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Node.js filehandle.read() Method
  • Last Updated : 29 Jun, 2020

The filehandle.read() method reads the file using a file descriptor. In order to read files without file descriptor the readFile() method of the filehandle package can be used.

Node.js is used for server-side scripting. Reading and writing files are the two most important operations that are performed in any application. Node.js offers a wide range of inbuilt functionalities to perform read and write operations. The fs package contains the functions required for file operations.

Syntax:

filehandle.read( buffer, offset, length, position );

Parameters: This function accept four parameters as mentioned above and described below:

  • buffer: Stores the data fetched from the file. It is the buffer in which the data will be written.
  • offset: Offset in the buffer indicating where to start writing.
  • length: An integer that specifies the number of bytes to read.
  • position: An integer that specifies where to begin reading from in the file. Position is an argument specifying where to begin reading from in the file. If position is null, data is read from the current file position.

Return value: It returns the Promise.



Note: “GFG.txt” should be present in the directory with the following text:

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Example:

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// Node.js program to demonstrate the
// Node.js filehandle.read() Method
  
// Import the filesystem module 
const fs = require('fs');
const fsPromises = fs.promises;
  
var buffer = new Buffer.alloc(1024);
  
console.log(fs.readFileSync('GFG.txt', 'utf8'));
  
// Using the async function to 
// ReadFile using filehandle
async function doRead() {
    let filehandle = null;
  
    try {
        // Using the filehandle method
        filehandle = await fsPromises
                    .open('GFG.txt', 'r+');
  
        // Calling the filehandle.read() method
        await filehandle.read(buffer,
                0, buffer.length, 0);
    } finally {
        if (filehandle) {
  
            // Close the file if it is opened.
            await filehandle.close();
        }
    }
}
  
doRead().catch(console.error);

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Run app.js file using the following command:

node app.js

Output:

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