tcsh: how do you get the exit status of a program?

BrianK · 10-30-2007, 07:10 PM

from the manual:

Quote:

Command exit status
Commands can be executed in expressions and their exit status returned by enclosing them in
braces ('{}'). Remember that the braces should be separated from the words of the command by
spaces. Command executions succeed, returning true, i.e., '1', if the command exits with status
0, otherwise they fail, returning false, i.e., '0'. If more detailed status information is
required then the command should be executed outside of an expression and the status shell vari-
able examined.

... but none of these work:

Code:

{ls}
{ ls }
'{ ls }'

am I reading the manual wrong?

rsashok · 10-30-2007, 07:54 PM

I use BASH in my civilian life, and I am not a tcsh-shelll specialist, but I tried following.
1. /bin/tcsh
It brought me to the C-shell
2. ls
3. echo $?
It returned 0, which means good command
4. kmya
This non existent command.
5. echo $?
It returned 1.

I didn't use any brackets, maybe it worthwhile to try. BTW: in BASH if you use command in braces, such as ( ls ), it will 'fork' it out as a separate process.

BrianK · 10-30-2007, 08:10 PM

Quote:

Originally Posted by rsashok

I use BASH in my civilian life, and I am not a tcsh-shelll specialist, but I tried following.

Looking at the status var (I believe that's what $? is called, right?) does give me the exist status, but it does it after the exit, at which point stderr has been filled with [useful] garbage.

what I was hoping to accomplish was to stop a failing command from running before it actually runs by testing its exit status first, then running the command if the exit status is 0.

AnanthaP · 10-31-2007, 07:08 AM

Quote:

... running before it actually runs ...

Hows that?

Anyway, sometimes it may be required, particularly before you commit any specific action.

Assuming that you can set the exit status in your program (if it isn't a standard command), then:

myCommand [args ..]
a=$?
if [$a -eq "0" ] then
myCommand [fresh set of args maybe ...]
fi

end

BrianK · 10-31-2007, 12:59 PM

Quote:

Originally Posted by AnanthaP

Hows that?

... sorry "test" before it actually runs...

the problem is I have a script that looks for a glob of files & does things with them. Sometimes the glob has no matches. When it has no matches, an error is reported (even if you "set nonomatch"). This is a problem when the script is run in a cron job because then you get mail every time the glob matches nothing... and this is the behavior I'm trying to avoid.

Currently, I just dump all output from the script to /dev/null which solves the problem, but sometimes I want the script to error out on other things... just not the glob - hence my wanting to test the glob before using with something like

Code:

if ( {ls *foo} == 0 ) then
 do something with *foo
endif