Node.js Command Line Applications

Node.js is an excellent choice for creating command-line applications due to its ability to handle input/output operations and its rich ecosystem of modules. In this guide, we will create a simple command-line application to demonstrate its capabilities.

 

Key Features of Command Line Applications in Node.js

1. Process Handling: Access to the process object for reading inputs and managing execution.
2. File System Operations: Perform read/write tasks efficiently.
3. Third-party Modules: Use libraries like commander and yargs for advanced CLI features.

 

Steps to Create a Node.js Command-Line Application

1. Set Up the Project

• Create a project directory:

mkdir my-cli-app
cd my-cli-app

• Initialize the project:

npm init -y

2. Write the Application Code

• Create a file app.js and add the following code:

const readline = require('readline');

// Set up readline interface
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
});

// Ask user for input
rl.question('What is your name? ', (name) => {
  console.log(`Hello, ${name}! Welcome to Node.js CLI.`);
  rl.close();
});

3. Run the Application

• Execute the app using Node.js:

node app.js

• Example Interaction:

What is your name? John
Hello, John! Welcome to Node.js CLI.

 

Adding Advanced Features

1. Using Arguments

• Modify app.js to accept command-line arguments:

const args = process.argv.slice(2);
const name = args[0] || 'User';
console.log(`Hello, ${name}!`);

• Run the app with an argument:

node app.js John

Output:

Hello, John!

2. Using commander Module

• Install commander:

npm install commander

• Add command parsing:

const { Command } = require('commander');
const program = new Command();

program
  .version('1.0.0')
  .description('Simple CLI App')
  .option('-n, --name <type>', 'User name');

program.parse(process.argv);
const options = program.opts();

console.log(`Hello, ${options.name || 'User'}!`);

• Run the app with options:

node app.js --name John

Output:

Hello, John!

 

Summary

Node.js makes it easy to create powerful command-line tools. Whether you're handling inputs directly with process.argv or using third-party libraries like commander, you can quickly build scalable and user-friendly CLI applications to streamline tasks and workflows. Start simple and expand with advanced features as needed!