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Message-ID: <42DD2E12.458D22A1@dessent.net>
Date: Tue, 19 Jul 2005 09:45:06 -0700
From: Brian Dessent <brian AT dessent DOT net>
MIME-Version: 1.0
To: cygwin AT cygwin DOT com
Subject: Re: OT: grep for \x00 = NUL
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Reply-To: cygwin AT cygwin DOT com

fergus wrote:

>         grep $'\x0d' # e.g. equivalent to grep "^M"

Using that method you're passing the literal character to grep through a
bash quoting mechanism.  You can't pass a literal NULL as part of a
command line because argv[] consists of NULL-delimited strings, as do
most C string functions.

Why not just tell grep to look for a NULL rather than trying to feed it
an actual literal NULL character?

$ grep -P '\000'

In pcre regexps you can use \nnn to match any character represented by
octal nnn.  This would work for any character, and it doesn't rely on a
bash-specific shell feature.  But it does rely on grep supporting -P for
pcre, which is not universal.  If that cannot be relied on then you can
use

$ perl -ne 'print if m/\000/'

or

$ awk '/\000/ { print }'

Brian

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