using command line parameters in node.js application

app.js

// have to have args npm package
// npm install args --save
var args = require('args');

// defining command line options
var args_options = args.Options.parse([
    {
        name: 'port',
        shortName: 'P',
        type: 'int',
        required: false,
        defaultValue: 3000,
        help: 'run server on specified port',
    },
    {
        name: 'help',
        shortName: 'h',
        type: 'bool',
        required: false,
        default: false,
        help: 'print this help info',
    }
]);

var argv;
try {
    // parser will parse process.args by default
    argv = new args.parser().parse(args_options);
} catch(e) {
    // will force the print of help page, which in term causes exit
    argv = { help: true };
    console.log('Error parsing command line parameters');
    console.log('%s %s %s', e.name, e.src, e.value);
}

// if help is requested print it and exit
if(argv.help === true) {
    console.log(args_options.getHelp());
    process.exit(0);
}

// accessing options is quite simple
console.log('listening on port %d', argv.port);