Node.js fs.createReadStream() Method
The fs.createReadStream() method in Node.js is used to create a readable stream to read data from a file. This method is part of the fs (file system) module and is ideal for reading large files, as it reads the file in chunks rather than loading the entire file into memory. T
fs.createReadStream Method
The createReadStream() method is an inbuilt application programming interface of fs module which allows you to open up a file/stream and read the data present in it.
Syntax:
// Import
const fs = require("fs");
// method syntax
fs.createReadStream( path, options )
Parameters: This method accept two parameters as mentioned above and described below:
- path: This parameter holds the path of the file where to read the file. It can be string, buffer or URL.
- options: It is an optional parameter that holds string or object.
Return Value: This method returns the fs.ReadStream object.
The fs.createReadStream() method is used to read files in chunks, improving performance in Node.js.
Features
- Efficient Memory Usage: Streams are memory-efficient because they don’t load the entire file into memory. This is particularly useful for large files.
- Event-Driven: Streams are event-driven, meaning you can listen for and react to various events like data, end, error, etc.
- Pipeable: Streams can be piped into other writable streams, enabling powerful chaining of operations, such as reading from a file and immediately writing to another file or a network connection.
Below examples illustrate the createReadStream() method in Node.js:
Example 1: This example uses the fs.createReadStream() method to read and display the contents of a file (input.txt) in chunks to the console.
// Filename - index.js
// Node.js program to demonstrate the
// fs.createReadStream() method
// Include fs module
let fs = require('fs'),
// Use fs.createReadStream() method
// to read the file
reader = fs.createReadStream('input.txt');
// Read and display the file data on console
reader.on('data', function (chunk) {
console.log(chunk.toString());
});
Output:
input.txt file data:
GeeksforGeeks: A computer science portal for geeks
Example 2: This example demonstrates the use of fs.createReadStream() to read a specific portion of a file (input.txt) with custom options like encoding, byte range, and buffer size, and then displays the read data in chunks on the console.
// Filename - index.js
// Node.js program to demonstrate the
// fs.createReadStream() method
// Include fs module
let fs = require('fs'),
// Use fs.createReadStream() method
// to read the file
reader = fs.createReadStream('input.txt', {
flag: 'a+',
encoding: 'UTF-8',
start: 5,
end: 64,
highWaterMark: 16
});
// Read and display the file data on console
reader.on('data', function (chunk) {
console.log(chunk);
});
Output:
forGeeks: A comp
uter science por
tal for geeks
Summary
The fs.createReadStream() method is a powerful tool for handling file input in a memory-efficient and scalable way. Whether you’re dealing with large files or just need to stream data efficiently, fs.createReadStream() provides the necessary functionality to handle such tasks seamlessly in Node.js.
Reference: https://nodejs.org/api/fs.html#fs_fs_createreadstream_path_options
