A ruby script to get all instances with a given tags.

deploy_utils.rb

require 'aws-sdk'
require 'awesome_print'

class AwsUtil

  def ec2_object
    # deployer user, has read-only access
    AWS::EC2.new(
      access_key_id: "<your_key_here>",
      secret_access_key: "<your_secret_here>",
      region: 'us-west-2'
    )
  end

  def deployed_app_server_dns_names
    ec2_object.instances.
      filter('tag:Role', 'app').
      filter('tag:Environment', 'production').
      filter('instance-state-name', 'running').
      map {|r| r.dns_name}
  end

  def print_dns_names
    ap deployed_app_server_dns_names
  end
end