Node.js fs.filehandle.chmod() Method

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