NetNews Usenet Archive 1992 #30/NN_1992_30.iso/spool/comp/unix/question/14644

Text File | 1992-12-13 | 1.8 KB | 49 lines

Newsgroups: comp.unix.questions
Path: sparky!uunet!haven.umd.edu!darwin.sura.net!news.udel.edu!udel!princeton!fish.Princeton.EDU!lhjensen
From: [e-mail] (Leif Jensen)
Subject: Re: failure by negation
Message-ID: <[e-mail]>
Originator: news@nimaster
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Organization: Princeton University
References: <[e-mail]> <[e-mail]>
Date: Sun, 13 Dec 1992 05:23:53 GMT
Lines: 35

In article <[e-mail]> [e-mail] (Ramez Naam) writes:
>[e-mail] (Elmer Fudd) writes:
>>the following c shell program does the opposite of what i want,
>>it checks to see that a file "alive.n.well" exists, then it stops
>>execution, i want it to do the same if the file doesn't exists!
>>how do i do it?
>>test -f alive.n.well && exit
>test -f [ ! alive.n.well ] && exit

I think Ramez confused two different things.  The answer he gives
doesn't work.  (Is it so hard to test something so simple before
posting or is this just a case of a major typo?) Since the original
poster had a csh script, there are several obvious possibilities.

test -f alive.n.well || exit
test \! -f alive.n.well && exit
if (! -f alive.n.well) exit

On many platforms [ is just a link to test, and when test's argv[0] is
"[" it checks that its last argument is "]", so the following two lines
may also work:

[ -f alive.n.well ] || exit
[ \! -f alive.n.well ] && exit

Notice that the space after "[" is essential.  Many Bourne shells
have [ built-in since it is used so much.  Actually, I would recommend
to the original poster that he practice scripting with /bin/sh instead
of with /bin/csh.

Hope this helps,

--
Leif Jensen
[e-mail]