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# amazon-ec2 gem
require 'AWS'

# Your keys
ACCESS_KEY_ID = 'your AWS ID'
SECRET_ACCESS_KEY = 'your AWS secret'

# open EC2 connection
ec2 = AWS::EC2::Base.new(:access_key_id => ACCESS_KEY_ID, :secret_access_key => SECRET_ACCESS_KEY)

# drop in static hosts file for things like localhost
IO.foreach('hosts') {|line| puts line}

# Generate the rest
puts "\n\n# Generated by dnsupdate.rb\n"
ec2.describe_instances.reservationSet.item.each do |instance|
  instance.instancesSet.item.first.tagSet.item.each do |tag|
    if tag['key'] == 'dns'
      # EC2 instances are tagged with 'dns' and a hostname as the value
      # I use things like appname_railsenv_app1, etc..
      puts "#{instance.instancesSet.item.first.ipAddress} #{tag['value']}"
      puts "#{instance.instancesSet.item.first.privateIpAddress} #{tag['value']}-int"
    end
  end
end