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Re: grep --perl-regexp and empty match
From: |
Stepan Kasal |
Subject: |
Re: grep --perl-regexp and empty match |
Date: |
Fri, 4 Jul 2003 13:25:08 +0200 |
User-agent: |
Mutt/1.2.5.1i |
Hello,
On Thu, Jul 03, 2003 at 10:11:38PM +0300, Jori Mantysalo wrote:
> > $ echo "<B>one</B> and <B>two</B>" | grep -o -P '<B>.*?</B>'
>
> > Are you sure you're using GNU grep?
> If I remember correctly, there was some compile-time setting that
> will make perl-style regexps available. I am using Red Hat Linux, maybe
> default grep installed with other distributions has compiled differently?
./configure searches for package ``pcre''---a shared library which
implements Perl Compatible RegExps. (This can be --disabled, but it's on
by default.)
This means Paul doesn't have pcre installed.
To the original problem:
the bug is that grep -o doesn't print empty matches. If it were fixed, then
echo abc | grep -o 'X*'
would output four empty lines. But it's probably ok, when someone calls grep
with a regexp which matches empty string, they get what they deserve.
Stepan Kasal