Beginner Question:Apache +Linux +Updates

I’ve seen on a few websites, a line at the bottom of the HTML page that shows an output similar to what you’d see from the command “uptime”.

When I view the source for the page that information is actually ‘hard coded’ onto the source, and is not some weird tag or HTML command I’ve never seen…

Can anyone give me any hints as to how I could do that? I run a small Linux server and it seems like that would be something interesting to show on a system information page.

Thanks,
-Ethan