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From: crc@abvax.icd.ab.com (Clive R. Charlwood)
Newsgroups: comp.unix.questions
Subject: Re: variables set in sh while loop don't get set?
Message-ID: <71@abvax.icd.ab.com>
Date: Mon, 28-Sep-87 18:50:07 EDT
Article-I.D.: abvax.71
Posted: Mon Sep 28 18:50:07 1987
Date-Received: Wed, 30-Sep-87 07:22:08 EDT
References: <212@ttrdd.UUCP>
Organization: Allen-Bradley Company, Inc; Industrial Computer Division, Highland Heights, OH
Lines: 32

in article <212@ttrdd.UUCP>, mellman@ttrdd.UUCP (Thomas Mellman) says:
> 
> When I set a variable in a while loop in a sh script, in some scripts
> it doesn't seem to get set.  For example, a common thing is to do a
> 
> 	pipeline | while read proc
> 	do
> 
> and then to test for some condition in a case statement.  Twice now, I
> have written scripts where a variable set in the case loop (or anywhere
> in the while loop, for that matter) won't have been changed from its
> initial value after the while loop terminates.  Can anyone explain to me
> why this is so.

In the bourne shell while/for loops that have stdin redirected are 
implemented as sub shells. Thus any changes to variables 'disapear'
when the shell exits.




Clive

		Clive R. Charlwood @ Allen-Bradley Company
		Industrial Computer Division
		747 Alpha Drive, Highland Heights, OH   44143
		...!{decvax,masscomp,pyramid,cwruecmp}!abic!crc
-- 
		Clive R. Charlwood @ Allen-Bradley Company
		Industrial Computer Division
		747 Alpha Drive, Highland Heights, OH   44143
		...!{decvax,masscomp,pyramid,cwruecmp}!abic!crc