NAME

Time::Out - Easily timeout long running operations

SYNOPSIS

use Time::Out qw( timeout );

timeout $timeout => sub {
  # your operation is implemented here and will be interrupted
  # if it runs for more than $timeout seconds
};
if ( $@ ) {
  # operation timed-out
}

DESCRIPTION

The Time::Out module provides an easy interface to alarm(2) based timeouts. Nested timeouts are supported. The module exports the timeout() function by default. The function returns whatever the code placed inside the subroutine reference returns:

use Time::Out qw( timeout );

my $result = timeout 5 => sub {
  return 7;
};
# $result == 7

If Time::Out sees that Time::HiRes has been loaded, it will use that alarm() function (if available) instead of the default one, allowing float timeout values to be used effectively:

use Time::HiRes qw();
use Time::Out   qw( timeout );

timeout 3.1416 => sub {
  # ...
};

CAVEATS

Blocking I/O on MSWin32

alarm(2) doesn't interrupt blocking I/O on MSWin32, so timeout() won't do that either.

@_

One drawback to using timeout() is that it masks @_ in the affected code. This happens because the affected code is actually wrapped inside another subroutine that provides it's own @_. You can get around this by specifically passing your @_ (or whatever you want for that matter) to timeout() as such:

use Time::Out qw( timeout );

sub foo {
  timeout 5, @_ => sub {
    @_;
  };
}
my @result = foo( 42, "Hello, World!" );
# @result == ( 42, "Hello, World!" );

Eval inside timeout

If the affected code has its own exception handling using Try::Tiny for example, the catch block has to be amended in a way so that it will rethrow an exception, if it refers to a timeout:

use Scalar::Util qw( blessed  );
use Time::Out    qw( timeout );
use Try::Tiny    qw( catch try );

timeout 5, sub {
  try {
    select( undef, undef, undef, 7 );
    die "bad\n";
  } catch {
    # rethrow exception, if it refers to a timeout
    die $_ if blessed $_ && $_->isa( 'Time::Out::Exception' );
    # handle all other exceptions
  }
};

SEE ALSO

alarm(2), Sys::AlarmCall

AUTHORS

Sven Willenbuecher, <sven.willenbuecher@gmx.de>

Patrick LeBoutillier, <patl@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2005-2008 Patrick LeBoutillier, 2023 by Sven Willenbuecher.

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