Node.js fs.fchmodSync()用法及代码示例

fs.fchmodSync()方法是fs模块的内置应用程序编程，用于同步更改给定文件描述符的权限。可以使用字符串常量或与它们各自的文件模式相对应的八进制数将这些权限指定为参数。

注意：Windows平台仅支持更改写权限。它还不支持区分用户权限，组权限或其他权限。

用法:

fs.fchmodSync( fd, mode )

参数：此方法接受上述和以下所述的两个参数：

fd:它是一个整数，表示必须更改权限的文件的文件描述符。
mode:它是字符串常量或八进制常量，表示要授予的权限。逻辑OR运算符可用于分隔多个权限。

以下示例说明了Node.js中的fs.fchmodSync方法：

范例1：此示例显示了使用字符串常量和OR运算符来授予文件权限的用法。

// Node.js program to demonstrate the 
// fs.fchmodSync method 
  
// Import the filesystem module 
const fs = require('fs'); 
  
// Getting the file descriptor 
const fd = fs.openSync('example_file.txt', 'r'); 
  
// Allowing only read permission 
console.log("Giving only read permission to user"); 
fs.fchmodSync(fd, fs.constants.S_IRUSR); 
  
// Check the file mode 
console.log("Current File Mode:", 
    fs.statSync("example_file.txt").mode); 
  
// Reading the file 
console.log("File Contents:", 
    fs.readFileSync("example_file.txt", 'utf8')); 
  
// Trying to write to file 
try { 
  console.log("Trying to write to file"); 
  fs.writeFileSync('example_file.txt', "Hello"); 
} 
catch (e) { 
  console.log("Error Found, Code:", e.code); 
} 
  
// Allowing both read and write permission 
console.log("\nGiving both read and write permission to user"); 
fs.fchmodSync(fd, fs.constants.S_IRUSR | fs.constants.S_IWUSR); 
  
// Check the file mode 
console.log("Current File Mode:", 
    fs.statSync("example_file.txt").mode); 
  
console.log("Trying to write to file"); 
fs.writeFileSync('example_file.txt',  
    "This file has been written over."); 
  
console.log("File Contents:",  
    fs.readFileSync("example_file.txt", 'utf8'));

输出：

Giving only read permission to user
Current File Mode:33024
File Contents:Hello World
Trying to write to file
Error Found, Code:EACCES

Giving both read and write permission to user
Current File Mode:33152
Trying to write to file
File Contents:This file has been written over.

范例2：本示例说明使用八进制常量来授予文件权限。

// Node.js program to demonstrate the 
// fs.fchmodSync method 
  
// Import the filesystem module 
const fs = require('fs'); 
  
// Getting the file descriptor 
const fd = fs.openSync('example_file.txt', 'r'); 
  
// Allowing only read permission 
console.log("Giving only read permission to everyone"); 
fs.fchmodSync(fd, 0o444); 
  
// Check the file mode 
console.log("Current File Mode:",  
    fs.statSync("example_file.txt").mode); 
  
// Reading the file 
console.log("File Contents:",  
    fs.readFileSync("example_file.txt", 'utf8')); 
  
// Trying to write to file 
try { 
  console.log("Trying to write to file"); 
  fs.writeFileSync('example_file.txt', "Hello"); 
} 
catch (e) { 
  console.log("Error Found, Code:", e.code); 
} 
  
// Allowing both read and write permission 
console.log("\nGiving both read and "
    + "write permission to everyone"); 
fs.fchmodSync(fd, 0o666); 
  
// Check the file mode 
console.log("Current File Mode:",  
    fs.statSync("example_file.txt").mode); 
  
console.log("Trying to write to file"); 
  
fs.writeFileSync('example_file.txt',  
    "This file has been written over."); 
  
console.log("File Contents:",  
    fs.readFileSync("example_file.txt", 'utf8'));

输出：

Giving only read permission to everyone
Current File Mode:33060
File Contents:Hello World
Trying to write to file
Error Found, Code:EACCES

Giving both read and write permission to everyone
Current File Mode:33206
Trying to write to file
File Contents:This file has been written over.

参考： https://nodejs.org/api/fs.html#fs_fs_fchmodsync_fd_mode

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注：本文由纯净天空筛选整理自sayantanm19大神的英文原创作品 Node.js | fs.fchmodSync() Method。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。