file that `configure' creates contains definitions that +describe features of the particular operating system where you are attempting to compile `gawk'. The three things described by this file are: what header files are available, so that they can be correctly included, what (supposedly) standard functions are actually available @@ -17295,15 +17493,15 @@ in your C libraries, and various miscellaneous facts about your variant of Unix. For example, there may not be an `st_blksize' element in the `stat' structure. In this case, `HAVE_ST_BLKSIZE' is undefined. - It is possible for your C compiler to lie to `configure'. It may do -so by not exiting with an error when a library function is not -available. To get around this, edit the file `custom.h'. Use an -`#ifdef' that is appropriate for your system, and either `#define' any -constants that `configure' should have defined but didn't, or `#undef' -any constants that `configure' defined and should not have. `custom.h' -is automatically included by `config.h'. +It is possible for your C compiler to lie to `configure'. It may do so +by not exiting with an error when a library function is not available. +To get around this, edit the file `custom.h'. Use an `#ifdef' that is +appropriate for your system, and either `#define' any constants that +`configure' should have defined but didn't, or `#undef' any constants +that `configure' defined and should not have. `custom.h' is +automatically included by `config.h'. - It is also possible that the `configure' program generated by +It is also possible that the `configure' program generated by `autoconf' will not work on your system in some other fashion. If you do have a problem, the file `configure.in' is the input for `autoconf'. You may be able to change this file and generate a new version of @@ -17314,10 +17512,10 @@ be used to send in updates to `configure.in' and/or `custom.h'. File: gawk.info, Node: Non-Unix Installation, Next: Unsupported, Prev: Unix Installation, Up: Installation -Installation on Other Operating Systems -======================================= +B.3 Installation on Other Operating Systems +=========================================== - This minor node describes how to install `gawk' on various non-Unix +This minor node describes how to install `gawk' on various non-Unix systems. * Menu: @@ -17331,16 +17529,16 @@ systems. File: gawk.info, Node: Amiga Installation, Next: BeOS Installation, Up: Non-Unix Installation -Installing `gawk' on an Amiga ------------------------------ +B.3.1 Installing `gawk' on an Amiga +----------------------------------- - You can install `gawk' on an Amiga system using a Unix emulation +You can install `gawk' on an Amiga system using a Unix emulation environment, available via anonymous `ftp' from `ftp.ninemoons.com' in the directory `pub/ade/current'. This includes a shell based on `pdksh'. The primary component of this environment is a Unix emulation library, `ixemul.lib'. - A more complete distribution for the Amiga is available on the Geek +A more complete distribution for the Amiga is available on the Geek Gadgets CD-ROM, available from: CRONUS @@ -17353,58 +17551,58 @@ Gadgets CD-ROM, available from: WWW: `http://www.ninemoons.com' Anonymous `ftp' site: `ftp.ninemoons.com' - Once you have the distribution, you can configure `gawk' simply by +Once you have the distribution, you can configure `gawk' simply by running `configure': configure -v m68k-amigaos - Then run `make' and you should be all set! If these steps do not -work, please send in a bug report (*note Bugs::). +Then run `make' and you should be all set! If these steps do not work, +please send in a bug report (*note Bugs::). File: gawk.info, Node: BeOS Installation, Next: PC Installation, Prev: Amiga Installation, Up: Non-Unix Installation -Installing `gawk' on BeOS -------------------------- +B.3.2 Installing `gawk' on BeOS +------------------------------- - Since BeOS DR9, all the tools that you should need to build `gawk' -are included with BeOS. The process is basically identical to the Unix +Since BeOS DR9, all the tools that you should need to build `gawk' are +included with BeOS. The process is basically identical to the Unix process of running `configure' and then `make'. Full instructions are given below. - You can compile `gawk' under BeOS by extracting the standard sources +You can compile `gawk' under BeOS by extracting the standard sources and running `configure'. You _must_ specify the location prefix for the installation directory. For BeOS DR9 and beyond, the best directory to use is `/boot/home/config', so the `configure' command is: configure --prefix=/boot/home/config - This installs the compiled application into `/boot/home/config/bin', +This installs the compiled application into `/boot/home/config/bin', which is already specified in the standard `PATH'. - Once the configuration process is completed, you can run `make', and +Once the configuration process is completed, you can run `make', and then `make install': $ make ... $ make install - BeOS uses `bash' as its shell; thus, you use `gawk' the same way you +BeOS uses `bash' as its shell; thus, you use `gawk' the same way you would under Unix. If these steps do not work, please send in a bug report (*note Bugs::). File: gawk.info, Node: PC Installation, Next: VMS Installation, Prev: BeOS Installation, Up: Non-Unix Installation -Installation on PC Operating Systems ------------------------------------- +B.3.3 Installation on PC Operating Systems +------------------------------------------ - This minor node covers installation and usage of `gawk' on x86 -machines running DOS, any version of Windows, or OS/2. In this minor -node, the term "Windows32" refers to any of Windows-95/98/ME/NT/2000. +This minor node covers installation and usage of `gawk' on x86 machines +running DOS, any version of Windows, or OS/2. In this minor node, the +term "Windows32" refers to any of Windows-95/98/ME/NT/2000. - The limitations of DOS (and DOS shells under Windows or OS/2) has -meant that various "DOS extenders" are often used with programs such as +The limitations of DOS (and DOS shells under Windows or OS/2) has meant +that various "DOS extenders" are often used with programs such as `gawk'. The varying capabilities of Microsoft Windows 3.1 and Windows32 can add to the confusion. For an overview of the considerations, please refer to `README_d/README.pc' in the @@ -17424,10 +17622,10 @@ distribution. File: gawk.info, Node: PC Binary Installation, Next: PC Compiling, Up: PC Installation -Installing a Prepared Distribution for PC Systems -................................................. +B.3.3.1 Installing a Prepared Distribution for PC Systems +......................................................... - If you have received a binary distribution prepared by the DOS +If you have received a binary distribution prepared by the DOS maintainers, then `gawk' and the necessary support files appear under the `gnu' directory, with executables in `gnu/bin', libraries in `gnu/lib/awk', and manual pages under `gnu/man'. This is designed for @@ -17436,11 +17634,11 @@ files can be installed anywhere provided `AWKPATH' is set properly. Regardless of the installation directory, the first line of `igawk.cmd' and `igawk.bat' (in `gnu/bin') may need to be edited. - The binary distribution contains a separate file describing the +The binary distribution contains a separate file describing the contents. In particular, it may include more than one version of the `gawk' executable. - OS/2 (32 bit, EMX) binary distributions are prepared for the `/usr' +OS/2 (32 bit, EMX) binary distributions are prepared for the `/usr' directory of your preferred drive. Set `UNIXROOT' to your installation drive (e.g., `e:') if you want to install `gawk' onto another drive than the hardcoded default `c:'. Executables appear in `/usr/bin', @@ -17453,19 +17651,19 @@ commands at your prompt (replace `x:' by your installation drive): install-info --info-dir=x:/usr/info x:/usr/info/gawk.info install-info --info-dir=x:/usr/info x:/usr/info/gawkinet.info - However, the files can be installed anywhere provided `AWKPATH' is -set properly. +However, the files can be installed anywhere provided `AWKPATH' is set +properly. - The binary distribution may contain a separate file containing +The binary distribution may contain a separate file containing additional or more detailed installation instructions. File: gawk.info, Node: PC Compiling, Next: PC Dynamic, Prev: PC Binary Installation, Up: PC Installation -Compiling `gawk' for PC Operating Systems -......................................... +B.3.3.2 Compiling `gawk' for PC Operating Systems +................................................. - `gawk' can be compiled for MS-DOS, Windows32, and OS/2 using the GNU +`gawk' can be compiled for MS-DOS, Windows32, and OS/2 using the GNU development tools from DJ Delorie (DJGPP; MS-DOS only) or Eberhard Mattes (EMX; MS-DOS, Windows32 and OS/2). Microsoft Visual C/C++ can be used to build a Windows32 version, and Microsoft C/C++ can be used @@ -17475,37 +17673,38 @@ it.) The file `README_d/README.pc' in the `gawk' distribution contains additional notes, and `pc/Makefile' contains important information on compilation options. - To build `gawk' for MS-DOS, Windows32, and OS/2 (16 bit only; for 32 -bit (EMX) you can use the `configure' script and skip the following +To build `gawk' for MS-DOS, Windows32, and OS/2 (16 bit only; for 32 bit +(EMX) you can use the `configure' script and skip the following paragraphs; for details see below), copy the files in the `pc' directory (_except_ for `ChangeLog') to the directory with the rest of the `gawk' sources. The `Makefile' contains a configuration section with comments and may need to be edited in order to work with your `make' utility. - The `Makefile' contains a number of targets for building various -MS-DOS, Windows32, and OS/2 versions. A list of targets is printed if -the `make' command is given without a target. As an example, to build -`gawk' using the DJGPP tools, enter `make djgpp'. - - Using `make' to run the standard tests and to install `gawk' -requires additional Unix-like tools, including `sh', `sed', and `cp'. -In order to run the tests, the `test/*.ok' files may need to be -converted so that they have the usual DOS-style end-of-line markers. -Most of the tests work properly with Stewartson's shell along with the -companion utilities or appropriate GNU utilities. However, some -editing of `test/Makefile' is required. It is recommended that you copy -the file `pc/Makefile.tst' over the file `test/Makefile' as a -replacement. Details can be found in `README_d/README.pc' and in the -file `pc/Makefile.tst'. - - The 32 bit EMX version of `gawk' works "out of the box" under OS/2. -In principle, it is possible to compile `gawk' the following way: +The `Makefile' contains a number of targets for building various MS-DOS, +Windows32, and OS/2 versions. A list of targets is printed if the `make' +command is given without a target. As an example, to build `gawk' using +the DJGPP tools, enter `make djgpp'. (The DJGPP tools may be found at +`ftp://ftp.delorie.com/pub/djgpp/current/v2gnu/'.) + +Using `make' to run the standard tests and to install `gawk' requires +additional Unix-like tools, including `sh', `sed', and `cp'. In order +to run the tests, the `test/*.ok' files may need to be converted so +that they have the usual DOS-style end-of-line markers. Most of the +tests work properly with Stewartson's shell along with the companion +utilities or appropriate GNU utilities. However, some editing of +`test/Makefile' is required. It is recommended that you copy the file +`pc/Makefile.tst' over the file `test/Makefile' as a replacement. +Details can be found in `README_d/README.pc' and in the file +`pc/Makefile.tst'. + +The 32 bit EMX version of `gawk' works "out of the box" under OS/2. In +principle, it is possible to compile `gawk' the following way: $ ./configure $ make - This is not recommended, though. To get an OMF executable you should +This is not recommended, though. To get an OMF executable you should use the following commands at your `sh' prompt: $ CPPFLAGS="-D__ST_MT_ERRNO__" @@ -17519,24 +17718,24 @@ use the following commands at your `sh' prompt: $ ./configure --prefix=c:/usr --without-included-gettext $ make AR=emxomfar - These are just suggestions. You may use any other set of +These are just suggestions. You may use any other set of (self-consistent) environment variables and compiler flags. - To get an FHS-compliant file hierarchy it is recommended to use the +To get an FHS-compliant file hierarchy it is recommended to use the additional `configure' options `--infodir=c:/usr/share/info', `--mandir=c:/usr/share/man' and `--libexecdir=c:/usr/lib'. - The internal `gettext' library tends to be problematic. It is -therefore recommended to use either an external one +The internal `gettext' library tends to be problematic. It is therefore +recommended to use either an external one (`--without-included-gettext') or to disable NLS entirely (`--disable-nls'). - If you use GCC 2.95 or newer it is recommended to use also: +If you use GCC 2.95 or newer it is recommended to use also: $ LIBS="-lgcc" $ export LIBS - You can also get an `a.out' executable if you prefer: +You can also get an `a.out' executable if you prefer: $ CPPFLAGS="-D__ST_MT_ERRNO__" $ export CPPFLAGS @@ -17548,52 +17747,52 @@ therefore recommended to use either an external one $ ./configure --prefix=c:/usr --without-included-gettext $ make - *Note:* Even if the compiled `gawk.exe' (`a.out') executable -contains a DOS header, it does _not_ work under DOS. To compile an -executable that runs under DOS, `"-DPIPES_SIMULATED"' must be added to -`CPPFLAGS'. But then some nonstandard extensions of `gawk' (e.g., -`|&') do not work! + NOTE: Even if the compiled `gawk.exe' (`a.out') executable + contains a DOS header, it does _not_ work under DOS. To compile an + executable that runs under DOS, `"-DPIPES_SIMULATED"' must be + added to `CPPFLAGS'. But then some nonstandard extensions of + `gawk' (e.g., `|&') do not work! - After compilation the internal tests can be performed. Enter `make +After compilation the internal tests can be performed. Enter `make check CMP="diff -a"' at your command prompt. All tests but the `pid' test are expected to work properly. The `pid' test fails because child processes are not started by `fork()'. - `make install' works as expected. +`make install' works as expected. - *Note:* Most OS/2 ports of GNU `make' are not able to handle the -Makefiles of this package. If you encounter any problems with `make' -try GNU Make 3.79.1 or later versions. You should find the latest -version on `http://www.unixos2.org/sw/pub/binary/make/' or on -`ftp://hobbes.nmsu.edu/pub/os2/'. + NOTE: Most OS/2 ports of GNU `make' are not able to handle the + Makefiles of this package. If you encounter any problems with + `make' try GNU Make 3.79.1 or later versions. You should find the + latest version on `http://www.unixos2.org/sw/pub/binary/make/' or + on `ftp://hobbes.nmsu.edu/pub/os2/'. File: gawk.info, Node: PC Dynamic, Next: PC Using, Prev: PC Compiling, Up: PC Installation -Compiling `gawk' For Dynamic Libraries -...................................... +B.3.3.3 Compiling `gawk' For Dynamic Libraries +.............................................. - To compile `gawk' with dynamic extension support, uncomment the +To compile `gawk' with dynamic extension support, uncomment the definitions of `DYN_FLAGS', `DYN_EXP', `DYN_OBJ', and `DYN_MAKEXP' in the configuration section of the `Makefile'. There are two definitions for `DYN_MAKEXP': pick the one that matches your target. - To build some of the example extension libraries, `cd' to the -extension directory and copy `Makefile.pc' to `Makefile'. You can then -build using the same two targets. To run the example `awk' scripts, -you'll need to either change the call to the `extension' function to -match the name of the library (for instance, change `"./ordchr.so"' to +To build some of the example extension libraries, `cd' to the extension +directory and copy `Makefile.pc' to `Makefile'. You can then build +using the same two targets. To run the example `awk' scripts, you'll +need to either change the call to the `extension' function to match the +name of the library (for instance, change `"./ordchr.so"' to `"ordchr.dll"' or simply `"ordchr"'), or rename the library to match the call (for instance, rename `ordchr.dll' to `ordchr.so'). - If you build `gawk.exe' with one compiler but want to build an +If you build `gawk.exe' with one compiler but want to build an extension library with the other, you need to copy the import library. Visual C uses a library called `gawk.lib', while MinGW uses a library called `libgawk.a'. These files are equivalent and will interoperate if you give them the correct name. The resulting shared libraries are also interoperable. - To create your own extension library, you can use the examples as +To create your own extension library, you can use the examples as models, but you're essentially on your own. Post to `comp.lang.awk' or send electronic mail to <ptjm@interlog.com> if you have problems getting started. If you need to access functions or variables which are not @@ -17601,7 +17800,7 @@ exported by `gawk.exe', add them to `gawkw32.def' and rebuild. You should also add `ATTRIBUTE_EXPORTED' to the declaration in `awk.h' of any variables you add to `gawkw32.def'. - Note that extension libraries have the name of the `awk' executable +Note that extension libraries have the name of the `awk' executable embedded in them at link time, so they will work only with `gawk.exe'. In particular, they won't work if you rename `gawk.exe' to `awk.exe' or if you try to use `pgawk.exe'. You can perform profiling by temporarily @@ -17609,28 +17808,28 @@ renaming `pgawk.exe' to `gawk.exe'. You can resolve this problem by changing the program name in the definition of `DYN_MAKEXP' for your compiler. - On Windows32, libraries are sought first in the current directory, -then in the directory containing `gawk.exe', and finally through the -`PATH' environment variable. +On Windows32, libraries are sought first in the current directory, then +in the directory containing `gawk.exe', and finally through the `PATH' +environment variable. File: gawk.info, Node: PC Using, Next: Cygwin, Prev: PC Dynamic, Up: PC Installation -Using `gawk' on PC Operating Systems -.................................... +B.3.3.4 Using `gawk' on PC Operating Systems +............................................ - With the exception of the Cygwin environment, the `|&' operator and +With the exception of the Cygwin environment, the `|&' operator and TCP/IP networking (*note TCP/IP Networking::) are not supported for MS-DOS or MS-Windows. EMX (OS/2 only) does support at least the `|&' operator. - The OS/2 and MS-DOS versions of `gawk' search for program files as +The OS/2 and MS-DOS versions of `gawk' search for program files as described in *Note AWKPATH Variable::. However, semicolons (rather than colons) separate elements in the `AWKPATH' variable. If `AWKPATH' is not set or is empty, then the default search path for OS/2 (16 bit) and MS-DOS versions is `".;c:/lib/awk;c:/gnu/lib/awk"'. - The search path for OS/2 (32 bit, EMX) is determined by the prefix +The search path for OS/2 (32 bit, EMX) is determined by the prefix directory (most likely `/usr' or `c:/usr') that has been specified as an option of the `configure' script like it is the case for the Unix versions. If `c:/usr' is the prefix directory then the default search @@ -17642,7 +17841,7 @@ specific drive is also searched for program files. E.g., if `UNIXROOT' is set to `e:' the complete default search path is `".;c:/usr/share/awk;e:/usr/share/awk"'. - An `sh'-like shell (as opposed to `command.com' under MS-DOS or +An `sh'-like shell (as opposed to `command.com' under MS-DOS or `cmd.exe' under OS/2) may be useful for `awk' programming. Ian Stewartson has written an excellent shell for MS-DOS and OS/2, Daisuke Aoyama has ported GNU `bash' to MS-DOS using the DJGPP tools, and @@ -17653,7 +17852,7 @@ documentation for handling command lines; in particular, the setting for `gawk' in the shell configuration may need to be changed and the `ignoretype' option may also be of interest. - Under OS/2 and DOS, `gawk' (and many other text programs) silently +Under OS/2 and DOS, `gawk' (and many other text programs) silently translate end-of-line `"\r\n"' to `"\n"' on input and `"\n"' to `"\r\n"' on output. A special `BINMODE' variable allows control over these translations and is interpreted as follows: @@ -17678,18 +17877,18 @@ accomplished by using an appropriate `-v BINMODE=N' option on the command line. `BINMODE' is set at the time a file or pipe is opened and cannot be changed mid-stream. - The name `BINMODE' was chosen to match `mawk' (*note Other -Versions::). Both `mawk' and `gawk' handle `BINMODE' similarly; -however, `mawk' adds a `-W BINMODE=N' option and an environment -variable that can set `BINMODE', `RS', and `ORS'. The files -`binmode[1-3].awk' (under `gnu/lib/awk' in some of the prepared -distributions) have been chosen to match `mawk''s `-W BINMODE=N' -option. These can be changed or discarded; in particular, the setting -of `RS' giving the fewest "surprises" is open to debate. `mawk' uses -`RS = "\r\n"' if binary mode is set on read, which is appropriate for -files with the DOS-style end-of-line. - - To illustrate, the following examples set binary mode on writes for +The name `BINMODE' was chosen to match `mawk' (*note Other Versions::). +Both `mawk' and `gawk' handle `BINMODE' similarly; however, `mawk' adds +a `-W BINMODE=N' option and an environment variable that can set +`BINMODE', `RS', and `ORS'. The files `binmode[1-3].awk' (under +`gnu/lib/awk' in some of the prepared distributions) have been chosen +to match `mawk''s `-W BINMODE=N' option. These can be changed or +discarded; in particular, the setting of `RS' giving the fewest +"surprises" is open to debate. `mawk' uses `RS = "\r\n"' if binary +mode is set on read, which is appropriate for files with the DOS-style +end-of-line. + +To illustrate, the following examples set binary mode on writes for standard output and other files, and set `ORS' as the "usual" DOS-style end-of-line: @@ -17715,39 +17914,39 @@ moved into the `BEGIN' rule. File: gawk.info, Node: Cygwin, Prev: PC Using, Up: PC Installation -Using `gawk' In The Cygwin Environment -...................................... +B.3.3.5 Using `gawk' In The Cygwin Environment +.............................................. - `gawk' can be used "out of the box" under Windows if you are using -the Cygwin environment.(1) This environment provides an excellent +`gawk' can be used "out of the box" under Windows if you are using the +Cygwin environment.(1) This environment provides an excellent simulation of Unix, using the GNU tools, such as `bash', the GNU Compiler Collection (GCC), GNU Make, and other GNU tools. Compilation and installation for Cygwin is the same as for a Unix system: - tar -xvpzf gawk-3.1.3.tar.gz - cd gawk-3.1.3 + tar -xvpzf gawk-3.1.4.tar.gz + cd gawk-3.1.4 ./configure make - When compared to GNU/Linux on the same system, the `configure' step -on Cygwin takes considerably longer. However, it does finish, and then +When compared to GNU/Linux on the same system, the `configure' step on +Cygwin takes considerably longer. However, it does finish, and then the `make' proceeds as usual. - *Note:* The `|&' operator and TCP/IP networking (*note TCP/IP -Networking::) are fully supported in the Cygwin environment. This is -not true for any other environment for MS-DOS or MS-Windows. + NOTE: The `|&' operator and TCP/IP networking (*note TCP/IP + Networking::) are fully supported in the Cygwin environment. This + is not true for any other environment for MS-DOS or MS-Windows. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) `http://www.cygwin.com' +(1) `http://www.cygwin.com' File: gawk.info, Node: VMS Installation, Prev: PC Installation, Up: Non-Unix Installation -How to Compile and Install `gawk' on VMS ----------------------------------------- +B.3.4 How to Compile and Install `gawk' on VMS +---------------------------------------------- - This node describes how to compile and install `gawk' under VMS. +This node describes how to compile and install `gawk' under VMS. * Menu: @@ -17759,10 +17958,10 @@ How to Compile and Install `gawk' on VMS File: gawk.info, Node: VMS Compilation, Next: VMS Installation Details, Up: VMS Installation -Compiling `gawk' on VMS -....................... +B.3.4.1 Compiling `gawk' on VMS +............................... - To compile `gawk' under VMS, there is a `DCL' command procedure that +To compile `gawk' under VMS, there is a `DCL' command procedure that issues all the necessary `CC' and `LINK' commands. There is also a `Makefile' for use with the `MMS' utility. From the source directory, use either: @@ -17773,7 +17972,7 @@ or: $ MMS/DESCRIPTION=[.VMS]DESCRIP.MMS GAWK - Depending upon which C compiler you are using, follow one of the sets +Depending upon which C compiler you are using, follow one of the sets of instructions in this table: VAX C V3.x @@ -17797,17 +17996,16 @@ DEC C Edit `vmsbuild.com' or `descrip.mms' according to their comments. No changes to `config.h' are needed. - `gawk' has been tested under VAX/VMS 5.5-1 using VAX C V3.2, and GNU -C 1.40 and 2.3. It should work without modifications for VMS V4.6 and -up. +`gawk' has been tested under VAX/VMS 5.5-1 using VAX C V3.2, and GNU C +1.40 and 2.3. It should work without modifications for VMS V4.6 and up. File: gawk.info, Node: VMS Installation Details, Next: VMS Running, Prev: VMS Compilation, Up: VMS Installation -Installing `gawk' on VMS -........................ +B.3.4.2 Installing `gawk' on VMS +................................ - To install `gawk', all you need is a "foreign" command, which is a +To install `gawk', all you need is a "foreign" command, which is a `DCL' symbol whose value begins with a dollar sign. For example: $ GAWK :== $disk1:[gnubin]GAWK @@ -17818,7 +18016,7 @@ symbol should be placed in the `login.com' of any user who wants to run Alternatively, the symbol may be placed in the system-wide `sylogin.com' procedure, which allows all users to run `gawk'. - Optionally, the help entry can be loaded into a VMS help library: +Optionally, the help entry can be loaded into a VMS help library: $ LIBRARY/HELP SYS$HELP:HELPLIB [.VMS]GAWK.HLP @@ -17831,7 +18029,7 @@ command: provides information about both the `gawk' implementation and the `awk' programming language. - The logical name `AWK_LIBRARY' can designate a default location for +The logical name `AWK_LIBRARY' can designate a default location for `awk' program files. For the `-f' option, if the specified file name has no device or directory path information in it, `gawk' looks in the current directory first, then in the directory specified by the @@ -17844,15 +18042,15 @@ benignly. File: gawk.info, Node: VMS Running, Next: VMS POSIX, Prev: VMS Installation Details, Up: VMS Installation -Running `gawk' on VMS -..................... +B.3.4.3 Running `gawk' on VMS +............................. - Command-line parsing and quoting conventions are significantly -different on VMS, so examples in this Info file or from other sources -often need minor changes. They _are_ minor though, and all `awk' -programs should run correctly. +Command-line parsing and quoting conventions are significantly different +on VMS, so examples in this Info file or from other sources often need +minor changes. They _are_ minor though, and all `awk' programs should +run correctly. - Here are a couple of trivial tests: +Here are a couple of trivial tests: $ gawk -- "BEGIN {print ""Hello, World!""}" $ gawk -"W" version @@ -17860,8 +18058,8 @@ programs should run correctly. Note that uppercase and mixed-case text must be quoted. - The VMS port of `gawk' includes a `DCL'-style interface in addition -to the original shell-style interface (see the help entry for details). +The VMS port of `gawk' includes a `DCL'-style interface in addition to +the original shell-style interface (see the help entry for details). One side effect of dual command-line parsing is that if there is only a single parameter (as in the quoted string program above), the command becomes ambiguous. To work around this, the normally optional `--' @@ -17869,21 +18067,21 @@ flag is required to force Unix style rather than `DCL' parsing. If any other dash-type options (or multiple parameters such as data files to process) are present, there is no ambiguity and `--' can be omitted. - The default search path, when looking for `awk' program files -specified by the `-f' option, is `"SYS$DISK:[],AWK_LIBRARY:"'. The -logical name `AWKPATH' can be used to override this default. The format -of `AWKPATH' is a comma-separated list of directory specifications. -When defining it, the value should be quoted so that it retains a single +The default search path, when looking for `awk' program files specified +by the `-f' option, is `"SYS$DISK:[],AWK_LIBRARY:"'. The logical name +`AWKPATH' can be used to override this default. The format of +`AWKPATH' is a comma-separated list of directory specifications. When +defining it, the value should be quoted so that it retains a single translation and not a multitranslation `RMS' searchlist. File: gawk.info, Node: VMS POSIX, Prev: VMS Running, Up: VMS Installation -Building and Using `gawk' on VMS POSIX -...................................... +B.3.4.4 Building and Using `gawk' on VMS POSIX +.............................................. - Ignore the instructions above, although `vms/gawk.hlp' should still -be made available in a help library. The source tree should be unpacked +Ignore the instructions above, although `vms/gawk.hlp' should still be +made available in a help library. The source tree should be unpacked into a container file subsystem rather than into the ordinary VMS filesystem. Make sure that the two scripts, `configure' and `vms/posix-cc.sh', are executable; use `chmod +x' on them if necessary. @@ -17899,21 +18097,20 @@ compiler directly; ignore any warnings from `make' about being unable to redefine `CC'. `configure' takes a very long time to execute, but at least it provides incremental feedback as it runs. - This has been tested with VAX/VMS V6.2, VMS POSIX V2.0, and DEC C -V5.2. +This has been tested with VAX/VMS V6.2, VMS POSIX V2.0, and DEC C V5.2. - Once built, `gawk' works like any other shell utility. Unlike the +Once built, `gawk' works like any other shell utility. Unlike the normal VMS port of `gawk', no special command-line manipulation is needed in the VMS POSIX environment. File: gawk.info, Node: Unsupported, Next: Bugs, Prev: Non-Unix Installation, Up: Installation -Unsupported Operating System Ports -================================== +B.4 Unsupported Operating System Ports +====================================== - This sections describes systems for which the `gawk' port is no -longer supported. +This sections describes systems for which the `gawk' port is no longer +supported. * Menu: @@ -17923,19 +18120,19 @@ longer supported. File: gawk.info, Node: Atari Installation, Next: Tandem Installation, Up: Unsupported -Installing `gawk' on the Atari ST ---------------------------------- +B.4.1 Installing `gawk' on the Atari ST +--------------------------------------- - The Atari port is no longer supported. It is included for those who +The Atari port is no longer supported. It is included for those who might want to use it but it is no longer being actively maintained. - There are no substantial differences when installing `gawk' on -various Atari models. Compiled `gawk' executables do not require a -large amount of memory with most `awk' programs, and should run on all +There are no substantial differences when installing `gawk' on various +Atari models. Compiled `gawk' executables do not require a large +amount of memory with most `awk' programs, and should run on all Motorola processor-based models (called further ST, even if that is not exactly right). - In order to use `gawk', you need to have a shell, either text or +In order to use `gawk', you need to have a shell, either text or graphics, that does not map all the characters of a command line to uppercase. Maintaining case distinction in option flags is very important (*note Options::). These days this is the default and it may @@ -17953,36 +18150,36 @@ vital. File: gawk.info, Node: Atari Compiling, Next: Atari Using, Up: Atari Installation -Compiling `gawk' on the Atari ST -................................ +B.4.1.1 Compiling `gawk' on the Atari ST +........................................ - A proper compilation of `gawk' sources when `sizeof(int)' differs -from `sizeof(void *)' requires an ISO C compiler. An initial port was -done with `gcc'. You may actually prefer executables where `int's are -four bytes wide but the other variant works as well. +A proper compilation of `gawk' sources when `sizeof(int)' differs from +`sizeof(void *)' requires an ISO C compiler. An initial port was done +with `gcc'. You may actually prefer executables where `int's are four +bytes wide but the other variant works as well. - You may need quite a bit of memory when trying to recompile the -`gawk' sources, as some source files (`regex.c' in particular) are quite -big. If you run out of memory compiling such a file, try reducing the +You may need quite a bit of memory when trying to recompile the `gawk' +sources, as some source files (`regex.c' in particular) are quite big. +If you run out of memory compiling such a file, try reducing the optimization level for this particular file, which may help. - With a reasonable shell (`bash' will do), you have a pretty good -chance that the `configure' utility will succeed, and in particular if -you run GNU/Linux, MiNT or a similar operating system. Otherwise -sample versions of `config.h' and `Makefile.st' are given in the -`atari' subdirectory and can be edited and copied to the corresponding -files in the main source directory. Even if `configure' produces -something, it might be advisable to compare its results with the sample -versions and possibly make adjustments. +With a reasonable shell (`bash' will do), you have a pretty good chance +that the `configure' utility will succeed, and in particular if you run +GNU/Linux, MiNT or a similar operating system. Otherwise sample +versions of `config.h' and `Makefile.st' are given in the `atari' +subdirectory and can be edited and copied to the corresponding files in +the main source directory. Even if `configure' produces something, it +might be advisable to compare its results with the sample versions and +possibly make adjustments. - Some `gawk' source code fragments depend on a preprocessor define +Some `gawk' source code fragments depend on a preprocessor define `atarist'. This basically assumes the TOS environment with `gcc'. Modify these sections as appropriate if they are not right for your environment. Also see the remarks about `AWKPATH' and `envsep' in *Note Atari Using::. - As shipped, the sample `config.h' claims that the `system' function -is missing from the libraries, which is not true, and an alternative +As shipped, the sample `config.h' claims that the `system' function is +missing from the libraries, which is not true, and an alternative implementation of this function is provided in `unsupported/atari/system.c'. Depending upon your particular combination of shell and operating system, you might want to change the @@ -17991,13 +18188,13 @@ file to indicate that `system' is available. File: gawk.info, Node: Atari Using, Prev: Atari Compiling, Up: Atari Installation -Running `gawk' on the Atari ST -.............................. +B.4.1.2 Running `gawk' on the Atari ST +...................................... - An executable version of `gawk' should be placed, as usual, anywhere -in your `PATH' where your shell can find it. +An executable version of `gawk' should be placed, as usual, anywhere in +your `PATH' where your shell can find it. - While executing, the Atari version of `gawk' creates a number of +While executing, the Atari version of `gawk' creates a number of temporary files. When using `gcc' libraries for TOS, `gawk' looks for either of the environment variables, `TEMP' or `TMPDIR', in that order. If either one is found, its value is assumed to be a directory for @@ -18006,21 +18203,20 @@ memory, it is a good idea to put it on a RAM drive. If neither `TEMP' nor `TMPDIR' are found, then `gawk' uses the current directory for its temporary files. - The ST version of `gawk' searches for its program files, as -described in *Note AWKPATH Variable::. The default value for the -`AWKPATH' variable is taken from `DEFPATH' defined in `Makefile'. The -sample `gcc'/TOS `Makefile' for the ST in the distribution sets -`DEFPATH' to `".,c:\lib\awk,c:\gnu\lib\awk"'. The search path can be -modified by explicitly setting `AWKPATH' to whatever you want. Note -that colons cannot be used on the ST to separate elements in the -`AWKPATH' variable, since they have another reserved meaning. Instead, -you must use a comma to separate elements in the path. When -recompiling, the separating character can be modified by initializing -the `envsep' variable in `unsupported/atari/gawkmisc.atr' to another -value. - - Although `awk' allows great flexibility in doing I/O redirections -from within a program, this facility should be used with care on the ST +The ST version of `gawk' searches for its program files, as described in +*Note AWKPATH Variable::. The default value for the `AWKPATH' variable +is taken from `DEFPATH' defined in `Makefile'. The sample `gcc'/TOS +`Makefile' for the ST in the distribution sets `DEFPATH' to +`".,c:\lib\awk,c:\gnu\lib\awk"'. The search path can be modified by +explicitly setting `AWKPATH' to whatever you want. Note that colons +cannot be used on the ST to separate elements in the `AWKPATH' +variable, since they have another reserved meaning. Instead, you must +use a comma to separate elements in the path. When recompiling, the +separating character can be modified by initializing the `envsep' +variable in `unsupported/atari/gawkmisc.atr' to another value. + +Although `awk' allows great flexibility in doing I/O redirections from +within a program, this facility should be used with care on the ST running under TOS. In some circumstances, the OS routines for file-handle pool processing lose track of certain events, causing the computer to crash and requiring a reboot. Often a warm reboot is @@ -18030,7 +18226,7 @@ program using `print' statements explicitly redirected to `/dev/stdout', while other `print' statements use the default standard output, and a calling shell has redirected standard output to a file. - When `gawk' is compiled with the ST version of `gcc' and its usual +When `gawk' is compiled with the ST version of `gcc' and its usual libraries, it accepts both `/' and `\' as path separators. While this is convenient, it should be remembered that this removes one technically valid character (`/') from your file name. It may also @@ -18044,36 +18240,35 @@ Sequences::). File: gawk.info, Node: Tandem Installation, Prev: Atari Installation, Up: Unsupported -Installing `gawk' on a Tandem ------------------------------ +B.4.2 Installing `gawk' on a Tandem +----------------------------------- - The Tandem port is only minimally supported. The port's contributor -no longer has access to a Tandem system. +The Tandem port is only minimally supported. The port's contributor no +longer has access to a Tandem system. - The Tandem port was done on a Cyclone machine running D20. The port -is pretty clean and all facilities seem to work except for the I/O -piping facilities (*note Getline/Pipe::, *Note Getline/Variable/Pipe::, -and *Note Redirection::), which is just too foreign a concept for -Tandem. +The Tandem port was done on a Cyclone machine running D20. The port is +pretty clean and all facilities seem to work except for the I/O piping +facilities (*note Getline/Pipe::, *Note Getline/Variable/Pipe::, and +*Note Redirection::), which is just too foreign a concept for Tandem. - To build a Tandem executable from source, download all of the files -so that the file names on the Tandem box conform to the restrictions of +To build a Tandem executable from source, download all of the files so +that the file names on the Tandem box conform to the restrictions of D20. For example, `array.c' becomes `ARRAYC', and `awk.h' becomes `AWKH'. The totally Tandem-specific files are in the `tandem' "subvolume" (`unsupported/tandem' in the `gawk' distribution) and should be copied to the main source directory before building `gawk'. - The file `compit' can then be used to compile and bind an executable. +The file `compit' can then be used to compile and bind an executable. Alas, there is no `configure' or `make'. - Usage is the same as for Unix, except that D20 requires all `{' and -`}' characters to be escaped with `~' on the command line (but _not_ in +Usage is the same as for Unix, except that D20 requires all `{' and `}' +characters to be escaped with `~' on the command line (but _not_ in script files). Also, the standard Tandem syntax for `/in filename,out filename/' must be used instead of the usual Unix `<' and `>' for file redirection. (Redirection options on `getline', `print' etc., are supported.) - The `-mr VAL' option (*note Options::) has been "stolen" to enable +The `-mr VAL' option (*note Options::) has been "stolen" to enable Tandem users to process fixed-length records with no "end-of-line" character. That is, `-mr 74' tells `gawk' to read the input file as fixed 74-byte records. @@ -18081,59 +18276,58 @@ fixed 74-byte records. File: gawk.info, Node: Bugs, Next: Other Versions, Prev: Unsupported, Up: Installation -Reporting Problems and Bugs -=========================== +B.5 Reporting Problems and Bugs +=============================== There is nothing more dangerous than a bored archeologist. The Hitchhiker's Guide to the Galaxy - If you have problems with `gawk' or think that you have found a bug, +If you have problems with `gawk' or think that you have found a bug, please report it to the developers; we cannot promise to do anything but we might well want to fix it. - Before reporting a bug, make sure you have actually found a real bug. +Before reporting a bug, make sure you have actually found a real bug. Carefully reread the documentation and see if it really says you can do what you're trying to do. If it's not clear whether you should be able to do something or not, report that too; it's a bug in the documentation! - Before reporting a bug or trying to fix it yourself, try to isolate -it to the smallest possible `awk' program and input data file that +Before reporting a bug or trying to fix it yourself, try to isolate it +to the smallest possible `awk' program and input data file that reproduces the problem. Then send us the program and data file, some idea of what kind of Unix system you're using, the compiler you used to compile `gawk', and the exact results `gawk' gave you. Also say what you expected to occur; this helps us decide whether the problem is really in the documentation. - Once you have a precise problem, send email to <bug-gawk@gnu.org>. +Once you have a precise problem, send email to <bug-gawk@gnu.org>. - Please include the version number of `gawk' you are using. You can -get this information with the command `gawk --version'. Using this -address automatically sends a carbon copy of your mail to me. If -necessary, I can be reached directly at <arnold@gnu.org>. The bug -reporting address is preferred since the email list is archived at the -GNU Project. _All email should be in English, since that is my native -language._ +Please include the version number of `gawk' you are using. You can get +this information with the command `gawk --version'. Using this address +automatically sends a carbon copy of your mail to me. If necessary, I +can be reached directly at <arnold@gnu.org>. The bug reporting address +is preferred since the email list is archived at the GNU Project. _All +email should be in English, since that is my native language._ - *Caution:* Do _not_ try to report bugs in `gawk' by posting to the +*Caution:* Do _not_ try to report bugs in `gawk' by posting to the Usenet/Internet newsgroup `comp.lang.awk'. While the `gawk' developers do occasionally read this newsgroup, there is no guarantee that we will see your posting. The steps described above are the official recognized ways for reporting bugs. - Non-bug suggestions are always welcome as well. If you have -questions about things that are unclear in the documentation or are -just obscure features, ask me; I will try to help you out, although I -may not have the time to fix the problem. You can send me electronic -mail at the Internet address noted previously. +Non-bug suggestions are always welcome as well. If you have questions +about things that are unclear in the documentation or are just obscure +features, ask me; I will try to help you out, although I may not have +the time to fix the problem. You can send me electronic mail at the +Internet address noted previously. - If you find bugs in one of the non-Unix ports of `gawk', please send -an electronic mail message to the person who maintains that port. They +If you find bugs in one of the non-Unix ports of `gawk', please send an +electronic mail message to the person who maintains that port. They are named in the following list, as well as in the `README' file in the `gawk' distribution. Information in the `README' file should be considered authoritative if it conflicts with this Info file. - The people maintaining the non-Unix ports of `gawk' are as follows: +The people maintaining the non-Unix ports of `gawk' are as follows: Amiga Fred Fish, <fnf@ninemoons.com>. BeOS Martin Brown, <mc@whoever.com>. @@ -18145,20 +18339,20 @@ OS/2 The Unix for OS/2 team, Tandem Stephen Davies, <scldad@sdc.com.au>. VMS Pat Rankin, <rankin@pactechdata.com>. - If your bug is also reproducible under Unix, please send a copy of -your report to the <bug-gawk@gnu.org> email list as well. +If your bug is also reproducible under Unix, please send a copy of your +report to the <bug-gawk@gnu.org> email list as well. File: gawk.info, Node: Other Versions, Prev: Bugs, Up: Installation -Other Freely Available `awk' Implementations -============================================ +B.6 Other Freely Available `awk' Implementations +================================================ It's kind of fun to put comments like this in your awk code. `// Do C++ comments work? answer: yes! of course' Michael Brennan - There are three other freely available `awk' implementations. This +There are three other freely available `awk' implementations. This minor node briefly describes where to get them: Unix `awk' @@ -18245,19 +18439,19 @@ Unix `awk' `http://www.math.utah.edu/pub/pawk/pawk-20020210.tar.gz'. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) `http://cm.bell-labs.com/who/bwk' +(1) `http://cm.bell-labs.com/who/bwk' File: gawk.info, Node: Notes, Next: Basic Concepts, Prev: Installation, Up: Top -Implementation Notes -******************** +Appendix C Implementation Notes +******************************* - This appendix contains information mainly of interest to -implementors and maintainers of `gawk'. Everything in it applies -specifically to `gawk' and not to other implementations. +This appendix contains information mainly of interest to implementors +and maintainers of `gawk'. Everything in it applies specifically to +`gawk' and not to other implementations. * Menu: @@ -18271,39 +18465,39 @@ specifically to `gawk' and not to other implementations. File: gawk.info, Node: Compatibility Mode, Next: Additions, Up: Notes -Downward Compatibility and Debugging -==================================== +C.1 Downward Compatibility and Debugging +======================================== - *Note POSIX/GNU::, for a summary of the GNU extensions to the `awk' +*Note POSIX/GNU::, for a summary of the GNU extensions to the `awk' language and program. All of these features can be turned off by invoking `gawk' with the `--traditional' option or with the `--posix' option. - If `gawk' is compiled for debugging with `-DDEBUG', then there is -one more option available on the command line: +If `gawk' is compiled for debugging with `-DDEBUG', then there is one +more option available on the command line: `-W parsedebug' `--parsedebug' Prints out the parse stack information as the program is being parsed. - This option is intended only for serious `gawk' developers and not -for the casual user. It probably has not even been compiled into your +This option is intended only for serious `gawk' developers and not for +the casual user. It probably has not even been compiled into your version of `gawk', since it slows down execution. File: gawk.info, Node: Additions, Next: Dynamic Extensions, Prev: Compatibility Mode, Up: Notes -Making Additions to `gawk' -========================== +C.2 Making Additions to `gawk' +============================== - If you find that you want to enhance `gawk' in a significant -fashion, you are perfectly free to do so. That is the point of having -free software; the source code is available and you are free to change -it as you want (*note Copying::). +If you find that you want to enhance `gawk' in a significant fashion, +you are perfectly free to do so. That is the point of having free +software; the source code is available and you are free to change it as +you want (*note Copying::). - This minor node discusses the ways you might want to change `gawk' -as well as any considerations you should bear in mind. +This minor node discusses the ways you might want to change `gawk' as +well as any considerations you should bear in mind. * Menu: @@ -18315,13 +18509,13 @@ as well as any considerations you should bear in mind. File: gawk.info, Node: Adding Code, Next: New Ports, Up: Additions -Adding New Features -------------------- +C.2.1 Adding New Features +------------------------- - You are free to add any new features you like to `gawk'. However, -if you want your changes to be incorporated into the `gawk' -distribution, there are several steps that you need to take in order to -make it possible for me to include your changes: +You are free to add any new features you like to `gawk'. However, if +you want your changes to be incorporated into the `gawk' distribution, +there are several steps that you need to take in order to make it +possible for me to include your changes: 1. Before building the new feature into `gawk' itself, consider writing it as an extension module (*note Dynamic Extensions::). @@ -18399,8 +18593,9 @@ make it possible for me to include your changes: worth the minor benefit of not having to free the storage. Instead, use `malloc' and `free'. - *Note:* If I have to reformat your code to follow the coding style - used in `gawk', I may not bother to integrate your changes at all. + NOTE: If I have to reformat your code to follow the coding + style used in `gawk', I may not bother to integrate your + changes at all. 5. Be prepared to sign the appropriate paperwork. In order for the FSF to distribute your changes, you must either place those @@ -18439,19 +18634,19 @@ make it possible for me to include your changes: This helps further minimize the amount of work I have to do, making it easier for me to accept patches. - Although this sounds like a lot of work, please remember that while -you may write the new code, I have to maintain it and support it. If it +Although this sounds like a lot of work, please remember that while you +may write the new code, I have to maintain it and support it. If it isn't possible for me to do that with a minimum of extra work, then I probably will not. File: gawk.info, Node: New Ports, Prev: Adding Code, Up: Additions -Porting `gawk' to a New Operating System ----------------------------------------- +C.2.2 Porting `gawk' to a New Operating System +---------------------------------------------- - If you want to port `gawk' to a new operating system, there are -several steps: +If you want to port `gawk' to a new operating system, there are several +steps: 1. Follow the guidelines in *Note Adding Code::, concerning coding style, submission of diffs, and so on. @@ -18518,33 +18713,33 @@ several steps: actions are easy to do and _many_ people have done so already. If you have questions, please contact me, or <gnu@gnu.org>. - Following these steps makes it much easier to integrate your changes +Following these steps makes it much easier to integrate your changes into `gawk' and have them coexist happily with other operating systems' code that is already there. - In the code that you supply and maintain, feel free to use a coding +In the code that you supply and maintain, feel free to use a coding style and brace layout that suits your taste. File: gawk.info, Node: Dynamic Extensions, Next: Future Extensions, Prev: Additions, Up: Notes -Adding New Built-in Functions to `gawk' -======================================= +C.3 Adding New Built-in Functions to `gawk' +=========================================== Danger Will Robinson! Danger!! Warning! Warning! The Robot - Beginning with `gawk' 3.1, it is possible to add new built-in -functions to `gawk' using dynamically loaded libraries. This facility -is available on systems (such as GNU/Linux) that support the `dlopen' -and `dlsym' functions. This minor node describes how to write and use -dynamically loaded extentions for `gawk'. Experience with programming +Beginning with `gawk' 3.1, it is possible to add new built-in functions +to `gawk' using dynamically loaded libraries. This facility is +available on systems (such as GNU/Linux) that support the `dlopen' and +`dlsym' functions. This minor node describes how to write and use +dynamically loaded extensions for `gawk'. Experience with programming in C or C++ is necessary when reading this minor node. - *Caution:* The facilities described in this minor node are very much -subject to change in the next `gawk' release. Be aware that you may -have to re-do everything, perhaps from scratch, upon the next release. +*Caution:* The facilities described in this minor node are very much +subject to change in a future `gawk' release. Be aware that you may +have to re-do everything, perhaps from scratch, at some future time. * Menu: @@ -18554,10 +18749,10 @@ have to re-do everything, perhaps from scratch, upon the next release. File: gawk.info, Node: Internals, Next: Sample Library, Up: Dynamic Extensions -A Minimal Introduction to `gawk' Internals ------------------------------------------- +C.3.1 A Minimal Introduction to `gawk' Internals +------------------------------------------------ - The truth is that `gawk' was not designed for simple extensibility. +The truth is that `gawk' was not designed for simple extensibility. The facilities for adding functions using shared libraries work, but are something of a "bag on the side." Thus, this tour is brief and simplistic; would-be `gawk' hackers are encouraged to spend some time @@ -18566,7 +18761,7 @@ material presented here. Of particular note are the files `awk.h', `builtin.c', and `eval.c'. Reading `awk.y' in order to see how the parse tree is built would also be of use. - With the disclaimers out of the way, the following types, structure +With the disclaimers out of the way, the following types, structure members, functions, and macros are declared in `awk.h' and are of use when writing extensions. The next minor node shows how they are used: @@ -18588,9 +18783,18 @@ when writing extensions. The next minor node shows how they are used: may end up calling an internal `gawk' function. It also guarantees that the string is zero-terminated. +`size_t get_curfunc_arg_count(void)' + This function returns the actual number of parameters passed to + the current function. Inside the code of an extension this can be + used to determine the maximum index which is safe to use with + `stack_ptr'. If this value is greater than `tree->param_cnt', the + function was called incorrectly from the `awk' program. + + *Caution:* This function is new as of `gawk' 3.1.4. + `n->param_cnt' - The number of parameters actually passed in a function call at - runtime. + Inside an extension function, this is the maximum number of + expected parameters, as set by the `make_builtin' function. `n->stptr' `n->stlen' @@ -18656,7 +18860,7 @@ when writing extensions. The next minor node shows how they are used: should be written in the following manner: /* do_xxx --- do xxx function for gawk */ - + NODE * do_xxx(NODE *tree) { @@ -18668,6 +18872,26 @@ when writing extensions. The next minor node shows how they are used: the `i'-th argument from the function call. The first argument is argument zero. +`NODE *get_actual_argument(NODE *tree, unsigned int i,' +` int optional, int wantarray);' + This function retrieves a particular argument `i'. `wantarray' is + `TRUE' if the argument should be an array, `FALSE' otherwise. If + `optional' is `TRUE', the argument need not have been supplied. + If it wasn't, the return value is `NULL'. It is a fatal error if + `optional' is `TRUE' but the argument was not provided. + + *Caution:* This function is new as of `gawk' 3.1.4. + +`get_scalar_argument(t, i, opt)' + This is a convenience macro that calls `get_actual_argument'. + + *Caution:* This macro is new as of `gawk' 3.1.4. + +`get_array_argument(t, i, opt)' + This is a convenience macro that calls `get_actual_argument'. + + *Caution:* This macro is new as of `gawk' 3.1.4. + `void set_value(NODE *tree)' This function is called from within a C extension function to set the return value from the extension function. This value is what @@ -18679,57 +18903,64 @@ when writing extensions. The next minor node shows how they are used: the value of `gawk''s `ERRNO' variable, based on the current value of the C `errno' variable. It is provided as a convenience. - An argument that is supposed to be an array needs to be handled with +An argument that is supposed to be an array needs to be handled with some extra code, in case the array being passed in is actually from a function parameter. - In versions of `gawk' up to and including 3.1.2, the following +In versions of `gawk' up to and including 3.1.2, the following boilerplate code shows how to do this: NODE *the_arg; - + the_arg = get_argument(tree, 2); /* assume need 3rd arg, 0-based */ - + /* if a parameter, get it off the stack */ if (the_arg->type == Node_param_list) the_arg = stack_ptr[the_arg->param_cnt]; - + /* parameter referenced an array, get it */ if (the_arg->type == Node_array_ref) the_arg = the_arg->orig_array; - + /* check type */ if (the_arg->type != Node_var && the_arg->type != Node_var_array) fatal("newfunc: third argument is not an array"); - + /* force it to be an array, if necessary, clear it */ the_arg->type = Node_var_array; assoc_clear(the_arg); - For versions 3.1.3 and later, the internals changed. In particular, +For versions 3.1.3 and later, the internals changed. In particular, the interface was actually _simplified_ drastically. The following boilerplate code now suffices: NODE *the_arg; - + the_arg = get_argument(tree, 2); /* assume need 3rd arg, 0-based */ - + /* force it to be an array: */ the_arg = get_array(the_arg); - + /* if necessary, clear it: */ assoc_clear(the_arg); - Again, you should spend time studying the `gawk' internals; don't -just blindly copy this code. +As of version 3.1.4, the internals improved again, and became even +simpler: + + NODE *the_arg; + + the_arg = get_array_argument(tree, 2, FALSE); /* assume need 3rd arg, 0-based */ + +Again, you should spend time studying the `gawk' internals; don't just +blindly copy this code. File: gawk.info, Node: Sample Library, Prev: Internals, Up: Dynamic Extensions -Directory and File Operation Built-ins --------------------------------------- +C.3.2 Directory and File Operation Built-ins +-------------------------------------------- - Two useful functions that are not in `awk' are `chdir' (so that an +Two useful functions that are not in `awk' are `chdir' (so that an `awk' program can change its directory) and `stat' (so that an `awk' program can gather information about a file). This minor node implements these functions for `gawk' in an external extension library. @@ -18743,11 +18974,11 @@ implements these functions for `gawk' in an external extension library. File: gawk.info, Node: Internal File Description, Next: Internal File Ops, Up: Sample Library -Using `chdir' and `stat' -........................ +C.3.2.1 Using `chdir' and `stat' +................................ - This minor node shows how to use the new functions at the `awk' -level once they've been integrated into the running `gawk' interpreter. +This minor node shows how to use the new functions at the `awk' level +once they've been integrated into the running `gawk' interpreter. Using `chdir' is very straightforward. It takes one argument, the new directory to change to: @@ -18761,11 +18992,11 @@ directory to change to: } ... - The return value is negative if the `chdir' failed, and `ERRNO' -(*note Built-in Variables::) is set to a string indicating the error. +The return value is negative if the `chdir' failed, and `ERRNO' (*note +Built-in Variables::) is set to a string indicating the error. - Using `stat' is a bit more complicated. The C `stat' function fills -in a structure that has a fair amount of information. The right way to +Using `stat' is a bit more complicated. The C `stat' function fills in +a structure that has a fair amount of information. The right way to model this in `awk' is to fill in an associative array with the appropriate information: @@ -18779,7 +19010,7 @@ appropriate information: } printf("size of %s is %d bytes\n", file, fdata["size"]) - The `stat' function always clears the data array, even if the `stat' +The `stat' function always clears the data array, even if the `stat' fails. It fills in the following elements: `"name"' @@ -18843,10 +19074,9 @@ fails. It fills in the following elements: `"symlink"' The file is a symbolic link. - Several additional elements may be present depending upon the -operating system and the type of the file. You can test for them in -your `awk' program by using the `in' operator (*note Reference to -Elements::): +Several additional elements may be present depending upon the operating +system and the type of the file. You can test for them in your `awk' +program by using the `in' operator (*note Reference to Elements::): `"blksize"' The preferred block size for I/O to the file. This field is not @@ -18866,72 +19096,72 @@ Elements::): File: gawk.info, Node: Internal File Ops, Next: Using Internal File Ops, Prev: Internal File Description, Up: Sample Library -C Code for `chdir' and `stat' -............................. +C.3.2.2 C Code for `chdir' and `stat' +..................................... - Here is the C code for these extensions. They were written for +Here is the C code for these extensions. They were written for GNU/Linux. The code needs some more work for complete portability to other POSIX-compliant systems:(1) #include "awk.h" - + #include <sys/sysmacros.h> - + /* do_chdir --- provide dynamically loaded chdir() builtin for gawk */ - + static NODE * do_chdir(tree) NODE *tree; { NODE *newdir; int ret = -1; - - newdir = get_argument(tree, 0); - The file includes the `"awk.h"' header file for definitions for the + if (do_lint && get_curfunc_arg_count() != 1) + lintwarn("chdir: called with incorrect number of arguments"); + + newdir = get_scalar_argument(tree, 0); + +The file includes the `"awk.h"' header file for definitions for the `gawk' internals. It includes `<sys/sysmacros.h>' for access to the `major' and `minor' macros. - By convention, for an `awk' function `foo', the function that +By convention, for an `awk' function `foo', the function that implements it is called `do_foo'. The function should take a `NODE *' argument, usually called `tree', that represents the argument list to the function. The `newdir' variable represents the new directory to change to, retrieved with `get_argument'. Note that the first argument is numbered zero. - This code actually accomplishes the `chdir'. It first forces the +This code actually accomplishes the `chdir'. It first forces the argument to be a string and passes the string value to the `chdir' system call. If the `chdir' fails, `ERRNO' is updated. The result of `force_string' has to be freed with `free_temp': - if (newdir != NULL) { - (void) force_string(newdir); - ret = chdir(newdir->stptr); - if (ret < 0) - update_ERRNO(); - - free_temp(newdir); - } + (void) force_string(newdir); + ret = chdir(newdir->stptr); + if (ret < 0) + update_ERRNO(); + free_temp(newdir); - Finally, the function returns the return value to the `awk' level, +Finally, the function returns the return value to the `awk' level, using `set_value'. Then it must return a value from the call to the new built-in (this value ignored by the interpreter): /* Set the return value */ set_value(tmp_number((AWKNUM) ret)); - + /* Just to make the interpreter happy */ return tmp_number((AWKNUM) 0); } - The `stat' built-in is more involved. First comes a function that +The `stat' built-in is more involved. First comes a function that turns a numeric mode into a printable representation (e.g., 644 becomes `-rw-r--r--'). This is omitted here for brevity: /* format_mode --- turn a stat mode field into something readable */ - + static char * format_mode(fmode) unsigned long fmode; @@ -18939,11 +19169,11 @@ turns a numeric mode into a printable representation (e.g., 644 becomes ... } - Next comes the actual `do_stat' function itself. First come the +Next comes the actual `do_stat' function itself. First come the variable declarations and argument checking: /* do_stat --- provide a stat() function for gawk */ - + static NODE * do_stat(tree) NODE *tree; @@ -18951,76 +19181,70 @@ variable declarations and argument checking: NODE *file, *array; struct stat sbuf; int ret; - char *msg; NODE **aptr; char *pmode; /* printable mode */ char *type = "unknown"; - - /* check arg count */ - if (tree->param_cnt != 2) - fatal( - "stat: called with %d arguments, should be 2", - tree->param_cnt); - - Then comes the actual work. First, we get the arguments. Then, we + + + if (do_lint && get_curfunc_arg_count() > 2) + lintwarn("stat: called with too many arguments"); + +Then comes the actual work. First, we get the arguments. Then, we always clear the array. To get the file information, we use `lstat', in case the file is a symbolic link. If there's an error, we set `ERRNO' and return: - /* - * directory is first arg, - * array to hold results is second - */ - file = get_argument(tree, 0); - array = get_argument(tree, 1); - + /* directory is first arg, array to hold results is second */ + file = get_scalar_argument(tree, 0, FALSE); + array = get_array_argument(tree, 1, FALSE); + /* empty out the array */ assoc_clear(array); - + /* lstat the file, if error, set ERRNO and return */ (void) force_string(file); ret = lstat(file->stptr, & sbuf); if (ret < 0) { update_ERRNO(); - + set_value(tmp_number((AWKNUM) ret)); - + free_temp(file); return tmp_number((AWKNUM) 0); } - Now comes the tedious part: filling in the array. Only a few of the +Now comes the tedious part: filling in the array. Only a few of the calls are shown here, since they all follow the same pattern: /* fill in the array */ aptr = assoc_lookup(array, tmp_string("name", 4), FALSE); *aptr = dupnode(file); - + aptr = assoc_lookup(array, tmp_string("mode", 4), FALSE); *aptr = make_number((AWKNUM) sbuf.st_mode); - + aptr = assoc_lookup(array, tmp_string("pmode", 5), FALSE); pmode = format_mode(sbuf.st_mode); *aptr = make_string(pmode, strlen(pmode)); - When done, we free the temporary value containing the file name, set +When done, we free the temporary value containing the file name, set the return value, and return: free_temp(file); - + /* Set the return value */ set_value(tmp_number((AWKNUM) ret)); - + /* Just to make the interpreter happy */ return tmp_number((AWKNUM) 0); } - Finally, it's necessary to provide the "glue" that loads the new +Finally, it's necessary to provide the "glue" that loads the new function(s) into `gawk'. By convention, each library has a routine named `dlload' that does the job: /* dlload --- load new builtins in this library */ - + NODE * dlload(tree, dl) NODE *tree; @@ -19031,31 +19255,31 @@ named `dlload' that does the job: return tmp_number((AWKNUM) 0); } - And that's it! As an exercise, consider adding functions to -implement system calls such as `chown', `chmod', and `umask'. +And that's it! As an exercise, consider adding functions to implement +system calls such as `chown', `chmod', and `umask'. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) This version is edited slightly for presentation. The complete +(1) This version is edited slightly for presentation. The complete version can be found in `extension/filefuncs.c' in the `gawk' distribution. File: gawk.info, Node: Using Internal File Ops, Prev: Internal File Ops, Up: Sample Library -Integrating the Extensions -.......................... +C.3.2.3 Integrating the Extensions +.................................. - Now that the code is written, it must be possible to add it at -runtime to the running `gawk' interpreter. First, the code must be -compiled. Assuming that the functions are in a file named -`filefuncs.c', and IDIR is the location of the `gawk' include files, -the following steps create a GNU/Linux shared library: +Now that the code is written, it must be possible to add it at runtime +to the running `gawk' interpreter. First, the code must be compiled. +Assuming that the functions are in a file named `filefuncs.c', and IDIR +is the location of the `gawk' include files, the following steps create +a GNU/Linux shared library: $ gcc -shared -DHAVE_CONFIG_H -c -O -g -IIDIR filefuncs.c $ ld -o filefuncs.so -shared filefuncs.o - Once the library exists, it is loaded by calling the `extension' +Once the library exists, it is loaded by calling the `extension' built-in function. This function takes two arguments: the name of the library to load and the name of a function to call when the library is first loaded. This function adds the new functions to `gawk'. It @@ -19065,9 +19289,9 @@ shared library: # file testff.awk BEGIN { extension("./filefuncs.so", "dlload") - + chdir(".") # no-op - + data[1] = 1 # force `data' to be an array print "Info for testff.awk" ret = stat("testff.awk", data) @@ -19078,7 +19302,7 @@ shared library: strftime("%m %d %y %H:%M:%S", data["mtime"]) } - Here are the results of running the program: +Here are the results of running the program: $ gawk -f testff.awk -| Info for testff.awk @@ -19103,8 +19327,8 @@ shared library: File: gawk.info, Node: Future Extensions, Prev: Dynamic Extensions, Up: Notes -Probable Future Extensions -========================== +C.4 Probable Future Extensions +============================== AWK is a language similar to PERL, only considerably more elegant. Arnold Robbins @@ -19112,12 +19336,12 @@ Probable Future Extensions Hey! Larry Wall - This minor node briefly lists extensions and possible improvements -that indicate the directions we are currently considering for `gawk'. -The file `FUTURES' in the `gawk' distribution lists these extensions as +This minor node briefly lists extensions and possible improvements that +indicate the directions we are currently considering for `gawk'. The +file `FUTURES' in the `gawk' distribution lists these extensions as well. - Following is a list of probable future changes visible at the `awk' +Following is a list of probable future changes visible at the `awk' language level: Loadable module interface @@ -19144,12 +19368,15 @@ Databases Large character sets It would be nice if `gawk' could handle UTF-8 and other character - sets that are larger than eight bits. + sets that are larger than eight bits. (`gawk' currently has + partial multi-byte support, but it needs an expert to really think + out the multi-byte issues and consult with the maintainer on the + appropriate changes.) More `lint' warnings There are more things that could be checked for portability. - Following is a list of probable improvements that will make `gawk''s +Following is a list of probable improvements that will make `gawk''s source code easier to work with: Loadable module mechanics @@ -19175,7 +19402,7 @@ Integrating the DBUG library Integrating Fred Fish's DBUG library would be helpful during development, but it's a lot of work to do. - Following is a list of probable improvements that will make `gawk' +Following is a list of probable improvements that will make `gawk' perform better: Compilation of `awk' programs @@ -19198,24 +19425,24 @@ Compilation of `awk' programs intermediate in speed between running a compiled program and doing what `gawk' does now. - Finally, the programs in the test suite could use documenting in -this Info file. +Finally, the programs in the test suite could use documenting in this +Info file. - *Note Additions::, if you are interested in tackling any of these +*Note Additions::, if you are interested in tackling any of these projects. File: gawk.info, Node: Basic Concepts, Next: Glossary, Prev: Notes, Up: Top -Basic Programming Concepts -************************** +Appendix D Basic Programming Concepts +************************************* - This major node attempts to define some of the basic concepts and -terms that are used throughout the rest of this Info file. As this -Info file is specifically about `awk', and not about computer -programming in general, the coverage here is by necessity fairly -cursory and simplistic. (If you need more background, there are many -other introductory texts that you should refer to instead.) +This major node attempts to define some of the basic concepts and terms +that are used throughout the rest of this Info file. As this Info file +is specifically about `awk', and not about computer programming in +general, the coverage here is by necessity fairly cursory and +simplistic. (If you need more background, there are many other +introductory texts that you should refer to instead.) * Menu: @@ -19226,23 +19453,23 @@ other introductory texts that you should refer to instead.) File: gawk.info, Node: Basic High Level, Next: Basic Data Typing, Up: Basic Concepts -What a Program Does -=================== +D.1 What a Program Does +======================= - At the most basic level, the job of a program is to process some -input data and produce results. +At the most basic level, the job of a program is to process some input +data and produce results. _______ +------+ / \ +---------+ | Data | -----> < Program > -----> | Results | +------+ \_______/ +---------+ - The "program" in the figure can be either a compiled program(1) -(such as `ls'), or it may be "interpreted". In the latter case, a +The "program" in the figure can be either a compiled program(1) (such +as `ls'), or it may be "interpreted". In the latter case, a machine-executable program such as `awk' reads your program, and then uses the instructions in your program to process the data. - When you write a program, it usually consists of the following, very +When you write a program, it usually consists of the following, very basic set of steps: ______ @@ -19289,145 +19516,145 @@ Clean Up plastic wrap to keep anyone from tasting it, as well as wash the mixing bowls and utensils. - An "algorithm" is a detailed set of instructions necessary to -accomplish a task, or process data. It is much the same as a recipe -for baking a cake. Programs implement algorithms. Often, it is up to -you to design the algorithm and implement it, simultaneously. +An "algorithm" is a detailed set of instructions necessary to accomplish +a task, or process data. It is much the same as a recipe for baking a +cake. Programs implement algorithms. Often, it is up to you to design +the algorithm and implement it, simultaneously. - The "logical chunks" we talked about previously are called "records", +The "logical chunks" we talked about previously are called "records", similar to the records a company keeps on employees, a school keeps for students, or a doctor keeps for patients. Each record has many component parts, such as first and last names, date of birth, address, and so on. The component parts are referred to as the "fields" of the record. - The act of reading data is termed "input", and that of generating +The act of reading data is termed "input", and that of generating results, not too surprisingly, is termed "output". They are often referred to together as "input/output," and even more often, as "I/O" for short. (You will also see "input" and "output" used as verbs.) - `awk' manages the reading of data for you, as well as the breaking -it up into records and fields. Your program's job is to tell `awk' -what to with the data. You do this by describing "patterns" in the -data to look for, and "actions" to execute when those patterns are -seen. This "data-driven" nature of `awk' programs usually makes them -both easier to write and easier to read. +`awk' manages the reading of data for you, as well as the breaking it +up into records and fields. Your program's job is to tell `awk' what +to with the data. You do this by describing "patterns" in the data to +look for, and "actions" to execute when those patterns are seen. This +"data-driven" nature of `awk' programs usually makes them both easier +to write and easier to read. