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From: schung@cory.Berkeley.EDU (Stephen the Greatest)
Newsgroups: comp.unix.questions
Subject: Re: csh core dump  (was: if-then-else in csh alias?)
Message-ID: <3571@zen.berkeley.edu>
Date: Wed, 31-Dec-69 18:59:59 EDT
Article-I.D.: zen.3571
Posted: Wed Dec 31 18:59:59 1969
Date-Received: Sat, 5-Sep-87 10:52:07 EDT
References: <16128@teknowledge-vaxc.ARPA> <1376@bloom-beacon.MIT.EDU> <2133@umn-cs.UUCP> <1454@epimass.EPI.COM> <183@intelisc.UUCP> <3565@zen.berkeley.edu>
Sender: news@zen.berkeley.edu
Reply-To: schung@cory.Berkeley.EDU.UUCP (Stephen the Greatest)
Organization: University of California, Berkeley
Lines: 25
Keywords: csh core dump

In article <3565@zen.berkeley.edu> I wrote:
>
>Csh bomber:
>
>mkdir x x/y
>set home = x/y
>cd x/y			<==== Typo
>cd ../..
>*** BOOM! ***
>core dumped
>

Oh, my mistake.  It should be a mere 'cd' that goes to $home instead of
'cd x/y'.  :-(

After the command 'cd', the working directory will be set to $home which
is x/y.  The *shell variable* 'cwd' is also set to $home, which is x/y.
Note that the string in cwd is not a full directory path, so when you
do a cd .., it first goes up one directory and sets cwd to x.  The next
cd .. you do, it goes up yet another directory and tries to set cwd 
right...... Oops!  BOOM!  The variable becomes undefined because it was
not a full path to begin with!  Therefore, to prevent such a core-dump,
do not set home to something other than a full path.

- Stephen