Reverse Dns check

172:rp young$ cat iptodns.rb 

#!/usr/bin/env ruby

require 'resolv'

def check

 if ARGV[0] == nil

   abort 'Please input ARGV[0]'

 end

end

check

def ipdcheck

 begin 

   puts Resolv.getname(ARGV[0])

 rescue

   puts "No hostname associated with #{ARGV[0]}"

 end

end

ipdcheck

Example)

172:rp young$ ruby iptodns.rb 202.131.30.12

No hostname associated with 202.131.30.12

172:rp young$ ruby iptodns.rb 127.0.0.1

localhost

172:rp young$ ruby iptodns.rb 192.0.34.166

34-166.lax.icann.org

172:rp young$