ssh.rb

require 'net/ssh'

print "Enter host: "
host=gets.chomp
print "Enter username: "
user=gets.chomp
print "Enter password: "
password=gets.chomp

Net::SSH.start(host, user, :password => password) do |ssh|
  channel = ssh.open_channel do |ch|
    ch.exec "iptables -L" do |ch, success|
      raise "error running command" unless success
      
      #stdout
      ch.on_data do |c, data|
        puts data
      end
      
      #stderr
      ch.on_extended_data do |c, type, data|
        puts data
      end
      
      ch.on_close { puts "work complete!" }
    end
    channel.wait
  end  
end