package Cron::AvoidMultipleRuns;

use strict;
use warnings;

use Errno qw( EWOULDBLOCK );
use Fcntl qw( LOCK_EX LOCK_NB );

our $lock_fh;

{
    open($lock_fh, '<', $0)
        or die("Can't open script \"$0\": $!\n");

    if (!flock($lock_fh, LOCK_EX|LOCK_NB)) {
        undef $lock_fh;

        if ($! == ($^O =~ /Win32/ ? 33 : EWOULDBLOCK)) {
            die("Another instance of this program is running. Exiting.\n");
        } else {
            die("Cannot lock script \"$0\": $!\n");
        }
    }
}

1;