Op 26-03-18 om 14:12 schreef Harald van Dijk:
> On 26/03/2018 13:57, Martijn Dekker wrote:
>> I don't see any inconsistency. Expansions are consistently treated
>> differently within 'case' than outside it. Among other things,
>> expansions within 'case' are *not* subject to pathname expansion; it's
>> string pattern matching using glob patterns, which is something
>> completely different.
>
> It's not something completely different. Pathname expansion is defined
> in terms of pattern matching (the pattern matching used in e.g. case
> statements), plus a specific set of differences. See 2.6.6 Pathname
> Expansion:
>
>> After field splitting, if set -f is not in effect, each field in the
>> resulting command line shall be expanded using the algorithm described
>> in Pattern Matching Notation, qualified by the rules in Patterns Used
>> for Filename Expansion.
>
> That specific set of differences, 2.13.3 Patterns Used for Filename
> Expansion, doesn't include different treatment of backslashes.
I see your point now. You're absolutely right.
Hmmm...
If we backslash-escape a glob character, '?':
$ touch '_foo?bar_'
$ testshells -c 'p='\''*o\?b*'\''; printf %s $p'
The backslash is correctly honoured by:
bash 2.05b through git: _foo?bar_
dash 0.5.5.1: _foo?bar_
dash-hvdijk: _foo?bar_
zsh as sh: _foo?bar_
The backslash is *not* honoured by:
dash 0.5.6 through 0.5.9.1: *o\?b*
ksh93: *o\?b*
mksh/lksh: *o\?b*
yash -o posix: *o\?b*
And if we backslash-escape a non-glob character, 'b':
$ touch '_foo?bar_'
$ testshells -c 'p='\''*o?\b*'\''; printf %s $p'
The backslash is correctly honoured by:
bash 2.05b through git: _foo?bar_
dash 0.5.5.1: _foo?bar_
dash-hvdijk: _foo?bar_
The backslash is *not* honoured by:
dash 0.5.6 through 0.5.9.1: *o\?b*
ksh93: *o\?b*
mksh/lksh: *o\?b*
yash -o posix: *o\?b*
zsh as sh: *o\?b*
Funny how these results are different from the results I get when doing
the same test with 'case' pattern matching. As you point out, they are
supposed to be subject to the same rules with some modifications *not*
including backslash parsing. So the results should at least be identical
for each shell.
So yes, dash is inconsistent. But given what POSIX says, I think dash
should probably go back to honouring the backslash for pathname
expansion as it did in 0.5.5.1 and does in your fork.
Maybe you should argue the case with the Austin Group. It would be nice
to get clarification on the issue.
- M.
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