Many services and applications require you to know your external (WAN) IP address. There are plenty of web sites that allow you to do this, but here are a couple of simple ways to do this from the command line in Linux.
The first method uses the cURL utility, which is basically a command-line utility for retrieving data using URL syntax. In Ubuntu or Debian, you can install cURL from the repositories using the command:
sudo apt-get install curl
After installing cURL, just run this command to get your external IP address:
You can replace ifconfig.me with other service hostnames/URLs, such as:
The second method is really a variation on the one above and uses the wget command. You can use the same hostnames/URLs as above with this command:
wget -qO- ifconfig.me/ip
Have fun! And let me know your tips for this in the comments.