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Path: utzoo!watmath!clyde!burl!we13!ihnp4!ihuxx!ignatz
From: ignatz@ihuxx.UUCP (Dave Ihnat, Chicago, IL)
Newsgroups: net.unix
Subject: Re: HELP! (What's wrong with this sh scr - (nf)
Message-ID: <728@ihuxx.UUCP>
Date: Thu, 26-Apr-84 19:54:29 EST
Article-I.D.: ihuxx.728
Posted: Thu Apr 26 19:54:29 1984
Date-Received: Fri, 27-Apr-84 06:28:20 EST
References: <3164@fortune.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 27

Esp. RE: X$var vs. "$var":

This solution probably came from the example used in the USG (now WE)
Unix(Tm, of course) manual for the expr(1) command.  On the very last
page of the man entry, they address the problem of null strings and
the shell getting to them as follows:

if

a='='

expr $a = '='

then looks like

expr = = =
and fails! (note that expr "$a" = '=' also fails)

Thus, they suggest

expr X$a = X=

to get around the problem.

Dave Ihnat
ihuxx!ignatz