Crontab\CrontabFileHandler::parseExistingCrontab PHP Method

    public function parseExistingCrontab(Crontab $crontab)
    {
        // parsing cron file
        $process = new Process($this->crontabCommand($crontab) . ' -l');
        $process->run();
        foreach ($this->parseString($process->getOutput()) as $item) {
            $crontab->addItem($item);
        }
        $this->error = $process->getErrorOutput();
        return $this;
    }