How to get the subdomain value from a url?

Question

how can I get the subdomain value in rails, is there a built-in way to do this?

e.g.

test123.example.com

I want the test123 part of

Answer 1

Simple in your controller just do the following

unless request.subdomains.any?
   #No domains available redirect
   redirect_to subdomain: 'www'
end

Answer 2

For anyone looking to get the subdomains on localhost using WEBrick:

Put config.action_dispatch.tld_length = 0 into config/environments/development.rb and everything should work.

Link to SO post here: Can I make Rails / WEBrick recognize entries in /etc/hosts as subdomains (instead of domains)?

Link to Github post: https://github.com/rails/rails/issues/12438

Answer 3

current domain with subdomains:

"#{request.subdomain}.#{request.domain}"
# or
"#{request.subdomains.join(".")}.#{request.domain}"