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bug#22655: grep -Pz '^' now fails!
From: |
Stephane Chazelas |
Subject: |
bug#22655: grep -Pz '^' now fails! |
Date: |
Fri, 18 Nov 2016 17:06:36 +0000 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
2016-11-18 08:48:04 -0800, Paul Eggert:
> Stephane Chazelas wrote:
> >Why would it make it slower. AFAICT, PCRE_MULTILINE *adds*
> >some overhead.
>
> As I understand it, PCRE_MULTILINE lets 'grep' apply a pattern to an
> entire buffer that contains many lines, and this lets PCRE
> efficiently find the first match in the whole buffer. If grep
> doesn't use PCRE_MULTILINE, grep would have to apply the pattern to
> each line separately, which could be significantly slower.
[...]
That might have been the case a long time ago, as I remember
some discussion about it as it explained some wrong information
in the documentation, but as far as I and gdb can tell, grep
2.26 at least call pcre_exec for every line of the input with
grep -P.
If it didn't
echo test | grep -P '\n$'
would match.
I'll try and dig up the old discussions.
--
Stephane
- bug#22655: grep -Pz '^' now fails!, Stephane Chazelas, 2016/11/18
- bug#22655: grep -Pz '^' now fails!, Paul Eggert, 2016/11/18
- bug#22655: grep -Pz '^' now fails!, Stephane Chazelas, 2016/11/18
- bug#22655: grep -Pz '^' now fails!, Stephane Chazelas, 2016/11/18
- bug#22655: grep -Pz '^' now fails!, Paul Eggert, 2016/11/18
- bug#22655: grep -Pz '^' now fails!, Stephane Chazelas, 2016/11/18
- bug#22655: grep -Pz '^' now fails!, Paul Eggert, 2016/11/19
- bug#22655: grep -Pz '^' now fails!, Zev Weiss, 2016/11/19
- bug#22655: grep -Pz '^' now fails!, Paul Eggert, 2016/11/19
- bug#22655: grep -Pz '^' now fails!, Paul Eggert, 2016/11/18
- bug#22655: grep -Pz '^' now fails!,
Stephane Chazelas <=
- bug#22655: grep -Pz '^' now fails!, Stephane Chazelas, 2016/11/18
- bug#22655: grep -Pz '^' now fails!, Stephane Chazelas, 2016/11/18
- bug#22655: grep -Pz '^' now fails!, Paul Eggert, 2016/11/18
- bug#22655: grep -Pz '^' now fails!, Stephane Chazelas, 2016/11/19
- bug#22655: grep -Pz '^' now fails!, Paul Eggert, 2016/11/19
- bug#22655: grep -Pz '^' now fails!, Aaron Crane, 2016/11/19
- bug#22655: grep -Pz '^' now fails!, Paul Eggert, 2016/11/19
- bug#22655: grep -Pz '^' now fails!, Stephane Chazelas, 2016/11/20
- bug#22655: grep -Pz '^' now fails!, Paul Eggert, 2016/11/20
- bug#22655: grep -Pz '^' now fails!, Stephane Chazelas, 2016/11/19