get RDS ARN for tags API

arn.rb

require 'aws-sdk'

# return 12 digits account number
# if failed, raise RuntimeError
def get_account_id
  iam = AWS::IAM::Client.new
  begin
    iam.get_user.user.arn =~ /arn:aws:iam::(\d{12}):user\/.*/
  rescue => e
    e.message =~ /arn:aws:iam::(\d{12}):user\/.*/
  end
  raise RuntimeError if $1.nil?
  $1
end

# return Array of RDS ARN
def get_rds_arn
  rds = AWS::RDS.new
  account_id = get_account_id

  rds.instances.map{ |i| "arn:aws:rds:#{AWS.config.region}:#{account_id}:db:#{i.db_instance_identifier}" }
end