Get redirect of a URL in Ruby

This was already answered correctly, but there's a much simpler way:

res = Net::HTTP.get_response(URI('https://graph.facebook.com/1489686594/picture'))
res['location']

You can use Net::Http and read the Location: header from the response

require 'net/http'
require 'uri'

url = URI.parse('http://www.example.com/index.html')
res = Net::HTTP.start(url.host, url.port) {|http|
  http.get('/index.html')
}
res['location']