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From: flee@gondor.psu.edu (Felix Lee)
Newsgroups: comp.unix.questions
Subject: Re: Environment variables.  And csh bogosity.
Message-ID: <2885@psuvax1.psu.edu>
Date: Sat, 29-Aug-87 00:07:10 EDT
Article-I.D.: psuvax1.2885
Posted: Sat Aug 29 00:07:10 1987
Date-Received: Sun, 30-Aug-87 06:37:26 EDT
References: <626@unmvax.unm.edu> <2876@phri.UUCP> <7173@ism780c.UUCP>
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Reply-To: flee@gondor.psu.edu (Felix Lee)
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In article <7173@ism780c.UUCP> mikep@ism780c.UUCP (Michael A. Petonic) writes:
>>In <626@unmvax.unm.edu> mike@turing.UNM.EDU.UUCP (Michael I. Bushnell) writes:
>>> How can I determine if an environment variable is set using csh?
>A better was is to use printenv and the "status" variable, like this:
>	printenv FOO > /dev/null
>	if ( $status == 1 ) then
>		variable is not set
>	else
>		variable is set
>	fi

A different way is to use printenv like this:
	if ( { printenv FOO } ) echo Yes
Unfortunately,
	if ( { printenv FOO >/dev/null } ) echo Yes
doesn't work.  Csh ignores the redirection.  You have to say:
	if ( { ( printenv FOO >/dev/null ) } ) echo Yes

Or, if you're using a block if, you can say
	if ( { printenv FOO } ) then >/dev/null
		echo Yes
	else
		echo No
	endif

Isn't csh wonderful?  Let's hear it for ad-hoc parsing.

--
Felix Lee	flee@gondor.psu.edu	{cbosgd,cmcl2}!psuvax1!gondor!flee
Copyright (C) 1987 by Felix Lee.  Reprinted with permission.