double_fork.py

import os
import sys

def DOUBLE_FORK():
    """Perform a UNIX double-fork to detach, and re attach process to init so it's not a child of web worker"""
    # do the UNIX double-fork magic, see Stevens' "Advanced
    # Programming in the UNIX Environment" for details (ISBN 0201563177)
    try:
        pid = os.fork()
        if pid > 0:
            # exit first parent
            sys.exit(0)
    except OSError as e:
        print("fork #1 failed: %d (%s)" % (e.errno, e.strerror))
        sys.exit(1)

    # decouple from parent environment
    os.setsid()
    os.umask(0)

    # do second fork
    try:
        pid = os.fork()
        if pid > 0:
            # exit from second parent, print eventual PID before
            sys.exit(0)
    except OSError as e:
        print("fork #2 failed: %d (%s)" % (e.errno, e.strerror))
        sys.exit(1)
        
        
if __name__ == '__main__':
      print('in main process')
      DOUBLE_FORK()
      print('this running code now has a separate pid, parent of originall process can exit without this being killed')