The fs.filehandle.datasync() method is an inbuilt application programming interface of class fs.filehandle within File System module which is used to sync the data of the file.
Syntax:
const filehandle.datasync()
Parameter: This method does not accept any parameter.
Return value: This method returns an pending promise which contain no value in it.
Below programs illustrates the use of fs.filehandle.datasync() method.
Example 1: Filename: index.js
// Node program to demonstrate the // filehandle.datasync() method const fs = require( 'fs' );
const fsPromises = fs.promises; console.log( "File content 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+' );
// Syncing the data by using
// datasync() method
await filehandle.datasync();
} finally {
if (filehandle) {
// Close the file if it is opened.
console.log( "data synced successfully" );
console.log( "Content after operation: "
+ (fs.readFileSync( 'example.txt' )));
await filehandle.close();
}
}
} funct(). catch (console.error);
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Directory structure of the program:
Run index.js file using the following command:
node index.js
Output:
File content before operation: Content of the example.txt file data synced successfully Content after operation: Content of the example.txt file
Example 2: Filename: index.js
// Node.js program to demonstrate the // filehandle.datasync() 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+' );
// Syncing the data by using
// datasync() method
await filehandle.datasync();
} finally {
if (filehandle) {
// Close the file if it is opened.
console.log( "data synced successfully" );
console.log( "content of file after"
+ " operation: " +
(fs.readFileSync(file)));
await filehandle.close();
}
}
} funct(). catch (console.error);
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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. data synced successfully content of file after operation: This is a file containing a collection of books.
Directory structure before running the program:
Directory structure after running the program:
Reference: https://nodejs.org/dist/latest-v12.x/docs/api/fs.html#fs_filehandle_datasync