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javascript - 如何解释从 statSync 返回的数字

问题描述

我想获取特定 .js 文件的文件状态。所以我使用了下面发布的代码。但第一个日志语句返回

33204

while the second one returned:

144

输出：

Stats {
dev: 2049,
mode: 33204,
 nlink: 2,
 uid: 1000,
}

但我想解释这些数字以了解文件是否可访问（读、写）

代码：

const fs = require('fs');
var mode = fs.statSync('../../var/opt/personal/guest/op/op_12201/data/persGuesOapDataFolder00/test0.js').mode;
var writePermissions = mode & 0x92; // 010010010

console.log(mode);
console.log(writePermissions);

标签： javascriptnode.jsfs

解决方案

此模式指示有关文件的一些信息，例如：

  • 权限（用于用户、组和其他）
  • 文件类型

为了过滤这些数据，操作系统定义了一些掩码来提取我们需要的信息。这些面具是：

* For filter permissions (user, group and other)

    The following mask values are defined for the file mode component of the st_mode field:

    S_ISUID     04000   set-user-ID bit
    S_ISGID     02000   set-group-ID bit (see below)
    S_ISVTX     01000   sticky bit (see below)

    S_IRWXU     00700   owner has read, write, and execute permission
    S_IRUSR     00400   owner has read permission
    S_IWUSR     00200   owner has write permission
    S_IXUSR     00100   owner has execute permission

    S_IRWXG     00070   group has read, write, and execute permission
    S_IRGRP     00040   group has read permission
    S_IWGRP     00020   group has write permission
    S_IXGRP     00010   group has execute permission

    S_IRWXO     00007   others (not in group) have read, write, and
                       execute permission
    S_IROTH     00004   others have read permission
    S_IWOTH     00002   others have write permission
    S_IXOTH     00001   others have execute permission

* For detect type of file

The following mask values are defined for the file type:
  S_IFMT     0170000   bit mask for the file type bit field
  S_IFSOCK   0140000   socket
  S_IFLNK    0120000   symbolic link
  S_IFREG    0100000   regular file
  S_IFBLK    0060000   block device
  S_IFDIR    0040000   directory
  S_IFCHR    0020000   character device
  S_IFIFO    0010000   FIFO

场景 1：文件具有读取权限（适用于所有人）

const fs = require('fs');

const mode = fs.statSync('./yourfile.txt').mode;

if (mode & (fs.constants.S_IRUSR | fs.constants.S_IRGRP | fs.constants.S_IROTH)) {
  console.log('file has read permissions');
}

场景二：是符号链接

if (mode & fs.constants.S_IFLNK) {
  console.log("It's a symbolic link");
} else {
  console.log("It's not a symbolic link");
}

希望这可以帮助您了解操作系统的工作原理（unix 系统）。更多信息： http: //man7.org/linux/man-pages/man7/inode.7.html

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