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-rw-r--r--doc/ChangeLog4
-rw-r--r--doc/gawkinet.info124
-rw-r--r--doc/gawkinet.texi45
3 files changed, 109 insertions, 64 deletions
diff --git a/doc/ChangeLog b/doc/ChangeLog
index 6cb20896..b0a1de9c 100644
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,3 +1,7 @@
+2020-12-26 Juergen Kahrs <Juergen.Kahrs@googlemail.com>
+
+ * gawkinet.texi: Update datetime client.
+
2020-12-26 Arnold D. Robbins <arnold@skeeve.com>
* gawktexi.in (More CSV): Add indexing and reference to
diff --git a/doc/gawkinet.info b/doc/gawkinet.info
index 71724910..16313b60 100644
--- a/doc/gawkinet.info
+++ b/doc/gawkinet.info
@@ -700,22 +700,26 @@ File: gawkinet.info, Node: TCP Connecting, Next: Troubleshooting, Prev: Gawk
Let's observe a network connection at work. Type in the following
program and watch the output. Within a second, it connects via TCP
-('/inet/tcp') to the machine it is running on ('localhost') and asks the
-service 'daytime' on the machine what time it is:
+('/inet/tcp') to a remote server and asks the service 'daytime' on the
+machine what time it is:
BEGIN {
- "/inet/tcp/0/localhost/daytime" |& getline
+ daytime_server = "time-a-g.nist.gov"
+ daytime_connection = "/inet/tcp/0/" daytime_server "/daytime"
+ daytime_connection |& getline
print $0
- close("/inet/tcp/0/localhost/daytime")
+ daytime_connection |& getline
+ print $0
+ close(daytime_connection)
}
- Even experienced 'awk' users will find the second line strange in two
-respects:
+ Even experienced 'awk' users will find the fourth and sixth line
+strange in two respects:
- * A special file is used as a shell command that pipes its output
- into 'getline'. One would rather expect to see the special file
- being read like any other file ('getline <
- "/inet/tcp/0/localhost/daytime"').
+ * A string containg the name of a special file is used as a shell
+ command that pipes its output into 'getline'. One would rather
+ expect to see the special file being read like any other file
+ ('getline < "/inet/tcp/0/time-a-g.nist.gov/daytime"').
* The operator '|&' has not been part of any 'awk' implementation
(until now). It is actually the only extension of the 'awk'
@@ -738,12 +742,26 @@ operator except for two additions:
written to, just like a full-duplex network connection.
In the earlier example, the '|&' operator tells 'getline' to read a
-line from the special file '/inet/tcp/0/localhost/daytime'. We could
-also have printed a line into the special file. But instead we just
-read a line with the time, printed it, and closed the connection.
-(While we could just let 'gawk' close the connection by finishing the
-program, in this Info file we are pedantic and always explicitly close
-the connections.)
+line from the special file '/inet/tcp/0/time-a-g.nist.gov/daytime'. We
+could also have printed a line into the special file. But instead we
+just consumed an empty leading line, printed it, then read a line with
+the time, printed that, and closed the connection. (While we could just
+let 'gawk' close the connection by finishing the program, in this Info
+file we are pedantic and always explicitly close the connections.)
+
+ Network services like 'daytime' are not really useful because there
+are so many better ways to print the current time. In the early days of
+TCP networking, such a service may have looked like a good idea for
+testing purposes. Later, simple TCP services like these have been used
+to teach TCP/IP networking and therefore you can still find much
+educational material of good quality on the Internet about such outdated
+services. The list of servers (https://tf.nist.gov/tf-cgi/servers.cgi)
+that still support the legacy service daytime
+(https://en.wikipedia.org/wiki/Daytime_Protocol) can be found at
+Wikipedia. We hesitated to use this service in this manual because it
+is hard to find servers that still support services like 'daytime'
+openly to the Internet. Later on we will see that some of these
+nostalgic protocols have turned into security risks.

