Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!PRC.UNISYS.COM!lang
From: lang@PRC.UNISYS.COM
Newsgroups: gnu.utils.bug
Subject: Grep bug?
Message-ID: <8909121817.AA11159@gem>
Date: 12 Sep 89 18:17:21 GMT
Sender: daemon@tut.cis.ohio-state.edu
Distribution: gnu
Organization: GNUs Not Usenet
Lines: 27

This may not be a bug, but rather my misunderstanding
the documentation, but this strikes me as odd....

% grep '\wx\w' foo
finds all occurrences in foo of 'x' flanked by alphanumerics.

% grep '\Wx\W' foo
finds all occurrences in foo of 'x' flanked by non-alphanumerics.

Fine.  So far so good.
Suppose now I want to find all occurrences of 'x'
flanked by non-alphanumerics, but I want the match
on 'x' not to be case-sensitive.  Well, the -i flag
makes grep ignore case difference when comparing strings,
so I try

% grep -i '\Wx\W' foo

But the effect here is that the -i flag makes the '\W'
meta-character non-case-sensitive as well, and I get
all occurrences of x in foo, regardless of the case of x
(which is fine) but also regardless of whether or not
the x (or X) is flanked by non-alphanumerics!

Is this a feature?

--Francois Lang