Path: utzoo!utgpu!water!watmath!clyde!ima!bbn!bbn.com!rsalz
From: rsalz@bbn.com (Rich Salz)
Newsgroups: comp.lang.c
Subject: Re: exit(-1), 0 is sometimes magic
Keywords: exit, zero, shells
Message-ID: <310@fig.bbn.com>
Date: 23 Jan 88 21:32:05 GMT
References: <502@cresswell.quintus.UUCP> <6935@brl-smoke.ARPA> <1179@wjvax.UUCP> <1234@nmtsun.nmt.edu> <562@cresswell.quintus.UUCP>
Followup-To: comp.unix.questions
Organization: BBN Laboratories, Cambridge MA
Lines: 28

>>I might be wrong.
>You are.
So are you. :-)

>    sh(1):
...
>	Control structures:  Cmd1 && Cmd2 executes Cmd2 iff Cmd1 returns
>	a zero exit status,  Cmd1 || Cmd2 executes Cmd2 iff Cmd1 returns
...
>    csh(1):
>	...  && and || are as in sh(1);
...

Nope.  The use of && and || in csh is the opposite of that in /bin/sh.
	/bin/sh -c "/bin/test -d foo || mkdir foo"
Means if the foo directory doesn't exist, make it.  That is, /bin/sh does
the "conceptually right thing" in that it takes a||b to mean, do b if a
failed.

The Cshell takes a||b in the mathematical sense; do b if a does an exit(0):
	/bin/csh -c "/bin/test -d foo || mkdir foo"
will never make the directory, or mkdir will spit if it already exists.

This has stopped being an comp.lang.c.ansii-bash issue, so I'm directing
followups to comp.unix.questions
	/r$
-- 
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