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From: dfoster@jarthur.Claremont.EDU (Derek R. Foster)
Newsgroups: comp.unix.shell
Subject: csh exit(status)
Message-ID: <11074@jarthur.Claremont.EDU>
Date: 5 Mar 91 00:44:38 GMT
Distribution: usa
Organization: Harvey Mudd College, Claremont, CA 91711
Lines: 37

Can anyone explain the following output? I looked at the csh man page under
"exit" and it said that exit(stat) would terminate a shell and return
exit status 'stat', where stat was an expression. However, I tried it, and
received the following results ( the '%' is my prompt):  

% if { exit( 1 == 1 ) } echo "y"
% if { exit( 1 == 0 ) } echo "y"
y
% if { exit( 1 != 1 ) } echo "y"
y
% if { exit( 0 == 0 ) } echo "y"

As you can see, it appears that the opposite truth value is being returned.
When the expression ( 1 == 1, etc. ) is true, the value given to the 'if'
statement is false, and vice versa. This seems to be quite consistent.
(It makes no difference if I run the 'exit' command in a subshell by enclosing
the { } in ( ), just in case you were wondering.)

Why is this happening? Is this a bug or a feature? Can anyone else reproduce
these results?

The reason I am trying to do this is so that I can write, in effect,
user-defined functions along the lines of:

alias isxxxfile 'exit ( "\!*" =~ xxx* )'

if { isxxxfile $somefile } dosomething;

If there is an easier way to do this, I would appreciate information on it.
Mostly, however, I would like to understand why exit( ) seems to be logically
inverting its operands.

Any help would be greatly appreciated.

Thanks!

Derek Riippa Foster