How to run script with Daemons

#!/usr/bin/env ruby
#automatically called

#this is the current path where this is run in
dir = File.expand_path(File.join(File.dirname(__FILE__), '..'))

daemon_options = {
  :multiple => false,
  :dir_mode => :normal,
  :dir => File.join(dir, 'tmp', 'pids'), #this puts the pid files in /rails_path/tmp/pids
  :backtrace => true
}



#this runs the first delayed job process
Daemons.run_proc('delayed_job_1', daemon_options) do
 
  if ARGV.include?('--')
    ARGV.slice! 0..ARGV.index('--')
  else
    ARGV.clear
  end

  Dir.chdir dir
  RAILS_ENV = ARGV.first || ENV['RAILS_ENV'] || 'development'
  require File.join('config', 'environment')

  Delayed::Worker.new(
    :min_priority => ENV['MIN_PRIORITY'],
    :max_priority => ENV['MAX_PRIORITY']
  ).start
end

bundle exec script/delayed_delta stop

script/delayed_delta:19:in `<main>': uninitialized constant Daemons (NameError)

gem 'daemons', '1.1.8' # latest