How to Control Exit Values?

Posted on 2006-02-24 18:30:23-08 by je44ery

Now that I am using Exception::Class to throw exceptions, when my programs halts suddenly due to one of these exceptions, I notice that the exit value is 0, which means that all went OK. I still have a program harness that looks at exit values to perform control operations. How do I set what the exit value will be when my thrown exceptions cause a program halt? Thanks.

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Posted on 2006-02-24 20:14:04-08 by jdhedden in response to 1849

Re: How to Control Exit Values?

I notice that the exit value is 0

This doesn't make sense. Exception::Class exits using die(). This results in a non-zero exit status, usually 255. (I tested this to be sure.)

To set your own exit status, you can set a __DIE__ handler and supply exit() with whatever value you want:

$SIG{__DIE__} = sub { print(STDERR @_); exit(99); };

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Posted on 2006-02-24 22:21:32-08 by je44ery in response to 1851

Re: How to Control Exit Values?

Thanks for the signal handling advice, but, yeah, I know it doesn't make any sense to exit 0 when ending the program due to an exception, that's why I posted, but you know what?! Now, I can't recreate it!?

This says that it was all probably an error in my usage/perception. I'll keep hunting for the situations in which I had thought I was getting exit values of 0 during an exception, but for the moment, I have tried 3 different situations, and none are now exiting with a value of 0! I'm glad I was mistaken, but I'm also now mystified.

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Posted on 2006-02-28 19:14:26-08 by je44ery in response to 1851

Re: How to Control Exit Values?

I knew I wasn't hallucinating!

Missing file during compare Results were: Trace begun at My/Class/Compare.pm line 133 My::Class::Compare::_compare('My::Class::Compare=SCALAR(0x3036f5a8)', 'ARRAY(0x302a79a4)', 'ARRAY(0 +x3068ae40)') called at My/Class/Compare.pm line 173 My::Class::Compare::run('My::Class::Compare=SCALAR(0x3036f5a8)') called at do_something.pl line 66 root@mybox:/home/me # echo $? 0

I have Exception::Class::Base->Trace(1); so that is why the full trace appears. I also know it was my Exception that was called because of the first 2 lines. Those are my own error messages from my overridden full_message() method of the exception class. So here is an example of an exception being thrown, and the exit value being 0.

Names have been changed to protect the innocent.

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Posted on 2006-03-14 17:48:12-08 by je44ery in response to 1870

Re: How to Control Exit Values?

OK, this follow-up to to show that my exit-0-on-exception was not a problem with Exception::Class nor die. I was getting exit values of 0 for 3 different reasons. I hunted them all down, and it was all my fault.

1. This one is embarassing. When I was testing my code, firing from the hip on the command line, you might say, I did this:

my_prog.pl 2>&1 | tee /tmp/my_prog.out

Of course, then I did echo $? I was getting the return value of tee! Doh!

2. I was using rsh on some commands. rsh does NOT return the exit value of the command it ran, but it returns 0 if it was able to run a command at all, even if that command returned non-zero. You must come up with a workaround to acquire the exit value of an rshed command.

3. This one actually involved my Perl code. In some scripts, I was using END{} subroutines, and I was not handing off the bad exit value. So the exit value of my perl progran during an exception was 0 if my last command in the END{} sub was good.

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