Nette\Caching\Storages\FileStorage::read PHP Method

    public function read($key)
    {
        $meta = $this->readMetaAndLock($this->getCacheFile($key), LOCK_SH);
        if ($meta && $this->verify($meta)) {
            return $this->readData($meta);
            // calls fclose()
        } else {
            return NULL;
        }
    }