• LockingWrapperScript

Simple file locking wrapper

From MySQL Performance Blog

<?php
if ($argc < 3) {
    echo("USE: exclusive.php <lockname> <command to run>\n");
    exit;
}

$lock = $argv[1];
$cmd = array_slice($argv, 2);
$command = implode(' ', $cmd);
$filename = "/tmp/$lock.lck";

$fp = fopen($filename, "w+");
if (!$fp) {
    die('Unable to create lock file');
}

/* WARNING: LOCK_NB behaves tricky. true is still returned in case of wait but $l is set to 1 */
$r = flock($fp, LOCK_EX | LOCK_NB,$l);
if ($r & !$l) /* Lock successfull */ {
    system($command, $res);
    flock($fp, LOCK_UN); // release the lock

    /* Unlink file just in case so we do not have problem running with different users */
    unlink($filename);
    exit($res);
} else {
    echo "Couldn't lock the file !";
}

fclose($fp);
?>

CategoryProgramming