* doc/autoconf.texi (Parentheses): Mention problem with (( in

shells.

diff --git a/ChangeLog b/ChangeLog
index d7e35a9e0af8b95dd7188ed9b99b25099ec8555d..07dfd75c9b5dc0603d5439f5cde0774de780a3aa 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2007-02-08  Paul Eggert  <eggert@cs.ucla.edu>
+
+       * doc/autoconf.texi (Parentheses): Mention problem with (( in
+       shells.
+
 2007-02-07  Ralf Wildenhues  <Ralf.Wildenhues@gmx.de>
        and Paul Eggert  <eggert@cs.ucla.edu>
 

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 7e47ee7b770c8a17329e479d54ec9c45325e065f..557d3666e290b1d5686d00a4ce6e2ff6cdb4d64a 100644 (file)
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -11896,9 +11896,13 @@ for the rationale.
 @section Parentheses in Shell Scripts
 @cindex Shell parentheses
 
-Beware of two opening parentheses in a row, as some shell
-implementations mishandle them.  For example, @samp{pdksh} 5.2.14
-misparses the following code:
+Beware of two opening parentheses in a row, as many shell
+implementations treat them specially.  Posix requires that the command
+@samp{((cat))} must behave like @samp{(cat)}, but many shells, including
+Bash and the Korn shell, treat @samp{((cat))} as an arithmetic
+expression equivalent to @samp{let "cat"}, and may or may not report an
+error when they detect that @samp{cat} is not a number.  As another
+example, @samp{pdksh} 5.2.14 misparses the following code:
 
 @example
 if ((true) || false); then