Use BRE by default, with optional ERE.

1 files changed, 33 insertions, 4 deletions

diff --git a/pw.1 b/pw.1
index c651588..afaaa62 100644
--- a/pw.1
+++ b/pw.1
@@ -30,7 +30,7 @@
 pw \- Pipe Watch: monitor recent lines of output from pipe
 
 .SH SYNOPSIS
-command | pw [-i interval] [-l interval] [-n number-of-lines] [-d]
+command | pw [-i interval] [-l interval] [-n number-of-lines] [-dEB]
 
 .SH DESCRIPTION
 .I pw
@@ -210,7 +210,8 @@ the top of the display.  In tail trigger mode, the status string
 appears, showing the pattern preceded by a question mark.
 The
 .I pattern
-is an extended regular expression (ERE).
+is interpreted as either an extended regular expression (ERE)
+or (BRE) depending on the current setting.
 Trigger patterns saved in a history which may be navigated for
 recall using the up and down arrow keys or
 .B Ctrl-P
@@ -271,7 +272,7 @@ pattern onto the grep stack. The
 command pushes a plain pattern; the
 .B :v
 command pushes a logically inverted pattern. The grep stack holds up to 64
-patterns, which are extended regular expressions (EREs).
+patterns.
 If the pattern is successfully pushed onto the stack, it
 restricts which lines are admitted into the FIFO and available for display.
 The plain pattern admits only the lines which match
@@ -318,7 +319,18 @@ command option for the argument format and the
 option for the semantics.
 .PP
 
-Any other command results in a brief error message.
+.IP "\fB:E\fP, \fB:B\fP"
+Enable extended regular expressions (EREs) or basic regular expressions (BREs),
+respectively. If no
+.B -E
+option is given to the program, then BRE mode is in effect on start up.
+This setting does not affect the meaning of patterns that are currently in
+effect in the grep stack or in the trigger.  The setting affects new patterns
+that will subsequently be presented to the program.  Note that the currently
+active patterns shown in the status line are not accompanied by any indication
+of whether they were compiled as ERE or BRE.
+
+Any other command string results in a brief error message.
 
 .SH OPTIONS
 
@@ -369,6 +381,23 @@ and staying in the interactive mode. This is useful when the last portion
 of the input is of interest, and contains long lines that require
 horizontal scrolling.
 
+.IP \fB-E\fP
+Enable extended regular expressions (EREs). By default, regular expressions
+processed by
+.I pw
+are treated as basic regular expressions (BREs). The mode can be switched
+at run time using the
+.B :E
+and
+.B :B
+commands.
+
+.IP \fB-B\fP
+Disable extended regular expressions (EREs), switching to basic (BREs). Since
+that is the default, this option has no effect unless it appears after a
+.B -E
+option.
+
 .SH TERMINATION STATUS
 
 If