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
// 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
// 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