File: gawkinet.info, Node: Troubleshooting, Next: Interacting, Prev: TCP Connecting, Up: Using Networking
@@ -4179,7 +4197,7 @@ Index
* /inet/ files (gawk): Gawk Special Files. (line 34)
* /inet/tcp special files (gawk): File /inet/tcp. (line 6)
* /inet/udp special files (gawk): File /inet/udp. (line 6)
-* | (vertical bar), |& operator (I/O): TCP Connecting. (line 25)
+* | (vertical bar), |& operator (I/O): TCP Connecting. (line 29)
* advanced features, network connections: Troubleshooting. (line 6)
* agent: Challenges. (line 75)
* agent <1>: MOBAGWHO. (line 6)
@@ -4283,7 +4301,7 @@ Index
* Perl: Using Networking. (line 14)
* Perl, gawk networking and: Using Networking. (line 24)
* Perlis, Alan: MAZE. (line 6)
-* pipes, networking and: TCP Connecting. (line 30)
+* pipes, networking and: TCP Connecting. (line 34)
* PNG image format: Web page. (line 45)
* PNG image format <1>: STATIST. (line 6)
* POP (Post Office Protocol): Email. (line 6)
@@ -4342,7 +4360,7 @@ Index
* UDP (User Datagram Protocol), TCP and: Interacting. (line 48)
* Unix, network ports and: Setting Up. (line 37)
* URLCHK program: URLCHK. (line 6)
-* vertical bar (|), |& operator (I/O): TCP Connecting. (line 25)
+* vertical bar (|), |& operator (I/O): TCP Connecting. (line 29)
* VRML: MAZE. (line 6)
* web pages: Web page. (line 6)
* web pages, images in: Interacting Service. (line 190)
@@ -4381,40 +4399,40 @@ Node: File /inet/tcp26947
Node: File /inet/udp27933
Ref: File /inet/udp-Footnote-129645
Node: TCP Connecting29899
-Node: Troubleshooting32245
-Ref: Troubleshooting-Footnote-135073
-Node: Interacting36030
-Node: Setting Up38754
-Node: Email42726
-Node: Web page45109
-Ref: Web page-Footnote-147929
-Ref: Web page-Footnote-248127
-Node: Primitive Service48621
-Node: Interacting Service51355
-Ref: Interacting Service-Footnote-160510
-Node: CGI Lib60542
-Node: Simple Server67542
-Ref: Simple Server-Footnote-175344
-Node: Caveats75445
-Node: Challenges76588
-Ref: Challenges-Footnote-185330
-Node: Some Applications and Techniques85431
-Node: PANIC87892
-Node: GETURL89618
-Node: REMCONF92251
-Node: URLCHK97747
-Node: WEBGRAB101591
-Node: STATIST106055
-Ref: STATIST-Footnote-1119203
-Node: MAZE119646
-Node: MOBAGWHO125871
-Ref: MOBAGWHO-Footnote-1139773
-Node: STOXPRED139841
-Node: PROTBASE154133
-Ref: PROTBASE-Footnote-1167300
-Node: Links167415
-Node: GNU Free Documentation License170306
-Node: Index195426
+Node: Troubleshooting33332
+Ref: Troubleshooting-Footnote-136160
+Node: Interacting37117
+Node: Setting Up39841
+Node: Email43813
+Node: Web page46196
+Ref: Web page-Footnote-149016
+Ref: Web page-Footnote-249214
+Node: Primitive Service49708
+Node: Interacting Service52442
+Ref: Interacting Service-Footnote-161597
+Node: CGI Lib61629
+Node: Simple Server68629
+Ref: Simple Server-Footnote-176431
+Node: Caveats76532
+Node: Challenges77675
+Ref: Challenges-Footnote-186417
+Node: Some Applications and Techniques86518
+Node: PANIC88979
+Node: GETURL90705
+Node: REMCONF93338
+Node: URLCHK98834
+Node: WEBGRAB102678
+Node: STATIST107142
+Ref: STATIST-Footnote-1120290
+Node: MAZE120733
+Node: MOBAGWHO126958
+Ref: MOBAGWHO-Footnote-1140860
+Node: STOXPRED140928
+Node: PROTBASE155220
+Ref: PROTBASE-Footnote-1168387
+Node: Links168502
+Node: GNU Free Documentation License171393
+Node: Index196513

End Tag Table
diff --git a/doc/gawkinet.texi b/doc/gawkinet.texi
index a2454e31..e6482832 100644
--- a/doc/gawkinet.texi
+++ b/doc/gawkinet.texi
@@ -234,6 +234,8 @@ Arnold Robbins @*
Nof Ayalon, ISRAEL @*
March, 2001
+@c system if test ! -d eg ; then mkdir eg ; fi
+@c system if test ! -d eg/network ; then mkdir eg/network ; fi
@node Introduction, Using Networking, Preface, Top
@chapter Networking Concepts
@@ -867,27 +869,33 @@ the original versions of NFS.
