Octroprint: Turn off webcam automatically

Seen a post about webcam at jcode, i made my own version because:
1. need no additional python libraries
2. need camera stay on while printer is on, ready for next print, not depending on octoprint status

Running cron script every minute:

* * * * * /home/pi/autocam.py

and script autocam.py:

#!/usr/bin/python

import os
import subprocess

SERIAL_DEV = "/dev/serial/by-id/your-serial-port-id"

def checkserial():
  return os.path.exists(SERIAL_DEV)

def checkwebcam():
  r = subprocess.check_output("ps ax | grep mjpg_streamer -c",shell=True)
  c = int(r)-2
  return c > 0

if __name__ == "__main__":
  if checkserial() and not checkwebcam():
    os.system("echo $(date '+%Y-%m-%d %H:%M:%S') start >> autocam.log")
    os.system("service webcamd start")
  elif not checkserial() and checkwebcam():
    os.system("echo $(date '+%Y-%m-%d %H:%M:%S') stop >> autocam.log")
    os.system("service webcamd stop")

Source: https://jcode.me/octoprint-turning-off-webcam-automatically/