Path: utzoo!utgpu!water!watmath!clyde!att!rutgers!mailrus!ames!haven!umd5!adm!smoke!gwyn
From: gwyn@smoke.ARPA (Doug Gwyn )
Newsgroups: comp.unix.wizards
Subject: Re: what should egrep '|root' /etc/passwd print?
Message-ID: <8492@smoke.ARPA>
Date: 14 Sep 88 09:55:16 GMT
References: <44414@beno.seismo.CSS.GOV>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 13

In article <44414@beno.seismo.CSS.GOV> rick@seismo.CSS.GOV (Rick Adams) writes:
>What should 
>	egrep '|root' /etc/passwd
>print?

The question of how to handle empty strings in regular expressions
does not have a clear-cut answer.  "sam", which has the most powerful
regular expression mechanism of any of the editor-like programs I use,
says the following:
	?no operand for `|'
which is yet another solution.  (Getting the description right for
where empty strings do and don't match was the hardest task when I
was overhauling sam's manual entry.)