lock_and_process.pl

#!/usr/bin/perl -w
use strict;
use Fcntl qw(:DEFAULT :flock);

use constant LOCKFILE => '/tmp/default.lck';
use constant TIMEOUT  => 10;

my $cmd = shift || die ("You must give a sub command to run\n");
my $timeout = shift || TIMEOUT;
my $filename = shift || LOCKFILE;

local $SIG{ALRM} = sub { die "Timeout $timeout exceeded\n"; };
alarm $timeout;

open FD, "<$filename"
        or die( "Cannot open $filename: $!\n" );

unless( flock( FD, LOCK_EX | LOCK_NB ) ){
        local $| = 1;
        print "Waiting for lock on filename... ($timeout second timeout)";
        flock( FD, LOCK_SH ) or die( "Can't lock file: $!\n" );
        print "\n";
}
# Received the lock, disable the alarm..
print "Received the lock, disabling the alarm\n";
alarm 0;

# Execute the sub command
print "Executing: $cmd\n";
unless( system( "$cmd" ) == 0 ){
        die( "Couldn't exec $cmd: $!" );
}
close( FD );
exit 0;