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) Compiled programs are typically written in lower-level languages +(1) Compiled programs are typically written in lower-level languages such as C, C++, Fortran, or Ada, and then translated, or "compiled", into a form that the computer can execute directly. File: gawk.info, Node: Basic Data Typing, Next: Floating Point Issues, Prev: Basic High Level, Up: Basic Concepts -Data Values in a Computer -========================= +D.2 Data Values in a Computer +============================= - In a program, you keep track of information and values in things -called "variables". A variable is just a name for a given value, such -as `first_name', `last_name', `address', and so on. `awk' has several +In a program, you keep track of information and values in things called +"variables". A variable is just a name for a given value, such as +`first_name', `last_name', `address', and so on. `awk' has several predefined variables, and it has special names to refer to the current input record and the fields of the record. You may also group multiple associated values under one name, as an array. - Data, particularly in `awk', consists of either numeric values, such -as 42 or 3.1415927, or string values. String values are essentially +Data, particularly in `awk', consists of either numeric values, such as +42 or 3.1415927, or string values. String values are essentially anything that's not a number, such as a name. Strings are sometimes referred to as "character data", since they store the individual characters that comprise them. Individual variables, as well as numeric and string variables, are referred to as "scalar" values. Groups of values, such as arrays, are not scalars. - Within computers, there are two kinds of numeric values: "integers" -and "floating-point". In school, integer values were referred to as +Within computers, there are two kinds of numeric values: "integers" and +"floating-point". In school, integer values were referred to as "whole" numbers--that is, numbers without any fractional part, such as 1, 42, or -17. The advantage to integer numbers is that they represent values exactly. The disadvantage is that their range is limited. On most modern systems, this range is -2,147,483,648 to 2,147,483,647. - Integer values come in two flavors: "signed" and "unsigned". Signed +Integer values come in two flavors: "signed" and "unsigned". Signed values may be negative or positive, with the range of values just described. Unsigned values are always positive. On most modern systems, the range is from 0 to 4,294,967,295. - Floating-point numbers represent what are called "real" numbers; -i.e., those that do have a fractional part, such as 3.1415927. The -advantage to floating-point numbers is that they can represent a much -larger range of values. The disadvantage is that there are numbers -that they cannot represent exactly. `awk' uses "double-precision" -floating-point numbers, which can hold more digits than -"single-precision" floating-point numbers. Floating-point issues are -discussed more fully in *Note Floating Point Issues::. +Floating-point numbers represent what are called "real" numbers; i.e., +those that do have a fractional part, such as 3.1415927. The advantage +to floating-point numbers is that they can represent a much larger +range of values. The disadvantage is that there are numbers that they +cannot represent exactly. `awk' uses "double-precision" floating-point +numbers, which can hold more digits than "single-precision" +floating-point numbers. Floating-point issues are discussed more fully +in *Note Floating Point Issues::. - At the very lowest level, computers store values as groups of binary +At the very lowest level, computers store values as groups of binary digits, or "bits". Modern computers group bits into groups of eight, called "bytes". Advanced applications sometimes have to manipulate bits directly, and `gawk' provides functions for doing so. - While you are probably used to the idea of a number without a value +While you are probably used to the idea of a number without a value (i.e., zero), it takes a bit more getting used to the idea of zero-length character data. Nevertheless, such a thing exists. It is called the "null string". The null string is character data that has no value. In other words, it is empty. It is written in `awk' programs like this: `""'. - Humans are used to working in decimal; i.e., base 10. In base 10, +Humans are used to working in decimal; i.e., base 10. In base 10, numbers go from 0 to 9, and then "roll over" into the next column. (Remember grade school? 42 is 4 times 10 plus 2.) - There are other number bases though. Computers commonly use base 2 -or "binary", base 8 or "octal", and base 16 or "hexadecimal". In -binary, each column represents two times the value in the column to its -right. Each column may contain either a 0 or a 1. Thus, binary 1010 +There are other number bases though. Computers commonly use base 2 or +"binary", base 8 or "octal", and base 16 or "hexadecimal". In binary, +each column represents two times the value in the column to its right. +Each column may contain either a 0 or a 1. Thus, binary 1010 represents 1 times 8, plus 0 times 4, plus 1 times 2, plus 0 times 1, or decimal 10. Octal and hexadecimal are discussed more in *Note Nondecimal-numbers::. - Programs are written in programming languages. Hundreds, if not +Programs are written in programming languages. Hundreds, if not thousands, of programming languages exist. One of the most popular is the C programming language. The C language had a very strong influence on the design of the `awk' language. - There have been several versions of C. The first is often referred -to as "K&R" C, after the initials of Brian Kernighan and Dennis Ritchie, +There have been several versions of C. The first is often referred to +as "K&R" C, after the initials of Brian Kernighan and Dennis Ritchie, the authors of the first book on C. (Dennis Ritchie created the language, and Brian Kernighan was one of the creators of `awk'.) - In the mid-1980s, an effort began to produce an international -standard for C. This work culminated in 1989, with the production of -the ANSI standard for C. This standard became an ISO standard in 1990. -Where it makes sense, POSIX `awk' is compatible with 1990 ISO C. +In the mid-1980s, an effort began to produce an international standard +for C. This work culminated in 1989, with the production of the ANSI +standard for C. This standard became an ISO standard in 1990. Where +it makes sense, POSIX `awk' is compatible with 1990 ISO C. - In 1999, a revised ISO C standard was approved and released. Future +In 1999, a revised ISO C standard was approved and released. Future versions of `gawk' will be as compatible as possible with this standard. File: gawk.info, Node: Floating Point Issues, Prev: Basic Data Typing, Up: Basic Concepts -Floating-Point Number Caveats -============================= +D.3 Floating-Point Number Caveats +================================= - As mentioned earlier, floating-point numbers represent what are -called "real" numbers, i.e., those that have a fractional part. `awk' -uses double-precision floating-point numbers to represent all numeric +As mentioned earlier, floating-point numbers represent what are called +"real" numbers, i.e., those that have a fractional part. `awk' uses +double-precision floating-point numbers to represent all numeric values. This minor node describes some of the issues involved in using floating-point numbers. - There is a very nice paper on floating-point arithmetic by David +There is a very nice paper on floating-point arithmetic by David Goldberg, "What Every Computer Scientist Should Know About Floating-point Arithmetic," `ACM Computing Surveys' *23*, 1 (1991-03), 5-48.(1) This is worth reading if you are interested in the details, but it does require a background in computer science. - Internally, `awk' keeps both the numeric value (double-precision +Internally, `awk' keeps both the numeric value (double-precision floating-point) and the string value for a variable. Separately, `awk' keeps track of what type the variable has (*note Typing and Comparison::), which plays a role in how variables are used in comparisons. - It is important to note that the string value for a number may not +It is important to note that the string value for a number may not reflect the full value (all the digits) that the numeric value actually contains. The following program (`values.awk') illustrates this: @@ -19446,26 +19673,26 @@ This program shows the full value of the sum of `$2' and `$3' using `printf', and then prints the string values obtained from both automatic conversion (via `CONVFMT') and from printing (via `OFMT'). - Here is what happens when the program is run: +Here is what happens when the program is run: $ echo 2 3.654321 1.2345678 | awk -f values.awk -| $1 = 4.8888888 -| a = <4.88889> -| $1 = 4.88889 - This makes it clear that the full numeric value is different from -what the default string representations show. +This makes it clear that the full numeric value is different from what +the default string representations show. - `CONVFMT''s default value is `"%.6g"', which yields a value with at +`CONVFMT''s default value is `"%.6g"', which yields a value with at least six significant digits. For some applications, you might want to change it to specify more precision. On most modern machines, most of the time, 17 digits is enough to capture a floating-point number's value exactly.(2) - Unlike numbers in the abstract sense (such as what you studied in -high school or college math), numbers stored in computers are limited -in certain ways. They cannot represent an infinite number of digits, -nor can they always represent things exactly. In particular, +Unlike numbers in the abstract sense (such as what you studied in high +school or college math), numbers stored in computers are limited in +certain ways. They cannot represent an infinite number of digits, nor +can they always represent things exactly. In particular, floating-point numbers cannot always represent values exactly. Here is an example: @@ -19484,14 +19711,14 @@ This shows that some values can be represented exactly, whereas others are only approximated. This is not a "bug" in `awk', but simply an artifact of how computers represent numbers. - Another peculiarity of floating-point numbers on modern systems is -that they often have more than one representation for the number zero! -In particular, it is possible to represent "minus zero" as well as +Another peculiarity of floating-point numbers on modern systems is that +they often have more than one representation for the number zero! In +particular, it is possible to represent "minus zero" as well as regular, or "positive" zero. - This example shows that negative and positive zero are distinct -values when stored internally, but that they are in fact equal to each -other, as well as to "regular" zero: +This example shows that negative and positive zero are distinct values +when stored internally, but that they are in fact equal to each other, +as well as to "regular" zero: $ gawk 'BEGIN { mz = -0 ; pz = 0 > printf "-0 = %g, +0 = %g, (-0 == +0) -> %d\n", mz, pz, mz == pz @@ -19500,16 +19727,16 @@ other, as well as to "regular" zero: -| -0 = -0, +0 = 0, (-0 == +0) -> 1 -| mz == 0 -> 1, pz == 0 -> 1 - It helps to keep this in mind should you process numeric data that +It helps to keep this in mind should you process numeric data that contains negative zero values; the fact that the zero is negative is noted and can affect comparisons. - ---------- Footnotes ---------- +---------- Footnotes ---------- - (1) `http://www.validlab.com/goldberg/paper.ps'. +(1) `http://www.validlab.com/goldberg/paper.ps'. - (2) Pathological cases can require up to 752 digits (!), but we -doubt that you need to worry about this. +(2) Pathological cases can require up to 752 digits (!), but we doubt +that you need to worry about this. File: gawk.info, Node: Glossary, Next: Copying, Prev: Basic Concepts, Up: Top @@ -20118,16 +20345,16 @@ GNU General Public License Version 2, June 1991 Copyright (C) 1989, 1991 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111, USA - + Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Preamble ======== - The licenses for most software are designed to take away your -freedom to share and change it. By contrast, the GNU General Public -License is intended to guarantee your freedom to share and change free +The licenses for most software are designed to take away your freedom +to share and change it. By contrast, the GNU General Public License is +intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to @@ -20135,42 +20362,41 @@ using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too. - When we speak of free software, we are referring to freedom, not -price. Our General Public Licenses are designed to make sure that you -have the freedom to distribute copies of free software (and charge for -this service if you wish), that you receive source code or can get it -if you want it, that you can change the software or use pieces of it in -new free programs; and that you know you can do these things. +When we speak of free software, we are referring to freedom, not price. +Our General Public Licenses are designed to make sure that you have +the freedom to distribute copies of free software (and charge for this +service if you wish), that you receive source code or can get it if you +want it, that you can change the software or use pieces of it in new +free programs; and that you know you can do these things. - To protect your rights, we need to make restrictions that forbid -anyone to deny you these rights or to ask you to surrender the rights. -These restrictions translate to certain responsibilities for you if you +To protect your rights, we need to make restrictions that forbid anyone +to deny you these rights or to ask you to surrender the rights. These +restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it. - For example, if you distribute copies of such a program, whether -gratis or for a fee, you must give the recipients all the rights that -you have. You must make sure that they, too, receive or can get the -source code. And you must show them these terms so they know their -rights. +For example, if you distribute copies of such a program, whether gratis +or for a fee, you must give the recipients all the rights that you +have. You must make sure that they, too, receive or can get the source +code. And you must show them these terms so they know their rights. - We protect your rights with two steps: (1) copyright the software, -and (2) offer you this license which gives you legal permission to copy, +We protect your rights with two steps: (1) copyright the software, and +(2) offer you this license which gives you legal permission to copy, distribute and/or modify the software. - Also, for each author's protection and ours, we want to make certain +Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations. - Finally, any free program is threatened constantly by software -patents. We wish to avoid the danger that redistributors of a free -program will individually obtain patent licenses, in effect making the -program proprietary. To prevent this, we have made it clear that any -patent must be licensed for everyone's free use or not licensed at all. +Finally, any free program is threatened constantly by software patents. +We wish to avoid the danger that redistributors of a free program will +individually obtain patent licenses, in effect making the program +proprietary. To prevent this, we have made it clear that any patent +must be licensed for everyone's free use or not licensed at all. - The precise terms and conditions for copying, distribution and +The precise terms and conditions for copying, distribution and modification follow. TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION @@ -20408,38 +20634,37 @@ modification follow. How to Apply These Terms to Your New Programs ============================================= - If you develop a new program, and you want it to be of the greatest +If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms. - To do so, attach the following notices to the program. It is safest -to attach them to the start of each source file to most effectively -convey the exclusion of warranty; and each file should have at least -the "copyright" line and a pointer to where the full notice is found. +To do so, attach the following notices to the program. It is safest to +attach them to the start of each source file to most effectively convey +the exclusion of warranty; and each file should have at least the +"copyright" line and a pointer to where the full notice is found. ONE LINE TO GIVE THE PROGRAM'S NAME AND AN IDEA OF WHAT IT DOES. Copyright (C) YEAR NAME OF AUTHOR - + This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. - + This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. - + You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA. - Also add information on how to contact you by electronic and paper -mail. +Also add information on how to contact you by electronic and paper mail. - If the program is interactive, make it output a short notice like -this when it starts in an interactive mode: +If the program is interactive, make it output a short notice like this +when it starts in an interactive mode: Gnomovision version 69, Copyright (C) YEAR NAME OF AUTHOR Gnomovision comes with ABSOLUTELY NO WARRANTY; for details @@ -20447,27 +20672,27 @@ this when it starts in an interactive mode: to redistribute it under certain conditions; type `show c' for details. - The hypothetical commands `show w' and `show c' should show the +The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than `show w' and `show c'; they could even be mouse-clicks or menu items--whatever suits your program. - You should also get your employer (if you work as a programmer) or -your school, if any, to sign a "copyright disclaimer" for the program, -if necessary. Here is a sample; alter the names: +You should also get your employer (if you work as a programmer) or your +school, if any, to sign a "copyright disclaimer" for the program, if +necessary. Here is a sample; alter the names: Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (which makes passes at compilers) written by James Hacker. - + SIGNATURE OF TY COON, 1 April 1989 Ty Coon, President of Vice - This General Public License does not permit incorporating your -program into proprietary programs. If your program is a subroutine -library, you may consider it more useful to permit linking proprietary +This General Public License does not permit incorporating your program +into proprietary programs. If your program is a subroutine library, +you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. @@ -20480,7 +20705,7 @@ GNU Free Documentation License Version 1.2, November 2002 Copyright (C) 2000,2001,2002 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA - + Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. @@ -20874,7 +21099,7 @@ GNU Free Documentation License ADDENDUM: How to use this License for your documents ==================================================== - To use this License in a document you have written, include a copy of +To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page: @@ -20886,18 +21111,18 @@ notices just after the title page: A copy of the license is included in the section entitled ``GNU Free Documentation License''. - If you have Invariant Sections, Front-Cover Texts and Back-Cover -Texts, replace the "with...Texts." line with this: +If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, +replace the "with...Texts." line with this: with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. - If you have Invariant Sections without Cover Texts, or some other +If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation. - If your document contains nontrivial examples of program code, we +If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software. @@ -20910,2395 +21135,2892 @@ Index * Menu: -* ! (exclamation point), ! operator: Boolean Ops. -* ! (exclamation point), ! operator <1>: Egrep Program. -* ! (exclamation point), ! operator: Precedence. -* ! (exclamation point), != operator <1>: Precedence. +* ! (exclamation point), ! operator: Boolean Ops. (line 6516) +* ! (exclamation point), ! operator <1>: Egrep Program. (line 14645) +* ! (exclamation point), ! operator: Precedence. (line 6690) +* ! (exclamation point), != operator <1>: Precedence. (line 6703) * ! (exclamation point), != operator: Typing and Comparison. + (line 6334) * ! (exclamation point), !~ operator <1>: Expression Patterns. -* ! (exclamation point), !~ operator <2>: Precedence. + (line 6843) +* ! (exclamation point), !~ operator <2>: Precedence. (line 6719) * ! (exclamation point), !~ operator <3>: Typing and Comparison. -* ! (exclamation point), !~ operator <4>: Regexp Constants. -* ! (exclamation point), !~ operator <5>: Computed Regexps. -* ! (exclamation point), !~ operator <6>: Case-sensitivity. -* ! (exclamation point), !~ operator: Regexp Usage. -* ! operator <1>: Egrep Program. -* ! operator: Ranges. -* " (double quote) <1>: Quoting. -* " (double quote): Read Terminal. -* " (double quote), regexp constants: Computed Regexps. + (line 6334) +* ! (exclamation point), !~ operator <4>: Regexp Constants. (line 5524) +* ! (exclamation point), !~ operator <5>: Computed Regexps. (line 2656) +* ! (exclamation point), !~ operator <6>: Case-sensitivity. (line 2569) +* ! (exclamation point), !~ operator: Regexp Usage. (line 1989) +* ! operator <1>: Egrep Program. (line 14653) +* ! operator: Ranges. (line 6947) +* " (double quote) <1>: Quoting. (line 1376) +* " (double quote): Read Terminal. (line 1165) +* " (double quote), regexp constants: Computed Regexps. (line 2677) * # (number sign), #! (executable scripts): Executable Scripts. + (line 1233) * # (number sign), #! (executable scripts), portability issues with: Executable Scripts. -* # (number sign), commenting: Comments. -* $ (dollar sign): Regexp Operators. -* $ (dollar sign), $ field operator <1>: Precedence. -* $ (dollar sign), $ field operator: Fields. + (line 1233) +* # (number sign), commenting: Comments. (line 1296) +* $ (dollar sign): Regexp Operators. (line 2210) +* $ (dollar sign), $ field operator <1>: Precedence. (line 6681) +* $ (dollar sign), $ field operator: Fields. (line 3019) * $ (dollar sign), incrementing fields and arrays: Increment Ops. -* $ field operator: Fields. -* % (percent sign), % operator: Precedence. -* % (percent sign), %= operator <1>: Precedence. -* % (percent sign), %= operator: Assignment Ops. -* & (ampersand), && operator <1>: Precedence. -* & (ampersand), && operator: Boolean Ops. + (line 6176) +* $ field operator: Fields. (line 3019) +* % (percent sign), % operator: Precedence. (line 6693) +* % (percent sign), %= operator <1>: Precedence. (line 6734) +* % (percent sign), %= operator: Assignment Ops. (line 6103) +* & (ampersand), && operator <1>: Precedence. (line 6725) +* & (ampersand), && operator: Boolean Ops. (line 6506) * & (ampersand), gsub/gensub/sub functions and: Gory Details. -* ' (single quote) <1>: Quoting. -* ' (single quote) <2>: Long. -* ' (single quote): One-shot. -* ' (single quote), vs. apostrophe: Comments. -* ' (single quote), with double quotes: Quoting. -* () (parentheses): Regexp Operators. -* () (parentheses), pgawk program: Profiling. + (line 9622) +* ' (single quote) <1>: Quoting. (line 1370) +* ' (single quote) <2>: Long. (line 1223) +* ' (single quote): One-shot. (line 1126) +* ' (single quote), vs. apostrophe: Comments. (line 1317) +* ' (single quote), with double quotes: Quoting. (line 1392) +* () (parentheses): Regexp Operators. (line 2253) +* () (parentheses), pgawk program: Profiling. (line 11862) * * (asterisk), * operator, as multiplication operator: Precedence. + (line 6693) * * (asterisk), * operator, as regexp operator: Regexp Operators. + (line 2261) * * (asterisk), * operator, null strings, matching: Gory Details. -* * (asterisk), ** operator <1>: Options. -* * (asterisk), ** operator <2>: Precedence. -* * (asterisk), ** operator: Arithmetic Ops. -* * (asterisk), **= operator <1>: Options. -* * (asterisk), **= operator <2>: Precedence. -* * (asterisk), **= operator: Assignment Ops. -* * (asterisk), *= operator <1>: Precedence. -* * (asterisk), *= operator: Assignment Ops. -* + (plus sign): Regexp Operators. -* + (plus sign), + operator: Precedence. -* + (plus sign), ++ operator <1>: Precedence. -* + (plus sign), ++ operator: Increment Ops. -* + (plus sign), += operator <1>: Precedence. -* + (plus sign), += operator: Assignment Ops. + (line 9776) +* * (asterisk), ** operator <1>: Options. (line 12157) +* * (asterisk), ** operator <2>: Precedence. (line 6687) +* * (asterisk), ** operator: Arithmetic Ops. (line 5890) +* * (asterisk), **= operator <1>: Options. (line 12157) +* * (asterisk), **= operator <2>: Precedence. (line 6734) +* * (asterisk), **= operator: Assignment Ops. (line 6103) +* * (asterisk), *= operator <1>: Precedence. (line 6734) +* * (asterisk), *= operator: Assignment Ops. (line 6103) +* + (plus sign): Regexp Operators. (line 2276) +* + (plus sign), + operator: Precedence. (line 6690) +* + (plus sign), ++ operator <1>: Precedence. (line 6684) +* + (plus sign), ++ operator: Increment Ops. (line 6186) +* + (plus sign), += operator <1>: Precedence. (line 6734) +* + (plus sign), += operator: Assignment Ops. (line 6056) * + (plus sign), decrement/increment operators: Increment Ops. -* , (comma), in range patterns: Ranges. -* - (hyphen), - operator: Precedence. + (line 6157) +* , (comma), in range patterns: Ranges. (line 6905) +* - (hyphen), - operator: Precedence. (line 6690) * - (hyphen), -- (decrement/increment) operator: Precedence. -* - (hyphen), -- operator: Increment Ops. -* - (hyphen), -= operator <1>: Precedence. -* - (hyphen), -= operator: Assignment Ops. -* - (hyphen), filenames beginning with: Options. -* - (hyphen), in character lists: Character Lists. -* --assign option: Options. -* --compat option: Options. -* --copyleft option: Options. -* --copyright option: Options. + (line 6684) +* - (hyphen), -- operator: Increment Ops. (line 6194) +* - (hyphen), -= operator <1>: Precedence. (line 6734) +* - (hyphen), -= operator: Assignment Ops. (line 6103) +* - (hyphen), filenames beginning with: Options. (line 12058) +* - (hyphen), in character lists: Character Lists. (line 2364) +* --assign option: Options. (line 12021) +* --compat option: Options. (line 12070) +* --copyleft option: Options. (line 12083) +* --copyright option: Options. (line 12078) * --disable-lint configuration option: Additional Configuration Options. + (line 17446) * --disable-nls configuration option: Additional Configuration Options. -* --dump-variables option <1>: Library Names. -* --dump-variables option: Options. + (line 17461) +* --dump-variables option <1>: Library Names. (line 12546) +* --dump-variables option: Options. (line 12086) * --enable-portals configuration option <1>: Additional Configuration Options. -* --enable-portals configuration option: Portal Files. + (line 17432) +* --enable-portals configuration option: Portal Files. (line 11710) * --enable-switch configuration option: Additional Configuration Options. -* --field-separator option: Options. -* --file option: Options. -* --gen-po option <1>: Options. -* --gen-po option: String Extraction. -* --help option: Options. -* --lint option <1>: Options. -* --lint option: Command Line. -* --lint-old option: Options. -* --non-decimal-data option <1>: Options. -* --non-decimal-data option: Nondecimal Data. + (line 17436) +* --field-separator option: Options. (line 12012) +* --file option: Options. (line 12016) +* --gen-po option <1>: Options. (line 12102) +* --gen-po option: String Extraction. (line 11157) +* --help option: Options. (line 12111) +* --lint option <1>: Options. (line 12116) +* --lint option: Command Line. (line 11987) +* --lint-old option: Options. (line 12128) +* --non-decimal-data option <1>: Options. (line 12133) +* --non-decimal-data option: Nondecimal Data. (line 11465) * --non-decimal-data option, strtonum function and: Nondecimal Data. -* --posix option: Options. -* --posix option, --traditional option and: Options. -* --profile option <1>: Options. -* --profile option: Profiling. -* --re-interval option: Options. -* --source option: Options. -* --traditional option: Options. -* --traditional option, --posix option and: Options. -* --usage option: Options. -* --version option: Options. + (line 11495) +* --posix option: Options. (line 12141) +* --posix option, --traditional option and: Options. (line 12168) +* --profile option <1>: Options. (line 12174) +* --profile option: Profiling. (line 11734) +* --re-interval option: Options. (line 12186) +* --source option: Options. (line 12193) +* --traditional option: Options. (line 12070) +* --traditional option, --posix option and: Options. (line 12168) +* --usage option: Options. (line 12111) +* --version option: Options. (line 12201) * --with-included-gettext configuration option <1>: Additional Configuration Options. -* --with-included-gettext configuration option: Gawk I18N. + (line 17440) +* --with-included-gettext configuration option: Gawk I18N. (line 11423) * --with-included-gettext configuration option, configuring gawk with: Additional Configuration Options. -* -f option: Options. -* -F option <1>: Options. + (line 17440) +* -f option: Options. (line 12016) +* -F option <1>: Options. (line 12012) * -F option: Command Line Field Separator. -* -f option: Long. -* -F option, -Ft sets FS to TAB: Options. -* -f option, on command line: Options. -* -F option, troubleshooting: Known Bugs. -* -mf/-mr options: Options. -* -v option: Options. + (line 3419) +* -f option: Long. (line 1202) +* -F option, -Ft sets FS to TAB: Options. (line 12209) +* -f option, on command line: Options. (line 12214) +* -F option, troubleshooting: Known Bugs. (line 12420) +* -mf/-mr options: Options. (line 12036) +* -v option: Options. (line 12021) * -v option, variables, assigning: Assignment Options. -* -W option: Options. -* . (period): Regexp Operators. + (line 5669) +* -W option: Options. (line 12046) +* . (period): Regexp Operators. (line 2218) * .mo files: Explaining gettext. -* .mo files, converting from .po: I18N Example. -* .mo files, specifying directory of <1>: Programmer i18n. + (line 10934) +* .mo files, converting from .po: I18N Example. (line 11380) +* .mo files, specifying directory of <1>: Programmer i18n. (line 11070) * .mo files, specifying directory of: Explaining gettext. -* .po files <1>: Translator i18n. + (line 10946) +* .po files <1>: Translator i18n. (line 11136) * .po files: Explaining gettext. -* .po files, converting to .mo: I18N Example. -* / (forward slash): Regexp. -* / (forward slash), / operator: Precedence. -* / (forward slash), /= operator <1>: Precedence. -* / (forward slash), /= operator: Assignment Ops. + (line 10931) +* .po files, converting to .mo: I18N Example. (line 11380) +* / (forward slash): Regexp. (line 1949) +* / (forward slash), / operator: Precedence. (line 6693) +* / (forward slash), /= operator <1>: Precedence. (line 6734) +* / (forward slash), /= operator: Assignment Ops. (line 6103) * / (forward slash), /= operator, vs. /=.../ regexp constant: Assignment Ops. + (line 6129) * / (forward slash), patterns and: Expression Patterns. -* /= operator vs. /=.../ regexp constant: Assignment Ops. -* /dev/... special files (gawk): Special FD. -* /inet/ files (gawk): TCP/IP Networking. -* /p files (gawk): Portal Files. -* ; (semicolon): Statements/Lines. -* ; (semicolon), AWKPATH variable and: PC Using. + (line 6843) +* /= operator vs. /=.../ regexp constant: Assignment Ops. (line 6129) +* /dev/... special files (gawk): Special FD. (line 5046) +* /inet/ files (gawk): TCP/IP Networking. (line 11643) +* /p files (gawk): Portal Files. (line 11710) +* ; (semicolon): Statements/Lines. (line 1853) +* ; (semicolon), AWKPATH variable and: PC Using. (line 17826) * ; (semicolon), separating statements in actions <1>: Statements. + (line 7220) * ; (semicolon), separating statements in actions: Action Overview. -* < (left angle bracket), < operator <1>: Precedence. + (line 7170) +* < (left angle bracket), < operator <1>: Precedence. (line 6703) * < (left angle bracket), < operator: Typing and Comparison. -* < (left angle bracket), < operator (I/O): Getline/File. -* < (left angle bracket), <= operator <1>: Precedence. + (line 6334) +* < (left angle bracket), < operator (I/O): Getline/File. (line 3971) +* < (left angle bracket), <= operator <1>: Precedence. (line 6703) * < (left angle bracket), <= operator: Typing and Comparison. -* = (equals sign), = operator: Assignment Ops. -* = (equals sign), == operator <1>: Precedence. + (line 6334) +* = (equals sign), = operator: Assignment Ops. (line 5981) +* = (equals sign), == operator <1>: Precedence. (line 6703) * = (equals sign), == operator: Typing and Comparison. -* > (right angle bracket), > operator <1>: Precedence. + (line 6334) +* > (right angle bracket), > operator <1>: Precedence. (line 6703) * > (right angle bracket), > operator: Typing and Comparison. -* > (right angle bracket), > operator (I/O): Redirection. -* > (right angle bracket), >= operator <1>: Precedence. + (line 6334) +* > (right angle bracket), > operator (I/O): Redirection. (line 4856) +* > (right angle bracket), >= operator <1>: Precedence. (line 6703) * > (right angle bracket), >= operator: Typing and Comparison. + (line 6334) * > (right angle bracket), >> operator (I/O) <1>: Precedence. -* > (right angle bracket), >> operator (I/O): Redirection. + (line 6703) +* > (right angle bracket), >> operator (I/O): Redirection. (line 4884) * ? (question mark) <1>: GNU Regexp Operators. -* ? (question mark): Regexp Operators. -* ? (question mark), ?: operator: Precedence. -* [] (square brackets): Regexp Operators. -* \ (backslash) <1>: Regexp Operators. -* \ (backslash) <2>: Quoting. -* \ (backslash) <3>: Comments. -* \ (backslash): Read Terminal. -* \ (backslash), \" escape sequence: Escape Sequences. + (line 2506) +* ? (question mark): Regexp Operators. (line 2285) +* ? (question mark), ?: operator: Precedence. (line 6731) +* [] (square brackets): Regexp Operators. (line 2230) +* \ (backslash) <1>: Regexp Operators. (line 2193) +* \ (backslash) <2>: Quoting. (line 1370) +* \ (backslash) <3>: Comments. (line 1339) +* \ (backslash): Read Terminal. (line 1165) +* \ (backslash), \" escape sequence: Escape Sequences. (line 2108) * \ (backslash), \' operator (gawk): GNU Regexp Operators. -* \ (backslash), \/ escape sequence: Escape Sequences. + (line 2503) +* \ (backslash), \/ escape sequence: Escape Sequences. (line 2101) * \ (backslash), \< operator (gawk): GNU Regexp Operators. + (line 2477) * \ (backslash), \> operator (gawk): GNU Regexp Operators. + (line 2481) * \ (backslash), \` operator (gawk): GNU Regexp Operators. -* \ (backslash), \a escape sequence: Escape Sequences. -* \ (backslash), \b escape sequence: Escape Sequences. + (line 2501) +* \ (backslash), \a escape sequence: Escape Sequences. (line 2066) +* \ (backslash), \b escape sequence: Escape Sequences. (line 2070) * \ (backslash), \B operator (gawk): GNU Regexp Operators. -* \ (backslash), \f escape sequence: Escape Sequences. -* \ (backslash), \n escape sequence: Escape Sequences. -* \ (backslash), \NNN escape sequence: Escape Sequences. -* \ (backslash), \r escape sequence: Escape Sequences. -* \ (backslash), \t escape sequence: Escape Sequences. -* \ (backslash), \v escape sequence: Escape Sequences. + (line 2490) +* \ (backslash), \f escape sequence: Escape Sequences. (line 2073) +* \ (backslash), \n escape sequence: Escape Sequences. (line 2076) +* \ (backslash), \NNN escape sequence: Escape Sequences. (line 2088) +* \ (backslash), \r escape sequence: Escape Sequences. (line 2079) +* \ (backslash), \t escape sequence: Escape Sequences. (line 2082) +* \ (backslash), \v escape sequence: Escape Sequences. (line 2085) * \ (backslash), \W operator (gawk): GNU Regexp Operators. + (line 2473) * \ (backslash), \w operator (gawk): GNU Regexp Operators. -* \ (backslash), \x escape sequence: Escape Sequences. + (line 2468) +* \ (backslash), \x escape sequence: Escape Sequences. (line 2093) * \ (backslash), \y operator (gawk): GNU Regexp Operators. + (line 2485) * \ (backslash), as field separators: Command Line Field Separator. -* \ (backslash), continuing lines and <1>: Egrep Program. -* \ (backslash), continuing lines and: Statements/Lines. + (line 3440) +* \ (backslash), continuing lines and <1>: Egrep Program. (line 14703) +* \ (backslash), continuing lines and: Statements/Lines. (line 1783) * \ (backslash), continuing lines and, comments and: Statements/Lines. + (line 1838) * \ (backslash), continuing lines and, in csh <1>: Statements/Lines. + (line 1807) * \ (backslash), continuing lines and, in csh: More Complex. + (line 1708) * \ (backslash), gsub/gensub/sub functions and: Gory Details. -* \ (backslash), in character lists: Character Lists. -* \ (backslash), in escape sequences: Escape Sequences. + (line 9622) +* \ (backslash), in character lists: Character Lists. (line 2364) +* \ (backslash), in escape sequences: Escape Sequences. (line 2038) * \ (backslash), in escape sequences, POSIX and: Escape Sequences. -* \ (backslash), regexp constants: Computed Regexps. + (line 2145) +* \ (backslash), regexp constants: Computed Regexps. (line 2677) * ^ (caret) <1>: GNU Regexp Operators. -* ^ (caret): Regexp Operators. -* ^ (caret), ^ operator <1>: Options. -* ^ (caret), ^ operator: Precedence. -* ^ (caret), ^= operator <1>: Options. -* ^ (caret), ^= operator <2>: Precedence. -* ^ (caret), ^= operator: Assignment Ops. -* ^ (caret), in character lists: Character Lists. + (line 2506) +* ^ (caret): Regexp Operators. (line 2197) +* ^ (caret), ^ operator <1>: Options. (line 12157) +* ^ (caret), ^ operator: Precedence. (line 6687) +* ^ (caret), ^= operator <1>: Options. (line 12157) +* ^ (caret), ^= operator <2>: Precedence. (line 6734) +* ^ (caret), ^= operator: Assignment Ops. (line 6103) +* ^ (caret), in character lists: Character Lists. (line 2364) * _ (underscore), _ C macro: Explaining gettext. + (line 10963) * _ (underscore), in names of private variables: Library Names. -* _ (underscore), translatable string: Programmer i18n. -* _gr_init user-defined function: Group Functions. -* _pw_init user-defined function: Passwd Functions. -* accessing fields: Fields. -* account information <1>: Group Functions. -* account information: Passwd Functions. -* actions: Action Overview. -* actions, control statements in: Statements. -* actions, default: Very Simple. -* actions, empty: Very Simple. -* adding, features to gawk: Adding Code. -* adding, fields: Changing Fields. + (line 12530) +* _ (underscore), translatable string: Programmer i18n. (line 11092) +* _gr_init user-defined function: Group Functions. (line 14008) +* _pw_init user-defined function: Passwd Functions. (line 13794) +* accessing fields: Fields. (line 3006) +* account information <1>: Group Functions. (line 13934) +* account information: Passwd Functions. (line 13719) +* actions: Action Overview. (line 7157) +* actions, control statements in: Statements. (line 7216) +* actions, default: Very Simple. (line 1559) +* actions, empty: Very Simple. (line 1564) +* adding, features to gawk: Adding Code. (line 18515) +* adding, fields: Changing Fields. (line 3169) * adding, functions to gawk: Dynamic Extensions. -* advanced features, buffering: I/O Functions. + (line 18733) +* advanced features, buffering: I/O Functions. (line 9884) * advanced features, close function: Close Files And Pipes. + (line 5315) * advanced features, constants, values of: Nondecimal-numbers. -* advanced features, data files as single record: Records. -* advanced features, fixed-width data: Constant Size. -* advanced features, FNR/NR variables: Auto-set. -* advanced features, gawk: Advanced Features. -* advanced features, gawk, BSD portals: Portal Files. + (line 5510) +* advanced features, data files as single record: Records. (line 2971) +* advanced features, fixed-width data: Constant Size. (line 3597) +* advanced features, FNR/NR variables: Auto-set. (line 8140) +* advanced features, gawk: Advanced Features. (line 11434) +* advanced features, gawk, BSD portals: Portal Files. (line 11710) * advanced features, gawk, network programming: TCP/IP Networking. + (line 11643) * advanced features, gawk, nondecimal input data: Nondecimal Data. + (line 11465) * advanced features, gawk, processes, communicating with: Two-way I/O. + (line 11524) * advanced features, network connections, See Also networks, connections: Advanced Features. -* advanced features, null strings, matching: Gory Details. -* advanced features, operators, precedence: Increment Ops. -* advanced features, piping into sh: Redirection. -* advanced features, regexp constants: Assignment Ops. -* Aho, Alfred <1>: Contributors. -* Aho, Alfred: History. -* alarm clock example program: Alarm Program. -* alarm.awk program: Alarm Program. -* algorithms: Basic High Level. -* Alpha (DEC): Manual History. -* amazing awk assembler (aaa): Glossary. -* amazingly workable formatter (awf): Glossary. + (line 11434) +* advanced features, null strings, matching: Gory Details. (line 9776) +* advanced features, operators, precedence: Increment Ops. (line 6207) +* advanced features, piping into sh: Redirection. (line 4973) +* advanced features, regexp constants: Assignment Ops. (line 6129) +* Aho, Alfred <1>: Contributors. (line 17022) +* Aho, Alfred: History. (line 640) +* alarm clock example program: Alarm Program. (line 15446) +* alarm.awk program: Alarm Program. (line 15464) +* algorithms: Basic High Level. (line 19519) +* Alpha (DEC): Manual History. (line 886) +* amazing awk assembler (aaa): Glossary. (line 19753) +* amazingly workable formatter (awf): Glossary. (line 19761) * ambiguity, syntactic: /= operator vs. /=.../ regexp constant: Assignment Ops. + (line 6129) * amiga: Amiga Installation. -* ampersand (&), && operator: Boolean Ops. -* ampersand (&), &&operator: Precedence. + (line 17535) +* ampersand (&), && operator: Boolean Ops. (line 6506) +* ampersand (&), &&operator: Precedence. (line 6725) * ampersand (&), gsub/gensub/sub functions and: Gory Details. -* AND bitwise operation: Bitwise Functions. -* and Boolean-logic operator: Boolean Ops. -* and function (gawk): Bitwise Functions. -* ANSI: Glossary. -* archeologists: Bugs. -* ARGC/ARGV variables <1>: ARGC and ARGV. -* ARGC/ARGV variables: Auto-set. + (line 9622) +* AND bitwise operation: Bitwise Functions. (line 10294) +* and Boolean-logic operator: Boolean Ops. (line 6455) +* and function (gawk): Bitwise Functions. (line 10327) +* ANSI: Glossary. (line 19772) +* archeologists: Bugs. (line 18282) +* ARGC/ARGV variables <1>: ARGC and ARGV. (line 8172) +* ARGC/ARGV variables: Auto-set. (line 7964) * ARGC/ARGV variables, command-line arguments: Other Arguments. + (line 12277) * ARGC/ARGV variables, portability and: Executable Scripts. -* ARGIND variable: Auto-set. -* ARGIND variable, command-line arguments: Other Arguments. -* arguments, command-line <1>: Other Arguments. -* arguments, command-line <2>: ARGC and ARGV. -* arguments, command-line: Auto-set. -* arguments, command-line, invoking awk: Command Line. -* arguments, in function calls: Function Calls. -* arguments, processing: Getopt Function. -* arguments, retrieving: Internals. -* arithmetic operators: Arithmetic Ops. -* arrays: Arrays. -* arrays, as parameters to functions: Function Caveats. -* arrays, associative: Array Intro. -* arrays, associative, clearing: Internals. + (line 1270) +* ARGIND variable: Auto-set. (line 7993) +* ARGIND variable, command-line arguments: Other Arguments. (line 12277) +* arguments, command-line <1>: Other Arguments. (line 12271) +* arguments, command-line <2>: ARGC and ARGV. (line 8172) +* arguments, command-line: Auto-set. (line 7964) +* arguments, command-line, invoking awk: Command Line. (line 11973) +* arguments, in function calls: Function Calls. (line 6595) +* arguments, processing: Getopt Function. (line 13426) +* arguments, retrieving: Internals. (line 18870) +* arithmetic operators: Arithmetic Ops. (line 5815) +* arrays: Arrays. (line 8268) +* arrays, as parameters to functions: Function Caveats. (line 10696) +* arrays, associative: Array Intro. (line 8348) +* arrays, associative, clearing: Internals. (line 18815) * arrays, associative, library functions and: Library Names. -* arrays, deleting entire contents: Delete. + (line 12558) +* arrays, deleting entire contents: Delete. (line 8610) * arrays, elements, assigning: Assigning Elements. -* arrays, elements, deleting: Delete. -* arrays, elements, installing: Internals. -* arrays, elements, order of: Scanning an Array. + (line 8452) +* arrays, elements, deleting: Delete. (line 8577) +* arrays, elements, installing: Internals. (line 18819) +* arrays, elements, order of: Scanning an Array. (line 8563) * arrays, elements, referencing: Reference to Elements. -* arrays, elements, retrieving number of: String Functions. -* arrays, for statement and: Scanning an Array. -* arrays, IGNORECASE variable and: Array Intro. -* arrays, indexing: Array Intro. -* arrays, merging into strings: Join Function. -* arrays, multidimensional: Multi-dimensional. -* arrays, multidimensional, scanning: Multi-scanning. -* arrays, names of: Arrays. -* arrays, scanning: Scanning an Array. -* arrays, sorting: Array Sorting. -* arrays, sorting, IGNORECASE variable and: Array Sorting. -* arrays, sparse: Array Intro. + (line 8405) +* arrays, elements, retrieving number of: String Functions. (line 9168) +* arrays, for statement and: Scanning an Array. (line 8536) +* arrays, IGNORECASE variable and: Array Intro. (line 8390) +* arrays, indexing: Array Intro. (line 8348) +* arrays, merging into strings: Join Function. (line 13033) +* arrays, multidimensional: Multi-dimensional. (line 8746) +* arrays, multidimensional, scanning: Multi-scanning. (line 8832) +* arrays, names of: Arrays. (line 8279) +* arrays, scanning: Scanning an Array. (line 8522) +* arrays, sorting: Array Sorting. (line 8867) +* arrays, sorting, IGNORECASE variable and: Array Sorting. (line 8945) +* arrays, sparse: Array Intro. (line 8369) * arrays, subscripts: Numeric Array Subscripts. + (line 8648) * arrays, subscripts, uninitialized variables as: Uninitialized Subscripts. + (line 8699) * artificial intelligence, gawk and: Distribution contents. -* ASCII: Ordinal Functions. -* asort function (gawk) <1>: String Functions. -* asort function (gawk): Array Sorting. -* asort function (gawk), arrays, sorting: Array Sorting. -* asorti function (gawk): String Functions. -* assert function (C library): Assert Function. -* assert user-defined function: Assert Function. -* assertions: Assert Function. -* assignment operators: Assignment Ops. -* assignment operators, evaluation order: Assignment Ops. -* assignment operators, lvalues/rvalues: Assignment Ops. -* assignments as filenames: Ignoring Assigns. -* assoc_clear internal function: Internals. -* assoc_lookup internal function: Internals. -* associative arrays: Array Intro. + (line 17254) +* ASCII: Ordinal Functions. (line 12980) +* asort function (gawk) <1>: String Functions. (line 9168) +* asort function (gawk): Array Sorting. (line 8867) +* asort function (gawk), arrays, sorting: Array Sorting. (line 8867) +* asorti function (gawk): String Functions. (line 9197) +* assert function (C library): Assert Function. (line 12781) +* assert user-defined function: Assert Function. (line 12803) +* assertions: Assert Function. (line 12781) +* assignment operators: Assignment Ops. (line 5981) +* assignment operators, evaluation order: Assignment Ops. (line 6085) +* assignment operators, lvalues/rvalues: Assignment Ops. (line 6006) +* assignments as filenames: Ignoring Assigns. (line 13384) +* assoc_clear internal function: Internals. (line 18815) +* assoc_lookup internal function: Internals. (line 18819) +* associative arrays: Array Intro. (line 8348) * asterisk (*), * operator, as multiplication operator: Precedence. + (line 6693) * asterisk (*), * operator, as regexp operator: Regexp Operators. + (line 2261) * asterisk (*), * operator, null strings, matching: Gory Details. -* asterisk (*), ** operator <1>: Options. -* asterisk (*), ** operator <2>: Precedence. -* asterisk (*), ** operator: Arithmetic Ops. -* asterisk (*), **= operator <1>: Options. -* asterisk (*), **= operator <2>: Precedence. -* asterisk (*), **= operator: Assignment Ops. -* asterisk (*), *= operator <1>: Precedence. -* asterisk (*), *= operator: Assignment Ops. -* atan2 function: Numeric Functions. + (line 9776) +* asterisk (*), ** operator <1>: Options. (line 12157) +* asterisk (*), ** operator <2>: Precedence. (line 6687) +* asterisk (*), ** operator: Arithmetic Ops. (line 5890) +* asterisk (*), **= operator <1>: Options. (line 12157) +* asterisk (*), **= operator <2>: Precedence. (line 6734) +* asterisk (*), **= operator: Assignment Ops. (line 6103) +* asterisk (*), *= operator <1>: Precedence. (line 6734) +* asterisk (*), *= operator: Assignment Ops. (line 6103) +* atan2 function: Numeric Functions. (line 9074) * atari: Atari Installation. -* awf (amazingly workable formatter) program: Glossary. -* awk language, POSIX version: Assignment Ops. -* awk programs <1>: Two Rules. + (line 18129) +* awf (amazingly workable formatter) program: Glossary. (line 19761) +* awk language, POSIX version: Assignment Ops. (line 6114) +* awk programs <1>: Two Rules. (line 1647) * awk programs <2>: Executable Scripts. -* awk programs: Getting Started. -* awk programs, complex: When. -* awk programs, documenting <1>: Library Names. -* awk programs, documenting: Comments. -* awk programs, examples of: Sample Programs. -* awk programs, execution of: Next Statement. -* awk programs, internationalizing <1>: Programmer i18n. -* awk programs, internationalizing: I18N Functions. -* awk programs, lengthy: Long. -* awk programs, lengthy, assertions: Assert Function. -* awk programs, location of: Options. -* awk programs, one-line examples: Very Simple. -* awk programs, profiling: Profiling. -* awk programs, profiling, enabling: Options. -* awk programs, running <1>: Long. -* awk programs, running: Running gawk. -* awk programs, running, from shell scripts: One-shot. + (line 1233) +* awk programs: Getting Started. (line 1038) +* awk programs, complex: When. (line 1923) +* awk programs, documenting <1>: Library Names. (line 12507) +* awk programs, documenting: Comments. (line 1296) +* awk programs, examples of: Sample Programs. (line 14166) +* awk programs, execution of: Next Statement. (line 7637) +* awk programs, internationalizing <1>: Programmer i18n. (line 11031) +* awk programs, internationalizing: I18N Functions. (line 10416) +* awk programs, lengthy: Long. (line 1196) +* awk programs, lengthy, assertions: Assert Function. (line 12781) +* awk programs, location of: Options. (line 12016) +* awk programs, one-line examples: Very Simple. (line 1570) +* awk programs, profiling: Profiling. (line 11725) +* awk programs, profiling, enabling: Options. (line 12174) +* awk programs, running <1>: Long. (line 1196) +* awk programs, running: Running gawk. (line 1084) +* awk programs, running, from shell scripts: One-shot. (line 1133) * awk programs, running, without input files: Read Terminal. + (line 1157) * awk programs, shell variables in: Using Shell Variables. -* awk, function of: Getting Started. -* awk, gawk and <1>: This Manual. -* awk, gawk and: Preface. -* awk, history of: History. -* awk, implementation issues, pipes: Redirection. -* awk, implementations: Other Versions. -* awk, implementations, limits: Getline Notes. -* awk, invoking: Command Line. -* awk, new vs. old: Names. -* awk, new vs. old, OFMT variable: Conversion. -* awk, POSIX and: Preface. -* awk, POSIX and, See Also POSIX awk: Preface. + (line 7106) +* awk, function of: Getting Started. (line 1032) +* awk, gawk and <1>: This Manual. (line 718) +* awk, gawk and: Preface. (line 569) +* awk, history of: History. (line 640) +* awk, implementation issues, pipes: Redirection. (line 4965) +* awk, implementations: Other Versions. (line 18351) +* awk, implementations, limits: Getline Notes. (line 4185) +* awk, invoking: Command Line. (line 11973) +* awk, new vs. old: Names. (line 677) +* awk, new vs. old, OFMT variable: Conversion. (line 5759) +* awk, POSIX and: Preface. (line 569) +* awk, POSIX and, See Also POSIX awk: Preface. (line 569) * awk, regexp constants and: Typing and Comparison. -* awk, See Also gawk: Preface. -* awk, terms describing: This Manual. -* awk, uses for <1>: When. -* awk, uses for <2>: Getting Started. -* awk, uses for: Preface. -* awk, versions of <1>: V7/SVR3.1. -* awk, versions of: Names. -* awk, versions of, changes between SVR3.1 and SVR4: SVR4. + (line 6434) +* awk, See Also gawk: Preface. (line 582) +* awk, terms describing: This Manual. (line 711) +* awk, uses for <1>: When. (line 1899) +* awk, uses for <2>: Getting Started. (line 1038) +* awk, uses for: Preface. (line 569) +* awk, versions of <1>: V7/SVR3.1. (line 16631) +* awk, versions of: Names. (line 681) +* awk, versions of, changes between SVR3.1 and SVR4: SVR4. (line 16690) * awk, versions of, changes between SVR4 and POSIX awk: POSIX. + (line 16731) * awk, versions of, changes between V7 and SVR3.1: V7/SVR3.1. -* awk, versions of, See Also Bell Laboratories awk: BTL. -* awk.h file (internal): Internals. -* awka compiler for awk: Other Versions. -* AWKNUM internal type: Internals. -* AWKPATH environment variable <1>: PC Using. -* AWKPATH environment variable: AWKPATH Variable. -* awkprof.out file: Profiling. -* awksed.awk program: Simple Sed. -* awkvars.out file: Options. -* backslash (\) <1>: Regexp Operators. -* backslash (\) <2>: Quoting. -* backslash (\) <3>: Comments. -* backslash (\): Read Terminal. -* backslash (\), \" escape sequence: Escape Sequences. + (line 16631) +* awk, versions of, See Also Bell Laboratories awk: BTL. (line 16775) +* awk.h file (internal): Internals. (line 18764) +* awka compiler for awk: Other Versions. (line 18421) +* AWKNUM internal type: Internals. (line 18768) +* AWKPATH environment variable <1>: PC Using. (line 17826) +* AWKPATH environment variable: AWKPATH Variable. (line 12327) +* awkprof.out file: Profiling. (line 11729) +* awksed.awk program: Simple Sed. (line 16155) +* awkvars.out file: Options. (line 12086) +* backslash (\) <1>: Regexp Operators. (line 2193) +* backslash (\) <2>: Quoting. (line 1370) +* backslash (\) <3>: Comments. (line 1339) +* backslash (\): Read Terminal. (line 1165) +* backslash (\), \" escape sequence: Escape Sequences. (line 2108) * backslash (\), \' operator (gawk): GNU Regexp Operators. -* backslash (\), \/ escape sequence: Escape Sequences. + (line 2503) +* backslash (\), \/ escape sequence: Escape Sequences. (line 2101) * backslash (\), \< operator (gawk): GNU Regexp Operators. + (line 2477) * backslash (\), \> operator (gawk): GNU Regexp Operators. + (line 2481) * backslash (\), \` operator (gawk): GNU Regexp Operators. -* backslash (\), \a escape sequence: Escape Sequences. -* backslash (\), \b escape sequence: Escape Sequences. + (line 2501) +* backslash (\), \a escape sequence: Escape Sequences. (line 2066) +* backslash (\), \b escape sequence: Escape Sequences. (line 2070) * backslash (\), \B operator (gawk): GNU Regexp Operators. -* backslash (\), \f escape sequence: Escape Sequences. -* backslash (\), \n escape sequence: Escape Sequences. -* backslash (\), \NNN escape sequence: Escape Sequences. -* backslash (\), \r escape sequence: Escape Sequences. -* backslash (\), \t escape sequence: Escape Sequences. -* backslash (\), \v escape sequence: Escape Sequences. + (line 2490) +* backslash (\), \f escape sequence: Escape Sequences. (line 2073) +* backslash (\), \n escape sequence: Escape Sequences. (line 2076) +* backslash (\), \NNN escape sequence: Escape Sequences. (line 2088) +* backslash (\), \r escape sequence: Escape Sequences. (line 2079) +* backslash (\), \t escape sequence: Escape Sequences. (line 2082) +* backslash (\), \v escape sequence: Escape Sequences. (line 2085) * backslash (\), \W operator (gawk): GNU Regexp Operators. + (line 2473) * backslash (\), \w operator (gawk): GNU Regexp Operators. -* backslash (\), \x escape sequence: Escape Sequences. + (line 2468) +* backslash (\), \x escape sequence: Escape Sequences. (line 2093) * backslash (\), \y operator (gawk): GNU Regexp Operators. + (line 2485) * backslash (\), as field separators: Command Line Field Separator. -* backslash (\), continuing lines and <1>: Egrep Program. -* backslash (\), continuing lines and: Statements/Lines. + (line 3440) +* backslash (\), continuing lines and <1>: Egrep Program. (line 14703) +* backslash (\), continuing lines and: Statements/Lines. (line 1783) * backslash (\), continuing lines and, comments and: Statements/Lines. + (line 1838) * backslash (\), continuing lines and, in csh <1>: Statements/Lines. + (line 1807) * backslash (\), continuing lines and, in csh: More Complex. + (line 1708) * backslash (\), gsub/gensub/sub functions and: Gory Details. -* backslash (\), in character lists: Character Lists. -* backslash (\), in escape sequences: Escape Sequences. + (line 9622) +* backslash (\), in character lists: Character Lists. (line 2364) +* backslash (\), in escape sequences: Escape Sequences. (line 2038) * backslash (\), in escape sequences, POSIX and: Escape Sequences. -* backslash (\), regexp constants: Computed Regexps. -* BBS-list file: Sample Data Files. -* Beebe, Nelson: Acknowledgments. -* Beebe, Nelson H.F.: Other Versions. -* BEGIN pattern <1>: BEGIN/END. -* BEGIN pattern <2>: Field Separators. -* BEGIN pattern: Records. + (line 2145) +* backslash (\), regexp constants: Computed Regexps. (line 2677) +* BBS-list file: Sample Data Files. (line 1461) +* Beebe, Nelson: Acknowledgments. (line 995) +* Beebe, Nelson H.F.: Other Versions. (line 18433) +* BEGIN pattern <1>: BEGIN/END. (line 6972) +* BEGIN pattern <2>: Field Separators. (line 3292) +* BEGIN pattern: Records. (line 2839) * BEGIN pattern, assert user-defined function and: Assert Function. + (line 12857) * BEGIN pattern, Boolean patterns and: Expression Patterns. -* BEGIN pattern, exit statement and: Exit Statement. -* BEGIN pattern, getline and: Getline Notes. -* BEGIN pattern, headings, adding: Print Examples. + (line 6892) +* BEGIN pattern, exit statement and: Exit Statement. (line 7735) +* BEGIN pattern, getline and: Getline Notes. (line 4190) +* BEGIN pattern, headings, adding: Print Examples. (line 4342) * BEGIN pattern, next/nextfile statements and <1>: Next Statement. + (line 7660) * BEGIN pattern, next/nextfile statements and: I/O And BEGIN/END. + (line 7080) * BEGIN pattern, OFS/ORS variables, assigning values to: Output Separators. -* BEGIN pattern, operators and: Using BEGIN/END. -* BEGIN pattern, pgawk program: Profiling. -* BEGIN pattern, print statement and: I/O And BEGIN/END. -* BEGIN pattern, pwcat program: Passwd Functions. -* BEGIN pattern, running awk programs and: Cut Program. -* BEGIN pattern, TEXTDOMAIN variable and: Programmer i18n. + (line 4399) +* BEGIN pattern, operators and: Using BEGIN/END. (line 7002) +* BEGIN pattern, pgawk program: Profiling. (line 11787) +* BEGIN pattern, print statement and: I/O And BEGIN/END. (line 7060) +* BEGIN pattern, pwcat program: Passwd Functions. (line 13828) +* BEGIN pattern, running awk programs and: Cut Program. (line 14297) +* BEGIN pattern, TEXTDOMAIN variable and: Programmer i18n. (line 11083) * beginfile user-defined function: Filetrans Function. -* Bell Laboratories awk extensions: BTL. -* Benzinger, Michael: Contributors. -* BeOS: BeOS Installation. -* Berry, Karl: Acknowledgments. -* binary input/output: User-modified. + (line 13231) +* Bell Laboratories awk extensions: BTL. (line 16775) +* Benzinger, Michael: Contributors. (line 17095) +* BeOS: BeOS Installation. (line 17568) +* Berry, Karl: Acknowledgments. (line 972) +* binary input/output: User-modified. (line 7809) * bindtextdomain function (C library): Explaining gettext. -* bindtextdomain function (gawk) <1>: Programmer i18n. -* bindtextdomain function (gawk): I18N Functions. + (line 10942) +* bindtextdomain function (gawk) <1>: Programmer i18n. (line 11070) +* bindtextdomain function (gawk): I18N Functions. (line 10436) * bindtextdomain function (gawk), portability and: I18N Portability. -* BINMODE variable <1>: PC Using. -* BINMODE variable: User-modified. -* bits2str user-defined function: Bitwise Functions. -* bitwise, complement: Bitwise Functions. -* bitwise, operations: Bitwise Functions. -* bitwise, shift: Bitwise Functions. -* body, in actions: Statements. -* body, in loops: While Statement. -* Boolean expressions: Boolean Ops. + (line 11286) +* BINMODE variable <1>: PC Using. (line 17855) +* BINMODE variable: User-modified. (line 7809) +* bits2str user-defined function: Bitwise Functions. (line 10348) +* bitwise, complement: Bitwise Functions. (line 10313) +* bitwise, operations: Bitwise Functions. (line 10294) +* bitwise, shift: Bitwise Functions. (line 10320) +* body, in actions: Statements. (line 7220) +* body, in loops: While Statement. (line 7299) +* Boolean expressions: Boolean Ops. (line 6455) * Boolean expressions, as patterns: Expression Patterns. -* Boolean operators, See Boolean expressions: Boolean Ops. -* Bourne shell, quoting rules for: Quoting. -* braces ({}), actions and: Action Overview. -* braces ({}), pgawk program: Profiling. -* braces ({}), statements, grouping: Statements. + (line 6860) +* Boolean operators, See Boolean expressions: Boolean Ops. (line 6455) +* Bourne shell, quoting rules for: Quoting. (line 1357) +* braces ({}), actions and: Action Overview. (line 7170) +* braces ({}), pgawk program: Profiling. (line 11858) +* braces ({}), statements, grouping: Statements. (line 7220) * bracket expressions, See character lists: Regexp Operators. -* break statement: Break Statement. -* Brennan, Michael <1>: Other Versions. -* Brennan, Michael <2>: Simple Sed. -* Brennan, Michael <3>: Two-way I/O. -* Brennan, Michael: Delete. -* Broder, Alan J.: Contributors. -* Brown, Martin <1>: Bugs. -* Brown, Martin <2>: Contributors. -* Brown, Martin: Acknowledgments. -* BSD portals: Portal Files. -* BSD-based operating systems: Glossary. -* Buening, Andreas <1>: Contributors. -* Buening, Andreas: Acknowledgments. -* buffering, input/output <1>: Two-way I/O. -* buffering, input/output: I/O Functions. -* buffering, interactive vs. noninteractive: I/O Functions. -* buffers, flushing: I/O Functions. + (line 2230) +* break statement: Break Statement. (line 7517) +* Brennan, Michael <1>: Other Versions. (line 18351) +* Brennan, Michael <2>: Simple Sed. (line 16155) +* Brennan, Michael <3>: Two-way I/O. (line 11507) +* Brennan, Michael: Delete. (line 8622) +* Broder, Alan J.: Contributors. (line 17086) +* Brown, Martin <1>: Bugs. (line 18332) +* Brown, Martin <2>: Contributors. (line 17081) +* Brown, Martin: Acknowledgments. (line 995) +* BSD portals: Portal Files. (line 11710) +* BSD-based operating systems: Glossary. (line 20320) +* Buening, Andreas <1>: Contributors. (line 17090) +* Buening, Andreas: Acknowledgments. (line 995) +* buffering, input/output <1>: Two-way I/O. (line 11572) +* buffering, input/output: I/O Functions. (line 9916) +* buffering, interactive vs. noninteractive: I/O Functions. (line 9884) +* buffers, flushing: I/O Functions. (line 9818) * buffers, operators for: GNU Regexp Operators. -* bug reports, email address, bug-gawk@gnu.org: Bugs. -* bug-gawk@gnu.org bug reporting address: Bugs. -* built-in functions: Functions. -* built-in functions, evaluation order: Calling Built-in. + (line 2495) +* bug reports, email address, bug-gawk@gnu.org: Bugs. (line 18303) +* bug-gawk@gnu.org bug reporting address: Bugs. (line 18303) +* built-in functions: Functions. (line 8956) +* built-in functions, evaluation order: Calling Built-in. (line 9023) * built-in variables: Built-in Variables. -* built-in variables, -v option, setting with: Options. -* built-in variables, conveying information: Auto-set. -* built-in variables, user-modifiable: User-modified. -* call by reference: Function Caveats. -* call by value: Function Caveats. + (line 7779) +* built-in variables, -v option, setting with: Options. (line 12029) +* built-in variables, conveying information: Auto-set. (line 7959) +* built-in variables, user-modifiable: User-modified. (line 7805) +* call by reference: Function Caveats. (line 10696) +* call by value: Function Caveats. (line 10667) * caret (^) <1>: GNU Regexp Operators. -* caret (^): Regexp Operators. -* caret (^), ^ operator <1>: Options. -* caret (^), ^ operator: Precedence. -* caret (^), ^= operator <1>: Options. -* caret (^), ^= operator <2>: Precedence. -* caret (^), ^= operator: Assignment Ops. -* caret (^), in character lists: Character Lists. -* case keyword: Switch Statement. -* case sensitivity, array indices and: Array Intro. -* case sensitivity, converting case: String Functions. -* case sensitivity, example programs: Library Functions. -* case sensitivity, gawk: Case-sensitivity. -* case sensitivity, regexps and <1>: User-modified. -* case sensitivity, regexps and: Case-sensitivity. -* case sensitivity, string comparisons and: User-modified. -* character encodings: Ordinal Functions. -* character lists <1>: Character Lists. -* character lists: Regexp Operators. -* character lists, character classes: Character Lists. -* character lists, collating elements: Character Lists. -* character lists, collating symbols: Character Lists. -* character lists, complemented: Regexp Operators. -* character lists, equivalence classes: Character Lists. -* character lists, non-ASCII: Character Lists. -* character lists, range expressions: Character Lists. -* character sets: Ordinal Functions. -* character sets (machine character encodings): Glossary. + (line 2506) +* caret (^): Regexp Operators. (line 2197) +* caret (^), ^ operator <1>: Options. (line 12157) +* caret (^), ^ operator: Precedence. (line 6687) +* caret (^), ^= operator <1>: Options. (line 12157) +* caret (^), ^= operator <2>: Precedence. (line 6734) +* caret (^), ^= operator: Assignment Ops. (line 6103) +* caret (^), in character lists: Character Lists. (line 2364) +* case keyword: Switch Statement. (line 7456) +* case sensitivity, array indices and: Array Intro. (line 8390) +* case sensitivity, converting case: String Functions. (line 9591) +* case sensitivity, example programs: Library Functions. (line 12472) +* case sensitivity, gawk: Case-sensitivity. (line 2569) +* case sensitivity, regexps and <1>: User-modified. (line 7867) +* case sensitivity, regexps and: Case-sensitivity. (line 2549) +* case sensitivity, string comparisons and: User-modified. (line 7867) +* character encodings: Ordinal Functions. (line 12980) +* character lists <1>: Character Lists. (line 2353) +* character lists: Regexp Operators. (line 2230) +* character lists, character classes: Character Lists. (line 2377) +* character lists, collating elements: Character Lists. (line 2430) +* character lists, collating symbols: Character Lists. (line 2437) +* character lists, complemented: Regexp Operators. (line 2237) +* character lists, equivalence classes: Character Lists. (line 2443) +* character lists, non-ASCII: Character Lists. (line 2430) +* character lists, range expressions: Character Lists. (line 2353) +* character sets: Ordinal Functions. (line 12980) +* character sets (machine character encodings): Glossary. (line 19879) * character sets, See Also character lists: Regexp Operators. -* characters, counting: Wc Program. -* characters, transliterating: Translate Program. -* characters, values of as numbers: Ordinal Functions. -* Chassell, Robert J.: Acknowledgments. -* chdir function, implementing in gawk: Sample Library. -* chem utility: Glossary. -* chr user-defined function: Ordinal Functions. + (line 2230) +* characters, counting: Wc Program. (line 15230) +* characters, transliterating: Translate Program. (line 15567) +* characters, values of as numbers: Ordinal Functions. (line 12942) +* Chassell, Robert J.: Acknowledgments. (line 972) +* chdir function, implementing in gawk: Sample Library. (line 18963) +* chem utility: Glossary. (line 19887) +* chr user-defined function: Ordinal Functions. (line 12952) * Cliff random numbers: Cliff Random Function. + (line 12911) * cliff_rand user-defined function: Cliff Random Function. -* close function <1>: I/O Functions. + (line 12916) +* close function <1>: I/O Functions. (line 9799) * close function <2>: Close Files And Pipes. -* close function <3>: Getline/Pipe. + (line 5203) +* close function <3>: Getline/Pipe. (line 4061) * close function: Getline/Variable/File. + (line 4028) * close function, return values: Close Files And Pipes. -* close function, two-way pipes and: Two-way I/O. -* Close, Diane <1>: Contributors. -* Close, Diane: Manual History. -* collating elements: Character Lists. -* collating symbols: Character Lists. -* columns, aligning: Print Examples. -* columns, cutting: Cut Program. -* comma (,), in range patterns: Ranges. -* command line, arguments <1>: Other Arguments. -* command line, arguments <2>: ARGC and ARGV. -* command line, arguments: Auto-set. -* command line, formats: Running gawk. + (line 5315) +* close function, two-way pipes and: Two-way I/O. (line 11579) +* Close, Diane <1>: Contributors. (line 17031) +* Close, Diane: Manual History. (line 898) +* collating elements: Character Lists. (line 2430) +* collating symbols: Character Lists. (line 2437) +* columns, aligning: Print Examples. (line 4369) +* columns, cutting: Cut Program. (line 14237) +* comma (,), in range patterns: Ranges. (line 6905) +* command line, arguments <1>: Other Arguments. (line 12271) +* command line, arguments <2>: ARGC and ARGV. (line 8172) +* command line, arguments: Auto-set. (line 7964) +* command line, formats: Running gawk. (line 1090) * command line, FS on, setting: Command Line Field Separator. -* command line, invoking awk from: Command Line. -* command line, options <1>: Options. + (line 3419) +* command line, invoking awk from: Command Line. (line 11973) +* command line, options <1>: Options. (line 11997) * command line, options <2>: Command Line Field Separator. -* command line, options: Long. -* command line, options, end of: Options. + (line 3419) +* command line, options: Long. (line 1202) +* command line, options, end of: Options. (line 12053) * command line, variables, assigning on: Assignment Options. -* command-line options, processing: Getopt Function. + (line 5663) +* command-line options, processing: Getopt Function. (line 13426) * command-line options, string extraction: String Extraction. -* commenting: Comments. -* commenting, backslash continuation and: Statements/Lines. -* comp.lang.awk newsgroup: Bugs. + (line 11157) +* commenting: Comments. (line 1296) +* commenting, backslash continuation and: Statements/Lines. (line 1838) +* comp.lang.awk newsgroup: Bugs. (line 18312) * comparison expressions: Typing and Comparison. + (line 6269) * comparison expressions, as patterns: Expression Patterns. + (line 6833) * comparison expressions, string vs. regexp: Typing and Comparison. -* compatibility mode (gawk), extensions: POSIX/GNU. -* compatibility mode (gawk), file names: Special Caveats. + (line 6411) +* compatibility mode (gawk), extensions: POSIX/GNU. (line 16818) +* compatibility mode (gawk), file names: Special Caveats. (line 5159) * compatibility mode (gawk), hexadecimal numbers: Nondecimal-numbers. + (line 5503) * compatibility mode (gawk), octal numbers: Nondecimal-numbers. -* compatibility mode (gawk), specifying: Options. -* compiled programs <1>: Glossary. -* compiled programs: Basic High Level. -* compl function (gawk): Bitwise Functions. -* complement, bitwise: Bitwise Functions. -* compound statements, control statements and: Statements. -* concatenating: Concatenation. -* conditional expressions: Conditional Exp. + (line 5503) +* compatibility mode (gawk), specifying: Options. (line 12070) +* compiled programs <1>: Glossary. (line 19897) +* compiled programs: Basic High Level. (line 19467) +* compl function (gawk): Bitwise Functions. (line 10331) +* complement, bitwise: Bitwise Functions. (line 10313) +* compound statements, control statements and: Statements. (line 7220) +* concatenating: Concatenation. (line 5903) +* conditional expressions: Conditional Exp. (line 6545) * configuration option, --disable-lint: Additional Configuration Options. + (line 17446) * configuration option, --disable-nls: Additional Configuration Options. + (line 17461) * configuration option, --enable-portals: Additional Configuration Options. + (line 17432) * configuration option, --enable-switch: Additional Configuration Options. + (line 17436) * configuration option, --with-included-gettext <1>: Additional Configuration Options. -* configuration option, --with-included-gettext: Gawk I18N. + (line 17440) +* configuration option, --with-included-gettext: Gawk I18N. (line 11423) * configuration options, gawk: Additional Configuration Options. -* constants, nondecimal: Nondecimal Data. -* constants, types of: Constants. + (line 17429) +* constants, nondecimal: Nondecimal Data. (line 11465) +* constants, types of: Constants. (line 5397) * continue statement: Continue Statement. -* control statements: Statements. -* converting, case: String Functions. -* converting, dates to timestamps: Time Functions. + (line 7574) +* control statements: Statements. (line 7216) +* converting, case: String Functions. (line 9591) +* converting, dates to timestamps: Time Functions. (line 10030) * converting, during subscripting: Numeric Array Subscripts. -* converting, numbers: Conversion. -* converting, numbers, to strings: Bitwise Functions. -* converting, strings to numbers: Conversion. -* CONVFMT variable <1>: User-modified. -* CONVFMT variable: Conversion. + (line 8673) +* converting, numbers: Conversion. (line 5711) +* converting, numbers, to strings: Bitwise Functions. (line 10387) +* converting, strings to numbers: Conversion. (line 5711) +* CONVFMT variable <1>: User-modified. (line 7825) +* CONVFMT variable: Conversion. (line 5734) * CONVFMT variable, array subscripts and: Numeric Array Subscripts. -* coprocesses <1>: Two-way I/O. -* coprocesses: Redirection. + (line 8648) +* coprocesses <1>: Two-way I/O. (line 11545) +* coprocesses: Redirection. (line 4936) * coprocesses, closing: Close Files And Pipes. -* coprocesses, getline from: Getline/Coprocess. -* cos function: Numeric Functions. -* counting: Wc Program. -* csh utility: Statements/Lines. -* csh utility, backslash continuation and: More Complex. + (line 5191) +* coprocesses, getline from: Getline/Coprocess. (line 4129) +* cos function: Numeric Functions. (line 9071) +* counting: Wc Program. (line 15230) +* csh utility: Statements/Lines. (line 1807) +* csh utility, backslash continuation and: More Complex. (line 1708) * csh utility, POSIXLY_CORRECT environment variable: Options. -* csh utility, |& operator, comparison with: Two-way I/O. -* ctime user-defined function: Function Example. + (line 12252) +* csh utility, |& operator, comparison with: Two-way I/O. (line 11545) +* ctime user-defined function: Function Example. (line 10629) * currency symbols, localization: Explaining gettext. + (line 10994) * custom.h file: Configuration Philosophy. -* cut utility: Cut Program. -* cut.awk program: Cut Program. -* d.c., See dark corner: Conventions. -* dark corner <1>: Glossary. -* dark corner <2>: Truth Values. -* dark corner <3>: Assignment Ops. -* dark corner <4>: Format Modifiers. -* dark corner: Conventions. + (line 17496) +* cut utility: Cut Program. (line 14237) +* cut.awk program: Cut Program. (line 14275) +* d.c., See dark corner: Conventions. (line 850) +* dark corner <1>: Glossary. (line 19929) +* dark corner <2>: Truth Values. (line 6256) +* dark corner <3>: Assignment Ops. (line 6129) +* dark corner <4>: Format Modifiers. (line 4659) +* dark corner: Conventions. (line 850) * dark corner, array subscripts: Uninitialized Subscripts. -* dark corner, break statement: Break Statement. + (line 8735) +* dark corner, break statement: Break Statement. (line 7558) * dark