Creating a Command-Line Interface (CLI) Tool with NodeJS: A Step-by-Step Guide

Command-line interface (CLI) tools are essential for developers, providing a way to automate tasks, interact with
applications, and streamline workflows. In this guide, we will walk you through the process of creating a simple CLI
tool using Node.js.

Prerequisites

Before you start, make sure you have the following installed:

• Node.js (latest version)
• A text editor (like Visual Studio Code, Atom, or Sublime Text)
• Basic knowledge of JavaScript and the command line

Step 1: Set Up Your Project

1. Create a new directory for your project:

mkdir my-cli-tool
cd my-cli-tool

2. Initialize a new Node.js project:

npm init -y

This will create a package.json file in your project directory.

3. Install necessary dependencies:

For this tutorial, we’ll use the commander package for command-line argument parsing.
npm install commander

Step 2: Create the CLI Script

1. Create a new JavaScript file for your CLI tool:

touch index.js

2. Open index.js in your text editor and add the following code:

#!/usr/bin/env node

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

// Define CLI commands and options
program
.version('1.0.0')
.description('A simple CLI tool example')
.option('-n, --name ', 'specify a name')
.option('-g, --greet', 'greet the user');

// Handle the command and options
program.action(() => {
    if (program.greet && program.name) {
        console.log(`Hello, ${program.name}!`);
    } else if (program.greet) {
        console.log('Hello, World!');
    } else {
        console.log('No greeting specified.');
    }
});

program.parse(process.argv);

In this code:

• We import the commander package and create a new command program.
• We define a version, description, and options for the CLI tool.
• The action method handles the logic based on user input.

Step 3: Make the Script Executable

1. Add the following line at the top of index.js:

#!/usr/bin/env node

This shebang line allows the script to be run as an executable from the command line.

2. Make your script executable by running the following command:

chmod +x index.js

Step 4: Link the CLI Tool Globally

1. Update your package.json to include a bin field:

Add the following to your package.json:

"bin": {
"my-cli-tool": "./index.js"
}

Replace "my-cli-tool" with the desired name for your CLI command.

2. Link your package globally:

Run the following command:

npm link

1. This command makes your CLI tool accessible from anywhere in the terminal.

Step 5: Test Your CLI Tool

1. Run your CLI tool from the terminal:

You can greet the user by specifying a name:

my-cli-tool --greet --name John

This should output:

Hello, John!

2. Try other variations:

• Just greet without a name:

my-cli-tool --greet

Output:

Hello, World!

• Call the tool without the greet option:

my-cli-tool

Output:

No greeting specified.

Step 6: Expand Your CLI Tool

Now that you have a basic CLI tool, you can expand its functionality by adding more commands and options. Here
are a few ideas:

• Add more commands using program.command('commandName').
• Include file handling to read or write data.
• Integrate APIs or external services.
• Implement logging or configuration options.

Conclusion

Congratulations! You’ve built a simple CLI tool using Node.js. This guide has covered the basics, but the
possibilities are endless. With commander and Node.js, you can create robust command-line
applications tailored to your needs. Explore more features, enhance your tool, and make it a powerful addition
to your development toolkit. Happy coding!