Mention that ! COMMAND can be rewritten using if-then-else.

diff --git a/ChangeLog b/ChangeLog
index 31246b4e41488a1a82154501ff52f3d06cb6cae4..971b0425a48317770e693b36e399cdd735a065c1 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2004-05-26  Paul Eggert  <eggert@cs.ucla.edu>
+
+       * doc/autoconf.texi (Limitations of Builtins): Mention that ! COMMAND
+       can be rewritten using if-then-else.  Suggested by Bruno Haible.
+
 2004-05-25  Paul Eggert  <eggert@cs.ucla.edu>
 
        * doc/autoconf.texi (testsuite Scripts): Fix typo.

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 205e3d9c69bfa5b4e782c735667eaf125f46768d..27f30c8f4a5aec0bc1eee9a42f3e0f9280446479 100644 (file)
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -10382,6 +10382,11 @@ such code, e.g.:
 cmp file1 file2 >/dev/null 2>&1 || echo files differ or trouble
 @end example
 
+More generally, one can always rewrite @samp{! @var{command}} as:
+
+@example
+if @var{command}; then (exit 1); else :; fi
+@end example
 
 @item @command{break}
 @c ------------------