corner, close function: Close Files And Pipes. + (line 5315) * dark corner, command-line arguments: Assignment Options. + (line 5700) * dark corner, continue statement: Continue Statement. -* dark corner, CONVFMT variable: Conversion. -* dark corner, escape sequences: Other Arguments. + (line 7611) +* dark corner, CONVFMT variable: Conversion. (line 5745) +* dark corner, escape sequences: Other Arguments. (line 12296) * dark corner, escape sequences, for metacharacters: Escape Sequences. -* dark corner, exit statement: Exit Statement. + (line 2168) +* dark corner, exit statement: Exit Statement. (line 7752) * dark corner, field separators: Field Splitting Summary. -* dark corner, FILENAME variable <1>: Auto-set. -* dark corner, FILENAME variable: Getline Notes. -* dark corner, FNR/NR variables: Auto-set. -* dark corner, format-control characters: Control Letters. + (line 3547) +* dark corner, FILENAME variable <1>: Auto-set. (line 8041) +* dark corner, FILENAME variable: Getline Notes. (line 4190) +* dark corner, FNR/NR variables: Auto-set. (line 8140) +* dark corner, format-control characters: Control Letters. (line 4593) * dark corner, FS as null string: Single Character Fields. -* dark corner, input files: Records. -* dark corner, invoking awk: Command Line. -* dark corner, multiline records: Multiple Line. -* dark corner, NF variable, decrementing: Changing Fields. -* dark corner, OFMT variable: OFMT. + (line 3407) +* dark corner, input files: Records. (line 2908) +* dark corner, invoking awk: Command Line. (line 11983) +* dark corner, multiline records: Multiple Line. (line 3726) +* dark corner, NF variable, decrementing: Changing Fields. (line 3223) +* dark corner, OFMT variable: OFMT. (line 4447) * dark corner, regexp constants: Using Constant Regexps. + (line 5536) * dark corner, regexp constants, /= operator and: Assignment Ops. + (line 6129) * dark corner, regexp constants, as arguments to user-defined functions: Using Constant Regexps. -* dark corner, split function: String Functions. -* dark corner, strings, storing: Records. -* data, fixed-width: Constant Size. -* data-driven languages: Basic High Level. -* database, group, reading: Group Functions. -* database, users, reading: Passwd Functions. -* date utility, GNU: Time Functions. -* date utility, POSIX: Time Functions. -* dates, converting to timestamps: Time Functions. + (line 5574) +* dark corner, split function: String Functions. (line 9361) +* dark corner, strings, storing: Records. (line 2987) +* data, fixed-width: Constant Size. (line 3597) +* data-driven languages: Basic High Level. (line 19536) +* database, group, reading: Group Functions. (line 13934) +* database, users, reading: Passwd Functions. (line 13709) +* date utility, GNU: Time Functions. (line 9978) +* date utility, POSIX: Time Functions. (line 10225) +* dates, converting to timestamps: Time Functions. (line 10030) * dates, information related to, localization: Explaining gettext. -* Davies, Stephen <1>: Bugs. -* Davies, Stephen: Contributors. -* dcgettext function (gawk) <1>: Programmer i18n. -* dcgettext function (gawk): I18N Functions. + (line 11006) +* Davies, Stephen <1>: Bugs. (line 18337) +* Davies, Stephen: Contributors. (line 17078) +* dcgettext function (gawk) <1>: Programmer i18n. (line 11044) +* dcgettext function (gawk): I18N Functions. (line 10422) * dcgettext function (gawk), portability and: I18N Portability. -* dcngettext function (gawk) <1>: Programmer i18n. -* dcngettext function (gawk): I18N Functions. + (line 11286) +* dcngettext function (gawk) <1>: Programmer i18n. (line 11060) +* dcngettext function (gawk): I18N Functions. (line 10428) * dcngettext function (gawk), portability and: I18N Portability. -* deadlocks: Two-way I/O. -* debugging gawk: Known Bugs. -* debugging gawk, bug reports: Bugs. -* decrement operators: Increment Ops. -* default keyword: Switch Statement. -* Deifik, Scott <1>: Bugs. -* Deifik, Scott <2>: Contributors. -* Deifik, Scott: Acknowledgments. -* delete statement: Delete. -* deleting elements in arrays: Delete. -* deleting entire arrays: Delete. + (line 11286) +* deadlocks: Two-way I/O. (line 11572) +* debugging gawk: Known Bugs. (line 12420) +* debugging gawk, bug reports: Bugs. (line 18285) +* decrement operators: Increment Ops. (line 6181) +* default keyword: Switch Statement. (line 7456) +* Deifik, Scott <1>: Bugs. (line 18333) +* Deifik, Scott <2>: Contributors. (line 17062) +* Deifik, Scott: Acknowledgments. (line 995) +* delete statement: Delete. (line 8577) +* deleting elements in arrays: Delete. (line 8577) +* deleting entire arrays: Delete. (line 8610) * differences in awk and gawk, ARGC/ARGV variables: ARGC and ARGV. -* differences in awk and gawk, ARGIND variable: Auto-set. + (line 8251) +* differences in awk and gawk, ARGIND variable: Auto-set. (line 7993) * differences in awk and gawk, array elements, deleting: Delete. + (line 8610) * differences in awk and gawk, AWKPATH environment variable: AWKPATH Variable. + (line 12327) * differences in awk and gawk, BEGIN/END patterns: I/O And BEGIN/END. + (line 7060) * differences in awk and gawk, BINMODE variable <1>: PC Using. + (line 17855) * differences in awk and gawk, BINMODE variable: User-modified. + (line 7820) * differences in awk and gawk, close function: Close Files And Pipes. -* differences in awk and gawk, ERRNO variable: Auto-set. -* differences in awk and gawk, error messages: Special FD. + (line 5266) +* differences in awk and gawk, ERRNO variable: Auto-set. (line 8025) +* differences in awk and gawk, error messages: Special FD. (line 5020) * differences in awk and gawk, FIELDWIDTHS variable: User-modified. + (line 7832) * differences in awk and gawk, function arguments (gawk): Calling Built-in. -* differences in awk and gawk, getline command: Getline. + (line 9009) +* differences in awk and gawk, getline command: Getline. (line 3848) * differences in awk and gawk, IGNORECASE variable: User-modified. + (line 7867) * differences in awk and gawk, implementation limitations <1>: Redirection. + (line 4965) * differences in awk and gawk, implementation limitations: Getline Notes. + (line 4185) * differences in awk and gawk, input/output operators <1>: Redirection. + (line 4936) * differences in awk and gawk, input/output operators: Getline/Coprocess. + (line 4129) * differences in awk and gawk, line continuations: Conditional Exp. + (line 6573) * differences in awk and gawk, LINT variable: User-modified. + (line 7882) * differences in awk and gawk, match function: String Functions. + (line 9292) * differences in awk and gawk, next/nextfile statements: Nextfile Statement. + (line 7676) * differences in awk and gawk, print/printf statements: Format Modifiers. -* differences in awk and gawk, PROCINFO array: Auto-set. -* differences in awk and gawk, record separators: Records. + (line 4613) +* differences in awk and gawk, PROCINFO array: Auto-set. (line 8072) +* differences in awk and gawk, record separators: Records. (line 2921) * differences in awk and gawk, regexp constants: Using Constant Regexps. + (line 5574) * differences in awk and gawk, regular expressions: Case-sensitivity. -* differences in awk and gawk, RS/RT variables: Records. -* differences in awk and gawk, RT variable: Auto-set. + (line 2569) +* differences in awk and gawk, RS/RT variables: Records. (line 2963) +* differences in awk and gawk, RT variable: Auto-set. (line 8129) * differences in awk and gawk, single-character fields: Single Character Fields. + (line 3393) * differences in awk and gawk, split function: String Functions. -* differences in awk and gawk, strings: Scalar Constants. -* differences in awk and gawk, strings, storing: Records. + (line 9350) +* differences in awk and gawk, strings: Scalar Constants. (line 5431) +* differences in awk and gawk, strings, storing: Records. (line 2983) * differences in awk and gawk, strtonum function (gawk): String Functions. + (line 9388) * differences in awk and gawk, TEXTDOMAIN variable: User-modified. + (line 7937) * differences in awk and gawk, trunc-mod operation: Arithmetic Ops. -* directories, changing: Sample Library. -* directories, searching <1>: Igawk Program. -* directories, searching: AWKPATH Variable. -* division: Arithmetic Ops. -* do-while statement <1>: Do Statement. -* do-while statement: Regexp Usage. -* documentation, of awk programs: Library Names. -* documentation, online: Manual History. -* documents, searching: Dupword Program. -* dollar sign ($): Regexp Operators. -* dollar sign ($), $ field operator <1>: Precedence. -* dollar sign ($), $ field operator: Fields. + (line 5875) +* directories, changing: Sample Library. (line 18963) +* directories, searching <1>: Igawk Program. (line 16567) +* directories, searching: AWKPATH Variable. (line 12327) +* division: Arithmetic Ops. (line 5853) +* do-while statement <1>: Do Statement. (line 7338) +* do-while statement: Regexp Usage. (line 1989) +* documentation, of awk programs: Library Names. (line 12507) +* documentation, online: Manual History. (line 870) +* documents, searching: Dupword Program. (line 15395) +* dollar sign ($): Regexp Operators. (line 2210) +* dollar sign ($), $ field operator <1>: Precedence. (line 6681) +* dollar sign ($), $ field operator: Fields. (line 3019) * dollar sign ($), incrementing fields and arrays: Increment Ops. -* double quote (") <1>: Quoting. -* double quote ("): Read Terminal. -* double quote ("), regexp constants: Computed Regexps. -* double-precision floating-point: Basic Data Typing. -* Drepper, Ulrich: Acknowledgments. -* dupnode internal function: Internals. -* dupword.awk program: Dupword Program. -* EBCDIC: Ordinal Functions. -* egrep utility <1>: Egrep Program. -* egrep utility: Character Lists. -* egrep.awk program: Egrep Program. + (line 6176) +* double quote (") <1>: Quoting. (line 1376) +* double quote ("): Read Terminal. (line 1165) +* double quote ("), regexp constants: Computed Regexps. (line 2677) +* double-precision floating-point: Basic Data Typing. (line 19582) +* Drepper, Ulrich: Acknowledgments. (line 991) +* dupnode internal function: Internals. (line 18846) +* dupword.awk program: Dupword Program. (line 15420) +* EBCDIC: Ordinal Functions. (line 12980) +* egrep utility <1>: Egrep Program. (line 14491) +* egrep utility: Character Lists. (line 2371) +* egrep.awk program: Egrep Program. (line 14539) * elements in arrays: Reference to Elements. + (line 8405) * elements in arrays, assigning: Assigning Elements. -* elements in arrays, deleting: Delete. -* elements in arrays, order of: Scanning an Array. -* elements in arrays, scanning: Scanning an Array. -* email address for bug reports, bug-gawk@gnu.org: Bugs. -* EMISTERED: TCP/IP Networking. -* empty pattern: Empty. + (line 8452) +* elements in arrays, deleting: Delete. (line 8577) +* elements in arrays, order of: Scanning an Array. (line 8563) +* elements in arrays, scanning: Scanning an Array. (line 8522) +* email address for bug reports, bug-gawk@gnu.org: Bugs. (line 18303) +* EMISTERED: TCP/IP Networking. (line 11643) +* empty pattern: Empty. (line 7093) * empty strings, See null strings: Regexp Field Splitting. -* END pattern: BEGIN/END. + (line 3371) +* END pattern: BEGIN/END. (line 6972) * END pattern, assert user-defined function and: Assert Function. -* END pattern, backslash continuation and: Egrep Program. + (line 12849) +* END pattern, backslash continuation and: Egrep Program. (line 14703) * END pattern, Boolean patterns and: Expression Patterns. -* END pattern, exit statement and: Exit Statement. + (line 6892) +* END pattern, exit statement and: Exit Statement. (line 7735) * END pattern, next/nextfile statements and <1>: Next Statement. + (line 7660) * END pattern, next/nextfile statements and: I/O And BEGIN/END. -* END pattern, operators and: Using BEGIN/END. -* END pattern, pgawk program: Profiling. -* END pattern, print statement and: I/O And BEGIN/END. + (line 7080) +* END pattern, operators and: Using BEGIN/END. (line 7002) +* END pattern, pgawk program: Profiling. (line 11787) +* END pattern, print statement and: I/O And BEGIN/END. (line 7060) * endfile user-defined function: Filetrans Function. -* endgrent function (C library): Group Functions. -* endgrent user-defined function: Group Functions. -* endpwent function (C library): Passwd Functions. -* endpwent user-defined function: Passwd Functions. -* ENVIRON variable: Auto-set. -* environment variables: Auto-set. -* epoch, definition of: Glossary. -* equals sign (=), = operator: Assignment Ops. -* equals sign (=), == operator <1>: Precedence. + (line 13231) +* endgrent function (C library): Group Functions. (line 14141) +* endgrent user-defined function: Group Functions. (line 14144) +* endpwent function (C library): Passwd Functions. (line 13895) +* endpwent user-defined function: Passwd Functions. (line 13898) +* ENVIRON variable: Auto-set. (line 8013) +* environment variables: Auto-set. (line 8013) +* epoch, definition of: Glossary. (line 19971) +* equals sign (=), = operator: Assignment Ops. (line 5981) +* equals sign (=), == operator <1>: Precedence. (line 6703) * equals sign (=), == operator: Typing and Comparison. -* EREs (Extended Regular Expressions): Character Lists. -* ERRNO variable <1>: Internals. -* ERRNO variable <2>: Auto-set. -* ERRNO variable: Getline. -* error handling: Special FD. -* error handling, ERRNO variable and: Auto-set. -* error output: Special FD. + (line 6334) +* EREs (Extended Regular Expressions): Character Lists. (line 2371) +* ERRNO variable <1>: Internals. (line 18901) +* ERRNO variable <2>: Auto-set. (line 8025) +* ERRNO variable: Getline. (line 3848) +* error handling: Special FD. (line 5020) +* error handling, ERRNO variable and: Auto-set. (line 8025) +* error output: Special FD. (line 5011) * escape processing, gsub/gensub/sub functions: Gory Details. -* escape sequences: Escape Sequences. -* escape sequences, unrecognized: Options. -* evaluation order: Increment Ops. -* evaluation order, concatenation: Concatenation. -* evaluation order, functions: Calling Built-in. -* examining fields: Fields. -* exclamation point (!), ! operator <1>: Egrep Program. -* exclamation point (!), ! operator <2>: Precedence. -* exclamation point (!), ! operator: Boolean Ops. -* exclamation point (!), != operator <1>: Precedence. + (line 9622) +* escape sequences: Escape Sequences. (line 2038) +* escape sequences, unrecognized: Options. (line 12145) +* evaluation order: Increment Ops. (line 6207) +* evaluation order, concatenation: Concatenation. (line 5935) +* evaluation order, functions: Calling Built-in. (line 9023) +* examining fields: Fields. (line 3006) +* exclamation point (!), ! operator <1>: Egrep Program. (line 14645) +* exclamation point (!), ! operator <2>: Precedence. (line 6690) +* exclamation point (!), ! operator: Boolean Ops. (line 6516) +* exclamation point (!), != operator <1>: Precedence. (line 6703) * exclamation point (!), != operator: Typing and Comparison. + (line 6334) * exclamation point (!), !~ operator <1>: Expression Patterns. -* exclamation point (!), !~ operator <2>: Precedence. + (line 6843) +* exclamation point (!), !~ operator <2>: Precedence. (line 6719) * exclamation point (!), !~ operator <3>: Typing and Comparison. -* exclamation point (!), !~ operator <4>: Regexp Constants. -* exclamation point (!), !~ operator <5>: Computed Regexps. -* exclamation point (!), !~ operator <6>: Case-sensitivity. -* exclamation point (!), !~ operator: Regexp Usage. -* exit statement: Exit Statement. -* exp function: Numeric Functions. -* expand utility: Very Simple. -* expressions: Expressions. + (line 6334) +* exclamation point (!), !~ operator <4>: Regexp Constants. (line 5524) +* exclamation point (!), !~ operator <5>: Computed Regexps. (line 2656) +* exclamation point (!), !~ operator <6>: Case-sensitivity. (line 2569) +* exclamation point (!), !~ operator: Regexp Usage. (line 1989) +* exit statement: Exit Statement. (line 7729) +* exp function: Numeric Functions. (line 9059) +* expand utility: Very Simple. (line 1594) +* expressions: Expressions. (line 5354) * expressions, as patterns: Expression Patterns. -* expressions, assignment: Assignment Ops. -* expressions, Boolean: Boolean Ops. + (line 6825) +* expressions, assignment: Assignment Ops. (line 5981) +* expressions, Boolean: Boolean Ops. (line 6455) * expressions, comparison: Typing and Comparison. -* expressions, conditional: Conditional Exp. + (line 6269) +* expressions, conditional: Conditional Exp. (line 6545) * expressions, matching, See comparison expressions: Typing and Comparison. -* expressions, selecting: Conditional Exp. -* Extended Regular Expressions (EREs): Character Lists. + (line 6269) +* expressions, selecting: Conditional Exp. (line 6545) +* Extended Regular Expressions (EREs): Character Lists. (line 2371) * extension function (gawk): Using Internal File Ops. -* extensions, Bell Laboratories awk: BTL. -* extensions, in gawk, not in POSIX awk: POSIX/GNU. -* extensions, mawk: Other Versions. -* extract.awk program: Extract Program. + (line 19282) +* extensions, Bell Laboratories awk: BTL. (line 16775) +* extensions, in gawk, not in POSIX awk: POSIX/GNU. (line 16818) +* extensions, mawk: Other Versions. (line 18391) +* extract.awk program: Extract Program. (line 16016) * extraction, of marked strings (internationalization): String Extraction. -* false, logical: Truth Values. + (line 11157) +* false, logical: Truth Values. (line 6238) * FDL (Free Documentation License): GNU Free Documentation License. -* features, adding to gawk: Adding Code. -* features, advanced, See advanced features: Obsolete. -* features, deprecated: Obsolete. -* features, undocumented: Undocumented. -* Fenlason, Jay <1>: Contributors. -* Fenlason, Jay: History. -* fflush function: I/O Functions. -* fflush function, unsupported: Options. + (line 20705) +* features, adding to gawk: Adding Code. (line 18515) +* features, advanced, See advanced features: Obsolete. (line 12387) +* features, deprecated: Obsolete. (line 12387) +* features, undocumented: Undocumented. (line 12409) +* Fenlason, Jay <1>: Contributors. (line 17029) +* Fenlason, Jay: History. (line 653) +* fflush function: I/O Functions. (line 9814) +* fflush function, unsupported: Options. (line 12165) * field numbers: Nonconstant Fields. -* field operator $: Fields. -* field operators, dollar sign as: Fields. -* field separators <1>: User-modified. -* field separators: Field Separators. -* field separators, choice of: Field Separators. + (line 3077) +* field operator $: Fields. (line 3019) +* field operators, dollar sign as: Fields. (line 3019) +* field separators <1>: User-modified. (line 7842) +* field separators: Field Separators. (line 3263) +* field separators, choice of: Field Separators. (line 3298) * field separators, FIELDWIDTHS variable and: User-modified. -* field separators, in multiline records: Multiple Line. + (line 7832) +* field separators, in multiline records: Multiple Line. (line 3732) * field separators, on command line: Command Line Field Separator. + (line 3419) * field separators, POSIX and <1>: Field Splitting Summary. -* field separators, POSIX and: Fields. + (line 3541) +* field separators, POSIX and: Fields. (line 3006) * field separators, regular expressions as <1>: Regexp Field Splitting. + (line 3335) * field separators, regular expressions as: Field Separators. -* field separators, See Also OFS: Changing Fields. -* field separators, spaces as: Cut Program. -* fields <1>: Basic High Level. -* fields <2>: Fields. -* fields: Reading Files. -* fields, adding: Changing Fields. -* fields, changing contents of: Changing Fields. -* fields, cutting: Cut Program. -* fields, examining: Fields. -* fields, number of: Fields. + (line 3298) +* field separators, See Also OFS: Changing Fields. (line 3180) +* field separators, spaces as: Cut Program. (line 14337) +* fields <1>: Basic High Level. (line 19524) +* fields <2>: Fields. (line 3006) +* fields: Reading Files. (line 2788) +* fields, adding: Changing Fields. (line 3169) +* fields, changing contents of: Changing Fields. (line 3122) +* fields, cutting: Cut Program. (line 14237) +* fields, examining: Fields. (line 3006) +* fields, number of: Fields. (line 3033) * fields, numbers: Nonconstant Fields. -* fields, printing: Print Examples. -* fields, separating: Field Separators. + (line 3077) +* fields, printing: Print Examples. (line 4321) +* fields, separating: Field Separators. (line 3263) * fields, single-character: Single Character Fields. -* FIELDWIDTHS variable <1>: User-modified. -* FIELDWIDTHS variable: Constant Size. -* file descriptors: Special FD. -* file names, distinguishing: Auto-set. -* file names, in compatibility mode: Special Caveats. -* file names, standard streams in gawk: Special FD. -* FILENAME variable <1>: Auto-set. -* FILENAME variable: Reading Files. -* FILENAME variable, getline, setting with: Getline Notes. -* filenames, assignments as: Ignoring Assigns. + (line 3393) +* FIELDWIDTHS variable <1>: User-modified. (line 7832) +* FIELDWIDTHS variable: Constant Size. (line 3610) +* file descriptors: Special FD. (line 5011) +* file names, distinguishing: Auto-set. (line 8005) +* file names, in compatibility mode: Special Caveats. (line 5159) +* file names, standard streams in gawk: Special FD. (line 5046) +* FILENAME variable <1>: Auto-set. (line 8041) +* FILENAME variable: Reading Files. (line 2780) +* FILENAME variable, getline, setting with: Getline Notes. (line 4190) +* filenames, assignments as: Ignoring Assigns. (line 13384) * files, .mo: Explaining gettext. -* files, .mo, converting from .po: I18N Example. -* files, .mo, specifying directory of <1>: Programmer i18n. + (line 10934) +* files, .mo, converting from .po: I18N Example. (line 11380) +* files, .mo, specifying directory of <1>: Programmer i18n. (line 11070) * files, .mo, specifying directory of: Explaining gettext. -* files, .po <1>: Translator i18n. + (line 10946) +* files, .po <1>: Translator i18n. (line 11136) * files, .po: Explaining gettext. -* files, .po, converting to .mo: I18N Example. -* files, /dev/... special files: Special FD. -* files, /inet/ (gawk): TCP/IP Networking. -* files, /p (gawk): Portal Files. -* files, as single records: Records. -* files, awk programs in: Long. -* files, awkprof.out: Profiling. -* files, awkvars.out: Options. -* files, closing: I/O Functions. -* files, descriptors, See file descriptors: Special FD. -* files, for process information: Special Process. -* files, group: Group Functions. -* files, information about, retrieving: Sample Library. + (line 10931) +* files, .po, converting to .mo: I18N Example. (line 11380) +* files, /dev/... special files: Special FD. (line 5046) +* files, /inet/ (gawk): TCP/IP Networking. (line 11643) +* files, /p (gawk): Portal Files. (line 11710) +* files, as single records: Records. (line 2992) +* files, awk programs in: Long. (line 1196) +* files, awkprof.out: Profiling. (line 11729) +* files, awkvars.out: Options. (line 12086) +* files, closing: I/O Functions. (line 9799) +* files, descriptors, See file descriptors: Special FD. (line 5011) +* files, for process information: Special Process. (line 5078) +* files, group: Group Functions. (line 13934) +* files, information about, retrieving: Sample Library. (line 18963) * files, initialization and cleanup: Filetrans Function. -* files, input, See input files: Read Terminal. -* files, log, timestamps in: Time Functions. + (line 13177) +* files, input, See input files: Read Terminal. (line 1157) +* files, log, timestamps in: Time Functions. (line 9967) * files, managing: Data File Management. + (line 13160) * files, managing, data file boundaries: Filetrans Function. + (line 13177) * files, message object: Explaining gettext. + (line 10934) * files, message object, converting from portable object files: I18N Example. + (line 11380) * files, message object, specifying directory of <1>: Programmer i18n. + (line 11070) * files, message object, specifying directory of: Explaining gettext. -* files, multiple passes over: Other Arguments. -* files, multiple, duplicating output into: Tee Program. + (line 10946) +* files, multiple passes over: Other Arguments. (line 12314) +* files, multiple, duplicating output into: Tee Program. (line 14930) * files, output, See output files: Close Files And Pipes. -* files, password: Passwd Functions. -* files, portable object <1>: Translator i18n. + (line 5191) +* files, password: Passwd Functions. (line 13719) +* files, portable object <1>: Translator i18n. (line 11136) * files, portable object: Explaining gettext. + (line 10931) * files, portable object, converting to message object files: I18N Example. -* files, portable object, generating: Options. -* files, portal: Portal Files. -* files, processing, ARGIND variable and: Auto-set. -* files, reading: Rewind Function. -* files, reading, multiline records: Multiple Line. -* files, searching for regular expressions: Egrep Program. -* files, skipping: File Checking. -* files, source, search path for: Igawk Program. -* files, splitting: Split Program. + (line 11380) +* files, portable object, generating: Options. (line 12102) +* files, portal: Portal Files. (line 11710) +* files, processing, ARGIND variable and: Auto-set. (line 8000) +* files, reading: Rewind Function. (line 13258) +* files, reading, multiline records: Multiple Line. (line 3697) +* files, searching for regular expressions: Egrep Program. (line 14491) +* files, skipping: File Checking. (line 13300) +* files, source, search path for: Igawk Program. (line 16567) +* files, splitting: Split Program. (line 14828) * files, Texinfo, extracting programs from: Extract Program. -* Fish, Fred <1>: Bugs. -* Fish, Fred: Contributors. -* fixed-width data: Constant Size. -* flag variables <1>: Tee Program. -* flag variables: Boolean Ops. + (line 15945) +* Fish, Fred <1>: Bugs. (line 18332) +* Fish, Fred: Contributors. (line 17060) +* fixed-width data: Constant Size. (line 3597) +* flag variables <1>: Tee Program. (line 14944) +* flag variables: Boolean Ops. (line 6516) * floating-point: Floating Point Issues. -* floating-point, numbers: Basic Data Typing. -* floating-point, numbers, AWKNUM internal type: Internals. -* FNR variable <1>: Auto-set. -* FNR variable: Records. -* FNR variable, changing: Auto-set. -* for statement: For Statement. -* for statement, in arrays: Scanning an Array. -* force_number internal function: Internals. -* force_string internal function: Internals. + (line 19692) +* floating-point, numbers: Basic Data Typing. (line 19570) +* floating-point, numbers, AWKNUM internal type: Internals. (line 18768) +* FNR variable <1>: Auto-set. (line 8051) +* FNR variable: Records. (line 2817) +* FNR variable, changing: Auto-set. (line 8140) +* for statement: For Statement. (line 7374) +* for statement, in arrays: Scanning an Array. (line 8536) +* force_number internal function: Internals. (line 18776) +* force_string internal function: Internals. (line 18781) * format specifiers, mixing regular with positional specifiers: Printf Ordering. -* format specifiers, printf statement: Control Letters. + (line 11234) +* format specifiers, printf statement: Control Letters. (line 4519) * format specifiers, strftime function (gawk): Time Functions. -* format strings: Basic Printf. -* formats, numeric output: OFMT. -* formatting output: Printf. -* forward slash (/): Regexp. -* forward slash (/), / operator: Precedence. -* forward slash (/), /= operator <1>: Precedence. -* forward slash (/), /= operator: Assignment Ops. + (line 10043) +* format strings: Basic Printf. (line 4487) +* formats, numeric output: OFMT. (line 4426) +* formatting output: Printf. (line 4457) +* forward slash (/): Regexp. (line 1949) +* forward slash (/), / operator: Precedence. (line 6693) +* forward slash (/), /= operator <1>: Precedence. (line 6734) +* forward slash (/), /= operator: Assignment Ops. (line 6103) * forward slash (/), /= operator, vs. /=.../ regexp constant: Assignment Ops. + (line 6129) * forward slash (/), patterns and: Expression Patterns. + (line 6843) * Free Documentation License (FDL): GNU Free Documentation License. -* Free Software Foundation (FSF) <1>: Glossary. -* Free Software Foundation (FSF) <2>: Getting. -* Free Software Foundation (FSF): Manual History. -* free_temp internal macro: Internals. -* FreeBSD: Glossary. -* FS variable <1>: User-modified. -* FS variable: Field Separators. -* FS variable, --field-separator option and: Options. + (line 20705) +* Free Software Foundation (FSF) <1>: Glossary. (line 20025) +* Free Software Foundation (FSF) <2>: Getting. (line 17153) +* Free Software Foundation (FSF): Manual History. (line 865) +* free_temp internal macro: Internals. (line 18851) +* FreeBSD: Glossary. (line 20320) +* FS variable <1>: User-modified. (line 7842) +* FS variable: Field Separators. (line 3263) +* FS variable, --field-separator option and: Options. (line 12012) * FS variable, as null string: Single Character Fields. -* FS variable, as TAB character: Options. -* FS variable, changing value of <1>: Known Bugs. -* FS variable, changing value of: Field Separators. -* FS variable, running awk programs and: Cut Program. + (line 3407) +* FS variable, as TAB character: Options. (line 12161) +* FS variable, changing value of <1>: Known Bugs. (line 12420) +* FS variable, changing value of: Field Separators. (line 3282) +* FS variable, running awk programs and: Cut Program. (line 14297) * FS variable, setting from command line: Command Line Field Separator. -* FSF (Free Software Foundation) <1>: Glossary. -* FSF (Free Software Foundation) <2>: Getting. -* FSF (Free Software Foundation): Manual History. -* function calls: Function Calls. -* functions, arrays as parameters to: Function Caveats. -* functions, built-in <1>: Functions. -* functions, built-in: Function Calls. + (line 3419) +* FSF (Free Software Foundation) <1>: Glossary. (line 20025) +* FSF (Free Software Foundation) <2>: Getting. (line 17153) +* FSF (Free Software Foundation): Manual History. (line 865) +* function calls: Function Calls. (line 6585) +* functions, arrays as parameters to: Function Caveats. (line 10696) +* functions, built-in <1>: Functions. (line 8956) +* functions, built-in: Function Calls. (line 6589) * functions, built-in, adding to gawk: Dynamic Extensions. -* functions, built-in, evaluation order: Calling Built-in. -* functions, defining: Definition Syntax. -* functions, library: Library Functions. -* functions, library, assertions: Assert Function. + (line 18733) +* functions, built-in, evaluation order: Calling Built-in. (line 9023) +* functions, defining: Definition Syntax. (line 10472) +* functions, library: Library Functions. (line 12435) +* functions, library, assertions: Assert Function. (line 12781) * functions, library, associative arrays and: Library Names. -* functions, library, C library: Getopt Function. + (line 12558) +* functions, library, C library: Getopt Function. (line 13426) * functions, library, character values as numbers: Ordinal Functions. + (line 12942) * functions, library, Cliff random numbers: Cliff Random Function. + (line 12911) * functions, library, command-line options: Getopt Function. + (line 13426) * functions, library, example program for using: Igawk Program. + (line 16216) * functions, library, group database, reading: Group Functions. + (line 13934) * functions, library, managing data files: Data File Management. + (line 13160) * functions, library, managing time: Gettimeofday Function. + (line 13078) * functions, library, merging arrays into strings: Join Function. + (line 13033) * functions, library, nextfile statement: Nextfile Function. -* functions, library, rounding numbers: Round Function. + (line 12611) +* functions, library, rounding numbers: Round Function. (line 12866) * functions, library, user database, reading: Passwd Functions. -* functions, names of <1>: Definition Syntax. -* functions, names of: Arrays. -* functions, recursive: Definition Syntax. -* functions, return values, setting: Internals. -* functions, string-translation: I18N Functions. -* functions, undefined: Function Caveats. -* functions, user-defined: User-defined. -* functions, user-defined, calling: Function Caveats. -* functions, user-defined, counts: Profiling. -* functions, user-defined, library of: Library Functions. + (line 13709) +* functions, names of <1>: Definition Syntax. (line 10486) +* functions, names of: Arrays. (line 8279) +* functions, recursive: Definition Syntax. (line 10534) +* functions, return values, setting: Internals. (line 18895) +* functions, string-translation: I18N Functions. (line 10416) +* functions, undefined: Function Caveats. (line 10720) +* functions, user-defined: User-defined. (line 10452) +* functions, user-defined, calling: Function Caveats. (line 10647) +* functions, user-defined, counts: Profiling. (line 11853) +* functions, user-defined, library of: Library Functions. (line 12435) * functions, user-defined, next/nextfile statements and <1>: Nextfile Statement. + (line 7709) * functions, user-defined, next/nextfile statements and: Next Statement. -* G-d: Acknowledgments. -* Garfinkle, Scott: Contributors. -* gawk, awk and <1>: This Manual. -* gawk, awk and: Preface. -* gawk, bitwise operations in: Bitwise Functions. -* gawk, break statement in: Break Statement. + (line 7660) +* G-d: Acknowledgments. (line 1012) +* Garfinkle, Scott: Contributors. (line 17047) +* gawk, awk and <1>: This Manual. (line 718) +* gawk, awk and: Preface. (line 569) +* gawk, bitwise operations in: Bitwise Functions. (line 10327) +* gawk, break statement in: Break Statement. (line 7558) * gawk, built-in variables and: Built-in Variables. -* gawk, character classes and: Character Lists. -* gawk, coding style in: Adding Code. + (line 7787) +* gawk, character classes and: Character Lists. (line 2451) +* gawk, coding style in: Adding Code. (line 18541) * gawk, command-line options: GNU Regexp Operators. + (line 2517) * gawk, comparison operators and: Typing and Comparison. + (line 6382) * gawk, configuring: Configuration Philosophy. + (line 17473) * gawk, configuring, options: Additional Configuration Options. + (line 17429) * gawk, continue statement in: Continue Statement. -* gawk, debugging: Known Bugs. + (line 7611) +* gawk, debugging: Known Bugs. (line 12420) * gawk, distribution: Distribution contents. -* gawk, escape sequences: Escape Sequences. -* gawk, extensions, disabling: Options. -* gawk, features, adding: Adding Code. -* gawk, features, advanced: Advanced Features. -* gawk, fflush function in: I/O Functions. -* gawk, field separators and: User-modified. -* gawk, FIELDWIDTHS variable in: User-modified. -* gawk, file names in: Special Files. -* gawk, format-control characters: Control Letters. -* gawk, function arguments and: Calling Built-in. + (line 17213) +* gawk, escape sequences: Escape Sequences. (line 2157) +* gawk, extensions, disabling: Options. (line 12141) +* gawk, features, adding: Adding Code. (line 18515) +* gawk, features, advanced: Advanced Features. (line 11434) +* gawk, fflush function in: I/O Functions. (line 9834) +* gawk, field separators and: User-modified. (line 7862) +* gawk, FIELDWIDTHS variable in: User-modified. (line 7838) +* gawk, file names in: Special Files. (line 4994) +* gawk, format-control characters: Control Letters. (line 4593) +* gawk, function arguments and: Calling Built-in. (line 9009) * gawk, functions, adding: Dynamic Extensions. + (line 18733) * gawk, hexadecimal numbers and: Nondecimal-numbers. -* gawk, IGNORECASE variable in: User-modified. -* gawk, implementation issues: Notes. + (line 5485) +* gawk, IGNORECASE variable in: User-modified. (line 7878) +* gawk, implementation issues: Notes. (line 18452) * gawk, implementation issues, debugging: Compatibility Mode. + (line 18471) * gawk, implementation issues, downward compatibility: Compatibility Mode. -* gawk, implementation issues, limits: Getline Notes. -* gawk, implementation issues, pipes: Redirection. -* gawk, installing: Installation. -* gawk, internals: Internals. + (line 18471) +* gawk, implementation issues, limits: Getline Notes. (line 4185) +* gawk, implementation issues, pipes: Redirection. (line 4965) +* gawk, installing: Installation. (line 17111) +* gawk, internals: Internals. (line 18755) * gawk, internationalization and, See internationalization: Internationalization. -* gawk, interpreter, adding code to <1>: Future Extensions. + (line 10863) +* gawk, interpreter, adding code to <1>: Future Extensions. (line 19421) * gawk, interpreter, adding code to: Using Internal File Ops. -* gawk, interval expressions and: Regexp Operators. -* gawk, line continuation in: Conditional Exp. -* gawk, LINT variable in: User-modified. -* gawk, list of contributors to: Contributors. -* gawk, MS-DOS version of: PC Using. -* gawk, newlines in: Statements/Lines. + (line 19273) +* gawk, interval expressions and: Regexp Operators. (line 2313) +* gawk, line continuation in: Conditional Exp. (line 6573) +* gawk, LINT variable in: User-modified. (line 7891) +* gawk, list of contributors to: Contributors. (line 17016) +* gawk, MS-DOS version of: PC Using. (line 17826) +* gawk, newlines in: Statements/Lines. (line 1776) * gawk, next file statement in: Nextfile Statement. -* gawk, nextfile statement in <1>: Nextfile Function. + (line 7716) +* gawk, nextfile statement in <1>: Nextfile Function. (line 12611) * gawk, nextfile statement in: Nextfile Statement. + (line 7716) * gawk, octal numbers and: Nondecimal-numbers. -* gawk, OS/2 version of: PC Using. + (line 5485) +* gawk, OS/2 version of: PC Using. (line 17826) * gawk, regexp constants and: Using Constant Regexps. + (line 5558) * gawk, regular expressions, case sensitivity: Case-sensitivity. + (line 2569) * gawk, regular expressions, operators: GNU Regexp Operators. -* gawk, regular expressions, precedence: Regexp Operators. -* gawk, See Also awk: Preface. -* gawk, source code, obtaining: Getting. -* gawk, splitting fields and: Constant Size. -* gawk, string-translation functions: I18N Functions. -* gawk, timestamps: Time Functions. -* gawk, uses for: Preface. -* gawk, versions of, information about, printing: Options. + (line 2461) +* gawk, regular expressions, precedence: Regexp Operators. (line 2329) +* gawk, See Also awk: Preface. (line 582) +* gawk, source code, obtaining: Getting. (line 17149) +* gawk, splitting fields and: Constant Size. (line 3674) +* gawk, string-translation functions: I18N Functions. (line 10416) +* gawk, timestamps: Time Functions. (line 9967) +* gawk, uses for: Preface. (line 582) +* gawk, versions of, information about, printing: