How do I find out what my external IP address is?

Question

My computers are sitting behind a router/firewall. How do I programmatically find out what my external IP address is. I can use http://www.whatsmyip.org/ for ad-hoc queries,

Answer 1

Since this question was asked a while back, there's now a freely available web service designed specifically to allow you to determine your IP address programmatically, called ipify.

$ curl 'https://api.ipify.org?format=json'

Results in

{"ip": "1.2.3.4" /* your public IP */}