GNU bug report logs - #21414
-F string with tailing newline always matches

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Message #19 received at 21414 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Jim Meyering <jim <at> meyering.net>, 21414 <at> debbugs.gnu.org, ian.brown <at> hds.com
Cc: 21414-done <at> debbugs.gnu.org
Subject: Re: bug#21414: -F string with tailing newline always matches
Date: Fri, 4 Sep 2015 20:45:10 -0700

Jim Meyering wrote:
> I too find this behavior surprising:
>
> $ seq 3|grep -F xxx$'\n'
> 1
> 2
> 3
>
> This feels like a bug, since it's an artifact of how grep accumulates
> multiple keys internally: it uses newline as the separator
> (http://git.savannah.gnu.org/cgit/grep.git/tree/src/grep.c#n2308).
> Including a literal newline in the search string conflicts with that.

It's not an artifact; it's intended behavior.  POSIX says that xxx$'\n' (which 
expands to three 'x's followed by a newline) is a pattern_list, not a pattern. 
A pattern_list is defined to be a series of patterns separated by newlines (not 
terminated by newlines), so that pattern_list has two patterns, xxx and the 
empty pattern.

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