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From: tres@virga.rap.ucar.edu (Tres Hofmeister)
Newsgroups: comp.unix.shell
Subject: Puzzled by A Regexp...
Keywords: What's the extent of the match?
Message-ID: <10469@ncar.ucar.edu>
Date: 4 Mar 91 21:15:51 GMT
Sender: news@ncar.ucar.edu
Reply-To: tres@virga.rap.ucar.edu (Tres Hofmeister)
Distribution: usa
Organization: Research Applications Program/NCAR, Boulder, CO
Lines: 31


	I've run across a regular expression that I don't quite understand.
Not that this hasn't happened before, but this seems like it should be
fairly straightforward...

	I'm trying to match entries in /etc/group which have one or more
members.  The following works just fine, matching each of the colon
delimited fields individually followed by one or more characters:

	grep '^.*:.*:.*:..*' /etc/group

	What I don't understand is why the following doesn't work the same
way:

	grep '^.*:..*' /etc/group

	It grabs entries with one or more members, true, but also grabs
entries with no members, e.g. "news:*:6:".  I figured that this regexp
would match the longest possible string at the beginning of a line,
terminated by a colon, which in the group file should include the first
two colons, followed by at least one character.  It seems to be doing
something else, given that it will also match a line with no members.

	Any ideas?


Tres Hofmeister
tres@ncar.ucar.edu
--
Tres Hofmeister
tres@ncar.ucar.edu