Newsgroups: comp.unix.wizards
Path: utzoo!utgpu!watserv1!watcgl!idallen
From: idallen@watcgl.waterloo.edu (Ian! D. Allen [CGL])
Subject: Re: cd failure killing script [Re: Interactive 2.2 File zapper]
Message-ID: <1990Aug7.050700.27011@watcgl.waterloo.edu>
Organization: University of Waterloo
References: <772@essnj1.ESSNJAY.COM> <2108@cirrusl.UUCP> <1990Aug3.022641.28848@cbnewse.att.com> <3819@auspex.auspex.com> <1438@sixhub.UUCP>
Date: Tue, 7 Aug 90 05:07:00 GMT
Lines: 24

In article <1438@sixhub.UUCP> davidsen@sixhub.UUCP (bill davidsen) writes:
>  Yes, only ksh gives you the choice of catching the failure.

No, I think most any sh or csh shell will let you catch the failure,
but you have to put the failing command in a subshell.  Even if you're
stuck with a cd that kills your shell, you can get by using:

	( cd "$1" ) && cd "$1"

This puts the first cd in a subshell, which may well die but you don't
care since you're only interested in the return code.  Of course, this
has a small window between the first cd and the second, where things
might change, and so your shell may get blown away anyway; but, you
hope that happens rarely.

The above trick is the only way to test for failure in various other
built-in shell commands.  I often use:

	( trap "" 18 22 ) >/dev/null 2>&1 && trap "" 18 22

because many sh shells don't handle signals above 16, but some do.
-- 
-IAN! (Ian! D. Allen) idallen@watcgl.uwaterloo.ca idallen@watcgl.waterloo.edu
 [129.97.128.64]  Computer Graphics Lab/University of Waterloo/Ontario/Canada