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NodeJS fs.fsyncSync() Method
  • Last Updated : 08 Feb, 2021

In this article, we will be learning about fsyncSync() method in NodeJS. Before diving deep into the topic, let’s have a brief idea about what a fsync() method is.

Node.js provides us with a ‘fs’ module that helps us with both synchronous and asynchronous forms. An asynchronous form has a callback as the last argument whereas in case of synchronous, it only consists of the file descriptor. A fsync() function does not return any value but helps to get the file descriptor in a synchronous way. A fsyncSync() method is just the synchronized form of fsync(). It helps to synchronize the disc cache.



fd refers to the File Descriptor and its return value is undefined.

Parameter: File Descriptor.

Return Type: Undefined.

File descriptor is a number that uniquely identifies an open file in a computer. It provides an entry to the global file table that provides us with the location of that entry. Example : if the file descriptor is 3, it means that in the global file table it is saved as a read/write operation with offset : 12.

At first, we need to install ‘fs’ and ‘express’ module in our NodeJS project. 

npm install fs express --save

Create a file ‘example.txt’ inside your node.js project so that we can use any kind of operation for that file. After that write the necessary javascript code for our project.


const fs = require('fs'); 
const express = require('express'); 
const app = express(); 
// Retuns the file descriptor
const fd = fs.openSync('example.txt', 'r+'); 
// Function call 
fs.fsync(fd, (err) => { 
    if(err) { 
    } else {  
// Server setup 
app.listen(3000, function(error){ 
    if (error) console.log("Error"
    console.log("Server running to port 3000"
node app.js


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