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docs: update entry about unset.

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* doc/autoconf.texi (Limitations of Builtins): NetBSD sh unset
also fails upon `unset' of a variable that is not set.  Bash 2.01
could also dump core over `unset MAILPATH'.
Suggestion by Eric Blake.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>
This commit is contained in:
Ralf Wildenhues 2011-01-22 09:28:44 +01:00
parent 5f6115b10d
commit f272870140
2 changed files with 14 additions and 4 deletions
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@ -1,3 +1,11 @@
2011-01-22 Ralf Wildenhues <Ralf.Wildenhues@gmx.de>
docs: update entry about unset.
* doc/autoconf.texi (Limitations of Builtins): NetBSD sh unset
also fails upon `unset' of a variable that is not set. Bash 2.01
could also dump core over `unset MAILPATH'.
Suggestion by Eric Blake.
2011-01-21 Ralf Wildenhues <Ralf.Wildenhues@gmx.de>
Fix LEXLIB and YYTEXT_POINTER with IRIX 6.5 flex 2.5.4.

10
doc/autoconf.texi
View File

@ -17758,13 +17758,15 @@ and file name expansion.
@item @command{unset}
@c ------------------
@prindex @command{unset}
In some nonconforming shells (e.g., Bash 2.05a), @code{unset FOO} fails
when @code{FOO} is not set. You can use
In some nonconforming shells (e.g., NetBSD 5.99.43 sh or Bash 2.05a),
@code{unset FOO} fails when @code{FOO} is not set. This can interfere
with @code{set -e} operation. You can use
@smallexample
FOO=; unset FOO
@end smallexample
@noindent
if you are not sure that @code{FOO} is set.
A few ancient shells lack @command{unset} entirely. For some variables
@ -17777,8 +17779,8 @@ PS1='$ '
Usually, shells that do not support @command{unset} need less effort to
make the environment sane, so for example is not a problem if you cannot
unset @command{CDPATH} on those shells. However, Bash 2.01 mishandles
@code{unset MAIL} in some cases and dumps core. So, you should do
something like
@code{unset MAIL} and @code{unset MAILPATH} in some cases and dumps core.
So, you should do something like
@smallexample
( (unset MAIL) || exit 1) >/dev/null 2>&1 && unset MAIL || :