public function jobExists($job = '')
    {
        $process = new Process('crontab -l');
        $process->run();

        $output = ($process->getIncrementalOutput());

        $jobs = array_filter(explode(PHP_EOL, $output), function($line) {
            return '' != trim($line);
        });

        return is_array($jobs) ?  array_search($job, $jobs) : false;
    }