From abee382683d1b977f2ab4a91121b4277045e6d5a Mon Sep 17 00:00:00 2001
From: Eric Blake <ebb9@byu.net>
Date: Tue, 17 Mar 2009 19:33:08 -0600
Subject: [PATCH] Manual: mention more expr pitfalls.

* doc/autoconf.texi (Limitations of Usual Tools) <expr (:)>:
Mention HP-UX limitation, and $ ambiguity.
* THANKS: Update.
Reported by Jens Schmidt, in http://bugs.debian.org/466990.

Signed-off-by: Eric Blake <ebb9@byu.net>
---
 ChangeLog         |  8 ++++++++
 THANKS            |  1 +
 doc/autoconf.texi | 23 +++++++++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index 259004ef..3829924f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2009-03-18  Eric Blake  <ebb9@byu.net>
+
+	Manual: mention more expr pitfalls.
+	* doc/autoconf.texi (Limitations of Usual Tools) <expr (:)>:
+	Mention HP-UX limitation, and $ ambiguity.
+	* THANKS: Update.
+	Reported by Jens Schmidt, in http://bugs.debian.org/466990.
+
 2009-03-17  Jim Meyering  <meyering@redhat.com>
 
 	Manual: fix a typo.
diff --git a/THANKS b/THANKS
index c3e19a20..8d8bb37a 100644
--- a/THANKS
+++ b/THANKS
@@ -164,6 +164,7 @@ Jeffrey A Law               law@cygnus.com
 Jeffrey J. Barteet          ?
 Jennis Pruett               ?
 Jens Petersen               petersen@redhat.com
+Jens Schmidt                jens.schmidt35@arcor.de
 Jeremy Yallop               jeremy@yallop.org
 Jerker Bäck                 jerker.back@home.se
 Jim Blandy                  jimb@wookumz.gnu.ai.mit.edu
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index a0a19b8b..a4cb0d15 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -16642,6 +16642,21 @@ Portable @command{expr} regular expressions should not begin with
 @samp{^}.  Patterns are automatically anchored so leading @samp{^} is
 not needed anyway.
 
+On the other hand, the behavior of the @samp{$} anchor is not portable
+on multi-line strings.  Posix is ambiguous whether the anchor applies to
+each line, as was done in older versions of @acronym{GNU} Coreutils, or
+whether it applies only to the end of the overall string, as in
+Coreutils 6.0 and most other implementations.
+
+@example
+$ @kbd{baz='foo}
+> @kbd{bar'}
+$ @kbd{expr "X$baz" : 'X\(foo\)$'}
+
+$ @kbd{expr-5.97 "X$baz" : 'X\(foo\)$'}
+foo
+@end example
+
 The Posix standard is ambiguous as to whether
 @samp{expr 'a' : '\(b\)'} outputs @samp{0} or the empty string.
 In practice, it outputs the empty string on most platforms, but portable
@@ -16718,6 +16733,14 @@ $ @kbd{expr 00001 : '.*\(...\)'}
 1
 @end example
 
+On @acronym{HP-UX} 11, @command{expr} only supports a single
+sub-expression.
+
+@example
+$ @kbd{expr 'Xfoo' : 'X\(f\(oo\)*\)$'}
+expr: More than one '\(' was used.
+@end example
+
 
 @item @command{fgrep}
 @c ------------------