check if process pid is running and exit

asmodeus.rb

class Asmodeus
  attr_accessor :pid_file

  def info text
    puts 'Asmodeus: %s' % text
  end

  def pid_check no_check=false
    return unless @pid_file

    unless no_check
      running = Process.getpgid(File.read(@pid_file).to_i) rescue false

      if running
        info 'running, exit'
        exit
      end
    end

    File.write(@pid_file, Process.pid)
  end

  def check
    if block_given? && !yield
      info 'func check failed'
      pid_check true
    else
      pid_check
    end

    true
  end
end

#

test = Asmodeus.new
test.pid_file = 'looper.pid'
test.check { true }

loop do
  puts rand
  sleep 0.5
end