Remove subdomain from string in ruby

Question

I'm looping over a series of URLs and want to clean them up. I have the following code:

# Parse url to remove http, path and check format
o_url = URI.parse(node.attributes['href'])

# Remove www
new_url = o_url.host.gsub('www.', '').strip

How can I extend this to remove the subdomains that exist in some URLs?

Answer 1

Something like:

def remove_subdomain(host)
    # Not complete. Add all root domain to regexp
    host.sub(/.*?([^.]+(\.com|\.co\.uk|\.uk|\.nl))$/, "\\1")
end

puts remove_subdomain("www.example.com") # -> example.com
puts remove_subdomain("www.company.co.uk") # -> company.co.uk
puts remove_subdomain("www.sub.domain.nl") # -> domain.nl

You still need to add all (root) domains you consider root domain. So '.uk' might be the root domain, but you probably want to keep the host just before the '.co.uk' part.

Answer 2

I just wrote a library to do this called Domainatrix. You can find it here: http://github.com/pauldix/domainatrix

require 'rubygems'
require 'domainatrix'

url = Domainatrix.parse("http://www.pauldix.net")
url.public_suffix       # => "net"
url.domain    # => "pauldix"
url.canonical # => "net.pauldix"

url = Domainatrix.parse("http://foo.bar.pauldix.co.uk/asdf.html?q=arg")
url.public_suffix       # => "co.uk"
url.domain    # => "pauldix"
url.subdomain # => "foo.bar"
url.path      # => "/asdf.html?q=arg"
url.canonical # => "uk.co.pauldix.bar.foo/asdf.html?q=arg"