GNU bug report logs - #16865
grep -wP and backreferences

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Message #22 received at 16865-done <at> debbugs.gnu.org (full text, mbox):

From: Jim Meyering <jim <at> meyering.net>
To: Stephane Chazelas <stephane.chazelas <at> gmail.com>
Cc: 16865-done <at> debbugs.gnu.org
Subject: Re: bug#16865: grep -wP and backreferences
Date: Tue, 25 Feb 2014 10:03:28 -0800

[Message part 1 (text/plain, inline)]

On Tue, Feb 25, 2014 at 8:08 AM, Stephane Chazelas
<stephane.chazelas <at> gmail.com> wrote:
> 2014-02-24 20:55:42 -0800, Jim Meyering:
>> On Mon, Feb 24, 2014 at 1:20 PM, Stephane Chazelas
>> <stephane.chazelas <at> gmail.com> wrote:
>> > A last note: with -w, pcregrep wraps the regexp in \b...\b
>> > instead of \b(?:...)\b, so it could be that those brackets are
>> > not necessary in the first place.
>
> The brackets are actually needed in cases like:
>
> grep -Pw 'foo|bar'
>
> (pcregrep has a bug there).
>
>
>> > Maybe instead of \b(?:...)\b, we could use (?<!\w)...(?!\w)
>> >
>> > $ echo a%%b | grep -P '(?<!\w)%%(?!\w)'
>> > $ echo %aa% | grep -P '(?<!\w)aa(?!\w)'
>> > %aa%
>>
>> I like both suggestions. Making -wP work like grep's -w makes perfect sense.
>> Care to prepare a patch to make it do that, with a separate test case?
>> "git format-patch ..." output preferred, if you're game.
>>
>> I pushed the above patch, but would welcome another one.
>
> Please find the patch attached.

Thank you very much.  Nearly perfect.
I've uncapitalized the 1-line summary, changed a That to This
in the log, and added examples to NEWS, and added an empty
line to restore the 2-empty-line section delimiter.

> (note that tests/word-delim-multibyte fails for me, but it's not
> my doing, it was failing before).

That's an XFAIL test (as noted in tests/Makefile.am), hence, expected
to fail, and as long as it fails as expected, "make check" can still succeed.

I've closed this ticket, and will push once you ack these changes.

[0001-align-grep-Pw-with-grep-w.patch (application/octet-stream, attachment)]

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