@cindex @command{gawk} @subentry networking @subentry connections
Let's observe a network connection at work. Type in the following program
and watch the output. Within a second, it connects via TCP (@file{/inet/tcp})
-to the machine it is running on (@samp{localhost}) and asks the service
+to a remote server and asks the service
@samp{daytime} on the machine what time it is:
@cindex @code{getline} command
@example
+@c file eg/network/daytimeclient.awk
BEGIN @{
- "/inet/tcp/0/localhost/daytime" |& getline
+ daytime_server = "time-a-g.nist.gov"
+ daytime_connection = "/inet/tcp/0/" daytime_server "/daytime"
+ daytime_connection |& getline
print $0
- close("/inet/tcp/0/localhost/daytime")
+ daytime_connection |& getline
+ print $0
+ close(daytime_connection)
@}
+@c endfile
@end example
-Even experienced @command{awk} users will find the second line strange in two
-respects:
+Even experienced @command{awk} users will find the fourth and sixth line
+strange in two respects:
@itemize @bullet
@item
-A special file is used as a shell command that pipes its output
+A string containg the name of a special file is used as a shell command that pipes its output
into @code{getline}. One would rather expect to see the special file
being read like any other file (@samp{getline <
-"/inet/tcp/0/localhost/daytime"}).
+"/inet/tcp/0/time-a-g.nist.gov/daytime"}).
@item
@cindex @code{|} (vertical bar), @code{|&} operator (I/O)
@@ -919,13 +927,30 @@ like a full-duplex network connection.
@end itemize
In the earlier example, the @samp{|&} operator tells @code{getline}
-to read a line from the special file @file{/inet/tcp/0/localhost/daytime}.
+to read a line from the special file @file{/inet/tcp/0/time-a-g.nist.gov/daytime}.
We could also have printed a line into the special file. But instead we just
-read a line with the time, printed it, and closed the connection.
+consumed an empty leading line, printed it, then read a line with the time,
+printed that, and closed the connection.
(While we could just let @command{gawk} close the connection by finishing
the program, in this @value{DOCUMENT}
we are pedantic and always explicitly close the connections.)
+Network services like @file{daytime} are not really useful because
+there are so many better ways to print the current time.
+In the early days of TCP networking, such a service may have looked
+like a good idea for testing purposes. Later, simple TCP services
+like these have been used to teach TCP/IP networking and therefore
+you can still find much educational material of good quality on the
+Internet about such outdated services. The
+@uref{https://tf.nist.gov/tf-cgi/servers.cgi, list of servers}
+that still support the legacy service
+@uref{https://en.wikipedia.org/wiki/Daytime_Protocol, daytime}
+can be found at Wikipedia. We hesitated to use this service in
+this manual because it is hard to find servers that still support
+services like @file{daytime} openly to the Internet.
+Later on we will see that some of these nostalgic
+protocols have turned into security risks.
+
@node Troubleshooting, Interacting, TCP Connecting, Using Networking
@section Troubleshooting Connection Problems
@cindex advanced features, network connections
@@ -1028,8 +1053,6 @@ so-called @command{finger} service if a user of the machine is logged in. When
testing this program, try to change @samp{localhost} to
some other machine name in your local network:
-@c system if test ! -d eg ; then mkdir eg ; fi
-@c system if test ! -d eg/network ; then mkdir eg/network ; fi
@example
@c file eg/network/fingerclient.awk
BEGIN @{
generated by cgit v1.2.3 (git 2.25.1) at 2025-04-23 19:23:20 +0000