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From: scl@virginia.acc.virginia.edu (Steve Losen)
Newsgroups: comp.unix.questions
Subject: Re: variables set in sh while loop don't get set?
Message-ID: <431@virginia.acc.virginia.edu>
Date: Mon, 28-Sep-87 11:26:36 EDT
Article-I.D.: virginia.431
Posted: Mon Sep 28 11:26:36 1987
Date-Received: Sun, 11-Oct-87 09:19:49 EDT
References: <212@ttrdd.UUCP>
Reply-To: scl@virginia.UUCP (Steve Losen)
Organization: University of Va., Charlottesville, VA
Lines: 28
Keywords: sh, ksh scripts, loops

In article <212@ttrdd.UUCP> mellman@ttrdd.UUCP (Thomas Mellman) writes:
>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

	done  # assumed

What is happening is that the while loop is being run as a separate
process.  The shell is very fond of doing this sort of thing,
especially in pipelines.  At the "done" the "while loop process" exits,
giving control back to the parent shell, whose variables haven't
changed.  I suggest that you do this:

pipeline | (
	while read proc
	do
		# set some variables
	done
	# now use the variables set in while loop
)

This forces everything between the parentheses to happen in the child
process, so you can get some use out of those variables.
-- 
Steve Losen
University of Virginia Academic Computing Center