How to know the Server's Public IP Address on Wireless Interface?

I want to setup a web server by using my wireless interface. Just wanted to know for testing purpose as I have setup LAMP. I'm connected to Internet through Wifi and at the same time I want to serve a website. I am following this website to setup LAMP: "https://www.digitalocean.com/community/tutorials/how-to-install-linux-apache-mysql-php-lamp-stack-on-ubuntu-16-04"

Where they told me to know "Server's Public IP Address" After entering the command it shows:- "Device "eth0" does not exist" as I'm using my Wireless Interface. Someone clear me this concept.

Solution 1:

To find your public IP Address, either search google.com: https://www.google.dk/search?q=find+public+ip+address or use http://www.whatismypublicip.com/ or similar service.

Solution 2:

As a 2021 addition to the answer given by Soren A, you do indeed need to use a service hosted on the (external) internet to get your public IP.

I like the site ifconfig.me since one can use it with command line tools. I usually use curl ifconfig.me.