mirror/autoconf
2
0
Fork 0
mirror of git://git.sv.gnu.org/autoconf synced 2025-03-13 14:36:50 +08:00
Code Issues Packages Projects Releases Wiki Activity

* doc/autoconf.texi (Limitations of Builtins): Document

Browse Source 
'unset' bugs of Bash 2.01 and 2.05a.
This commit is contained in:
Paul Eggert 2006-09-03 19:41:12 +00:00
parent c9bf84b877
commit 8092331cbf
2 changed files with 15 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
ChangeLog
View File

@ -1,3 +1,8 @@
2006-09-03 Paul Eggert <eggert@cs.ucla.edu>
* doc/autoconf.texi (Limitations of Builtins): Document
'unset' bugs of Bash 2.01 and 2.05a.
2006-09-01 Paul Eggert <eggert@cs.ucla.edu>
* NEWS: New macro AC_CACHE_CHECK_INT. It replaces the

14
doc/autoconf.texi
View File

@ -12850,21 +12850,27 @@ for @command{true}.
@item @command{unset}
@c ------------------
@prindex @command{unset}
You cannot assume the support of @command{unset}. Nevertheless, because
In some nonconforming shells (e.g., Bash 2.05a), @code{unset FOO} fails
when @code{FOO} is not set. Also, Bash 2.01 mishandles @code{unset
MAIL} in some cases and dumps core.
A few ancient shells lack @command{unset} entirely. Nevertheless, because
it is extremely useful to disable embarrassing variables such as
@code{PS1}, you can test for its existence and use
it @emph{provided} you give a neutralizing value when @command{unset} is
not supported:
@example
if (unset FOO) >/dev/null 2>&1; then
@smallexample
# "|| exit" suppresses any "Segmentation fault" message.
if ( (MAIL=60; unset MAIL) || exit) >/dev/null 2>&1; then
unset=unset
else
unset=false
fi
$unset PS1 || PS1='$ '
@end example
@end smallexample
@noindent
@xref{Special Shell Variables}, for some neutralizing values. Also, see
@ref{Limitations of Builtins}, documentation of @command{export}, for
the case of environment variables.