process.py 文件源码

def _daemonize(self):
        # double-fork. refer to "Advanced Programming in the UNIX Environment"
        try: # first fork
            pid = os.fork()
            if pid > 0: # first parent
                os.waitpid(pid, 0) # wait for second child to start
                return False # return to caller of daemonize()
        except OSError, e:
            self.log('fork #1 failed: %s' % e)
            return # return caller of daemonize()

        # decouple first parent
        os.setsid()
        os.chdir("/")
        os.umask(0)

        ppid = os.getpid() # yes, getpid(). it will be the child's ppid

        try: # second fork
            self._pid = os.fork()
            if self._pid > 0: # second parent. just exit
                os._exit(0) # this is the wait() above
        except OSError, e:
            self.log('fork #2 failed: %s' % e)
            os._exit(1)

        # wait until ppid changes
        while os.getppid() == ppid:
            time.sleep(0.1)

        return True