Node.js can be used to create command line utilities. The example below reads the first argument from the command line and prints a Hello message.

To run this code on a Unix System:

  1. Create a new file and paste the code below. The filename is irrelevant.
  2. Make this file executable with chmod +x FILE_NAME
  3. Run the app with ./APP_NAME Dragon

On Windows, you do step 1 and run it with node APP_NAME Dragon

#!/usr/bn/env node ‘use strict’

/* The command line arguments are stored in the process.argv array, which has the following structure: [0] The path of the executable that started the Node.js process [1] The path to this application [2-n] the command line arguments Example: [ ‘/bin/node’, ‘/path/to/yourscript’, ‘arg1’, ‘arg2’, … ] src: https://nodejs.org/api/process.html#process_process_argv */

// Store the first argument as username. var username = process.argv[2];

// Check if the username hasn’t been provided. if (!username) { // Extract the filename var appName = process.argv[1].split(require(‘path’).sep).pop();

//  Give the user an example on how to use the app.
console.error('Missing argument! Example: %s YOUR_NAME', appName);
// Exit the app (success: 0, error: 1).
// An error will stop the execution chain. For example:
//   ./app.js && ls       -> won't execute ls
// ./app.js Dragon && ls -> will execute ls 
process.exit(1);

}

// Print the message to the console. console.log(‘Hello %s!’, username);