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Toby Inkster

NAME

Time::Limit - kill your broken Perl script

SYNOPSIS

   use strict;
   use warnings;
   use Time::Limit '0.5';
   
   while (1) {
      print "infinite loop\n";
   }

DESCRIPTION

It is oh so very easy to accidentally write a Perl script that dives straight into an infinite loop, or stumbles into a runaway recursion. In most cases, you can hit Ctrl + C and get on with the job of figuring out what went wrong. However, if you're not running the process in a local terminal (e.g. you're running it over a slow SSH connection, or not in a terminal at all), these processes might be tricky to kill.

The Time::Limit module starts a monitor process that shadows your script's execution, and kills it off if your script has overrun its allotted time limit. Because Time::Limit is global in effect its use in modules is discouraged. Instead, use it only in your main script, or pass it as a parameter to Perl on the command line:

   perl -MTime::Limit myscript.pl

The syntax for using Time::Limit is:

   use Time::Limit @flags, $limit;

Flags are strings prefixed with a hyphen. The following flags are supported:

-group

Send the signal to your script's process group instead of its individual process number. That is, your script and any child processes started with fork will be killed.

-quiet

Kill the script quietly.

-verbose

Output extra debugging information.

The $limit is a number indicating the time in seconds before your script gets killed. It does not have to be an integer. It defaults to a very generous 10.

Be careful to avoid triggering Perl's use MODULE VERSION syntax.

   use Time::Limit -verbose, 4.0;  # yep, kill after 4 seconds
   use Time::Limit '4.0';          # yep, kill after 4 seconds
   use Time::Limit 4.0;            # nah, want $VERSION==4.0

After $limit is reached, Time::Limit will try signalling your script to terminate cleanly (SIGTERM) a few times; if that fails, it will become more aggressive and send SIGKILL signals until it receives word of your script's timely death.

Some random examples using Time::Limit from the command-line:

   perl -MTime::Limit=-quiet,4 myscript.pl
   perl -MTime::Limit=-group,-verbose,4.1 myscript.pl
   perl -MTime::Limit=3 myscript.pl

BUGS

Please report any bugs to http://rt.cpan.org/Dist/Display.html?Queue=Time-Limit.

SEE ALSO

Time::Out - this allows you to apply a timeout to an individual block of code, and then gracefully carry on.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2013 by Toby Inkster.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.