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From: sja@ih1ap.UUCP (Steve Alesch)
Newsgroups: net.unix,net.unix-wizards
Subject: Re: question-- Bourne (and C) SHELL
Message-ID: <574@ih1ap.UUCP>
Date: Thu, 11-Sep-86 23:38:56 EDT
Article-I.D.: ih1ap.574
Posted: Thu Sep 11 23:38:56 1986
Date-Received: Sat, 13-Sep-86 04:21:55 EDT
References: <1751@ittatc.ATC.ITT.UUCP> <7028@utzoo.UUCP> <150@humming.UUCP> <6228@sun.uucp>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 45
Xref: watmath net.unix:9157 net.unix-wizards:19537
Summary: what's wrong with ``[ $? != 0 ]''?

In article <6228@sun.uucp>, guy@sun.uucp (Guy Harris) writes:
> > The  key  thing  here  is  the  ability  to NOT the value of status. How is
> > this similar thing done in Bourne shell.
> > 
> > if ! ls foo
> > then
> > 	echo foo does not exist
> > fi
> 
> Try
> 
> 	if ls foo
> 	then
> 		:
> 	else
> 		echo foo does not exist
> 	fi
> 
> The ":"  is the pseudo-comment from old Bourne shells; it's really a command
> that does nothing.
> 
> Not the cleanest syntax, but that's life.  (However, I'd rather have a shell
> that requires that crud, but allows you to redirect the output of a "for"
> loop, than one that permits you to negate exit status directly but won't let
> you redirect the output of loops!  At least with the Bourne shell you can
> get around the inability to negate exit status fairly easily.)
> 
> However, you may be better off doing
> 
> 	if test ! -f foo
> 
> or something like that; unfortunately, "test" doesn't have a predicate for
> "just test whether it exists", but you may really want a more restrictive
> predicate anyway.

Correct me if I'm missing something.  What's wrong with:

	ls foo
	if [ $? != 0 ]; then
		echo foo does not exist
	fi
-- 

Steve Alesch	AT&T
(312)510-7881, ...!ihnp4!ih1ap!sja