Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!uxc!uxc.cso.uiuc.edu!kailand!pwolfe
From: pwolfe@kailand.KAI.COM
Newsgroups: comp.sys.sequent
Subject: Re: Possible Sh bug?
Message-ID: <2400049@kailand>
Date: 19 May 89 13:20:00 GMT
References: <1002@syma.sussex.ac.uk>
Lines: 38
Nf-ID: #R:syma.sussex.ac.uk:1002:kailand:2400049:000:1016
Nf-From: kailand.KAI.COM!pwolfe    May 19 08:20:00 1989


> /* Written by andy@syma.sussex.ac.uk in kailand:comp.sys.sequent */
> 
> Symm. S81
> ---------
> % sh
> $ echo $?
> 0
> $ if [ $? != 0 ]; then exit 1; fi
> $ echo $?
> 1

First off, you are using the string comparison (!=) to compare numbers.  You
should be using "-ne".  See the manpage for test(1).

> What exit status (value) should the "if" return?

The status 1 after the "if" command is the one returned by the last command
executed, in this case "test".  ("[" is a link to test - see the man page for
test(1)).  You can demonstrate this by:

	$ echo $?
	$ if [ $? -eq 0 ]; then echo yes; fi
	yes
	$ echo $?
	0
	$ if [ $? -ne 0 ]; then echo no; fi
	$ echo $?
	1

Since $? is set so quickly, you'd be better off by assigning it to a variable,
and testing and displaying that variable.

I have no explanation why Sun's test returned a status of zero.  It might be
because of the character comparison.

Patrick Wolfe	(pat@kai.com, {uunet,uiucuxc,sequent}!kailand!pat)
System Manager, Kuck and Associates, Inc.