Question

I am trying to evaluate user-submitted urls to find out whether they contain valid hostnames (formatting) and if so, extract the hostname. Know of any libraries/methods that could help?

Example:

user_input = "www.google.com"

if user_input.has_valid_host?
  hostname = user_input.get_hostname #=> "google.com"
  url = "http://" + @hostname #=> "http://google.com"
else 
  puts "Invalid URL"
end

This example is very simple but I need the url checked against all valid domain extensions and the hostname extracted from any string (assuming that it’s present)

Answer 1

I don’t know ruby, but I wouldn’t think of this as a ruby question.

I would use regex to split out the hostname as you suggest.

Then I would do a system call to the nslookup routine.

On a Windows system from the command prompt it is nslookup.

C:\Users\xyz>nslookup www.google.com
Server:  UnKnown
Address:  192.168.237.2

Name:    www.l.google.com
Address:  173.194.73.99
Aliases:  www.google.com.localdomain

From Ruby you should do an API call instead of using the command line, but both will eventually interface to the DNS service on the local machine.

See: Is there a good DNS server library in ruby?