mirror/autoconf
2
0
Fork 0
mirror of git://git.sv.gnu.org/autoconf synced 2024-11-27 01:49:56 +08:00
Code Issues Packages Projects Releases Wiki Activity

Document dash ${*-unset} behavior

Browse Source 
* doc/autoconf.texi (Shell Substitutions): Document dash
incompatibility.  Problem reported by David Caldwell in:
http://bugs.gnu.org/22556
This commit is contained in:
Paul Eggert 2016-02-05 14:15:07 -08:00
parent 5ad3567c3c
commit 5483deb8ae
1 changed files with 14 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
doc/autoconf.texi
View File

@ -16063,7 +16063,8 @@ j a0
@cindex @code{$@{@var{var}-@var{value}@}}
Old BSD shells, including the Ultrix @code{sh}, don't accept the
colon for any shell substitution, and complain and die.
Similarly for $@{@var{var}:=@var{value}@}, $@{@var{var}:?@var{value}@}, etc.
Similarly for @code{$@{@var{var}:=@var{value}@}},
@code{$@{@var{var}:?@var{value}@}}, etc.
However, all shells that support functions allow the use of colon in
shell substitution, and since m4sh requires functions, you can portably
use null variable substitution patterns in configure scripts.
@ -16089,6 +16090,18 @@ EOF}
b c
@end example
Most shells treat the special parameters @code{*} and @code{@@} as being
unset if there are no positional parameters. However, some shells treat
them as being set to the empty string. Posix does not clearly specify
either behavior.
@example
$ @kbd{bash -c 'echo "* is $@{*-unset@}."'}
* is unset.
$ @kbd{dash -c 'echo "* is $@{*-unset@}."'}
* is .
@end example
According to Posix, if an expansion occurs inside double quotes, then
the use of unquoted double quotes within @var{value} is unspecified, and
any single quotes become literal characters; in that case, escaping must