Recognize search engines and spammers using user-agents.org

robot_user_agents.rb

require 'net/http'
require 'xmlsimple'
url = "http://www.user-agents.org/allagents.xml"
xml_data = Net::HTTP.get_response(URI.parse(url)).body
data = XmlSimple.xml_in(xml_data)
agents = data['user-agent'].select{|agent| type = agent["Type"].first; type.include?("R") || type.include?("S")}
agent_names = agents.collect {|agent| agent["String"].first}

In regards to your (very old...) question, here's what I ended up using!

url = "http://www.user-agents.org/allagents.xml"
xml_data = Net::HTTP.get_response(URI.parse(url)).body
xml_doc = Nokogiri::XML(xml_data)
bots = xml_doc.xpath('.//user-agent').collect{|u| u if u.xpath('.//Type').text.include?("R") || u.xpath('.//Type').text.include?("S")}
bots_list = bots.reject(&:blank?).reject{|b| b.xpath('.//String').blank?}
agent_names = bots_list.collect{|b| b.xpath('.//String').first.text}