#!/usr/bin/perl
use strict;
use warnings;
use Sem;
use Storable qw/lock_store lock_retrieve/;
use CGI;

my $q = new CGI;
my $sem = Sem->new('semaphore.txt');
my $x = lock_retrieve('k.dat') or die "Can't open k.dat: $!";
$x->{counter}++;
lock_store($x, 'k.dat') or die "Can't save k.dat: $!";
$sem->unlock;
print $q->header;
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package Sem;

sub new {
    my $class = shift(@_);
    use Carp ();
    my $filespec = shift(@_) || Carp::croak("What filespec?");
    open my $fh, ">", $filespec or Carp::croak("Can't open semaphore f
+ile $filespec: $!");
    chmod 0666, $filespec; # assuming you want it a+rw
    use Fcntl 'LOCK_EX';
    flock $fh, LOCK_EX;
    return bless {'fh' => $fh}, ref($class) || $class;
}

sub unlock {
    close(delete $_[0]{'fh'} or return 0);
    return 1;
}

1;
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You could write your own test using fork, LWP::UserAgent and HTTP::Request::Common.
LWP::Parallel::UserAgent might be handy also.

-Lee

"To be civilized is to deny one's nature."

shotgunefx++

Thanks for pointing out LWP::Parallel::UserAgent. I need that functionality in something I need to write today. I decided to do my daily voting here before heading off to the CPAN. Luckily I stumbled across this node and now I know what I'll be trying first.

Cheers.

-- vek --

It's up to you. You can have the program wait to retrieve a lock, or you can cause it to die.