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From: Stephane Chazelas <stephane@chazelas.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Harald van Dijk <harald@gigawatt.nl>,
	calestyo@scientia.org, dash@vger.kernel.org
Subject: Re: [v2 PATCH] expand: Always quote caret when using fnmatch
Date: Sun, 20 Feb 2022 07:15:44 +0000	[thread overview]
Message-ID: <20220220071544.7odyx5urgcwjsobd@chazelas.org> (raw)
In-Reply-To: <YeejsuVQaGCkQ97t@gondor.apana.org.au>

2022-01-19 16:37:54 +1100, Herbert Xu:
[...]
> This patch forces ^ to be a literal when we use fnmatch.
[...]

Hi,

I'm coming here from a discussion at
https://www.austingroupbugs.net/view.php?id=1558 where I'm
trying to get POSIX to mandate (or suggest that it will mandate
in the future) [^x] works like [!x] to negate a bracket
expression set like it does already in most
shell/fnmatch()/glob() implementations, and to remove that
non-sensical (to me at least) discrepancy with regexps and most
other shells / languages.

To me, that patch is a step in the wrong direction.

Other Ash-based shells already made the move (make [^x] an alias
for [!x]) a long time ago (FreeBSD / NetBSD sh in 1997), BSD
fnmatch() in 1994. The GNU libc and GNU shell have always
supported [^x] AFAIK. So has zsh. ksh made the move in 2005.

In dash, the move to fnmatch() in that case was a step in the
right direction, and reverting it would be an unfortunate step
back to me.

If the point of having dash use fnmatch() is to add consistency
with other tools used from the shell (like find -name/-path...),
then this change doesn't help either on the majority of systems.

The "fix" also seems incomplete and causes at least this
regression:

$ ltrace -e fnmatch ./bin/dash -c 'case "\\" in ($1) echo match; esac' sh '[\^]'
dash->fnmatch("[\\\\^]", "\\", 0)                              = 0
match

See how that added \ caused it to be included in the set. Compare with:

+++ exited (status 0) +++
$ ltrace -e fnmatch ./bin/dash -c 'case "\\" in ($1) echo match; esac' sh '[\!]'
dash->fnmatch("[\\!]", "\\", 0)                                = 1
+++ exited (status 0) +++
$ ltrace -e fnmatch ./bin/dash -c 'case "\\" in ($1) echo match; esac' sh '[\x]'
dash->fnmatch("[\\x]", "\\", 0)                                = 1
+++ exited (status 0) +++

(here on Debian with glibc 2.33)

-- 
Stephane

  reply	other threads:[~2022-02-20  7:30 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-12 16:25 possible wrong behaviour with patterns using a quoted ^ at the start of a bracket expression Christoph Anton Mitterer
2022-01-12 17:20 ` Harald van Dijk
2022-01-12 17:47   ` Christoph Anton Mitterer
2022-01-12 18:17     ` Harald van Dijk
2022-01-12 18:21       ` Christoph Anton Mitterer
2022-01-18  6:13   ` [PATCH] expand: Always quote caret when using fnmatch Herbert Xu
2022-01-18  8:44     ` Harald van Dijk
2022-01-19  5:37       ` [v2 PATCH] " Herbert Xu
2022-02-20  7:15         ` Stephane Chazelas [this message]
2022-02-21 16:39           ` Eric Blake
2022-02-21 17:06             ` Harald van Dijk
2022-02-21 19:15               ` Stephane Chazelas
2022-01-18 14:29     ` [PATCH] " Christoph Anton Mitterer
2022-01-18 14:54       ` Chet Ramey
2022-01-18 22:33       ` Herbert Xu

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