vnetman/pidfile

Python module for managing pid files

pidfile

Python module for managing pid files

Programs create .pid files (typically /var/run/user//.pid) to keep track of the PIDs of running instances of the program. One of the uses is to allow long-running programs or daemons to be killed using a script that reads the .pid file.

This module provides basic management for .pid files.

Example usage:

Part 1 (main program):

  from pidfile import PidFile

  def main():
      global pid
      pid = PidFile('my-name') # Use "/var/run/user/1000/my-name.pid"
      pid.add()                # Add this instance's PID

      global get_out
      get_out = False

      signal.signal(signal.SIGUSR1, my_usr1_handler) # listen to SIGUSR1

      while not get_out:       # main loop runs forever until SIGUSR1
          do_some_work()

      # We must have got SIGUSR1
      sys.exit(0)

  def my_usr1_handler():
      global get_out
      get_out = True

  @atexit.register
  def goodbye():
      pid.remove()             # Remove this instance's PID

Part 2 (program that kills the last running instance of 'my-name'):

  from pidfile import PidFile

  def main():
      pid = PidFile('my-name')
      pid_of_last_instance = p.last()
      if not pid_of_last_instance:
          print('No running instances of \'my-name\'')
      else:
          print('Killing {} ...'.format(pid_of_last_instance))
          os.kill(pid_of_last_instance, signal.SIGUSR1) # send SIGUSR1

Restrictions:

Linux only