Node.js filehandle.readFile() Method

The filehandle.readFile() method is used to asynchronously read the file contents. This method reads the entire file into the buffer. It Asynchronously reads the entire contents of a file.

Syntax:

filehandle.readFile( options )

Parameters: The method accepts single parameter as mentioned above and described below:

• options: It holds the encoding of file. Its default value is ‘utf8’. It is an object or a string.
  • encoding: It is a String or NULL. Default: null

Return Value: It returns a Promise.

• The Promise is resolved with the contents of the file. If no encoding is specified using options.encoding, the data is returned as a Buffer object. Otherwise, the data will be a string.
• If options is a string, then it specifies the encoding.
• The FileHandle has to support reading.

Example: Read the file contents of the file ‘GFG.txt’ 

Note: ‘GFG.txt’ should be present in the directory with the following text:

GeeksforGeeks - A computer science portal for geeks

Filename: app.js

// Node.js program to demonstrate the
// fsPromises.truncate() Method

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

// Using the async function to
// ReadFile using filehandle
async function doReadFile() {
    let filehandle = null;
    try {

        // Using the filehandle method
        filehandle =
        await fsPromises.open('GFG.txt', 'r+');

        var data =
        await filehandle.readFile("utf8");

        console.log(data);
    } catch (e) {
        console.log("Error", e);
    }
}

doReadFile().catch((error) => {
    console.log("Error", error)
});

Run app.js file using the following command:

node app.js

Output:

GeeksforGeeks - A computer science portal for geeks

Reference: https://nodejs.org/dist/latest-v14.x/docs/api/fs.html#fs_filehandle_readfile_options