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From: levy@ttrdc.UUCP (Daniel R. Levy)
Newsgroups: net.unix,net.unix-wizards
Subject: Re: question-- Bourne (and C) SHELL
Message-ID: <1139@ttrdc.UUCP>
Date: Sun, 17-Aug-86 14:31:50 EDT
Article-I.D.: ttrdc.1139
Posted: Sun Aug 17 14:31:50 1986
Date-Received: Tue, 19-Aug-86 08:22:20 EDT
References: <1751@ittatc.ATC.ITT.UUCP> <7028@utzoo.UUCP> <150@humming.UUCP>
Organization: AT&T, Computer Systems Division, Skokie, IL
Lines: 41
Xref: watmath net.unix:8933 net.unix-wizards:19264

In article <150@humming.UUCP>, arturo@humming.UUCP (Arturo Perez) writes:
>In the csh you can do something like
>
>ls foo
>if (! $status) then
>   echo "foo exists"
>endif
>
>The  key  thing  here  is  the  ability  to NOT the value of status. How is
>this similar thing done in Bourne shell.
>
>if ! ls foo
>then
>	echo foo does not exist
>fi

To follow your example literally:

ls foo
if test $? -ne 0	# or, "if [ $? -ne 0 ]" is supported by modern /bin/sh's
then
	echo foo does not exist
fi

Of course, there are other ways to check for nonexistence of foo, e.g.:

if [ ! -f foo -a ! -d foo -a ! -p foo -a ! -c foo -a ! -b foo ]

# foo is not a file, a directory, a pipe, a character special device, or a
# block special device

which though "wordier" does not require the spawning of another process
presuming that "test" is a builtin in your shell.
-- 
 -------------------------------    Disclaimer:  The views contained herein are
|       dan levy | yvel nad      |  my own and are not at all those of my em-
|         an engihacker @        |  ployer or the administrator of any computer
| at&t computer systems division |  upon which I may hack.
|        skokie, illinois        |
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