What defines all non-relative links?

I'm looking for a way d开发者_如何学Goo differ between relative and non-relative links on an html page.

What defines all non-relative links? I'm looking for some sort of regular expression.

for example, do all non-relative links contain :// and relative links never display it?

Absolute across the internet start with http:// or https:// (or whatever other scheme they may be using. I guess you could "contains" :// as you said).

Hrefs starting with a slash (/) are both absolute from and relative to the web-server path

Paths starting with letters/numbers/symbols or ../ are relative to the page's file path, with ../ meaning "next folder up".