Options. (line 12201) * gawk, word-boundary operator: GNU Regexp Operators. -* General Public License (GPL): Glossary. -* General Public License, See GPL: Manual History. -* gensub function (gawk) <1>: String Functions. + (line 2510) +* General Public License (GPL): Glossary. (line 20034) +* General Public License, See GPL: Manual History. (line 870) +* gensub function (gawk) <1>: String Functions. (line 9499) * gensub function (gawk): Using Constant Regexps. -* gensub function (gawk), escape processing: Gory Details. -* get_argument internal function: Internals. -* getgrent function (C library): Group Functions. -* getgrent user-defined function: Group Functions. -* getgrgid function (C library): Group Functions. -* getgrgid user-defined function: Group Functions. -* getgrnam function (C library): Group Functions. -* getgrnam user-defined function: Group Functions. -* getgruser function (C library): Group Functions. -* getgruser function, user-defined: Group Functions. -* getline command: Reading Files. + (line 5574) +* gensub function (gawk), escape processing: Gory Details. (line 9622) +* get_actual_argument internal function: Internals. (line 18875) +* get_argument internal function: Internals. (line 18870) +* get_array_argument internal macro: Internals. (line 18890) +* get_curfunc_arg_count internal function: Internals. (line 18786) +* get_scalar_argument internal macro: Internals. (line 18885) +* getgrent function (C library): Group Functions. (line 13934) +* getgrent user-defined function: Group Functions. (line 13934) +* getgrgid function (C library): Group Functions. (line 14108) +* getgrgid user-defined function: Group Functions. (line 14111) +* getgrnam function (C library): Group Functions. (line 14096) +* getgrnam user-defined function: Group Functions. (line 14100) +* getgruser function (C library): Group Functions. (line 14119) +* getgruser function, user-defined: Group Functions. (line 14122) +* getline command: Reading Files. (line 2794) * getline command, _gr_init user-defined function: Group Functions. -* getline command, _pw_init function: Passwd Functions. + (line 14008) +* getline command, _pw_init function: Passwd Functions. (line 13839) * getline command, coprocesses, using from <1>: Close Files And Pipes. + (line 5191) * getline command, coprocesses, using from: Getline/Coprocess. -* getline command, deadlock and: Two-way I/O. -* getline command, explicit input with: Getline. -* getline command, FILENAME variable and: Getline Notes. -* getline command, return values: Getline. -* getline command, variants: Getline Summary. -* getopt function (C library): Getopt Function. -* getopt user-defined function: Getopt Function. -* getpwent function (C library): Passwd Functions. -* getpwent user-defined function: Passwd Functions. -* getpwnam function (C library): Passwd Functions. -* getpwnam user-defined function: Passwd Functions. -* getpwuid function (C library): Passwd Functions. -* getpwuid user-defined function: Passwd Functions. -* getservbyname function (C library): TCP/IP Networking. + (line 4129) +* getline command, deadlock and: Two-way I/O. (line 11572) +* getline command, explicit input with: Getline. (line 3835) +* getline command, FILENAME variable and: Getline Notes. (line 4190) +* getline command, return values: Getline. (line 3848) +* getline command, variants: Getline Summary. (line 4211) +* getopt function (C library): Getopt Function. (line 13435) +* getopt user-defined function: Getopt Function. (line 13525) +* getpwent function (C library): Passwd Functions. (line 13719) +* getpwent user-defined function: Passwd Functions. (line 13719) +* getpwnam function (C library): Passwd Functions. (line 13859) +* getpwnam user-defined function: Passwd Functions. (line 13863) +* getpwuid function (C library): Passwd Functions. (line 13871) +* getpwuid user-defined function: Passwd Functions. (line 13875) +* getservbyname function (C library): TCP/IP Networking. (line 11671) * gettext function (C library): Explaining gettext. + (line 10955) * gettext library: Explaining gettext. + (line 10901) * gettext library, locale categories: Explaining gettext. + (line 10973) * gettimeofday user-defined function: Gettimeofday Function. -* GNITS mailing list: Acknowledgments. -* GNU awk, See gawk: Preface. + (line 13088) +* GNITS mailing list: Acknowledgments. (line 991) +* GNU awk, See gawk: Preface. (line 595) * GNU Free Documentation License: GNU Free Documentation License. -* GNU General Public License: Glossary. -* GNU Lesser General Public License: Glossary. -* GNU long options <1>: Options. -* GNU long options: Command Line. -* GNU long options, printing list of: Options. -* GNU Project <1>: Glossary. -* GNU Project: Manual History. -* GNU/Linux <1>: Glossary. -* GNU/Linux <2>: Atari Compiling. + (line 20705) +* GNU General Public License: Glossary. (line 20034) +* GNU Lesser General Public License: Glossary. (line 20111) +* GNU long options <1>: Options. (line 11997) +* GNU long options: Command Line. (line 11980) +* GNU long options, printing list of: Options. (line 12111) +* GNU Project <1>: Glossary. (line 20043) +* GNU Project: Manual History. (line 870) +* GNU/Linux <1>: Glossary. (line 20320) +* GNU/Linux <2>: Atari Compiling. (line 18166) * GNU/Linux <3>: Additional Configuration Options. -* GNU/Linux <4>: I18N Example. -* GNU/Linux: Manual History. -* GPL (General Public License) <1>: Glossary. -* GPL (General Public License): Manual History. -* GPL (General Public License), printing: Options. -* grcat program: Group Functions. -* Grigera, Juan <1>: Bugs. -* Grigera, Juan: Contributors. -* group database, reading: Group Functions. -* group file: Group Functions. -* groups, information about: Group Functions. -* gsub function <1>: String Functions. + (line 17440) +* GNU/Linux <4>: I18N Example. (line 11373) +* GNU/Linux: Manual History. (line 886) +* GPL (General Public License) <1>: Glossary. (line 20034) +* GPL (General Public License): Manual History. (line 870) +* GPL (General Public License), printing: Options. (line 12078) +* grcat program: Group Functions. (line 13943) +* Grigera, Juan <1>: Bugs. (line 18334) +* Grigera, Juan: Contributors. (line 17064) +* group database, reading: Group Functions. (line 13934) +* group file: Group Functions. (line 13934) +* groups, information about: Group Functions. (line 13934) +* gsub function <1>: String Functions. (line 9483) * gsub function: Using Constant Regexps. -* gsub function, arguments of: String Functions. -* gsub function, escape processing: Gory Details. -* Hankerson, Darrel <1>: Bugs. -* Hankerson, Darrel <2>: Contributors. -* Hankerson, Darrel: Acknowledgments. -* Hartholz, Elaine: Acknowledgments. -* Hartholz, Marshall: Acknowledgments. -* Hasegawa, Isamu <1>: Contributors. -* Hasegawa, Isamu: Acknowledgments. + (line 5574) +* gsub function, arguments of: String Functions. (line 9463) +* gsub function, escape processing: Gory Details. (line 9622) +* Hankerson, Darrel <1>: Bugs. (line 18333) +* Hankerson, Darrel <2>: Contributors. (line 17066) +* Hankerson, Darrel: Acknowledgments. (line 995) +* Hartholz, Elaine: Acknowledgments. (line 977) +* Hartholz, Marshall: Acknowledgments. (line 977) +* Hasegawa, Isamu <1>: Contributors. (line 17092) +* Hasegawa, Isamu: Acknowledgments. (line 995) * hexadecimal numbers: Nondecimal-numbers. -* hexadecimal, values, enabling interpretation of: Options. -* histsort.awk program: History Sorting. -* Hughes, Phil: Acknowledgments. -* HUP signal: Profiling. -* hyphen (-), - operator: Precedence. + (line 5449) +* hexadecimal values, enabling interpretation of: Options. (line 12133) +* histsort.awk program: History Sorting. (line 15919) +* Hughes, Phil: Acknowledgments. (line 982) +* HUP signal: Profiling. (line 11928) +* hyphen (-), - operator: Precedence. (line 6690) * hyphen (-), -- (decrement/increment) operators: Precedence. -* hyphen (-), -- operator: Increment Ops. -* hyphen (-), -= operator <1>: Precedence. -* hyphen (-), -= operator: Assignment Ops. -* hyphen (-), filenames beginning with: Options. -* hyphen (-), in character lists: Character Lists. -* id utility: Id Program. -* id.awk program: Id Program. -* if statement <1>: If Statement. -* if statement: Regexp Usage. -* if statement, actions, changing: Ranges. -* igawk.sh program: Igawk Program. -* IGNORECASE variable <1>: User-modified. -* IGNORECASE variable: Case-sensitivity. -* IGNORECASE variable, array sorting and: Array Sorting. -* IGNORECASE variable, array subscripts and: Array Intro. + (line 6684) +* hyphen (-), -- operator: Increment Ops. (line 6194) +* hyphen (-), -= operator <1>: Precedence. (line 6734) +* hyphen (-), -= operator: Assignment Ops. (line 6103) +* hyphen (-), filenames beginning with: Options. (line 12058) +* hyphen (-), in character lists: Character Lists. (line 2364) +* id utility: Id Program. (line 14721) +* id.awk program: Id Program. (line 14745) +* if statement <1>: If Statement. (line 7252) +* if statement: Regexp Usage. (line 1989) +* if statement, actions, changing: Ranges. (line 6924) +* igawk.sh program: Igawk Program. (line 16328) +* IGNORECASE variable <1>: User-modified. (line 7867) +* IGNORECASE variable: Case-sensitivity. (line 2569) +* IGNORECASE variable, array sorting and: Array Sorting. (line 8945) +* IGNORECASE variable, array subscripts and: Array Intro. (line 8390) * IGNORECASE variable, in example programs: Library Functions. -* implementation issues, gawk: Notes. + (line 12472) +* implementation issues, gawk: Notes. (line 18452) * implementation issues, gawk, debugging: Compatibility Mode. -* implementation issues, gawk, limits <1>: Redirection. -* implementation issues, gawk, limits: Getline Notes. -* in operator <1>: Id Program. -* in operator <2>: For Statement. -* in operator <3>: Precedence. + (line 18471) +* implementation issues, gawk, limits <1>: Redirection. (line 4965) +* implementation issues, gawk, limits: Getline Notes. (line 4185) +* in operator <1>: Id Program. (line 14808) +* in operator <2>: For Statement. (line 7441) +* in operator <3>: Precedence. (line 6722) * in operator: Typing and Comparison. -* in operator, arrays and <1>: Scanning an Array. + (line 6334) +* in operator, arrays and <1>: Scanning an Array. (line 8533) * in operator, arrays and: Reference to Elements. -* increment operators: Increment Ops. -* index function: String Functions. -* indexing arrays: Array Intro. -* initialization, automatic: More Complex. -* input files: Reading Files. + (line 8424) +* increment operators: Increment Ops. (line 6152) +* index function: String Functions. (line 9210) +* indexing arrays: Array Intro. (line 8348) +* initialization, automatic: More Complex. (line 1731) +* input files: Reading Files. (line 2780) * input files, closing: Close Files And Pipes. -* input files, counting elements in: Wc Program. -* input files, examples: Sample Data Files. -* input files, reading: Reading Files. -* input files, running awk without: Read Terminal. -* input files, skipping: Nextfile Function. -* input files, variable assignments and: Other Arguments. -* input pipeline: Getline/Pipe. -* input redirection: Getline/File. -* input, data, nondecimal: Nondecimal Data. -* input, explicit: Getline. -* input, files, See input files: Multiple Line. -* input, multiline records: Multiple Line. -* input, splitting into records: Records. -* input, standard <1>: Special FD. -* input, standard: Read Terminal. -* input/output, binary: User-modified. -* input/output, from BEGIN and END: I/O And BEGIN/END. -* input/output, two-way: Two-way I/O. -* insomnia, cure for: Alarm Program. + (line 5191) +* input files, counting elements in: Wc Program. (line 15230) +* input files, examples: Sample Data Files. (line 1461) +* input files, reading: Reading Files. (line 2780) +* input files, running awk without: Read Terminal. (line 1146) +* input files, skipping: Nextfile Function. (line 12611) +* input files, variable assignments and: Other Arguments. (line 12284) +* input pipeline: Getline/Pipe. (line 4043) +* input redirection: Getline/File. (line 3971) +* input, data, nondecimal: Nondecimal Data. (line 11465) +* input, explicit: Getline. (line 3835) +* input, files, See input files: Multiple Line. (line 3697) +* input, multiline records: Multiple Line. (line 3697) +* input, splitting into records: Records. (line 2817) +* input, standard <1>: Special FD. (line 5011) +* input, standard: Read Terminal. (line 1146) +* input/output, binary: User-modified. (line 7809) +* input/output, from BEGIN and END: I/O And BEGIN/END. (line 7050) +* input/output, two-way: Two-way I/O. (line 11545) +* insomnia, cure for: Alarm Program. (line 15443) * installation, amiga: Amiga Installation. + (line 17535) * installation, atari: Atari Installation. -* installation, beos: BeOS Installation. + (line 18129) +* installation, beos: BeOS Installation. (line 17568) * installation, tandem: Tandem Installation. -* installation, vms: VMS Installation. -* installing gawk: Installation. -* int function: Numeric Functions. -* INT signal (MS-DOS): Profiling. -* integers: Basic Data Typing. -* integers, unsigned: Basic Data Typing. -* interacting with other programs: I/O Functions. -* internationalization <1>: I18N and L10N. -* internationalization: I18N Functions. + (line 18246) +* installation, vms: VMS Installation. (line 17949) +* installing gawk: Installation. (line 17111) +* int function: Numeric Functions. (line 9048) +* INT signal (MS-DOS): Profiling. (line 11931) +* integers: Basic Data Typing. (line 19570) +* integers, unsigned: Basic Data Typing. (line 19577) +* interacting with other programs: I/O Functions. (line 9852) +* internationalization <1>: I18N and L10N. (line 10886) +* internationalization: I18N Functions. (line 10416) * internationalization, localization <1>: Internationalization. -* internationalization, localization: User-modified. + (line 10863) +* internationalization, localization: User-modified. (line 7937) * internationalization, localization, character classes: Character Lists. + (line 2451) * internationalization, localization, gawk and: Internationalization. + (line 10863) * internationalization, localization, locale categories: Explaining gettext. + (line 10973) * internationalization, localization, marked strings: Programmer i18n. + (line 11039) * internationalization, localization, portability and: I18N Portability. + (line 11260) * internationalizing a program: Explaining gettext. -* interpreted programs <1>: Glossary. -* interpreted programs: Basic High Level. -* interval expressions: Regexp Operators. -* inventory-shipped file: Sample Data Files. -* ISO: Glossary. -* ISO 8859-1: Glossary. -* ISO Latin-1: Glossary. -* Jacobs, Andrew: Passwd Functions. -* Jaegermann, Michal <1>: Contributors. -* Jaegermann, Michal: Acknowledgments. -* Jedi knights: Undocumented. -* join user-defined function: Join Function. -* Kahrs, Ju"rgen <1>: Contributors. -* Kahrs, Ju"rgen: Acknowledgments. -* Kenobi, Obi-Wan: Undocumented. -* Kernighan, Brian <1>: Basic Data Typing. -* Kernighan, Brian <2>: Other Versions. -* Kernighan, Brian <3>: Contributors. -* Kernighan, Brian <4>: BTL. -* Kernighan, Brian <5>: Concatenation. -* Kernighan, Brian <6>: Acknowledgments. -* Kernighan, Brian <7>: Conventions. -* Kernighan, Brian: History. -* kill command, dynamic profiling: Profiling. -* Knights, jedi: Undocumented. -* Kwok, Conrad: Contributors. -* labels.awk program: Labels Program. -* languages, data-driven: Basic High Level. + (line 10901) +* interpreted programs <1>: Glossary. (line 20083) +* interpreted programs: Basic High Level. (line 19467) +* interval expressions: Regexp Operators. (line 2290) +* inventory-shipped file: Sample Data Files. (line 1487) +* ISO: Glossary. (line 20094) +* ISO 8859-1: Glossary. (line 19879) +* ISO Latin-1: Glossary. (line 19879) +* Jacobs, Andrew: Passwd Functions. (line 13779) +* Jaegermann, Michal <1>: Contributors. (line 17055) +* Jaegermann, Michal: Acknowledgments. (line 995) +* Jedi knights: Undocumented. (line 12409) +* join user-defined function: Join Function. (line 13045) +* Kahrs, Ju"rgen <1>: Contributors. (line 17074) +* Kahrs, Ju"rgen: Acknowledgments. (line 995) +* Kenobi, Obi-Wan: Undocumented. (line 12409) +* Kernighan, Brian <1>: Basic Data Typing. (line 19620) +* Kernighan, Brian <2>: Other Versions. (line 18358) +* Kernighan, Brian <3>: Contributors. (line 17022) +* Kernighan, Brian <4>: BTL. (line 16775) +* Kernighan, Brian <5>: Concatenation. (line 5900) +* Kernighan, Brian <6>: Acknowledgments. (line 1002) +* Kernighan, Brian <7>: Conventions. (line 846) +* Kernighan, Brian: History. (line 640) +* kill command, dynamic profiling: Profiling. (line 11906) +* Knights, jedi: Undocumented. (line 12409) +* Kwok, Conrad: Contributors. (line 17047) +* labels.awk program: Labels Program. (line 15731) +* languages, data-driven: Basic High Level. (line 19536) * LC_ALL locale category: Explaining gettext. + (line 11011) * LC_COLLATE locale category: Explaining gettext. + (line 10984) * LC_CTYPE locale category: Explaining gettext. + (line 10988) * LC_MESSAGES locale category: Explaining gettext. + (line 10978) * LC_MESSAGES locale category, bindtextdomain function (gawk): Programmer i18n. + (line 11111) * LC_MONETARY locale category: Explaining gettext. + (line 10994) * LC_NUMERIC locale category: Explaining gettext. + (line 10998) * LC_RESPONSE locale category: Explaining gettext. + (line 11002) * LC_TIME locale category: Explaining gettext. -* left angle bracket (<), < operator <1>: Precedence. + (line 11006) +* left angle bracket (<), < operator <1>: Precedence. (line 6703) * left angle bracket (<), < operator: Typing and Comparison. -* left angle bracket (<), < operator (I/O): Getline/File. -* left angle bracket (<), <= operator <1>: Precedence. + (line 6334) +* left angle bracket (<), < operator (I/O): Getline/File. (line 3971) +* left angle bracket (<), <= operator <1>: Precedence. (line 6703) * left angle bracket (<), <= operator: Typing and Comparison. -* left shift, bitwise: Bitwise Functions. -* leftmost longest match: Multiple Line. -* length function: String Functions. -* Lesser General Public License (LGPL): Glossary. -* LGPL (Lesser General Public License): Glossary. -* libraries of awk functions: Library Functions. -* libraries of awk functions, assertions: Assert Function. + (line 6334) +* left shift, bitwise: Bitwise Functions. (line 10320) +* leftmost longest match: Multiple Line. (line 3717) +* length function: String Functions. (line 9221) +* Lesser General Public License (LGPL): Glossary. (line 20111) +* LGPL (Lesser General Public License): Glossary. (line 20111) +* libraries of awk functions: Library Functions. (line 12435) +* libraries of awk functions, assertions: Assert Function. (line 12781) * libraries of awk functions, associative arrays and: Library Names. + (line 12558) * libraries of awk functions, character values as numbers: Ordinal Functions. + (line 12942) * libraries of awk functions, command-line options: Getopt Function. + (line 13426) * libraries of awk functions, example program for using: Igawk Program. + (line 16216) * libraries of awk functions, group database, reading: Group Functions. + (line 13934) * libraries of awk functions, managing, data files: Data File Management. + (line 13160) * libraries of awk functions, managing, time: Gettimeofday Function. + (line 13078) * libraries of awk functions, merging arrays into strings: Join Function. + (line 13033) * libraries of awk functions, nextfile statement: Nextfile Function. + (line 12611) * libraries of awk functions, rounding numbers: Round Function. + (line 12866) * libraries of awk functions, user database, reading: Passwd Functions. -* line breaks: Statements/Lines. -* line continuations: Boolean Ops. -* line continuations, gawk: Conditional Exp. -* line continuations, in print statement: Print Examples. -* line continuations, with C shell: More Complex. -* lines, blank, printing: Print. -* lines, counting: Wc Program. -* lines, duplicate, removing: History Sorting. -* lines, matching ranges of: Ranges. -* lines, skipping between markers: Ranges. -* lint checking: User-modified. -* lint checking, array elements: Delete. + (line 13709) +* line breaks: Statements/Lines. (line 1770) +* line continuations: Boolean Ops. (line 6511) +* line continuations, gawk: Conditional Exp. (line 6573) +* line continuations, in print statement: Print Examples. (line 4375) +* line continuations, with C shell: More Complex. (line 1723) +* lines, blank, printing: Print. (line 4292) +* lines, counting: Wc Program. (line 15230) +* lines, duplicate, removing: History Sorting. (line 15900) +* lines, matching ranges of: Ranges. (line 6905) +* lines, skipping between markers: Ranges. (line 6942) +* lint checking: User-modified. (line 7882) +* lint checking, array elements: Delete. (line 8605) * lint checking, array subscripts: Uninitialized Subscripts. -* lint checking, empty programs: Command Line. -* lint checking, issuing warnings: Options. + (line 8735) +* lint checking, empty programs: Command Line. (line 11983) +* lint checking, issuing warnings: Options. (line 12116) * lint checking, POSIXLY_CORRECT environment variable: Options. -* lint checking, undefined functions: Function Caveats. -* LINT variable: User-modified. -* Linux <1>: Glossary. -* Linux <2>: Atari Compiling. + (line 12239) +* lint checking, undefined functions: Function Caveats. (line 10737) +* LINT variable: User-modified. (line 7882) +* Linux <1>: Glossary. (line 20320) +* Linux <2>: Atari Compiling. (line 18166) * Linux <3>: Additional Configuration Options. -* Linux <4>: I18N Example. -* Linux: Manual History. + (line 17440) +* Linux <4>: I18N Example. (line 11373) +* Linux: Manual History. (line 886) * locale categories: Explaining gettext. -* localization: I18N and L10N. + (line 10973) +* localization: I18N and L10N. (line 10886) * localization, See internationalization, localization: I18N and L10N. -* log files, timestamps in: Time Functions. -* log function: Numeric Functions. -* logical false/true: Truth Values. -* logical operators, See Boolean expressions: Boolean Ops. -* login information: Passwd Functions. -* long options: Command Line. -* loops: While Statement. -* loops, continue statements and: For Statement. -* loops, count for header: Profiling. -* loops, exiting: Break Statement. -* loops, See Also while statement: While Statement. + (line 10886) +* log files, timestamps in: Time Functions. (line 9967) +* log function: Numeric Functions. (line 9064) +* logical false/true: Truth Values. (line 6238) +* logical operators, See Boolean expressions: Boolean Ops. (line 6455) +* login information: Passwd Functions. (line 13719) +* long options: Command Line. (line 11980) +* loops: While Statement. (line 7291) +* loops, continue statements and: For Statement. (line 7430) +* loops, count for header: Profiling. (line 11847) +* loops, exiting: Break Statement. (line 7517) +* loops, See Also while statement: While Statement. (line 7291) * Lost In Space: Dynamic Extensions. -* ls utility: More Complex. -* lshift function (gawk): Bitwise Functions. -* lvalues/rvalues: Assignment Ops. -* mailing labels, printing: Labels Program. -* mailing list, GNITS: Acknowledgments. -* make_builtin internal function: Internals. -* make_number internal function: Internals. -* make_string internal function: Internals. -* mark parity: Ordinal Functions. + (line 18729) +* ls utility: More Complex. (line 1708) +* lshift function (gawk): Bitwise Functions. (line 10333) +* lvalues/rvalues: Assignment Ops. (line 6006) +* mailing labels, printing: Labels Program. (line 15689) +* mailing list, GNITS: Acknowledgments. (line 991) +* make_builtin internal function: Internals. (line 18856) +* make_number internal function: Internals. (line 18831) +* make_string internal function: Internals. (line 18826) +* mark parity: Ordinal Functions. (line 12980) * marked string extraction (internationalization): String Extraction. -* marked strings, extracting: String Extraction. -* Marx, Groucho: Increment Ops. -* match function: String Functions. + (line 11157) +* marked strings, extracting: String Extraction. (line 11157) +* Marx, Groucho: Increment Ops. (line 6207) +* match function: String Functions. (line 9239) * match function, RSTART/RLENGTH variables: String Functions. + (line 9256) * matching, expressions, See comparison expressions: Typing and Comparison. -* matching, leftmost longest: Multiple Line. -* matching, null strings: Gory Details. -* mawk program: Other Versions. -* McPhee, Patrick: Contributors. -* memory, releasing: Internals. -* memory, setting limits: Options. + (line 6269) +* matching, leftmost longest: Multiple Line. (line 3717) +* matching, null strings: Gory Details. (line 9776) +* mawk program: Other Versions. (line 18378) +* McPhee, Patrick: Contributors. (line 17098) +* memory, releasing: Internals. (line 18851) +* memory, setting limits: Options. (line 12036) * message object files: Explaining gettext. + (line 10934) * message object files, converting from portable object files: I18N Example. + (line 11380) * message object files, specifying directory of <1>: Programmer i18n. + (line 11070) * message object files, specifying directory of: Explaining gettext. -* metacharacters, escape sequences for: Escape Sequences. -* mktime function (gawk): Time Functions. -* modifiers, in format specifiers: Format Modifiers. + (line 10946) +* metacharacters, escape sequences for: Escape Sequences. (line 2164) +* mktime function (gawk): Time Functions. (line 9991) +* modifiers, in format specifiers: Format Modifiers. (line 4606) * monetary information, localization: Explaining gettext. -* msgfmt utility: I18N Example. -* names, arrays/variables <1>: Library Names. -* names, arrays/variables: Arrays. -* names, functions <1>: Library Names. -* names, functions: Definition Syntax. -* namespace issues <1>: Library Names. -* namespace issues: Arrays. -* namespace issues, functions: Definition Syntax. -* nawk utility: Names. + (line 10994) +* msgfmt utility: I18N Example. (line 11380) +* names, arrays/variables <1>: Library Names. (line 12507) +* names, arrays/variables: Arrays. (line 8279) +* names, functions <1>: Library Names. (line 12507) +* names, functions: Definition Syntax. (line 10486) +* namespace issues <1>: Library Names. (line 12507) +* namespace issues: Arrays. (line 8279) +* namespace issues, functions: Definition Syntax. (line 10486) +* nawk utility: Names. (line 688) * negative zero: Floating Point Issues. -* NetBSD: Glossary. -* networks, programming: TCP/IP Networking. -* networks, support for: Special Network. -* newlines <1>: Options. -* newlines <2>: Boolean Ops. -* newlines: Statements/Lines. -* newlines, as field separators: Field Separators. -* newlines, as record separators: Records. -* newlines, in dynamic regexps: Computed Regexps. -* newlines, in regexp constants: Computed Regexps. -* newlines, printing: Print Examples. + (line 19714) +* NetBSD: Glossary. (line 20320) +* networks, programming: TCP/IP Networking. (line 11643) +* networks, support for: Special Network. (line 5137) +* newlines <1>: Options. (line 12148) +* newlines <2>: Boolean Ops. (line 6516) +* newlines: Statements/Lines. (line 1770) +* newlines, as field separators: Field Separators. (line 3312) +* newlines, as record separators: Records. (line 2831) +* newlines, in dynamic regexps: Computed Regexps. (line 2708) +* newlines, in regexp constants: Computed Regexps. (line 2718) +* newlines, printing: Print Examples. (line 4312) * newlines, separating statements in actions <1>: Statements. + (line 7220) * newlines, separating statements in actions: Action Overview. -* next file statement: POSIX/GNU. -* next file statement, deprecated: Obsolete. + (line 7170) +* next file statement: POSIX/GNU. (line 16967) +* next file statement, deprecated: Obsolete. (line 12392) * next file statement, in gawk: Nextfile Statement. -* next statement <1>: Next Statement. -* next statement: Boolean Ops. + (line 7716) +* next statement <1>: Next Statement. (line 7627) +* next statement: Boolean Ops. (line 6533) * next statement, BEGIN/END patterns and: I/O And BEGIN/END. + (line 7080) * next statement, user-defined functions and: Next Statement. + (line 7660) * nextfile statement: Nextfile Statement. + (line 7676) * nextfile statement, BEGIN/END patterns and: I/O And BEGIN/END. -* nextfile statement, implementing: Nextfile Function. + (line 7080) +* nextfile statement, implementing: Nextfile Function. (line 12611) * nextfile statement, in gawk: Nextfile Statement. -* nextfile statement, next file statement and: Obsolete. + (line 7716) +* nextfile statement, next file statement and: Obsolete. (line 12392) * nextfile statement, user-defined functions and: Nextfile Statement. -* nextfile user-defined function: Nextfile Function. -* NF variable <1>: Auto-set. -* NF variable: Fields. -* NF variable, decrementing: Changing Fields. -* noassign.awk program: Ignoring Assigns. -* NODE internal type: Internals. -* nodes, duplicating: Internals. -* not Boolean-logic operator: Boolean Ops. -* NR variable <1>: Auto-set. -* NR variable: Records. -* NR variable, changing: Auto-set. -* null strings <1>: Basic Data Typing. -* null strings <2>: Truth Values. + (line 7709) +* nextfile user-defined function: Nextfile Function. (line 12643) +* NF variable <1>: Auto-set. (line 8056) +* NF variable: Fields. (line 3033) +* NF variable, decrementing: Changing Fields. (line 3223) +* noassign.awk program: Ignoring Assigns. (line 13393) +* NODE internal type: Internals. (line 18772) +* nodes, duplicating: Internals. (line 18846) +* not Boolean-logic operator: Boolean Ops. (line 6455) +* NR variable <1>: Auto-set. (line 8067) +* NR variable: Records. (line 2817) +* NR variable, changing: Auto-set. (line 8140) +* null strings <1>: Basic Data Typing. (line 19596) +* null strings <2>: Truth Values. (line 6238) * null strings <3>: Regexp Field Splitting. -* null strings: Records. -* null strings, array elements and: Delete. + (line 3371) +* null strings: Records. (line 2912) +* null strings, array elements and: Delete. (line 8598) * null strings, as array subscripts: Uninitialized Subscripts. -* null strings, converting numbers to strings: Conversion. -* null strings, matching: Gory Details. -* null strings, quoting and: Quoting. + (line 8735) +* null strings, converting numbers to strings: Conversion. (line 5726) +* null strings, matching: Gory Details. (line 9776) +* null strings, quoting and: Quoting. (line 1401) * number sign (#), #! (executable scripts): Executable Scripts. + (line 1233) * number sign (#), #! (executable scripts), portability issues with: Executable Scripts. -* number sign (#), commenting: Comments. -* numbers: Internals. + (line 1233) +* number sign (#), commenting: Comments. (line 1296) +* numbers: Internals. (line 18831) * numbers, as array subscripts: Numeric Array Subscripts. -* numbers, as values of characters: Ordinal Functions. + (line 8648) +* numbers, as values of characters: Ordinal Functions. (line 12942) * numbers, Cliff random: Cliff Random Function. -* numbers, converting: Conversion. -* numbers, converting, to strings <1>: Bitwise Functions. -* numbers, converting, to strings: User-modified. -* numbers, floating-point: Basic Data Typing. -* numbers, floating-point, AWKNUM internal type: Internals. + (line 12911) +* numbers, converting: Conversion. (line 5711) +* numbers, converting, to strings <1>: Bitwise Functions. (line 10387) +* numbers, converting, to strings: User-modified. (line 7825) +* numbers, floating-point: Basic Data Typing. (line 19570) +* numbers, floating-point, AWKNUM internal type: Internals. (line 18768) * numbers, hexadecimal: Nondecimal-numbers. -* numbers, NODE internal type: Internals. + (line 5449) +* numbers, NODE internal type: Internals. (line 18772) * numbers, octal: Nondecimal-numbers. -* numbers, random: Numeric Functions. -* numbers, rounding: Round Function. -* numeric, constants: Scalar Constants. -* numeric, output format: OFMT. + (line 5449) +* numbers, random: Numeric Functions. (line 9107) +* numbers, rounding: Round Function. (line 12866) +* numeric, constants: Scalar Constants. (line 5417) +* numeric, output format: OFMT. (line 4426) * numeric, strings: Typing and Comparison. -* numeric, values: Internals. -* oawk utility: Names. -* obsolete features: Obsolete. + (line 6273) +* numeric, values: Internals. (line 18776) +* oawk utility: Names. (line 688) +* obsolete features: Obsolete. (line 12387) * octal numbers: Nondecimal-numbers. -* octal values, enabling interpretation of: Options. -* OFMT variable <1>: User-modified. -* OFMT variable <2>: Conversion. -* OFMT variable: OFMT. -* OFMT variable, POSIX awk and: OFMT. -* OFS variable <1>: User-modified. -* OFS variable <2>: Output Separators. -* OFS variable: Changing Fields. -* OpenBSD: Glossary. -* operating systems, BSD-based <1>: Portal Files. -* operating systems, BSD-based: Manual History. -* operating systems, PC, gawk on: PC Using. + (line 5449) +* octal values, enabling interpretation of: Options. (line 12133) +* OFMT variable <1>: User-modified. (line 7899) +* OFMT variable <2>: Conversion. (line 5759) +* OFMT variable: OFMT. (line 4435) +* OFMT variable, POSIX awk and: OFMT. (line 4447) +* OFS variable <1>: User-modified. (line 7908) +* OFS variable <2>: Output Separators. (line 4385) +* OFS variable: Changing Fields. (line 3180) +* OpenBSD: Glossary. (line 20320) +* operating systems, BSD-based <1>: Portal Files. (line 11710) +* operating systems, BSD-based: Manual History. (line 886) +* operating systems, PC, gawk on: PC Using. (line 17821) * operating systems, PC, gawk on, installing: PC Installation. -* operating systems, porting gawk to: New Ports. + (line 17600) +* operating systems, porting gawk to: New Ports. (line 18648) * operating systems, See Also GNU/Linux, PC operating systems, Unix: Installation. -* operations, bitwise: Bitwise Functions. -* operators, arithmetic: Arithmetic Ops. -* operators, assignment: Assignment Ops. -* operators, assignment, evaluation order: Assignment Ops. -* operators, Boolean, See Boolean expressions: Boolean Ops. -* operators, decrement/increment: Increment Ops. + (line 17111) +* operations, bitwise: Bitwise Functions. (line 10294) +* operators, arithmetic: Arithmetic Ops. (line 5815) +* operators, assignment: Assignment Ops. (line 5981) +* operators, assignment, evaluation order: Assignment Ops. (line 6085) +* operators, Boolean, See Boolean expressions: Boolean Ops. (line 6455) +* operators, decrement/increment: Increment Ops. (line 6152) * operators, GNU-specific: GNU Regexp Operators. -* operators, input/output <1>: Precedence. -* operators, input/output <2>: Redirection. -* operators, input/output <3>: Getline/Coprocess. -* operators, input/output <4>: Getline/Pipe. -* operators, input/output: Getline/File. -* operators, logical, See Boolean expressions: Boolean Ops. -* operators, precedence <1>: Precedence. -* operators, precedence: Increment Ops. + (line 2461) +* operators, input/output <1>: Precedence. (line 6703) +* operators, input/output <2>: Redirection. (line 4856) +* operators, input/output <3>: Getline/Coprocess. (line 4129) +* operators, input/output <4>: Getline/Pipe. (line 4043) +* operators, input/output: Getline/File. (line 3971) +* operators, logical, See Boolean expressions: Boolean Ops. (line 6455) +* operators, precedence <1>: Precedence. (line 6649) +* operators, precedence: Increment Ops. (line 6207) * operators, relational, See operators, comparison: Typing and Comparison. -* operators, short-circuit: Boolean Ops. -* operators, string: Concatenation. -* operators, string-matching: Regexp Usage. + (line 6269) +* operators, short-circuit: Boolean Ops. (line 6506) +* operators, string: Concatenation. (line 5903) +* operators, string-matching: Regexp Usage. (line 1989) * operators, string-matching, for buffers: GNU Regexp Operators. + (line 2495) * operators, word-boundary (gawk): GNU Regexp Operators. -* options, command-line <1>: Options. + (line 2510) +* options, command-line <1>: Options. (line 11997) * options, command-line <2>: Command Line Field Separator. -* options, command-line: Long. -* options, command-line, end of: Options. -* options, command-line, invoking awk: Command Line. -* options, command-line, processing: Getopt Function. -* options, deprecated: Obsolete. -* options, long <1>: Options. -* options, long: Command Line. -* options, printing list of: Options. -* OR bitwise operation: Bitwise Functions. -* or Boolean-logic operator: Boolean Ops. -* or function (gawk): Bitwise Functions. -* ord user-defined function: Ordinal Functions. -* order of evaluation, concatenation: Concatenation. -* ORS variable <1>: User-modified. -* ORS variable: Output Separators. + (line 3419) +* options, command-line: Long. (line 1202) +* options, command-line, end of: Options. (line 12053) +* options, command-line, invoking awk: Command Line. (line 11973) +* options, command-line, processing: Getopt Function. (line 13426) +* options, deprecated: Obsolete. (line 12387) +* options, long <1>: Options. (line 11997) +* options, long: Command Line. (line 11980) +* options, printing list of: Options. (line 12111) +* OR bitwise operation: Bitwise Functions. (line 10294) +* or Boolean-logic operator: Boolean Ops. (line 6455) +* or function (gawk): Bitwise Functions. (line 10327) +* ord user-defined function: Ordinal Functions. (line 12952) +* order of evaluation, concatenation: Concatenation. (line 5935) +* ORS variable <1>: User-modified. (line 7913) +* ORS variable: Output Separators. (line 4399) * output field separator, See OFS variable: Changing Fields. + (line 3180) * output record separator, See ORS variable: Output Separators. -* output redirection: Redirection. -* output, buffering: I/O Functions. -* output, duplicating into files: Tee Program. + (line 4399) +* output redirection: Redirection. (line 4843) +* output, buffering: I/O Functions. (line 9818) +* output, duplicating into files: Tee Program. (line 14930) * output, files, closing: Close Files And Pipes. -* output, format specifier, OFMT: OFMT. -* output, formatted: Printf. -* output, pipes: Redirection. -* output, printing, See printing: Printing. -* output, records: Output Separators. -* output, standard: Special FD. -* P1003.2 POSIX standard: Glossary. -* param_cnt internal variable: Internals. -* parameters, number of: Internals. -* parentheses (): Regexp Operators. -* parentheses (), pgawk program: Profiling. -* password file: Passwd Functions. + (line 5191) +* output, format specifier, OFMT: OFMT. (line 