Node.js fs.truncateSync() Method

The fs.truncateSync() method is used to synchronously change the size of the file i.e. either increase or decrease the file size. It changes the length of the file at the path by len bytes. If len is shorter than the file’s current length, the file is truncated to that length. If it is greater than the file length, it is padded by appending null bytes (x00) until len is reached.

Syntax:

fs.truncateSync( path, len )

Parameters: This method accept two parameters as mentioned above and described below:

• path: It is a string, Buffer, URL that denotes the path of the file that has to be trruncated.
• len: It is an integer which specifies the length of the file after which the file will be truncated. It is an optional parameter. The default value is 0, which means that the whole file would be truncated.

Below examples illustrate the fs.truncateSync() method in Node.js:

Example 1:

// Node.js program to demonstrate the
// fs.truncateSync() method

// Import the filesystem module
const fs = require('fs');

console.log("Contents of file before truncate:")
console.log(fs.readFileSync('example_file.txt', 'utf8'));

fs.truncateSync('example_file.txt', 18);

console.log("Contents of file after truncate:")
console.log(fs.readFileSync('example_file.txt', 'utf8'));

Output:

Contents of file before truncate:
This is an example file for the truncateSync() method.
Contents of file after truncate:
This is an example

Example 2:

// Node.js program to demonstrate the
// fs.truncateSync() method

// Import the filesystem module
const fs = require('fs');

console.log("Contents of file before truncate:")
console.log(fs.readFileSync('example_file.txt', 'utf8'));

// Truncate the whole file
fs.truncateSync('example_file.txt');

console.log("Contents of file after truncate:")
console.log(fs.readFileSync('example_file.txt', 'utf8'));

Output:

Contents of file before truncate:
This is an example file for the truncateSync() method.
Contents of file after truncate:

Reference: https://nodejs.org/api/fs.html#fs_fs_truncatesync_path_len