How would you parse a url in Ruby to get the main domain?

Addressable is probably the right answer in 2018, especially uses the PublicSuffix gem to parse domains.

However, I need to do this kind of parsing in multiple places, from various data sources, and found it a bit verbose to use repeatedly. So I created a wrapper around it, Adomain:

require 'adomain'

Adomain["https://toolbar.google.com"]
# => "toolbar.google.com"

Adomain["https://www.google.com"]
# => "google.com"

Adomain["stackoverflow.com"]
# => "stackoverflow.com"

I hope this helps others.

Well you can write this method:

require 'URI'
def domain_name(url, arg={:with_dot_principal=>false})
  arg[:with_dot_principal] ? URI(url).hostname.split('.').last(2).join('.') : URI(url).hostname.split('.').last(2).first
end

And using:

domain_name("https://www.google.com/?gws_rd=ssl&safe=active&ssui=on")
# => "google"
domain_name("http://google.com", with_dot_principal: true)
# => "google.com"

Edit:Warning: This method is a basic answer, this have some observations by the community