Re: [Omaha.pm] Alarms in Perl.

[Jay Hannah <jay@jays.net>]

On Oct 25, 2007, at 11:08 AM, Daniel Linder wrote:
> What I would like to setup is a simple alarm based action that  
> would exit
> the script -- no matter what -- if it was still running after an  
> extended
> period of time.

Your example seems overly complicated to me. I think all you need is  
$SIG{ALRM} and alarm().

$ cat j.pl
local $SIG{ALRM} = \&timeout;
alarm(5);

sleep 10;   # My "long_running_code()"
print "I did not time out. \n";
exit;

sub timeout {
   print "Timed out\n";
   exit;
}

$ perl j.pl
Timed out


That said, I'll take a stab at your questions...

> 1: Will (should) this work even if the "long_running_code()" uses  
> system()
> and or back-ticks to call out to external programs?  (I realize those
> programs could be left running - I'm ok with having the admin clean  
> them
> up once they are alerted to the code not returning at all...)

... I haven't studied Object::Destroyer, but it's probably a safe bet  
that all children process will terminate when your parent process  
(your Perl program) does.

> 2: Are the alarm() and Object::Destroyer calls part of the base Perl
> modules, or will I be visiting CPAN to get this working?  (How do I  
> check
> what's included out of the box vs. what has been installed over time?)

You should be able to see what has been installed after Perl via:

perldoc perllocal

> 3: Is there any command-line magic that perl can be invoked with  
> that will
> cause Perl to call a specific function if it is left running for a  
> long
> period of time?  (i.e. perl --timeout 300 --timeout-sub
> 'MyExitSubroutine()' ./MyBigPerlScript.pl)

Whatever you set $SIG{ALRM} to is what will get called if the kernel  
sends the ALRM signal.

I wouldn't think you would want that to be based on a command-line  
argument, but if you did maybe you could try something like:

   $SIG{ALRM} = eval{ "\&$ARGV[0]" };

My favorite way of handling --timeout-sub args is via Getopt::Long.  
It's groovy.

HTH,

j