从域名到IP转换

#!/usr/bin/env ruby
   require 'open-uri'

  LOOKUP_URL = 'http://toolbar.netcraft.com/site_report?url=%s'
  MATCH_RE = /<td><b>IP address<\/b><\/td><td.*?>([\d\.]+)<\/td>/

  host = ARGV.select { |arg| arg !~ /^\-/ }.first
  open(LOOKUP_URL % host).read =~ MATCH_RE ?   
    puts("#{host} 对应的IP地址为: #{$1}") : 
         puts('主机解析失败!')