Fine by me, thanks.
BTW, as discussed in another bug, the -w/-x invalidate the
(*UCP) and other PCRE special sequences. Chances are we can't
easily do much about it, but it may still be worth documenting.
Like, one should use
grep -P '(*UCP)\bword\b'
as
grep -wP '(*UCP)word'
won't work (pcregrep has the same problem).
In another bug, I've seen someone commenting that
grep -wP 'a)(b'
doesn't give the error message that one would expect (not that
I'd expect anyone would care).
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.
Sorry I lied, it was not the last note ;-). Note the difference:
$ echo a@@b | grep -w @@
$ echo a@@b | grep -Pw @@
a@@b
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%
Full text of original email included for reference:
2014-02-24 12:00:08 -0800, Jim Meyering:
> On Mon, Feb 24, 2014 at 2:01 AM, Stephane Chazelas
> <stephane.chaze...@gmail.com> wrote:
> > Hello,
> >
> > Backreferences don't work with -w or -x in combination with -P:
> >
> > $ echo aa | grep -Pw '(.)\1'
> > $
> >
> > Or they work in an unexpected way:
> >
> > $ echo aa | grep -Pw '(.)\2'
> > aa
> >
> > The fix is simple:
> >
> >
> > --- src/pcresearch.c~ 2014-02-24 09:59:56.864374362 +0000
> > +++ src/pcresearch.c 2014-02-24 07:33:04.666398105 +0000
> > @@ -75,9 +75,9 @@ Pcompile (char const *pattern, size_t si
>
> Thanks a lot for the patch.
> I've converted it to a proper commit with NEWS and a test case.
> Please ack the attached if it's all ok with you (you're still the "Author:"):
> From bfd21931b3cd088d642a190e9f030214df04045d Mon Sep 17 00:00:00 2001
> From: Stephane Chazelas <stephane.chaze...@gmail.com>
> Date: Mon, 24 Feb 2014 11:54:09 -0800
> Subject: [PATCH] grep -P: fix it so backreferences now work with -w and -x
>
> To implement -w and -x, we bracket the search term with parentheses.
> However, that set of parentheses had the default semantics of
> "capturing", i.e., creating a backreferenceable matched quantity.
> Instead, use (?:...), to create a non-capturing group.
> * src/pcresearch.c (Pcompile): Use (?:...) rather than (...).
> * NEWS (Bug fixes): Mention it.
> * tests/pcre-wx-backref: New file.
> * tests/Makefile.am (TESTS): Add it.
> ---
> NEWS | 6 ++++++
> src/pcresearch.c | 4 ++--
> tests/Makefile.am | 1 +
> tests/pcre-wx-backref | 28 ++++++++++++++++++++++++++++
> 4 files changed, 37 insertions(+), 2 deletions(-)
> create mode 100755 tests/pcre-wx-backref
>
> diff --git a/NEWS b/NEWS
> index 771fd80..49fe984 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -2,6 +2,12 @@ GNU grep NEWS -*- outline
> -*-
>
> * Noteworthy changes in release ?.? (????-??-??) [?]
>
> +** Bug fixes
> +
> + grep -P now works with -w and -x and backreferences. Before,
> + echo aa|grep -Pw '(.)\1' would fail to match, yet
> + echo aa|grep -Pw '(.)\2' would match.
> +
>
> * Noteworthy changes in release 2.18 (2014-02-20) [stable]
>
> diff --git a/src/pcresearch.c b/src/pcresearch.c
> index 5b5ba3e..d4a20ff 100644
> --- a/src/pcresearch.c
> +++ b/src/pcresearch.c
> @@ -75,9 +75,9 @@ Pcompile (char const *pattern, size_t size)
>
> *n = '\0';
> if (match_lines)
> - strcpy (n, "^(");
> + strcpy (n, "^(?:");
> if (match_words)
> - strcpy (n, "\\b(");
> + strcpy (n, "\\b(?:");
> n += strlen (n);
>
> /* The PCRE interface doesn't allow NUL bytes in the pattern, so
> diff --git a/tests/Makefile.am b/tests/Makefile.am
> index 4ffea85..ecbe0e6 100644
> --- a/tests/Makefile.am
> +++ b/tests/Makefile.am
> @@ -83,6 +83,7 @@ TESTS = \
> pcre-abort \
> pcre-invalid-utf8-input \
> pcre-utf8 \
> + pcre-wx-backref \
> pcre-z \
> prefix-of-multibyte \
> r-dot \
> diff --git a/tests/pcre-wx-backref b/tests/pcre-wx-backref
> new file mode 100755
> index 0000000..643aa9b
> --- /dev/null
> +++ b/tests/pcre-wx-backref
> @@ -0,0 +1,28 @@
> +#! /bin/sh
> +# Before grep-2.19, grep -P and -w/-x would not with a backreference.
> +#
> +# Copyright (C) 2014 Free Software Foundation, Inc.
> +#
> +# Copying and distribution of this file, with or without modification,
> +# are permitted in any medium without royalty provided the copyright
> +# notice and this notice are preserved.
> +
> +. "${srcdir=.}/init.sh"; path_prepend_ ../src
> +require_pcre_
> +
> +echo aa > in || framework_failure_
> +echo 'grep: reference to non-existent subpattern' > exp-err \
> + || framework_failure_
> +
> +fail=0
> +
> +for xw in x w; do
> + grep -P$xw '(.)\1' in > out 2>&1 || fail=1
> + compare out in || fail=1
> +
> + grep -P$xw '(.)\2' in > out 2> err && fail=1
> + compare /dev/null out || fail=1
> + compare exp-err err || fail=1
> +done
> +
> +Exit $fail
> --
> 1.9.0
>
