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    Hello World command line

    Hello World command line

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