__dirname can be used to return your present working directory. For example, let's say you are on a Linux system and you are currently in the /home/john.doe directory.

[john.doe@localhost ~]$ pwd
/home/john.doe

And let's say /home/john.doe/app.js contains the following.

console.log(__dirname);

Running app.js should return the present working directory.

[john.doe@localhost ~]$ node app.js
/home/john.doe