4435) +* output, formatted: Printf. (line 4457) +* output, pipes: Redirection. (line 4891) +* output, printing, See printing: Printing. (line 4241) +* output, records: Output Separators. (line 4399) +* output, standard: Special FD. (line 5011) +* P1003.2 POSIX standard: Glossary. (line 20164) +* param_cnt internal variable: Internals. (line 18795) +* parameters, number of: Internals. (line 18795) +* parentheses (): Regexp Operators. (line 2253) +* parentheses (), pgawk program: Profiling. (line 11862) +* password file: Passwd Functions. (line 13719) * patterns: Patterns and Actions. + (line 6747) * patterns, comparison expressions as: Expression Patterns. -* patterns, counts: Profiling. -* patterns, default: Very Simple. -* patterns, empty: Empty. -* patterns, expressions as: Regexp Patterns. -* patterns, ranges in: Ranges. + (line 6833) +* patterns, counts: Profiling. (line 11834) +* patterns, default: Very Simple. (line 1559) +* patterns, empty: Empty. (line 7093) +* patterns, expressions as: Regexp Patterns. (line 6811) +* patterns, ranges in: Ranges. (line 6905) * patterns, regexp constants as: Expression Patterns. -* patterns, types of: Pattern Overview. -* pawk profiling Bell Labs awk: Other Versions. -* PC operating systems, gawk on: PC Using. + (line 6855) +* patterns, types of: Pattern Overview. (line 6780) +* pawk profiling Bell Labs awk: Other Versions. (line 18433) +* PC operating systems, gawk on: PC Using. (line 17821) * PC operating systems, gawk on, installing: PC Installation. -* percent sign (%), % operator: Precedence. -* percent sign (%), %= operator <1>: Precedence. -* percent sign (%), %= operator: Assignment Ops. -* period (.): Regexp Operators. -* PERL: Future Extensions. -* Peters, Arno: Contributors. -* Peterson, Hal: Contributors. -* pgawk program: Profiling. -* pgawk program, awkprof.out file: Profiling. -* pgawk program, dynamic profiling: Profiling. + (line 17600) +* percent sign (%), % operator: Precedence. (line 6693) +* percent sign (%), %= operator <1>: Precedence. (line 6734) +* percent sign (%), %= operator: Assignment Ops. (line 6103) +* period (.): Regexp Operators. (line 2218) +* PERL: Future Extensions. (line 19333) +* Peters, Arno: Contributors. (line 17083) +* Peterson, Hal: Contributors. (line 17050) +* pgawk program: Profiling. (line 11725) +* pgawk program, awkprof.out file: Profiling. (line 11729) +* pgawk program, dynamic profiling: Profiling. (line 11898) * pipes, closing: Close Files And Pipes. -* pipes, input: Getline/Pipe. -* pipes, output: Redirection. -* plus sign (+): Regexp Operators. -* plus sign (+), + operator: Precedence. -* plus sign (+), ++ operator <1>: Precedence. -* plus sign (+), ++ operator: Increment Ops. -* plus sign (+), += operator <1>: Precedence. -* plus sign (+), += operator: Assignment Ops. + (line 5191) +* pipes, input: Getline/Pipe. (line 4043) +* pipes, output: Redirection. (line 4891) +* plus sign (+): Regexp Operators. (line 2276) +* plus sign (+), + operator: Precedence. (line 6690) +* plus sign (+), ++ operator <1>: Precedence. (line 6684) +* plus sign (+), ++ operator: Increment Ops. (line 6186) +* plus sign (+), += operator <1>: Precedence. (line 6734) +* plus sign (+), += operator: Assignment Ops. (line 6056) * plus sign (+), decrement/increment operators: Increment Ops. -* portability: Escape Sequences. + (line 6157) +* portability: Escape Sequences. (line 2126) * portability, #! (executable scripts): Executable Scripts. -* portability, ** operator and: Arithmetic Ops. -* portability, **= operator and: Assignment Ops. + (line 1261) +* portability, ** operator and: Arithmetic Ops. (line 5890) +* portability, **= operator and: Assignment Ops. (line 6123) * portability, ARGV variable: Executable Scripts. + (line 1270) * portability, backslash continuation and: Statements/Lines. + (line 1793) * portability, backslash in escape sequences: Escape Sequences. + (line 2145) * portability, close function and: Close Files And Pipes. -* portability, data files as single record: Records. -* portability, deleting array elements: Delete. -* portability, example programs: Library Functions. -* portability, fflush function and: I/O Functions. -* portability, functions, defining: Definition Syntax. -* portability, gawk: New Ports. + (line 5266) +* portability, data files as single record: Records. (line 2971) +* portability, deleting array elements: Delete. (line 8622) +* portability, example programs: Library Functions. (line 12460) +* portability, fflush function and: I/O Functions. (line 9818) +* portability, functions, defining: Definition Syntax. (line 10554) +* portability, gawk: New Ports. (line 18648) * portability, gettext library and: Explaining gettext. -* portability, internationalization and: I18N Portability. -* portability, length function: String Functions. -* portability, new awk vs. old awk: Conversion. + (line 10905) +* portability, internationalization and: I18N Portability. (line 11260) +* portability, length function: String Functions. (line 9230) +* portability, new awk vs. old awk: Conversion. (line 5759) * portability, next statement in user-defined functions: Function Caveats. -* portability, NF variable, decrementing: Changing Fields. -* portability, operators: Increment Ops. -* portability, operators, not in POSIX awk: Precedence. + (line 10740) +* portability, NF variable, decrementing: Changing Fields. (line 3231) +* portability, operators: Increment Ops. (line 6207) +* portability, operators, not in POSIX awk: Precedence. (line 6738) * portability, POSIXLY_CORRECT environment variable: Options. -* portability, substr function: String Functions. -* portable object files <1>: Translator i18n. + (line 12257) +* portability, substr function: String Functions. (line 9581) +* portable object files <1>: Translator i18n. (line 11136) * portable object files: Explaining gettext. + (line 10931) * portable object files, converting to message object files: I18N Example. -* portable object files, generating: Options. -* portal files: Portal Files. -* porting gawk: New Ports. + (line 11380) +* portable object files, generating: Options. (line 12102) +* portal files: Portal Files. (line 11710) +* porting gawk: New Ports. (line 18648) * positional specifiers, printf statement <1>: Printf Ordering. + (line 11183) * positional specifiers, printf statement: Format Modifiers. + (line 4613) * positional specifiers, printf statement, mixing with regular formats: Printf Ordering. + (line 11234) * positive zero: Floating Point Issues. -* POSIX awk <1>: Assignment Ops. -* POSIX awk: This Manual. -* POSIX awk, **= operator and: Assignment Ops. -* POSIX awk, < operator and: Getline/File. -* POSIX awk, arithmetic operators and: Arithmetic Ops. + (line 19714) +* POSIX awk <1>: Assignment Ops. (line 6114) +* POSIX awk: This Manual. (line 718) +* POSIX awk, **= operator and: Assignment Ops. (line 6123) +* POSIX awk, < operator and: Getline/File. (line 3991) +* POSIX awk, arithmetic operators and: Arithmetic Ops. (line 5845) * POSIX awk, backslashes in string constants: Escape Sequences. -* POSIX awk, BEGIN/END patterns: I/O And BEGIN/END. -* POSIX awk, break statement and: Break Statement. -* POSIX awk, changes in awk versions: POSIX. -* POSIX awk, character lists and: Character Lists. + (line 2145) +* POSIX awk, BEGIN/END patterns: I/O And BEGIN/END. (line 7060) +* POSIX awk, break statement and: Break Statement. (line 7558) +* POSIX awk, changes in awk versions: POSIX. (line 16731) +* POSIX awk, character lists and: Character Lists. (line 2371) * POSIX awk, character lists and, character classes: Character Lists. + (line 2377) * POSIX awk, continue statement and: Continue Statement. -* POSIX awk, CONVFMT variable and: User-modified. -* POSIX awk, date utility and: Time Functions. + (line 7611) +* POSIX awk, CONVFMT variable and: User-modified. (line 7825) +* POSIX awk, date utility and: Time Functions. (line 10225) * POSIX awk, field separators and <1>: Field Splitting Summary. -* POSIX awk, field separators and: Fields. -* POSIX awk, FS variable and: User-modified. -* POSIX awk, function keyword in: Definition Syntax. -* POSIX awk, functions and, gsub/sub: Gory Details. -* POSIX awk, functions and, length: String Functions. -* POSIX awk, GNU long options and: Options. -* POSIX awk, interval expressions in: Regexp Operators. -* POSIX awk, next/nextfile statements and: Next Statement. + (line 3541) +* POSIX awk, field separators and: Fields. (line 3006) +* POSIX awk, FS variable and: User-modified. (line 7851) +* POSIX awk, function keyword in: Definition Syntax. (line 10539) +* POSIX awk, functions and, gsub/sub: Gory Details. (line 9669) +* POSIX awk, functions and, length: String Functions. (line 9230) +* POSIX awk, GNU long options and: Options. (line 12006) +* POSIX awk, interval expressions in: Regexp Operators. (line 2309) +* POSIX awk, next/nextfile statements and: Next Statement. (line 7660) * POSIX awk, numeric strings and: Typing and Comparison. -* POSIX awk, OFMT variable and <1>: Conversion. -* POSIX awk, OFMT variable and: OFMT. -* POSIX awk, period (.), using: Regexp Operators. -* POSIX awk, printf format strings and: Format Modifiers. -* POSIX awk, regular expressions and: Regexp Operators. -* POSIX awk, timestamps and: Time Functions. -* POSIX awk, | I/O operator and: Getline/Pipe. -* POSIX mode: Options. -* POSIX, awk and: Preface. -* POSIX, gawk extensions not included in: POSIX/GNU. -* POSIX, programs, implementing in awk: Clones. -* POSIXLY_CORRECT environment variable: Options. -* precedence <1>: Precedence. -* precedence: Increment Ops. -* precedence, regexp operators: Regexp Operators. -* print statement: Printing. + (line 6273) +* POSIX awk, OFMT variable and <1>: Conversion. (line 5759) +* POSIX awk, OFMT variable and: OFMT. (line 4447) +* POSIX awk, period (.), using: Regexp Operators. (line 2225) +* POSIX awk, printf format strings and: Format Modifiers. (line 4759) +* POSIX awk, regular expressions and: Regexp Operators. (line 2329) +* POSIX awk, timestamps and: Time Functions. (line 9967) +* POSIX awk, | I/O operator and: Getline/Pipe. (line 4089) +* POSIX mode: Options. (line 12141) +* POSIX, awk and: Preface. (line 569) +* POSIX, gawk extensions not included in: POSIX/GNU. (line 16818) +* POSIX, programs, implementing in awk: Clones. (line 14209) +* POSIXLY_CORRECT environment variable: Options. (line 12239) +* precedence <1>: Precedence. (line 6649) +* precedence: Increment Ops. (line 6207) +* precedence, regexp operators: Regexp Operators. (line 2324) +* print statement: Printing. (line 4251) * print statement, BEGIN/END patterns and: I/O And BEGIN/END. -* print statement, commas, omitting: Print Examples. -* print statement, I/O operators in: Precedence. -* print statement, line continuations and: Print Examples. -* print statement, OFMT variable and: User-modified. + (line 7060) +* print statement, commas, omitting: Print Examples. (line 4330) +* print statement, I/O operators in: Precedence. (line 6710) +* print statement, line continuations and: Print Examples. (line 4375) +* print statement, OFMT variable and: User-modified. (line 7908) * print statement, See Also redirection, of output: Redirection. -* print statement, sprintf function and: Round Function. -* printf statement <1>: Printf. -* printf statement: Printing. -* printf statement, columns, aligning: Print Examples. + (line 4851) +* print statement, sprintf function and: Round Function. (line 12866) +* printf statement <1>: Printf. (line 4457) +* printf statement: Printing. (line 4251) +* printf statement, columns, aligning: Print Examples. (line 4369) * printf statement, format-control characters: Control Letters. -* printf statement, I/O operators in: Precedence. -* printf statement, modifiers: Format Modifiers. + (line 4519) +* printf statement, I/O operators in: Precedence. (line 6710) +* printf statement, modifiers: Format Modifiers. (line 4606) * printf statement, positional specifiers <1>: Printf Ordering. + (line 11183) * printf statement, positional specifiers: Format Modifiers. + (line 4613) * printf statement, positional specifiers, mixing with regular formats: Printf Ordering. + (line 11234) * printf statement, See Also redirection, of output: Redirection. -* printf statement, sprintf function and: Round Function. -* printf statement, syntax of: Basic Printf. -* printing: Printing. -* printing, list of options: Options. -* printing, mailing labels: Labels Program. -* printing, unduplicated lines of text: Uniq Program. -* printing, user information: Id Program. -* private variables: Library Names. -* process information, files for: Special Process. -* processes, two-way communications with: Two-way I/O. -* processing data: Basic High Level. -* PROCINFO array <1>: Group Functions. -* PROCINFO array <2>: Passwd Functions. -* PROCINFO array <3>: Auto-set. -* PROCINFO array: Special Caveats. -* profiling awk programs: Profiling. -* profiling awk programs, dynamically: Profiling. -* profiling gawk, See pgawk program: Profiling. -* program, definition of: Getting Started. -* programmers, attractiveness of: Two-way I/O. + (line 4851) +* printf statement, sprintf function and: Round Function. (line 12866) +* printf statement, syntax of: Basic Printf. (line 4478) +* printing: Printing. (line 4241) +* printing, list of options: Options. (line 12111) +* printing, mailing labels: Labels Program. (line 15689) +* printing, unduplicated lines of text: Uniq Program. (line 15014) +* printing, user information: Id Program. (line 14721) +* private variables: Library Names. (line 12512) +* process information, files for: Special Process. (line 5078) +* processes, two-way communications with: Two-way I/O. (line 11524) +* processing data: Basic High Level. (line 19459) +* PROCINFO array <1>: Group Functions. (line 13934) +* PROCINFO array <2>: Passwd Functions. (line 13709) +* PROCINFO array <3>: Auto-set. (line 8072) +* PROCINFO array: Special Caveats. (line 5162) +* profiling awk programs: Profiling. (line 11725) +* profiling awk programs, dynamically: Profiling. (line 11898) +* profiling gawk, See pgawk program: Profiling. (line 11725) +* program, definition of: Getting Started. (line 1047) +* programmers, attractiveness of: Two-way I/O. (line 11507) * programming conventions, --non-decimal-data option: Nondecimal Data. -* programming conventions, ARGC/ARGV variables: Auto-set. -* programming conventions, exit statement: Exit Statement. + (line 11495) +* programming conventions, ARGC/ARGV variables: Auto-set. (line 7984) +* programming conventions, exit statement: Exit Statement. (line 7759) * programming conventions, function parameters: Return Statement. + (line 10783) * programming conventions, functions, calling: Calling Built-in. + (line 9003) * programming conventions, functions, writing: Definition Syntax. + (line 10516) * programming conventions, gawk internals: Internal File Ops. + (line 19129) * programming conventions, nextfile statement: Nextfile Function. + (line 12625) * programming conventions, private variable names: Library Names. -* programming language, recipe for: History. + (line 12524) +* programming language, recipe for: History. (line 630) * programming languages, data-driven vs. procedural: Getting Started. -* programming, basic steps: Basic High Level. -* programming, concepts: Basic Concepts. -* pwcat program: Passwd Functions. + (line 1038) +* programming, basic steps: Basic High Level. (line 19472) +* programming, concepts: Basic Concepts. (line 19440) +* pwcat program: Passwd Functions. (line 13726) * question mark (?) <1>: GNU Regexp Operators. -* question mark (?): Regexp Operators. -* question mark (?), ?: operator: Precedence. -* QUIT signal (MS-DOS): Profiling. -* quoting <1>: Comments. -* quoting <2>: Long. -* quoting: Read Terminal. -* quoting, rules for: Quoting. -* quoting, tricks for: Quoting. -* Rakitzis, Byron: History Sorting. -* rand function: Numeric Functions. + (line 2506) +* question mark (?): Regexp Operators. (line 2285) +* question mark (?), ?: operator: Precedence. (line 6731) +* QUIT signal (MS-DOS): Profiling. (line 11931) +* quoting <1>: Comments. (line 1317) +* quoting <2>: Long. (line 1216) +* quoting: Read Terminal. (line 1165) +* quoting, rules for: Quoting. (line 1349) +* quoting, tricks for: Quoting. (line 1410) +* Rakitzis, Byron: History Sorting. (line 15919) +* rand function: Numeric Functions. (line 9077) * random numbers, Cliff: Cliff Random Function. -* random numbers, rand/srand functions: Numeric Functions. -* random numbers, seed of: Numeric Functions. -* range expressions: Character Lists. -* range patterns: Ranges. -* Rankin, Pat <1>: Bugs. -* Rankin, Pat <2>: Contributors. -* Rankin, Pat <3>: Assignment Ops. -* Rankin, Pat: Acknowledgments. -* raw sockets: TCP/IP Networking. -* readable data files, checking: File Checking. -* readable.awk program: File Checking. -* recipe for a programming language: History. -* record separators <1>: User-modified. -* record separators: Records. -* record separators, changing: Records. -* record separators, regular expressions as: Records. -* record separators, with multiline records: Multiple Line. -* records <1>: Basic High Level. -* records: Reading Files. -* records, multiline: Multiple Line. -* records, printing: Print. -* records, splitting input into: Records. -* records, terminating: Records. -* records, treating files as: Records. -* recursive functions: Definition Syntax. -* redirection of input: Getline/File. -* redirection of output: Redirection. -* reference counting, sorting arrays: Array Sorting. + (line 12911) +* random numbers, rand/srand functions: Numeric Functions. (line 9077) +* random numbers, seed of: Numeric Functions. (line 9107) +* range expressions: Character Lists. (line 2353) +* range patterns: Ranges. (line 6905) +* Rankin, Pat <1>: Bugs. (line 18339) +* Rankin, Pat <2>: Contributors. (line 17045) +* Rankin, Pat <3>: Assignment Ops. (line 6074) +* Rankin, Pat: Acknowledgments. (line 995) +* raw sockets: TCP/IP Networking. (line 11667) +* readable data files, checking: File Checking. (line 13300) +* readable.awk program: File Checking. (line 13305) +* recipe for a programming language: History. (line 630) +* record separators <1>: User-modified. (line 7918) +* record separators: Records. (line 2825) +* record separators, changing: Records. (line 2891) +* record separators, regular expressions as: Records. (line 2921) +* record separators, with multiline records: Multiple Line. (line 3701) +* records <1>: Basic High Level. (line 19524) +* records: Reading Files. (line 2788) +* records, multiline: Multiple Line. (line 3697) +* records, printing: Print. (line 4292) +* records, splitting input into: Records. (line 2817) +* records, terminating: Records. (line 2921) +* records, treating files as: Records. (line 2992) +* recursive functions: Definition Syntax. (line 10534) +* redirection of input: Getline/File. (line 3971) +* redirection of output: Redirection. (line 4843) +* reference counting, sorting arrays: Array Sorting. (line 8938) * regexp constants <1>: Typing and Comparison. -* regexp constants <2>: Regexp Constants. -* regexp constants: Regexp Usage. + (line 6434) +* regexp constants <2>: Regexp Constants. (line 5524) +* regexp constants: Regexp Usage. (line 2028) * regexp constants, /=.../, /= operator and: Assignment Ops. + (line 6129) * regexp constants, as patterns: Expression Patterns. + (line 6855) * regexp constants, in gawk: Using Constant Regexps. -* regexp constants, slashes vs. quotes: Computed Regexps. -* regexp constants, vs. string constants: Computed Regexps. -* regexp, See regular expressions: Regexp. -* regular expressions: Regexp. + (line 5558) +* regexp constants, slashes vs. quotes: Computed Regexps. (line 2677) +* regexp constants, vs. string constants: Computed Regexps. (line 2687) +* regexp, See regular expressions: Regexp. (line 1945) +* regular expressions: Regexp. (line 1945) * regular expressions as field separators: Field Separators. -* regular expressions, anchors in: Regexp Operators. + (line 3298) +* regular expressions, anchors in: Regexp Operators. (line 2197) * regular expressions, as field separators: Regexp Field Splitting. -* regular expressions, as patterns <1>: Regexp Patterns. -* regular expressions, as patterns: Regexp Usage. -* regular expressions, as record separators: Records. -* regular expressions, case sensitivity <1>: User-modified. -* regular expressions, case sensitivity: Case-sensitivity. -* regular expressions, computed: Computed Regexps. + (line 3335) +* regular expressions, as patterns <1>: Regexp Patterns. (line 6811) +* regular expressions, as patterns: Regexp Usage. (line 1976) +* regular expressions, as record separators: Records. (line 2921) +* regular expressions, case sensitivity <1>: User-modified. (line 7867) +* regular expressions, case sensitivity: Case-sensitivity. (line 2549) +* regular expressions, computed: Computed Regexps. (line 2656) * regular expressions, constants, See regexp constants: Regexp Usage. -* regular expressions, dynamic: Computed Regexps. + (line 2028) +* regular expressions, dynamic: Computed Regexps. (line 2656) * regular expressions, dynamic, with embedded newlines: Computed Regexps. + (line 2708) * regular expressions, gawk, command-line options: GNU Regexp Operators. -* regular expressions, interval expressions and: Options. + (line 2517) +* regular expressions, interval expressions and: Options. (line 12186) * regular expressions, leftmost longest match: Leftmost Longest. -* regular expressions, operators <1>: Regexp Operators. -* regular expressions, operators: Regexp Usage. + (line 2626) +* regular expressions, operators <1>: Regexp Operators. (line 2181) +* regular expressions, operators: Regexp Usage. (line 1989) * regular expressions, operators, for buffers: GNU Regexp Operators. + (line 2495) * regular expressions, operators, for words: GNU Regexp Operators. + (line 2461) * regular expressions, operators, gawk: GNU Regexp Operators. + (line 2461) * regular expressions, operators, precedence of: Regexp Operators. -* regular expressions, searching for: Egrep Program. + (line 2324) +* regular expressions, searching for: Egrep Program. (line 14491) * relational operators, See comparison operators: Typing and Comparison. + (line 6269) * return statement, user-defined functions: Return Statement. + (line 10750) * return values, close function: Close Files And Pipes. -* rev user-defined function: Function Example. -* rewind user-defined function: Rewind Function. -* right angle bracket (>), > operator <1>: Precedence. + (line 5315) +* rev user-defined function: Function Example. (line 10609) +* rewind user-defined function: Rewind Function. (line 13268) +* right angle bracket (>), > operator <1>: Precedence. (line 6703) * right angle bracket (>), > operator: Typing and Comparison. -* right angle bracket (>), > operator (I/O): Redirection. -* right angle bracket (>), >= operator <1>: Precedence. + (line 6334) +* right angle bracket (>), > operator (I/O): Redirection. (line 4856) +* right angle bracket (>), >= operator <1>: Precedence. (line 6703) * right angle bracket (>), >= operator: Typing and Comparison. + (line 6334) * right angle bracket (>), >> operator (I/O) <1>: Precedence. -* right angle bracket (>), >> operator (I/O): Redirection. -* right shift, bitwise: Bitwise Functions. -* Ritchie, Dennis: Basic Data Typing. -* RLENGTH variable: Auto-set. -* RLENGTH variable, match function and: String Functions. -* Robbins, Arnold <1>: Future Extensions. -* Robbins, Arnold <2>: Bugs. -* Robbins, Arnold <3>: Contributors. -* Robbins, Arnold <4>: Alarm Program. -* Robbins, Arnold <5>: Passwd Functions. -* Robbins, Arnold <6>: Getline/Pipe. + (line 6703) +* right angle bracket (>), >> operator (I/O): Redirection. (line 4884) +* right shift, bitwise: Bitwise Functions. (line 10320) +* Ritchie, Dennis: Basic Data Typing. (line 19620) +* RLENGTH variable: Auto-set. (line 8116) +* RLENGTH variable, match function and: String Functions. (line 9256) +* Robbins, Arnold <1>: Future Extensions. (line 19333) +* Robbins, Arnold <2>: Bugs. (line 18305) +* Robbins, Arnold <3>: Contributors. (line 17101) +* Robbins, Arnold <4>: Alarm Program. (line 15443) +* Robbins, Arnold <5>: Passwd Functions. (line 13779) +* Robbins, Arnold <6>: Getline/Pipe. (line 4073) * Robbins, Arnold: Command Line Field Separator. -* Robbins, Bill: Getline/Pipe. -* Robbins, Harry: Acknowledgments. -* Robbins, Jean: Acknowledgments. -* Robbins, Miriam <1>: Passwd Functions. -* Robbins, Miriam <2>: Getline/Pipe. -* Robbins, Miriam: Acknowledgments. + (line 3493) +* Robbins, Bill: Getline/Pipe. (line 4073) +* Robbins, Harry: Acknowledgments. (line 1012) +* Robbins, Jean: Acknowledgments. (line 1012) +* Robbins, Miriam <1>: Passwd Functions. (line 13779) +* Robbins, Miriam <2>: Getline/Pipe. (line 4073) +* Robbins, Miriam: Acknowledgments. (line 1012) * Robinson, Will: Dynamic Extensions. + (line 18729) * robot, the: Dynamic Extensions. -* Rommel, Kai Uwe <1>: Contributors. -* Rommel, Kai Uwe: Acknowledgments. -* round user-defined function: Round Function. -* rounding: Round Function. -* rounding numbers: Round Function. -* RS variable <1>: User-modified. -* RS variable: Records. -* RS variable, multiline records and: Multiple Line. -* rshift function (gawk): Bitwise Functions. -* RSTART variable: Auto-set. -* RSTART variable, match function and: String Functions. -* RT variable <1>: Auto-set. -* RT variable <2>: Multiple Line. -* RT variable: Records. -* Rubin, Paul <1>: Contributors. -* Rubin, Paul: History. -* rule, definition of: Getting Started. -* rvalues/lvalues: Assignment Ops. -* scalar values: Basic Data Typing. -* Schreiber, Bert: Acknowledgments. -* Schreiber, Rita: Acknowledgments. -* search paths <1>: VMS Running. -* search paths: PC Using. -* search paths, for source files <1>: VMS Running. -* search paths, for source files <2>: Igawk Program. -* search paths, for source files: AWKPATH Variable. -* searching: String Functions. -* searching, files for regular expressions: Egrep Program. -* searching, for words: Dupword Program. -* sed utility <1>: Glossary. -* sed utility <2>: Simple Sed. + (line 18729) +* Rommel, Kai Uwe <1>: Contributors. (line 17052) +* Rommel, Kai Uwe: Acknowledgments. (line 995) +* round user-defined function: Round Function. (line 12876) +* rounding: Round Function. (line 12866) +* rounding numbers: Round Function. (line 12866) +* RS variable <1>: User-modified. (line 7918) +* RS variable: Records. (line 2831) +* RS variable, multiline records and: Multiple Line. (line 3708) +* rshift function (gawk): Bitwise Functions. (line 10334) +* RSTART variable: Auto-set. (line 8122) +* RSTART variable, match function and: String Functions. (line 9256) +* RT variable <1>: Auto-set. (line 8129) +* RT variable <2>: Multiple Line. (line 3820) +* RT variable: Records. (line 2921) +* Rubin, Paul <1>: Contributors. (line 17026) +* Rubin, Paul: History. (line 653) +* rule, definition of: Getting Started. (line 1047) +* rvalues/lvalues: Assignment Ops. (line 6006) +* scalar values: Basic Data Typing. (line 19562) +* Schreiber, Bert: Acknowledgments. (line 977) +* Schreiber, Rita: Acknowledgments. (line 977) +* search paths <1>: VMS Running. (line 18070) +* search paths: PC Using. (line 17826) +* search paths, for source files <1>: VMS Running. (line 18070) +* search paths, for source files <2>: Igawk Program. (line 16567) +* search paths, for source files: AWKPATH Variable. (line 12327) +* searching: String Functions. (line 9210) +* searching, files for regular expressions: Egrep Program. (line 14491) +* searching, for words: Dupword Program. (line 15395) +* sed utility <1>: Glossary. (line 19753) +* sed utility <2>: Simple Sed. (line 16136) * sed utility: Field Splitting Summary. -* semicolon (;): Statements/Lines. -* semicolon (;), AWKPATH variable and: PC Using. + (line 3547) +* semicolon (;): Statements/Lines. (line 1853) +* semicolon (;), AWKPATH variable and: PC Using. (line 17826) * semicolon (;), separating statements in actions <1>: Statements. + (line 7220) * semicolon (;), separating statements in actions: Action Overview. -* separators, field: User-modified. + (line 7170) +* separators, field: User-modified. (line 7842) * separators, field, FIELDWIDTHS variable and: User-modified. -* separators, field, POSIX and: Fields. -* separators, for records: Records. -* separators, for records, regular expressions as: Records. -* separators, for statements in actions: Action Overview. -* separators, record: User-modified. -* separators, subscript: User-modified. -* set_value internal function: Internals. -* shells, piping commands into: Redirection. + (line 7832) +* separators, field, POSIX and: Fields. (line 3006) +* separators, for records: Records. (line 2825) +* separators, for records, regular expressions as: Records. (line 2921) +* separators, for statements in actions: Action Overview. (line 7170) +* separators, record: User-modified. (line 7918) +* separators, subscript: User-modified. (line 7931) +* set_value internal function: Internals. (line 18895) +* shells, piping commands into: Redirection. (line 4973) * shells, quoting: Using Shell Variables. -* shells, quoting, rules for: Quoting. -* shells, scripts: One-shot. + (line 7112) +* shells, quoting, rules for: Quoting. (line 1357) +* shells, scripts: One-shot. (line 1133) * shells, variables: Using Shell Variables. -* shift, bitwise: Bitwise Functions. -* short-circuit operators: Boolean Ops. -* side effects <1>: Increment Ops. -* side effects: Concatenation. + (line 7106) +* shift, bitwise: Bitwise Functions. (line 10320) +* short-circuit operators: Boolean Ops. (line 6506) +* side effects <1>: Increment Ops. (line 6157) +* side effects: Concatenation. (line 5935) * side effects, array indexing: Reference to Elements. -* side effects, asort function: Array Sorting. -* side effects, assignment expressions: Assignment Ops. -* side effects, Boolean operators: Boolean Ops. -* side effects, conditional expressions: Conditional Exp. + (line 8429) +* side effects, asort function: Array Sorting. (line 8886) +* side effects, assignment expressions: Assignment Ops. (line 5997) +* side effects, Boolean operators: Boolean Ops. (line 6479) +* side effects, conditional expressions: Conditional Exp. (line 6561) * side effects, decrement/increment operators: Increment Ops. -* side effects, FILENAME variable: Getline Notes. -* side effects, function calls: Function Calls. -* side effects, statements: Action Overview. -* signals, HUP/SIGHUP: Profiling. -* signals, INT/SIGINT (MS-DOS): Profiling. -* signals, QUIT/SIGQUIT (MS-DOS): Profiling. -* signals, USR1/SIGUSR1: Profiling. -* sin function: Numeric Functions. -* single quote (') <1>: Quoting. -* single quote (') <2>: Long. -* single quote ('): One-shot. -* single quote ('), vs. apostrophe: Comments. -* single quote ('), with double quotes: Quoting. + (line 6157) +* side effects, FILENAME variable: Getline Notes. (line 4190) +* side effects, function calls: Function Calls. (line 6627) +* side effects, statements: Action Overview. (line 7183) +* signals, HUP/SIGHUP: Profiling. (line 11928) +* signals, INT/SIGINT (MS-DOS): Profiling. (line 11931) +* signals, QUIT/SIGQUIT (MS-DOS): Profiling. (line 11931) +* signals, USR1/SIGUSR1: Profiling. (line 11906) +* sin function: Numeric Functions. (line 9068) +* single quote (') <1>: Quoting. (line 1370) +* single quote (') <2>: Long. (line 1223) +* single quote ('): One-shot. (line 1126) +* single quote ('), vs. apostrophe: Comments. (line 1317) +* single quote ('), with double quotes: Quoting. (line 1392) * single-character fields: Single Character Fields. -* single-precision floating-point: Basic Data Typing. -* Skywalker, Luke: Undocumented. -* sleep utility: Alarm Program. -* sockets: TCP/IP Networking. -* sort function, arrays, sorting: Array Sorting. -* sort utility: Word Sorting. -* sort utility, coprocesses and: Two-way I/O. + (line 3393) +* single-precision floating-point: Basic Data Typing. (line 19582) +* Skywalker, Luke: Undocumented. (line 12409) +* sleep utility: Alarm Program. (line 15538) +* sockets: TCP/IP Networking. (line 11667) +* sort function, arrays, sorting: Array Sorting. (line 8867) +* sort utility: Word Sorting. (line 15842) +* sort utility, coprocesses and: Two-way I/O. (line 11585) * sorting characters in different languages: Explaining gettext. -* source code, awka: Other Versions. -* source code, Bell Laboratories awk: Other Versions. -* source code, gawk: Gawk Distribution. -* source code, mawk: Other Versions. -* source code, mixing: Options. -* source files, search path for: Igawk Program. -* sparse arrays: Array Intro. -* Spencer, Henry: Glossary. -* split function: String Functions. -* split function, array elements, deleting: Delete. -* split utility: Split Program. -* split.awk program: Split Program. -* sprintf function <1>: String Functions. -* sprintf function: OFMT. -* sprintf function, OFMT variable and: User-modified. + (line 10984) +* source code, awka: Other Versions. (line 18421) +* source code, Bell Laboratories awk: Other Versions. (line 18358) +* source code, gawk: Gawk Distribution. (line 17134) +* source code, mawk: Other Versions. (line 18378) +* source code, mixing: Options. (line 12193) +* source files, search path for: Igawk Program. (line 16567) +* sparse arrays: Array Intro. (line 8369) +* Spencer, Henry: Glossary. (line 19753) +* split function: String Functions. (line 9327) +* split function, array elements, deleting: Delete. (line 8627) +* split utility: Split Program. (line 14828) +* split.awk program: Split Program. (line 14852) +* sprintf function <1>: String Functions. (line 9380) +* sprintf function: OFMT. (line 4435) +* sprintf function, OFMT variable and: User-modified. (line 7908) * sprintf function, print/printf statements and: Round Function. -* sqrt function: Numeric Functions. -* square brackets ([]): Regexp Operators. -* srand function: Numeric Functions. -* Stallman, Richard <1>: Glossary. -* Stallman, Richard <2>: Contributors. -* Stallman, Richard <3>: Acknowledgments. -* Stallman, Richard: Manual History. -* standard input <1>: Special FD. -* standard input: Read Terminal. -* standard output: Special FD. -* stat function, implementing in gawk: Sample Library. -* statements, compound, control statements and: Statements. -* statements, control, in actions: Statements. -* statements, multiple: Statements/Lines. -* stlen internal variable: Internals. -* stptr internal variable: Internals. -* stream editors <1>: Simple Sed. + (line 12866) +* sqrt function: Numeric Functions. (line 9055) +* square brackets ([]): Regexp Operators. (line 2230) +* srand function: Numeric Functions. (line 9117) +* Stallman, Richard <1>: Glossary. (line 20025) +* Stallman, Richard <2>: Contributors. (line 17034) +* Stallman, Richard <3>: Acknowledgments. (line 960) +* Stallman, Richard: Manual History. (line 865) +* standard input <1>: Special FD. (line 5011) +* standard input: Read Terminal. (line 1146) +* standard output: Special FD. (line 5011) +* stat function, implementing in gawk: Sample Library. (line 18963) +* statements, compound, control statements and: Statements. (line 7220) +* statements, control, in actions: Statements. (line 7216) +* statements, multiple: Statements/Lines. (line 1853) +* stlen internal variable: Internals. (line 18799) +* stptr internal variable: Internals. (line 18799) +* stream editors <1>: Simple Sed. (line 16136) * stream editors: Field Splitting Summary. -* strftime function (gawk): Time Functions. -* string constants: Scalar Constants. -* string constants, vs. regexp constants: Computed Regexps. + (line 3547) +* strftime function (gawk): Time Functions. (line 10014) +* string constants: Scalar Constants. (line 5426) +* string constants, vs. regexp constants: Computed Regexps. (line 2687) * string extraction (internationalization): String Extraction. -* string operators: Concatenation. -* string-matching operators: Regexp Usage. -* strings: Internals. -* strings, converting: Conversion. -* strings, converting, numbers to <1>: Bitwise Functions. -* strings, converting, numbers to: User-modified. -* strings, empty, See null strings: Records. -* strings, extracting: String Extraction. -* strings, for localization: Programmer i18n. -* strings, length of: Scalar Constants. -* strings, merging arrays into: Join Function. -* strings, NODE internal type: Internals. + (line 11157) +* string operators: Concatenation. (line 5903) +* string-matching operators: Regexp Usage. (line 1989) +* strings: Internals. (line 18826) +* strings, converting: Conversion. (line 5711) +* strings, converting, numbers to <1>: Bitwise Functions. (line 10387) +* strings, converting, numbers to: User-modified. (line 7825) +* strings, empty, See null strings: Records. (line 2912) +* strings, extracting: String Extraction. (line 11157) +* strings, for localization: Programmer i18n. (line 11039) +* strings, length of: Scalar Constants. (line 5431) +* strings, merging arrays into: Join Function. (line 13033) +* strings, NODE internal type: Internals. (line 18772) * strings, null: Regexp Field Splitting. + (line 3371) * strings, numeric: Typing and Comparison. -* strings, splitting: String Functions. -* strtonum function (gawk): String Functions. + (line 6273) +* strings, splitting: String Functions. (line 9341) +* strtonum function (gawk): String Functions. (line 9388) * strtonum function (gawk), --non-decimal-data option and: Nondecimal Data. -* sub function <1>: String Functions. + (line 11495) +* sub function <1>: String Functions. (line 9406) * sub function: Using Constant Regexps. -* sub function, arguments of: String Functions. -* sub function, escape processing: Gory Details. -* subscript separators: User-modified. + (line 5574) +* sub function, arguments of: String Functions. (line 9463) +* sub function, escape processing: Gory Details. (line 9622) +* subscript separators: User-modified. (line 7931) * subscripts in arrays, multidimensional: Multi-dimensional. + (line 8746) * subscripts in arrays, multidimensional, scanning: Multi-scanning. + (line 8832) * subscripts in arrays, numbers as: Numeric Array Subscripts. + (line 8648) * subscripts in arrays, uninitialized variables as: Uninitialized Subscripts. -* SUBSEP variable: User-modified. + (line 8699) +* SUBSEP variable: User-modified. (line 7931) * SUBSEP variable, multidimensional arrays: Multi-dimensional. -* substr function: String Functions. -* Sumner, Andrew: Other Versions. -* switch statement: Switch Statement. + (line 8752) +* substr