daemonize.rb

#!/usr/bin/env ruby

fork do
  Process.setsid
  exit if fork

  if File.exists?('/path/to/pid.pid')
    puts 'Pidfile already exists, not starting.'
    exit 1
  end

  Dir.chdir '/'
  File.open('/path/to/pid.pid', 'w') { |file| file << Process.pid }
  File.umask 0000
  $stdin.reopen '/dev/null'
  $stdout.reopen File.new('/path/to/logfile', 'a')
  $stdout.sync = true
  $stderr.sync = true
  $stderr.reopen $stdout
  Signal.trap('TERM') { exit }

  while true do
  end
end