Node.js stats.mtimeNs Property

The stats.mtimeNs property is an inbuilt application programming interface of the fs.Stats class used to get the timestamp when the file is modified last time since the POSIX epoch expressed in nanoseconds.

Syntax:

stats.mtimeNs;

Parameters: Properties does not have any parameter, but during creation of stats object {bigint:true} must be passed as options.

Return Value: It returns a number or BigInt value which represents the timestamp when the file is modified last time since the POSIX epoch expressed in nanoseconds.

Below examples illustrate the use of stats.mtimeNs property in Node.js:

Example 1:

// Node.js program to demonstrate the
// stats.mtimeNs property

// Accessing fs module
const fs = require('fs');

// Calling fs.Stats stats.mtimeNs using stat
fs.stat('./', { bigint: true }, (err, stats) => {
    if (err) throw err;

    // The timestamp when the file
    // is last modified (in NS)
    console.log("Using stat: " + stats.mtimeNs);
});

// Using lstat
fs.lstat('./filename.txt',
    { bigint: true }, (err, stats) => {
        if (err) throw err;

        // The timestamp when the file
        // is last modified (in NS)
        console.log("Using lstat: " + stats.mtimeNs);
    });

Output:

Using stat: 1592665056784809
Using lstat: 15926651836820176

Example 2:

// Node.js program to demonstrate the
// stats.mtimeNs property

// Accessing fs module
const fs = require('fs').promises;

// Calling fs.Stats stats.mtimeNs
(async () => {
    const stats = await fs.stat(
        './filename.txt', { bigint: true });

    // The timestamp when the file
    // is last modified (in NS)
    console.log("Using stat synchronous: "
                + stats.mtimeNs);
})().catch(console.error)

Output:

Using stat synchronous: 15926651836820176

Note: The above program will compile and run by using the node filename.js command and use the file_path correctly.

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