public static function disk(String $dir, String $type = 'free') : Float
    {
        $dir = self::rpath($dir);

        if( ! is_dir($dir) )
        {
            throw new Exception\FolderNotFoundException(NULL, $dir);
        }

        if( $type === 'free' )
        {
            return disk_free_space($dir);
        }
        else
        {
            return disk_total_space($dir);
        }
    }