What is Node.js fs.filehandle.chmod() Method?

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Node.js fs.filehandle.chmod() Method - ❤️Node.js Tutorials In 2024

The fs.filehandle.chmod() method is an inbuilt application programming interface of class fs.filehandle within File System module which is used to change the permission of the particular file.

Syntax:

const filehandle.chmod( mode )

Parameter: This method accepts single parameter mode that holds the integer value.
Return Value: This method returns a pending promise which contain no value in it.

Below programs illustrates the use of fs.filehandle.chmod() method.

Example 1: Filename: index.js

Javascript

// Node.js program to demonstrate the 
// fs.filehandle.chmod() method
const fs = require('fs');
const fsPromises = fs.promises;
 
console.log("content of file before "
        + "operation :- " +
        (fs.readFileSync('example.txt')));
 
// Initiating asynchronise function
async function funct() {
 
    // Initializing filehandle
    let filehandle = null;
 
    try {
 
        // Creating and initiating filehandle
        filehandle = await fsPromises
                .open('example.txt', 'r+');
 
        // Modifying the file permission
        // by using chmod() method
        const prom = filehandle.chmod(1);
 
    } finally {
 
        if (filehandle) {
 
            // Close the file if it is opened.
            console.log("permission is changed"
                        + " to read only");
 
            console.log("content of file before"
                    + " operation :- " +
                (fs.readFileSync('example.txt')));
 
            await filehandle.close();
        }
    }
}
 
funct().catch(console.error);

Directory structure before running the program:

Directory structure after running the program:

Run index.js file using the following command:

node index.js

Output:

content of file before operation :- Content of example.txt file
permission is changed to read only
content of file after operation :- Content of example.txt file

Example 2: Filename: index.js

Javascript

// Node.js program to demonstrate the 
// fs.filehandle.chmod() method
const fs = require('fs');
const fsPromises = fs.promises;
 
// data for the new file
let data = "This is a file containing"
        + " a collection of books.";
 
// Name of the file to be created
let file = "books.txt";
 
// Creating the new file 'books.txt'
fs.writeFile(file, data, (err) => {
 
    // Catching error
    if (err) {
        console.log(err);
    }
});
 
// Using fs.exists() method 
fs.exists(file, (exists) => {
    if (exists) {
        console.log("content of file "
            + "before operation :- " +
            (fs.readFileSync(file)));
    }
});
 
// Initiating asynchronise function
async function funct() {
 
    // Initializing filehandle
    let filehandle = null;
 
    try {
 
        // Creating and initiating  filehandle
        filehandle = await fsPromises.open(file, 'r+');
 
        // Modifying the file permission
        // by using chmod() method
        const prom = filehandle.chmod(1);
 
    } finally {
 
        if (filehandle) {
 
            // Close the file if it is opened.
            console.log("permission is "
                + "changed to read only");
                 
            console.log("content of file"
                + "after operation :- " +
                (fs.readFileSync(file)));
 
            await filehandle.close();
        }
    }
}
 
funct().catch(console.error);

Directory structure before running the program:

Directory structure after running the program:

Run index.js file using the following command:

node index.js

Output:

content of file before operation :- This is a file containing a collection of books.
permission is changed to read only
content of file after operation :- This is a file containing a collection of books.

Reference: https://nodejs.org/dist/latest-v12.x/docs/api/fs.html#fs_filehandle_chmod_mode