php如何使用递归来计算一个目录中所有文件的大小 （代码）

sudo find /private/etc -exec ls -l {} \; | awk 'BEGIN {sum=0} {sum+=$5;} END {print sum}'  # 4947228
ls -ld /etc  #/etc -> private/etc

<?php
/**
 * Created by PhpStorm.
 * User: Mch
 * Date: 8/14/18
 * Time: 22:11
 */
class DirUtil {
    public static function getSize(string $path) {
        $totalSize = 0;
        $path = realpath($path);
        if (!file_exists($path)) {
            return $totalSize;
        }
        if (!is_dir($path)) {
            return filesize($path);
        }
        if ($dh = opendir($path)) {
            while (($file = readdir($dh)) !== false) {
                if ($file !== "." && $file !== "..") {
                    $abs = $path.DIRECTORY_SEPARATOR.$file;
                    if (is_dir($file)) {
                        $totalSize += self::getSize($abs);
                    } else {
                        $totalSize += filesize($abs);
                    }
                }
            }
            closedir($dh);
        }

        return $totalSize;
    }

    public static function entryForEach(string $path, callable $callback, mixed $data = null) {
        $path = realpath($path);
        if (!file_exists($path)) {
            return 0;
        }
        if (!is_dir($path)) {
            return call_user_func($callback, $path, $data);
        }
        if ($dh = opendir($path)) {
            while (($file = readdir($dh)) !== false) {
                if ($file !== "." && $file !== "..") {
                    $abs = $path.DIRECTORY_SEPARATOR.$file;
                    if (is_dir($file)) {
                        self::entryForEach($abs, $callback, $data);
                    } else {
                        call_user_func($callback, $abs, $data);
                    }
                }
            }
            closedir($dh);
        }
        return 0;
    }

    public static function entryReduce(string $path, callable $callback, $init) {
        $acc = $init;
        $path= realpath($path);
        if (!file_exists($path)) {
            return $acc;
        }
        if (!is_dir($path)) {
            return call_user_func($callback, $acc, $path);
        }
        if ($dh = opendir($path)) {
            while (($file = readdir($dh)) !== false) {
                if ($file !== "." && $file !== "..") {
                    $abs = $path.DIRECTORY_SEPARATOR.$file;
                    if (is_dir($file)) {
                        $acc = self::entryReduce($abs, $callback, $acc);
                    } else {
                        $acc= call_user_func($callback, $acc, $abs);
                    }
                }
            }
            closedir($dh);
        }

        return $acc;
    }
}

// php ./DirUtil.php /etc
if ($argc < 2) {
    printf("Usage: php %s [filename]\n", __FILE__);
    exit(1);
}
echo DirUtil::getSize($argv[1]).PHP_EOL; // 899768

$dir_get_size = function($path) {
    $size = 0;
    DirUtil::entryForEach($path, function($path) use (&$size) {
        $size += filesize($path);
    });
    return $size;
};
echo $dir_get_size($argv[1]).PHP_EOL;  // 899768

echo DirUtil::entryReduce($argv[1], function($sum, $path) {
    $sum += filesize($path);
    return $sum;
}, 0).PHP_EOL;  // 899768