Stephane Chazelas wrote:
The doc has a confusing statement ... Same confusion in tests/pcre:
Thanks, I installed the attached patch to fix those.
We can match a newline with grep -zP 'a\nb' (or '\x0a' or '\012' or '[\n]'...) but not easily without -P. Same for NUL characters.
Yes, that's a downside of the POSIX notation, and it'd be nice to extend POSIX to allow easy matching for newlines and/or null bytes. I'll mark this bug report as a wishlist bug.
From 2fd9ce3bcf55ec80aa5b1d3775fe00ccb078d7dd Mon Sep 17 00:00:00 2001 From: Paul Eggert <egg...@cs.ucla.edu> Date: Thu, 24 Apr 2014 21:24:22 -0700 Subject: [PATCH] misc: fix doc and test bugs re grep -z Problem reported by Stephane Chazelas in: http://bugs.gnu.org/16871 * doc/grep.texi (Usage): Remove incorrect example with -P. * tests/pcre: Improve test so that it actually tests whether \s matches a newline. --- doc/grep.texi | 16 +++++----------- tests/pcre | 4 ++-- 2 files changed, 7 insertions(+), 13 deletions(-) diff --git a/doc/grep.texi b/doc/grep.texi index f631f03..59d0d3c 100644 --- a/doc/grep.texi +++ b/doc/grep.texi @@ -1719,25 +1719,19 @@ How can I match across lines? Standard grep cannot do this, as it is fundamentally line-based. Therefore, merely using the @code{[:space:]} character class does not -match newlines in the way you might expect. However, if your grep is -compiled with Perl patterns enabled, the Perl @samp{s} -modifier (which makes @code{.} match newlines) can be used: - -@example -printf 'foo\nbar\n' | grep -P '(?s)foo.*?bar' -@end example +match newlines in the way you might expect. With the GNU @command{grep} option @code{-z} (@pxref{File and Directory Selection}), the input is terminated by null bytes. Thus, -you can match newlines in the input, but the output will be the whole -file, so this is really only useful to determine if the pattern is -present: +you can match newlines in the input, but typically if there is a match +the entire input is output, so this usage is often combined with +output-suppressing options like @option{-q}, e.g.: @example printf 'foo\nbar\n' | grep -z -q 'foo[[:space:]]\+bar' @end example -Failing either of those options, you need to transform the input +If this does not suffice, you can transform the input before giving it to @command{grep}, or turn to @command{awk}, @command{sed}, @command{perl}, or many other utilities that are designed to operate across lines. diff --git a/tests/pcre b/tests/pcre index cbe6884..7efa560 100755 --- a/tests/pcre +++ b/tests/pcre @@ -1,5 +1,5 @@ #! /bin/sh -# Ensure that with -P, \s*$ matches a newline. +# Ensure that with -P, \s matches a newline. # # Copyright (C) 2001, 2006, 2009-2014 Free Software Foundation, Inc. # @@ -12,7 +12,7 @@ require_pcre_ fail=0 -# See CVS revision 1.32 of "src/search.c". echo | grep -P '\s*$' || fail=1 +echo | grep -zP '\s$' || fail=1 Exit $fail -- 1.9.0
