From: Paolo Bonzini <bonzini@gnu.org>
Date: Thu, 21 Jan 2010 11:16:42 +0000 (+0100)
Subject: Add recommendation on (not) unsetting IFS.
X-Git-Tag: v2.66~88
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e51c9919f2cf70185b7916ac040bc0bbfd0f743b;p=thirdparty%2Fautoconf.git

Add recommendation on (not) unsetting IFS.

* doc/autoconf.texi (Special shell variables): Explain why it's
better not to unset IFS.
---

diff --git a/ChangeLog b/ChangeLog
index eaee96bf..70432f8a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2010-01-20  Paolo Bonzini  <bonzini@gnu.org>
+
+	Add recommendation on (not) unsetting IFS.
+	* doc/autoconf.texi (Special shell variables): Explain why it's
+	better not to unset IFS.
+
 2010-01-19  Ralf Wildenhues  <Ralf.Wildenhues@gmx.de>
 
 	config.status: consistent exit status with nonexistent config file input.
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 1549f895..e5cf9fd6 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -15750,6 +15750,22 @@ environment variables be set to @samp{C} if the C locale is desired;
 @file{configure} scripts and M4sh do that for you.
 Export these variables after setting them.
 
+Unsetting @code{IFS} instead of resetting it to the default sequence
+is not suggested, since code that tries to save and restore the
+variable's value will incorrectly reset it to an empty value, thus
+disabling field splitting:
+
+@example
+unset IFS
+# default separators used for field splitting
+
+save_IFS=$IFS
+IFS=:
+# ...
+IFS=$save_IFS
+# no field splitting performed
+@end example
+
 @c  However, some older, nonstandard
 @c  systems (notably @acronym{SCO}) break if locale environment variables
 @c  are set to @samp{C}, so when running on these systems