Public IP Of router?

So I'm writing a little networking command line called epsinet and I've realised that ipconfig in cmd returns the private IP Address of the router, not the public. Finding the private IP of the router is fairly easy if you already have the private IP of the user, but the public, for some reason? Not so much.
TL;DR: How do I get the public IP of a connected router through CMD? (still a bit lengthy but shorter)