function: String Functions. (line 9550) +* Sumner, Andrew: Other Versions. (line 18421) +* switch statement: Switch Statement. (line 7456) * syntactic ambiguity: /= operator vs. /=.../ regexp constant: Assignment Ops. -* system function: I/O Functions. -* systime function (gawk): Time Functions. + (line 6129) +* system function: I/O Functions. (line 9852) +* systime function (gawk): Time Functions. (line 9985) * tandem: Tandem Installation. -* Tcl: Library Names. -* TCP/IP: TCP/IP Networking. -* TCP/IP, support for: Special Network. -* tee utility: Tee Program. -* tee.awk program: Tee Program. -* terminating records: Records. -* testbits.awk program: Bitwise Functions. -* Texinfo <1>: Adding Code. + (line 18246) +* Tcl: Library Names. (line 12558) +* TCP/IP: TCP/IP Networking. (line 11643) +* TCP/IP, support for: Special Network. (line 5137) +* tee utility: Tee Program. (line 14930) +* tee.awk program: Tee Program. (line 14950) +* terminating records: Records. (line 2921) +* testbits.awk program: Bitwise Functions. (line 10348) +* Texinfo <1>: Adding Code. (line 18608) * Texinfo <2>: Distribution contents. -* Texinfo <3>: Extract Program. -* Texinfo <4>: Dupword Program. -* Texinfo <5>: Library Functions. -* Texinfo <6>: Sample Data Files. -* Texinfo: Conventions. -* Texinfo, chapter beginnings in files: Regexp Operators. + (line 17275) +* Texinfo <3>: Extract Program. (line 15951) +* Texinfo <4>: Dupword Program. (line 15406) +* Texinfo <5>: Library Functions. (line 12451) +* Texinfo <6>: Sample Data Files. (line 1521) +* Texinfo: Conventions. (line 819) +* Texinfo, chapter beginnings in files: Regexp Operators. (line 2197) * Texinfo, extracting programs from source files: Extract Program. -* text, printing: Print. -* text, printing, unduplicated lines of: Uniq Program. + (line 15945) +* text, printing: Print. (line 4292) +* text, printing, unduplicated lines of: Uniq Program. (line 15014) * textdomain function (C library): Explaining gettext. -* TEXTDOMAIN variable <1>: Programmer i18n. -* TEXTDOMAIN variable: User-modified. -* TEXTDOMAIN variable, BEGIN pattern and: Programmer i18n. -* TEXTDOMAIN variable, portability and: I18N Portability. + (line 10922) +* TEXTDOMAIN variable <1>: Programmer i18n. (line 11034) +* TEXTDOMAIN variable: User-modified. (line 7937) +* TEXTDOMAIN variable, BEGIN pattern and: Programmer i18n. (line 11083) +* TEXTDOMAIN variable, portability and: I18N Portability. (line 11274) * tilde (~), ~ operator <1>: Expression Patterns. -* tilde (~), ~ operator <2>: Precedence. + (line 6843) +* tilde (~), ~ operator <2>: Precedence. (line 6719) * tilde (~), ~ operator <3>: Typing and Comparison. -* tilde (~), ~ operator <4>: Regexp Constants. -* tilde (~), ~ operator <5>: Computed Regexps. -* tilde (~), ~ operator <6>: Case-sensitivity. -* tilde (~), ~ operator: Regexp Usage. -* time, alarm clock example program: Alarm Program. + (line 6334) +* tilde (~), ~ operator <4>: Regexp Constants. (line 5524) +* tilde (~), ~ operator <5>: Computed Regexps. (line 2656) +* tilde (~), ~ operator <6>: Case-sensitivity. (line 2569) +* tilde (~), ~ operator: Regexp Usage. (line 1989) +* time, alarm clock example program: Alarm Program. (line 15446) * time, localization and: Explaining gettext. + (line 11006) * time, managing: Gettimeofday Function. -* time, retrieving: Time Functions. -* timestamps: Time Functions. -* timestamps, converting dates to: Time Functions. + (line 13078) +* time, retrieving: Time Functions. (line 9978) +* timestamps: Time Functions. (line 9967) +* timestamps, converting dates to: Time Functions. (line 10030) * timestamps, formatted: Gettimeofday Function. -* tmp_number internal function: Internals. -* tmp_string internal function: Internals. -* tolower function: String Functions. -* toupper function: String Functions. -* tr utility: Translate Program. -* translate.awk program: Translate Program. -* troubleshooting, --non-decimal-data option: Options. -* troubleshooting, -F option: Known Bugs. + (line 13078) +* tmp_number internal function: Internals. (line 18841) +* tmp_string internal function: Internals. (line 18836) +* tolower function: String Functions. (line 9592) +* toupper function: String Functions. (line 9598) +* tr utility: Translate Program. (line 15567) +* translate.awk program: Translate Program. (line 15615) +* troubleshooting, --non-decimal-data option: Options. (line 12136) +* troubleshooting, -F option: Known Bugs. (line 12420) * troubleshooting, == operator: Typing and Comparison. -* troubleshooting, awk uses FS not IFS: Field Separators. + (line 6369) +* troubleshooting, awk uses FS not IFS: Field Separators. (line 3277) * troubleshooting, backslash before nonspecial character: Escape Sequences. -* troubleshooting, division: Arithmetic Ops. + (line 2145) +* troubleshooting, division: Arithmetic Ops. (line 5853) * troubleshooting, fatal errors, field widths, specifying: Constant Size. + (line 3610) * troubleshooting, fatal errors, printf format strings: Format Modifiers. -* troubleshooting, fflush function: I/O Functions. -* troubleshooting, function call syntax: Function Calls. + (line 4759) +* troubleshooting, fflush function: I/O Functions. (line 9840) +* troubleshooting, function call syntax: Function Calls. (line 6607) * troubleshooting, gawk <1>: Compatibility Mode. -* troubleshooting, gawk: Known Bugs. -* troubleshooting, gawk, bug reports: Bugs. + (line 18471) +* troubleshooting, gawk: Known Bugs. (line 12420) +* troubleshooting, gawk, bug reports: Bugs. (line 18285) * troubleshooting, gawk, fatal errors, function arguments: Calling Built-in. -* troubleshooting, getline function: File Checking. -* troubleshooting, gsub/sub functions: String Functions. -* troubleshooting, match function: String Functions. + (line 9009) +* troubleshooting, getline function: File Checking. (line 13318) +* troubleshooting, gsub/sub functions: String Functions. (line 9473) +* troubleshooting, match function: String Functions. (line 9322) * troubleshooting, print statement, omitting commas: Print Examples. -* troubleshooting, printing: Redirection. -* troubleshooting, quotes with file names: Special FD. -* troubleshooting, readable data files: File Checking. + (line 4330) +* troubleshooting, printing: Redirection. (line 4951) +* troubleshooting, quotes with file names: Special FD. (line 5068) +* troubleshooting, readable data files: File Checking. (line 13300) * troubleshooting, regexp constants vs. string constants: Computed Regexps. -* troubleshooting, string concatenation: Concatenation. -* troubleshooting, substr function: String Functions. -* troubleshooting, system function: I/O Functions. + (line 2687) +* troubleshooting, string concatenation: Concatenation. (line 5921) +* troubleshooting, substr function: String Functions. (line 9568) +* troubleshooting, system function: I/O Functions. (line 9876) * troubleshooting, typographical errors, global variables: Options. -* true, logical: Truth Values. -* Trueman, David <1>: Contributors. -* Trueman, David <2>: Acknowledgments. -* Trueman, David: History. -* trunc-mod operation: Arithmetic Ops. -* truth values: Truth Values. -* type conversion: Conversion. -* type internal variable: Internals. -* undefined functions: Function Caveats. + (line 12092) +* true, logical: Truth Values. (line 6238) +* Trueman, David <1>: Contributors. (line 17041) +* Trueman, David <2>: Acknowledgments. (line 986) +* Trueman, David: History. (line 653) +* trunc-mod operation: Arithmetic Ops. (line 5875) +* truth values: Truth Values. (line 6238) +* type conversion: Conversion. (line 5726) +* type internal variable: Internals. (line 18807) +* undefined functions: Function Caveats. (line 10720) * underscore (_), _ C macro: Explaining gettext. + (line 10963) * underscore (_), in names of private variables: Library Names. -* underscore (_), translatable string: Programmer i18n. -* undocumented features: Undocumented. + (line 12530) +* underscore (_), translatable string: Programmer i18n. (line 11092) +* undocumented features: Undocumented. (line 12409) * uninitialized variables, as array subscripts: Uninitialized Subscripts. -* uniq utility: Uniq Program. -* uniq.awk program: Uniq Program. -* Unix: Glossary. + (line 8699) +* uniq utility: Uniq Program. (line 15014) +* uniq.awk program: Uniq Program. (line 15073) +* Unix: Glossary. (line 20320) * Unix awk, backslashes in escape sequences: Escape Sequences. + (line 2157) * Unix awk, close function and: Close Files And Pipes. + (line 5315) * Unix awk, password files, field separators and: Command Line Field Separator. + (line 3485) * Unix, awk scripts and: Executable Scripts. -* unsigned integers: Basic Data Typing. -* update_ERRNO internal function: Internals. -* user database, reading: Passwd Functions. -* user-defined, functions: User-defined. -* user-defined, functions, counts: Profiling. -* user-defined, variables: Variables. -* user-modifiable variables: User-modified. -* users, information about, printing: Id Program. -* users, information about, retrieving: Passwd Functions. -* USR1 signal: Profiling. -* values, numeric: Basic Data Typing. -* values, string: Basic Data Typing. + (line 1233) +* unsigned integers: Basic Data Typing. (line 19577) +* update_ERRNO internal function: Internals. (line 18901) +* user database, reading: Passwd Functions. (line 13709) +* user-defined, functions: User-defined. (line 10452) +* user-defined, functions, counts: Profiling. (line 11853) +* user-defined, variables: Variables. (line 5613) +* user-modifiable variables: User-modified. (line 7805) +* users, information about, printing: Id Program. (line 14721) +* users, information about, retrieving: Passwd Functions. (line 13719) +* USR1 signal: Profiling. (line 11906) +* values, numeric: Basic Data Typing. (line 19562) +* values, string: Basic Data Typing. (line 19562) * variable typing: Typing and Comparison. -* variables <1>: Basic Data Typing. -* variables: Other Features. + (line 6269) +* variables <1>: Basic Data Typing. (line 19555) +* variables: Other Features. (line 1879) * variables, assigning on command line: Assignment Options. + (line 5663) * variables, built-in <1>: Built-in Variables. -* variables, built-in: Using Variables. -* variables, built-in, -v option, setting with: Options. -* variables, built-in, conveying information: Auto-set. -* variables, flag: Boolean Ops. + (line 7779) +* variables, built-in: Using Variables. (line 5642) +* variables, built-in, -v option, setting with: Options. (line 12029) +* variables, built-in, conveying information: Auto-set. (line 7959) +* variables, flag: Boolean Ops. (line 6516) * variables, getline command into, using <1>: Getline/Variable/Coprocess. + (line 4159) * variables, getline command into, using <2>: Getline/Variable/Pipe. + (line 4102) * variables, getline command into, using <3>: Getline/Variable/File. -* variables, getline command into, using: Getline/Variable. -* variables, global, for library functions: Library Names. -* variables, global, printing list of: Options. -* variables, initializing: Using Variables. -* variables, names of: Arrays. -* variables, private: Library Names. -* variables, setting: Options. -* variables, shadowing: Definition Syntax. -* variables, types of: Assignment Ops. + (line 4004) +* variables, getline command into, using: Getline/Variable. (line 3930) +* variables, global, for library functions: Library Names. (line 12512) +* variables, global, printing list of: Options. (line 12086) +* variables, initializing: Using Variables. (line 5642) +* variables, names of: Arrays. (line 8279) +* variables, private: Library Names. (line 12512) +* variables, setting: Options. (line 12021) +* variables, shadowing: Definition Syntax. (line 10522) +* variables, types of: Assignment Ops. (line 6014) * variables, types of, comparison expressions and: Typing and Comparison. + (line 6269) * variables, uninitialized, as array subscripts: Uninitialized Subscripts. -* variables, user-defined: Variables. -* vertical bar (|): Regexp Operators. -* vertical bar (|), | operator (I/O) <1>: Precedence. -* vertical bar (|), | operator (I/O): Getline/Pipe. -* vertical bar (|), |& I/O operator (I/O): Two-way I/O. -* vertical bar (|), |& operator (I/O) <1>: Precedence. -* vertical bar (|), |& operator (I/O): Getline/Coprocess. + (line 8699) +* variables, user-defined: Variables. (line 5613) +* vertical bar (|): Regexp Operators. (line 2243) +* vertical bar (|), | operator (I/O) <1>: Precedence. (line 6703) +* vertical bar (|), | operator (I/O): Getline/Pipe. (line 4043) +* vertical bar (|), |& I/O operator (I/O): Two-way I/O. (line 11545) +* vertical bar (|), |& operator (I/O) <1>: Precedence. (line 6703) +* vertical bar (|), |& operator (I/O): Getline/Coprocess. (line 4129) * vertical bar (|), |& operator (I/O), two-way communications: Portal Files. -* vertical bar (|), || operator <1>: Precedence. -* vertical bar (|), || operator: Boolean Ops. -* vname internal variable: Internals. -* w utility: Constant Size. -* Wall, Larry: Future Extensions. -* warnings, issuing: Options. -* wc utility: Wc Program. -* wc.awk program: Wc Program. -* Weinberger, Peter <1>: Contributors. -* Weinberger, Peter: History. -* while statement <1>: While Statement. -* while statement: Regexp Usage. -* whitespace, as field separators: Field Separators. -* whitespace, functions, calling: Calling Built-in. -* whitespace, newlines as: Options. -* Williams, Kent: Contributors. -* Woods, John: Contributors. + (line 11714) +* vertical bar (|), || operator <1>: Precedence. (line 6728) +* vertical bar (|), || operator: Boolean Ops. (line 6506) +* vname internal variable: Internals. (line 18811) +* w utility: Constant Size. (line 3610) +* Wall, Larry: Future Extensions. (line 19333) +* warnings, issuing: Options. (line 12116) +* wc utility: Wc Program. (line 15230) +* wc.awk program: Wc Program. (line 15269) +* Weinberger, Peter <1>: Contributors. (line 17022) +* Weinberger, Peter: History. (line 640) +* while statement <1>: While Statement. (line 7291) +* while statement: Regexp Usage. (line 1989) +* whitespace, as field separators: Field Separators. (line 3312) +* whitespace, functions, calling: Calling Built-in. (line 9003) +* whitespace, newlines as: Options. (line 12148) +* Williams, Kent: Contributors. (line 17047) +* Woods, John: Contributors. (line 17038) * word boundaries, matching: GNU Regexp Operators. + (line 2485) * word, regexp definition of: GNU Regexp Operators. + (line 2461) * word-boundary operator (gawk): GNU Regexp Operators. -* wordfreq.awk program: Word Sorting. -* words, counting: Wc Program. -* words, duplicate, searching for: Dupword Program. -* words, usage counts, generating: Word Sorting. -* xgettext utility: String Extraction. -* XOR bitwise operation: Bitwise Functions. -* xor function (gawk): Bitwise Functions. -* Zaretskii, Eli: Acknowledgments. + (line 2510) +* wordfreq.awk program: Word Sorting. (line 15848) +* words, counting: Wc Program. (line 15230) +* words, duplicate, searching for: Dupword Program. (line 15395) +* words, usage counts, generating: Word Sorting. (line 15794) +* xgettext utility: String Extraction. (line 11164) +* XOR bitwise operation: Bitwise Functions. (line 10294) +* xor function (gawk): Bitwise Functions. (line 10329) +* Zaretskii, Eli: Acknowledgments. (line 995) * zero, negative vs. positive: Floating Point Issues. -* zerofile.awk program: Empty Files. -* Zoulas, Christos: Contributors. -* {} (braces), actions and: Action Overview. -* {} (braces), pgawk program: Profiling. -* {} (braces), statements, grouping: Statements. -* | (vertical bar): Regexp Operators. -* | (vertical bar), | operator (I/O) <1>: Precedence. -* | (vertical bar), | operator (I/O) <2>: Redirection. -* | (vertical bar), | operator (I/O): Getline/Pipe. -* | (vertical bar), |& operator (I/O) <1>: Two-way I/O. -* | (vertical bar), |& operator (I/O) <2>: Precedence. -* | (vertical bar), |& operator (I/O) <3>: Redirection. -* | (vertical bar), |& operator (I/O): Getline/Coprocess. + (line 19714) +* zerofile.awk program: Empty Files. (line 13343) +* Zoulas, Christos: Contributors. (line 17071) +* {} (braces), actions and: Action Overview. (line 7170) +* {} (braces), pgawk program: Profiling. (line 11858) +* {} (braces), statements, grouping: Statements. (line 7220) +* | (vertical bar): Regexp Operators. (line 2243) +* | (vertical bar), | operator (I/O) <1>: Precedence. (line 6703) +* | (vertical bar), | operator (I/O) <2>: Redirection. (line 4891) +* | (vertical bar), | operator (I/O): Getline/Pipe. (line 4043) +* | (vertical bar), |& operator (I/O) <1>: Two-way I/O. (line 11545) +* | (vertical bar), |& operator (I/O) <2>: Precedence. (line 6703) +* | (vertical bar), |& operator (I/O) <3>: Redirection. (line 4936) +* | (vertical bar), |& operator (I/O): Getline/Coprocess. (line 4129) * | (vertical bar), |& operator (I/O), pipes, closing: Close Files And Pipes. + (line 5302) * | (vertical bar), |& operator (I/O), two-way communications: Portal Files. -* | (vertical bar), || operator <1>: Precedence. -* | (vertical bar), || operator: Boolean Ops. + (line 11714) +* | (vertical bar), || operator <1>: Precedence. (line 6728) +* | (vertical bar), || operator: Boolean Ops. (line 6506) * ~ (tilde), ~ operator <1>: Expression Patterns. -* ~ (tilde), ~ operator <2>: Precedence. + (line 6843) +* ~ (tilde), ~ operator <2>: Precedence. (line 6719) * ~ (tilde), ~ operator <3>: Typing and Comparison. -* ~ (tilde), ~ operator <4>: Regexp Constants. -* ~ (tilde), ~ operator <5>: Computed Regexps. -* ~ (tilde), ~ operator: Case-sensitivity. + (line 6334) +* ~ (tilde), ~ operator <4>: Regexp Constants. (line 5524) +* ~ (tilde), ~ operator <5>: Computed Regexps. (line 2656) +* ~ (tilde), ~ operator: Case-sensitivity. (line 2569) Tag Table: -Node: Top1322 -Node: Foreword26888 -Node: Preface31212 -Ref: Preface-Footnote-134094 -Node: History34326 -Node: Names36541 -Ref: Names-Footnote-138016 -Node: This Manual38088 -Ref: This Manual-Footnote-142846 -Node: Conventions42946 -Node: Manual History44823 -Ref: Manual History-Footnote-148271 -Ref: Manual History-Footnote-248312 -Node: How To Contribute48386 -Node: Acknowledgments48984 -Node: Getting Started52789 -Node: Running gawk55160 -Node: One-shot56341 -Node: Read Terminal57557 -Ref: Read Terminal-Footnote-159206 -Node: Long59377 -Node: Executable Scripts60744 -Ref: Executable Scripts-Footnote-162640 -Ref: Executable Scripts-Footnote-262791 -Node: Comments63242 -Node: Quoting65601 -Node: Sample Data Files69515 -Node: Very Simple72548 -Node: Two Rules77148 -Node: More Complex79290 -Ref: More Complex-Footnote-182204 -Ref: More Complex-Footnote-282652 -Node: Statements/Lines82735 -Ref: Statements/Lines-Footnote-187094 -Node: Other Features87359 -Node: When88206 -Node: Regexp90173 -Node: Regexp Usage91626 -Node: Escape Sequences93673 -Node: Regexp Operators99413 -Ref: Regexp Operators-Footnote-1106515 -Ref: Regexp Operators-Footnote-2106662 -Node: Character Lists106760 -Node: GNU Regexp Operators111229 -Node: Case-sensitivity114795 -Ref: Case-sensitivity-Footnote-1117813 -Node: Leftmost Longest118048 -Node: Computed Regexps119234 -Node: Locales122641 -Node: Reading Files124668 -Node: Records126424 -Ref: Records-Footnote-1134517 -Node: Fields134554 -Ref: Fields-Footnote-1137578 -Node: Nonconstant Fields137664 -Node: Changing Fields139860 -Node: Field Separators145136 -Node: Regexp Field Splitting148619 -Node: Single Character Fields151075 -Node: Command Line Field Separator152117 -Node: Field Splitting Summary155547 -Ref: Field Splitting Summary-Footnote-1158730 -Node: Constant Size158831 -Node: Multiple Line163306 -Ref: Multiple Line-Footnote-1169011 -Node: Getline169190 -Node: Plain Getline171253 -Node: Getline/Variable173267 -Node: Getline/File174399 -Node: Getline/Variable/File175714 -Node: Getline/Pipe177264 -Node: Getline/Variable/Pipe179317 -Node: Getline/Coprocess180415 -Node: Getline/Variable/Coprocess181646 -Node: Getline Notes182351 -Node: Getline Summary183985 -Node: Printing184692 -Node: Print186320 -Node: Print Examples187641 -Node: Output Separators190421 -Node: OFMT192177 -Node: Printf193527 -Node: Basic Printf194441 -Node: Control Letters195967 -Node: Format Modifiers198654 -Node: Printf Examples203656 -Node: Redirection206364 -Node: Special Files212947 -Node: Special FD213576 -Node: Special Process216593 -Node: Special Network218799 -Node: Special Caveats219632 -Ref: Special Caveats-Footnote-1220821 -Node: Close Files And Pipes221204 -Ref: Close Files And Pipes-Footnote-1228105 -Ref: Close Files And Pipes-Footnote-2228253 -Node: Expressions228401 -Node: Constants230589 -Node: Scalar Constants231265 -Ref: Scalar Constants-Footnote-1232111 -Node: Nondecimal-numbers232293 -Node: Regexp Constants235345 -Node: Using Constant Regexps235809 -Node: Variables238891 -Node: Using Variables239542 -Node: Assignment Options241043 -Node: Conversion242911 -Ref: Conversion-Footnote-1247679 -Node: Arithmetic Ops247788 -Node: Concatenation250285 -Node: Assignment Ops252980 -Node: Increment Ops259186 -Node: Truth Values262674 -Node: Typing and Comparison263719 -Ref: Typing and Comparison-Footnote-1270152 -Node: Boolean Ops270297 -Node: Conditional Exp274291 -Node: Function Calls276021 -Node: Precedence278914 -Node: Patterns and Actions282332 -Node: Pattern Overview283385 -Node: Regexp Patterns284814 -Node: Expression Patterns285348 -Node: Ranges288889 -Node: BEGIN/END291969 -Node: Using BEGIN/END292709 -Ref: Using BEGIN/END-Footnote-1295428 -Node: I/O And BEGIN/END295542 -Node: Empty297796 -Node: Using Shell Variables298095 -Node: Action Overview300371 -Node: Statements302723 -Node: If Statement304574 -Node: While Statement306064 -Node: Do Statement308087 -Node: For Statement309227 -Node: Switch Statement312358 -Node: Break Statement314216 -Node: Continue Statement316264 -Node: Next Statement318159 -Node: Nextfile Statement320430 -Node: Exit Statement323018 -Node: Built-in Variables325078 -Node: User-modified326168 -Ref: User-modified-Footnote-1333402 -Node: Auto-set333464 -Ref: Auto-set-Footnote-1341317 -Node: ARGC and ARGV341522 -Node: Arrays345226 -Node: Array Intro347133 -Node: Reference to Elements351326 -Node: Assigning Elements353188 -Node: Array Example353650 -Node: Scanning an Array355373 -Node: Delete357640 -Ref: Delete-Footnote-1360017 -Node: Numeric Array Subscripts360074 -Node: Uninitialized Subscripts362256 -Node: Multi-dimensional363857 -Node: Multi-scanning366870 -Node: Array Sorting368478 -Node: Functions371826 -Node: Built-in372560 -Node: Calling Built-in373525 -Node: Numeric Functions375483 -Ref: Numeric Functions-Footnote-1379226 -Ref: Numeric Functions-Footnote-2379552 -Node: String Functions379821 -Ref: String Functions-Footnote-1399010 -Ref: String Functions-Footnote-2399139 -Ref: String Functions-Footnote-3399386 -Node: Gory Details399473 -Ref: Gory Details-Footnote-1406035 -Ref: Gory Details-Footnote-2406086 -Node: I/O Functions406293 -Ref: I/O Functions-Footnote-1412864 -Node: Time Functions412955 -Ref: Time Functions-Footnote-1423681 -Ref: Time Functions-Footnote-2423749 -Ref: Time Functions-Footnote-3423907 -Ref: Time Functions-Footnote-4424018 -Ref: Time Functions-Footnote-5424143 -Ref: Time Functions-Footnote-6424370 -Node: Bitwise Functions424632 -Ref: Bitwise Functions-Footnote-1429291 -Node: I18N Functions429475 -Node: User-defined431187 -Node: Definition Syntax431963 -Node: Function Example436313 -Node: Function Caveats438894 -Node: Return Statement442751 -Node: Dynamic Typing445409 -Node: Internationalization446147 -Node: I18N and L10N447565 -Node: Explaining gettext448245 -Ref: Explaining gettext-Footnote-1453152 -Ref: Explaining gettext-Footnote-2453391 -Node: Programmer i18n453560 -Node: Translator i18n457778 -Node: String Extraction458563 -Ref: String Extraction-Footnote-1459504 -Node: Printf Ordering459630 -Ref: Printf Ordering-Footnote-1462373 -Node: I18N Portability462437 -Ref: I18N Portability-Footnote-1464875 -Node: I18N Example464938 -Ref: I18N Example-Footnote-1467550 -Node: Gawk I18N467622 -Node: Advanced Features468444 -Node: Nondecimal Data469837 -Node: Two-way I/O471389 -Ref: Two-way I/O-Footnote-1476885 -Node: TCP/IP Networking476962 -Node: Portal Files479381 -Node: Profiling480018 -Node: Invoking Gawk487644 -Node: Command Line488821 -Node: Options489599 -Ref: Options-Footnote-1500961 -Node: Other Arguments500986 -Node: AWKPATH Variable503660 -Ref: AWKPATH Variable-Footnote-1506394 -Node: Obsolete506654 -Node: Undocumented507647 -Node: Known Bugs507899 -Node: Library Functions508491 -Ref: Library Functions-Footnote-1511470 -Node: Library Names511641 -Ref: Library Names-Footnote-1515107 -Ref: Library Names-Footnote-2515326 -Node: General Functions515412 -Node: Nextfile Function516348 -Node: Assert Function520713 -Node: Round Function524016 -Node: Cliff Random Function525528 -Ref: Cliff Random Function-Footnote-1526511 -Node: Ordinal Functions526582 -Ref: Ordinal Functions-Footnote-1529656 -Node: Join Function529872 -Ref: Join Function-Footnote-1531621 -Node: Gettimeofday Function531821 -Node: Data File Management535543 -Node: Filetrans Function536168 -Node: Rewind Function539598 -Node: File Checking541048 -Node: Empty Files542089 -Node: Ignoring Assigns544318 -Node: Getopt Function545860 -Ref: Getopt Function-Footnote-1556912 -Node: Passwd Functions557113 -Ref: Passwd Functions-Footnote-1565797 -Node: Group Functions565885 -Node: Sample Programs573907 -Node: Running Examples574581 -Node: Clones575302 -Node: Cut Program576427 -Node: Egrep Program586158 -Ref: Egrep Program-Footnote-1593942 -Node: Id Program594052 -Node: Split Program597683 -Node: Tee Program601150 -Node: Uniq Program603821 -Node: Wc Program611238 -Ref: Wc Program-Footnote-1615491 -Node: Miscellaneous Programs615686 -Node: Dupword Program616675 -Node: Alarm Program618695 -Node: Translate Program623271 -Ref: Translate Program-Footnote-1627526 -Ref: Translate Program-Footnote-2627763 -Node: Labels Program627897 -Ref: Labels Program-Footnote-1631222 -Node: Word Sorting631306 -Node: History Sorting635593 -Node: Extract Program637425 -Node: Simple Sed644799 -Node: Igawk Program647863 -Ref: Igawk Program-Footnote-1662668 -Ref: Igawk Program-Footnote-2662869 -Node: Language History663007 -Node: V7/SVR3.1664374 -Node: SVR4666449 -Node: POSIX667883 -Node: BTL669388 -Node: POSIX/GNU670907 -Node: Contributors677998 -Node: Installation681436 -Node: Gawk Distribution682388 -Node: Getting682867 -Node: Extracting684087 -Node: Distribution contents685466 -Node: Unix Installation690677 -Node: Quick Installation691263 -Node: Additional Configuration Options692956 -Node: Configuration Philosophy694905 -Node: Non-Unix Installation697260 -Node: Amiga Installation697842 -Node: BeOS Installation698929 -Node: PC Installation700073 -Node: PC Binary Installation701294 -Node: PC Compiling703124 -Node: PC Dynamic707660 -Node: PC Using710008 -Node: Cygwin714608 -Ref: Cygwin-Footnote-1715583 -Node: VMS Installation715615 -Node: VMS Compilation716134 -Node: VMS Installation Details717698 -Node: VMS Running719315 -Node: VMS POSIX720899 -Node: Unsupported722163 -Node: Atari Installation722561 -Node: Atari Compiling723841 -Node: Atari Using725713 -Node: Tandem Installation728545 -Node: Bugs730216 -Node: Other Versions733501 -Ref: Other Versions-Footnote-1737100 -Node: Notes737142 -Node: Compatibility Mode737815 -Node: Additions738604 -Node: Adding Code739349 -Node: New Ports745372 -Node: Dynamic Extensions749424 -Node: Internals750440 -Node: Sample Library757218 -Node: Internal File Description757868 -Node: Internal File Ops761548 -Ref: Internal File Ops-Footnote-1766964 -Node: Using Internal File Ops767112 -Node: Future Extensions769133 -Node: Basic Concepts773214 -Node: Basic High Level773952 -Ref: Basic High Level-Footnote-1777979 -Node: Basic Data Typing778173 -Node: Floating Point Issues782605 -Ref: Floating Point Issues-Footnote-1786485 -Ref: Floating Point Issues-Footnote-2786538 -Node: Glossary786647 -Node: Copying810256 -Node: GNU Free Documentation License829453 -Node: Index851856 +Node: Top1314 +Node: Foreword26871 +Node: Preface31192 +Ref: Preface-Footnote-134053 +Node: History34282 +Node: Names36485 +Ref: Names-Footnote-137945 +Node: This Manual38014 +Ref: This Manual-Footnote-142699 +Node: Conventions42796 +Node: Manual History44658 +Ref: Manual History-Footnote-148078 +Ref: Manual History-Footnote-248116 +Node: How To Contribute48187 +Node: Acknowledgments48785 +Node: Getting Started52552 +Node: Running gawk54916 +Node: One-shot56096 +Node: Read Terminal57312 +Ref: Read Terminal-Footnote-158958 +Node: Long59126 +Node: Executable Scripts60496 +Ref: Executable Scripts-Footnote-162380 +Ref: Executable Scripts-Footnote-262528 +Node: Comments62976 +Node: Quoting65329 +Node: Sample Data Files69809 +Node: Very Simple72829 +Node: Two Rules77419 +Node: More Complex79557 +Ref: More Complex-Footnote-182461 +Ref: More Complex-Footnote-282906 +Node: Statements/Lines82986 +Ref: Statements/Lines-Footnote-187344 +Node: Other Features87606 +Node: When88452 +Ref: When-Footnote-190678 +Node: Regexp90756 +Node: Regexp Usage92207 +Node: Escape Sequences94244 +Node: Regexp Operators99960 +Ref: Regexp Operators-Footnote-1107049 +Ref: Regexp Operators-Footnote-2107193 +Node: Character Lists107288 +Ref: table-char-classes109232 +Node: GNU Regexp Operators112756 +Node: Case-sensitivity116327 +Ref: Case-sensitivity-Footnote-1119477 +Node: Leftmost Longest119709 +Node: Computed Regexps120891 +Node: Locales124254 +Node: Reading Files126274 +Node: Records128025 +Ref: Records-Footnote-1136064 +Node: Fields136098 +Ref: Fields-Footnote-1139110 +Node: Nonconstant Fields139193 +Node: Changing Fields141385 +Node: Field Separators146631 +Node: Regexp Field Splitting150100 +Node: Single Character Fields152556 +Node: Command Line Field Separator153605 +Node: Field Splitting Summary157022 +Ref: Field Splitting Summary-Footnote-1160200 +Node: Constant Size160298 +Node: Multiple Line164754 +Ref: Multiple Line-Footnote-1170417 +Node: Getline170593 +Node: Plain Getline172652 +Node: Getline/Variable174694 +Node: Getline/File175832 +Node: Getline/Variable/File177150 +Node: Getline/Pipe178697 +Node: Getline/Variable/Pipe180753 +Node: Getline/Coprocess181854 +Node: Getline/Variable/Coprocess183085 +Node: Getline Notes183793 +Node: Getline Summary185436 +Ref: table-getline-variants185720 +Node: Printing186885 +Node: Print188514 +Node: Print Examples189834 +Node: Output Separators192614 +Node: OFMT194366 +Node: Printf195718 +Node: Basic Printf196637 +Node: Control Letters198164 +Node: Format Modifiers201384 +Node: Printf Examples207419 +Node: Redirection210118 +Node: Special Files216680 +Node: Special FD217314 +Node: Special Process220328 +Node: Special Network222560 +Node: Special Caveats223399 +Ref: Special Caveats-Footnote-1224594 +Node: Close Files And Pipes224974 +Ref: Close Files And Pipes-Footnote-1231835 +Ref: Close Files And Pipes-Footnote-2231980 +Node: Expressions232125 +Node: Constants234311 +Node: Scalar Constants234989 +Ref: Scalar Constants-Footnote-1235838 +Node: Nondecimal-numbers236017 +Node: Regexp Constants239059 +Node: Using Constant Regexps239532 +Node: Variables242609 +Node: Using Variables243265 +Node: Assignment Options244766 +Node: Conversion246640 +Ref: Conversion-Footnote-1251389 +Node: Arithmetic Ops251495 +Node: Concatenation253990 +Node: Assignment Ops256674 +Ref: table-assign-ops261623 +Node: Increment Ops263527 +Node: Truth Values267002 +Node: Typing and Comparison268049 +Ref: table-relational-ops271096 +Ref: Typing and Comparison-Footnote-1275337 +Node: Boolean Ops275479 +Node: Conditional Exp279485 +Node: Function Calls281216 +Node: Precedence284099 +Node: Patterns and Actions287520 +Node: Pattern Overview288571 +Node: Regexp Patterns290005 +Node: Expression Patterns290548 +Node: Ranges294080 +Node: BEGIN/END297154 +Node: Using BEGIN/END297904 +Ref: Using BEGIN/END-Footnote-1300622 +Node: I/O And BEGIN/END300733 +Node: Empty302990 +Node: Using Shell Variables303298 +Node: Action Overview305569 +Node: Statements307921 +Node: If Statement309774 +Node: While Statement311270 +Node: Do Statement313299 +Node: For Statement314445 +Node: Switch Statement317561 +Node: Break Statement319802 +Node: Continue Statement321850 +Node: Next Statement323748 +Node: Nextfile Statement326016 +Node: Exit Statement328592 +Node: Built-in Variables330647 +Node: User-modified331739 +Ref: User-modified-Footnote-1338979 +Node: Auto-set339038 +Ref: Auto-set-Footnote-1347375 +Node: ARGC and ARGV347577 +Node: Arrays351271 +Node: Array Intro353173 +Node: Reference to Elements357347 +Node: Assigning Elements359202 +Node: Array Example359669 +Node: Scanning an Array361385 +Node: Delete363646 +Ref: Delete-Footnote-1365998 +Node: Numeric Array Subscripts366052 +Node: Uninitialized Subscripts368230 +Node: Multi-dimensional369821 +Node: Multi-scanning372817 +Node: Array Sorting374426 +Node: Functions378063 +Node: Built-in378795 +Node: Calling Built-in379765 +Node: Numeric Functions381720 +Ref: Numeric Functions-Footnote-1385459 +Ref: Numeric Functions-Footnote-2385782 +Node: String Functions386048 +Ref: String Functions-Footnote-1405281 +Ref: String Functions-Footnote-2405407 +Ref: String Functions-Footnote-3405651 +Node: Gory Details405735 +Ref: table-sub-escapes407361 +Ref: table-sub-posix-92408696 +Ref: table-sub-proposed410035 +Ref: table-posix-2001-sub411388 +Ref: table-gensub-escapes412725 +Ref: Gory Details-Footnote-1413908 +Node: I/O Functions413956 +Ref: I/O Functions-Footnote-1420518 +Node: Time Functions420606 +Ref: Time Functions-Footnote-1431290 +Ref: Time Functions-Footnote-2431355 +Ref: Time Functions-Footnote-3431510 +Ref: Time Functions-Footnote-4431618 +Ref: Time Functions-Footnote-5431740 +Ref: Time Functions-Footnote-6431964 +Node: Bitwise Functions432223 +Ref: table-bitwise-ops432798 +Ref: Bitwise Functions-Footnote-1437020 +Node: I18N Functions437201 +Node: User-defined438924 +Node: Definition Syntax439705 +Node: Function Example444031 +Node: Function Caveats446596 +Node: Return Statement450500 +Node: Dynamic Typing453139 +Node: Internationalization453873 +Node: I18N and L10N455289 +Node: Explaining gettext455973 +Ref: Explaining gettext-Footnote-1460861 +Ref: Explaining gettext-Footnote-2461097 +Node: Programmer i18n461263 +Node: Translator i18n465480 +Node: String Extraction466267 +Ref: String Extraction-Footnote-1467211 +Node: Printf Ordering467334 +Ref: Printf Ordering-Footnote-1470086 +Node: I18N Portability470147 +Ref: I18N Portability-Footnote-1472571 +Node: I18N Example472631 +Ref: I18N Example-Footnote-1475223 +Node: Gawk I18N475292 +Node: Advanced Features476113 +Node: Nondecimal Data477507 +Node: Two-way I/O479057 +Ref: Two-way I/O-Footnote-1484506 +Node: TCP/IP Networking484580 +Node: Portal Files486991 +Node: Profiling487632 +Node: Invoking Gawk495148 +Node: Command Line496325 +Node: Options497104 +Ref: Options-Footnote-1508439 +Node: Other Arguments508461 +Node: AWKPATH Variable511121 +Ref: AWKPATH Variable-Footnote-1513878 +Node: Obsolete514135 +Node: Undocumented515129 +Node: Known Bugs515388 +Node: Library Functions515990 +Ref: Library Functions-Footnote-1518944 +Node: Library Names519112 +Ref: Library Names-Footnote-1522559 +Ref: Library Names-Footnote-2522775 +Node: General Functions522858 +Node: Nextfile Function523917 +Node: Strtonum Function528256 +Node: Assert Function531178 +Node: Round Function534464 +Node: Cliff Random Function535971 +Ref: Cliff Random Function-Footnote-1536954 +Node: Ordinal Functions537022 +Ref: Ordinal Functions-Footnote-1540070 +Node: Join Function540283 +Ref: Join Function-Footnote-1542034 +Node: Gettimeofday Function542231 +Node: Data File Management545928 +Node: Filetrans Function546560 +Node: Rewind Function549968 +Node: File Checking551405 +Node: Empty Files552453 +Node: Ignoring Assigns554660 +Node: Getopt Function556196 +Ref: Getopt Function-Footnote-1567160 +Node: Passwd Functions567358 +Ref: Passwd Functions-Footnote-1575966 +Node: Group Functions576051 +Node: Sample Programs583990 +Node: Running Examples584664 +Node: Clones585386 +Node: Cut Program586512 +Node: Egrep Program596185 +Ref: Egrep Program-Footnote-1603887 +Node: Id Program603994 +Node: Split Program607584 +Node: Tee Program611032 +Node: Uniq Program613694 +Node: Wc Program621032 +Ref: Wc Program-Footnote-1625246 +Node: Miscellaneous Programs625439 +Node: Dupword Program626435 +Node: Alarm Program628457 +Node: Translate Program632982 +Ref: Translate Program-Footnote-1637201 +Ref: Translate Program-Footnote-2637435 +Node: Labels Program637566 +Ref: Labels Program-Footnote-1640839 +Node: Word Sorting640920 +Node: History Sorting645183 +Node: Extract Program647009 +Node: Simple Sed654330 +Node: Igawk Program657364 +Ref: Igawk Program-Footnote-1671993 +Ref: Igawk Program-Footnote-2672191 +Node: Language History672326 +Node: V7/SVR3.1673710 +Node: SVR4675790 +Node: POSIX677229 +Node: BTL678736 +Node: POSIX/GNU680258 +Node: Contributors687406 +Node: Installation690849 +Node: Gawk Distribution691820 +Node: Getting692304 +Node: Extracting693530 +Node: Distribution contents694912 +Node: Unix Installation700132 +Node: Quick Installation700723 +Node: Additional Configuration Options702414 +Node: Configuration Philosophy704372 +Node: Non-Unix Installation706720 +Node: Amiga Installation707307 +Node: BeOS Installation708394 +Node: PC Installation709535 +Node: PC Binary Installation710762 +Node: PC Compiling712593 +Node: PC Dynamic717232 +Node: PC Using719578 +Node: Cygwin724172 +Ref: Cygwin-Footnote-1725164 +Node: VMS Installation725193 +Node: VMS Compilation725721 +Node: VMS Installation Details727292 +Node: VMS Running728916 +Node: VMS POSIX730505 +Node: Unsupported731776 +Node: Atari Installation732179 +Node: Atari Compiling733462 +Node: Atari Using735334 +Node: Tandem Installation738167 +Node: Bugs739832 +Node: Other Versions743095 +Ref: Other Versions-Footnote-1746696 +Node: Notes746735 +Node: Compatibility Mode747427 +Node: Additions748215 +Node: Adding Code748962 +Node: New Ports755009 +Node: Dynamic Extensions759064 +Node: Internals760080 +Node: Sample Library768299 +Node: Internal File Description768958 +Node: Internal File Ops772639 +Ref: Internal File Ops-Footnote-1777929 +Node: Using Internal File Ops778074 +Node: Future Extensions780091 +Node: Basic Concepts784355 +Node: Basic High Level785112 +Ref: Basic High Level-Footnote-1789123 +Node: Basic Data Typing789314 +Node: Floating Point Issues793716 +Ref: Floating Point Issues-Footnote-1797569 +Ref: Floating Point Issues-Footnote-2797619 +Node: Glossary797725 +Node: Copying821334 +Node: GNU Free Documentation License840460 +Node: Index862846 End Tag Table |