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From: chris@mimsy.UUCP
Newsgroups: comp.unix.wizards
Subject: ${var?err} (was Re: /bin/test and stat(2))
Message-ID: <9127@mimsy.UUCP>
Date: Wed, 28-Oct-87 02:46:21 EST
Article-I.D.: mimsy.9127
Posted: Wed Oct 28 02:46:21 1987
Date-Received: Sat, 31-Oct-87 00:14:24 EST
References: <9974@brl-adm.ARPA> <179@nusdhub.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 20

In article <179@nusdhub.UUCP> rwhite@nusdhub.UUCP (Robert C. White Jr.) writes:
>... should become one of the following:
>	/bin/test -d "${FOO:? <error message>}"  # to terminate shell
>	/bin/test -d "${FOO:=/etc/system}"       # to garentee false
>	/bin/test -d "${FOO:-/etc/system}"	 # same without affecting
>						 # the value of FOO

... except that

	FOO=""
	: ${FOO?err}

continues running, while

	: ${FOO?err}

stops with `FOO: err' under `sh' (tested under 4.3BSD).
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris