Methods to detect public IP address in bash

As part of an installation script, I want to make an "educated guess" about the machines public IP address. It should be as robust as possible, working on a variety of hosts and platforms. Here is an example:

https://gist.github.com/4669037

This script uses 3 methods and then defaults to the value of /etc/hostname. I have only tested this on Ubuntu so far. Will this be likely to work on other distributions? And are there additional methods that I could add?

curl ipinfo.io/ip

Or

wget -q -O - ipinfo.io/ip

Or

lynx -source ipinfo.io/ip

get public ip address

You can find other ip reporting websites instead of ipinfo.io as well. To name a few:

• http://ip4only.me/api/
• http://ip6only.me/api/
• https://ipgrab.io/ ➡ (got from incogma's answer)
• https://icanhazip.com/ ➡ (got from MCurbelo's answer)
• https://api.ipify.org/ ➡ (got from teuber789's answer)

Also, what is my ip shows more information about that ip.