How to parse a URL and extract the required substring

Question

Say I have a string like this: "http://something.example.com/directory/"

What I want to do is to parse this string, and extract the "something" from the string.

The first step, is to obviously check to make sure that the string contains "http://" - otherwise, it should ignore the string.

But, how do I then just extract the "something" in that string? Assume that all the strings that this will be evaluating will have a similar structure (i.e. I am trying to extract the subdomain of the URL - if the string being examined is indeed a valid URL - where valid is starts with "http://").

Thanks.

P.S. I know how to check the first part, i.e. I can just simply split the string at the "http://" but that doesn't solve the full problem because that will produce "http://something.example.com/directory/". All I want is the "something", nothing else.

Answer 1

I'd do it this way:

require 'uri'

uri = URI.parse('http://something.example.com/directory/')
uri.host.split('.').first
=> "something"

URI is built into Ruby. It's not the most full-featured but it's plenty capable of doing this task for most URLs. If you have IRIs then look at Addressable::URI.