java中的chmod根据模式而不是字符串

Question

我在 java 中有一个动态 int 代表模式，例如：450、777 等我需要更改现有文件权限，我尝试探索 Files.setPosixFilePermissions Api 但这需要字符串格式的模式，如 -rw-r--r--

Files.setPosixFilePermissions(

    path,

    PosixFilePermissions.fromString("-rw-r--r--")

);

但是，如果它的数字而不是像 450、777 这样的字符串在运行时可以是任何东西，我该如何实现呢？

Answer 1

您可以通过如下简单的转换来做到这一点：&nbsp; &nbsp; public class Chmod {&nbsp; &nbsp; &nbsp; &nbsp; public Set<PosixFilePermission> fromInt(int perms) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; final char[] ds = Integer.toString(perms).toCharArray();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; final char[] ss = {'-','-','-','-','-','-','-','-','-'};&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; for (int i = ds.length-1; i >= 0; i--) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; int n = ds[i] - '0';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (i == ds.length-1) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ((n & 1) != 0) ss[8] = 'x';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ((n & 2) != 0) ss[7] = 'w';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ((n & 4) != 0) ss[6] = 'r';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; else if (i == ds.length-2) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ((n & 1) != 0) ss[5] = 'x';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ((n & 2) != 0) ss[4] = 'w';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ((n & 4) != 0) ss[3] = 'r';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; else if (i == ds.length-3) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ((n & 1) != 0) ss[2] = 'x';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ((n & 2) != 0) ss[1] = 'w';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ((n & 4) != 0) ss[0] = 'r';&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; String sperms = new String(ss);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; System.out.printf("%d -> %s\n", perms, sperms);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return PosixFilePermissions.fromString(sperms);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; public static void main(String[] args) throws Exception {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Chmod test = new Chmod();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; test.fromInt(444);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; test.fromInt(1);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; test.fromInt(777);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; test.fromInt(666);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; test.fromInt(604);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; test.fromInt(0);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }

Answer 2

引用维基百科，您只需弄清楚这些数字是如何产生的：数字符号另一种表示 Unix 权限的方法是八进制（base-8）表示法，如 stat -c %a 所示。该符号至少由三位数字组成。最右边的三个数字中的每一个都代表权限的不同组成部分：所有者、组和其他。（如果存在第四位数字，则最左边（高位）数字地址三个附加属性，setuid 位、setgid 位和粘性位。）这些数字中的每一个都是二进制数字系统中其组成位的总和。结果，特定位添加到总和中，因为它由数字表示：读取位的总数加 4（二进制 100），写入位的总数加 2（二进制 010），并且执行位将其总数加 1（二进制 001）。...结束报价换句话说：您需要做一些二进制掩码来计算表达该数字所需的 r、w、x 字符。您可以手动执行此操作，请参见此处或此处。