Concatenating user.username

The first way is to remove world! and concatenate user.username. Then we can concatenate another string using the + (plus) operator, as shown in the following code:

console.log('Starting app.');

const fs = require('fs');
const os = require('os');

var user = os.userInfo();

fs.appendFile('greetings.txt', 'Hello' + user.username + '!');

Now if we run this, everything is going to work as expected. Over in Terminal, we can rerun our app. It prints Starting app:

Over in the greetings.txt file, you should see something like Hello Gary! printing to the screen, as shown here:

Using the fs module and the os module, we were able to grab the user's username, create a new file, and store it.