Node.js fs.fchmodSync() Method
Last Updated :
08 Oct, 2021
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The fs.fchmodSync() method is an inbuilt application programming of fs module which is used to synchronously change the permissions of a given file descriptor. These permissions can be specified as a parameter using string constants or octal numbers that corresponding to their respective file modes.
Note: The Windows platform only supports the changing of the write permission. It also does not support the distinction between the permissions of user, group, or others.
Syntax:
javascript
Output:
javascript
Output:
fs.fchmodSync( fd, mode )Parameters: This method accepts two parameters as mentioned above and described below:
- fd: It is an integer which denotes the file descriptor of the file of which the permission has to be changed.
- mode: It is string constant or octal constant that denotes the permission to be granted. The logical OR operator can be used to separate multiple permissions.
// 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'));
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.Example 2: This example shows the usage of octal constants to give the file permissions.
// 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'));
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.Reference: https://nodejs.org/api/fs.html#fs_fs_fchmodsync_fd_mode
