How do I cleanly stop a python routine.

[Douglas6]

Lots of ways to do that. You could get the time of day in your loop, compare if it's later than the time you want to stop, and if so 'break' out of the loop. Or you could run a cron script with a 'kill' command to abruptly end your program. In that case you should have a signal handler to clean things up.

[DougieLawson]

In cron you can use

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30 8 * * * /bin/kill -USR1 `cat /var/run/processname.pid`
00 9 * * * /bin/kill -USR2 `cat /var/run/processname.pid`

In your python process

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import signal

def sigUSR1handler(signum, stack):
  # do stuff when signalled with USR1

def sigUSR2handler(signum, stack):
  # different stuff to do for USR2 signal

signal.signal(signal.SIGUSR1, sigUSR1handler)
signal.signal(signal.SIGUSR2, sigUSR2handler)

The hard part is capturing the process id (pid) when the process starts and writing it somewhere where your cronjobs can read it. If you do that from an /etc/init.d script then it's done for you.

[ame]

Lots of ways to do that. You could get the time of day in your loop, compare if it's later than the time you want to stop, and if so 'break' out of the loop. Or you could run a cron script with a 'kill' command to abruptly end your program. In that case you should have a signal handler to clean things up.

I'd do it the first way. Use cron to start the process, then something inside the program to decide when to stop.

[gordon77]

You could just start and stop it from python at appropriate times,

To start

Import subprocess
Import os

p=subprocess.Popen(rpistr,shell=True, preexec_fn=os.setsid) where rpistr is your raspistill command etc eg "raspistill -t 0 -tl 0 etc.

To stop it use. os.killpg(p.pid, signal.SIGTERM)

Example

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import RPi.GPIO as GPIO
import time
import subprocess, os
import signal
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO_switch = 24  # pin 18
GPIO.setup(GPIO_switch,GPIO.IN)

print "  Press Ctrl & C to Quit"

try:
    
   run = 0
   while True :
      if GPIO.input(GPIO_switch)==0 and run == 0:
         print "  Started"
         rpistr = "raspistill -o /run/shm/test.jpg -t 0 -tl 0  "
         p=subprocess.Popen(rpistr,shell=True, preexec_fn=os.setsid)
         run = 1
         while GPIO.input(GPIO_switch)==0:
             time.sleep(0.1)
      if GPIO.input(GPIO_switch)==0 and run == 1:
         print "  Stopped " 
         run = 0
         os.killpg(p.pid, signal.SIGTERM)
         while GPIO.input(GPIO_switch)==0:
             time.sleep(0.1)
       

except KeyboardInterrupt:
  print "  Quit"
  GPIO.cleanup()   

To get the hour you could use

now = datetime.datetime.now()
hour = now.hour
if hour > 8 and hour < 20:
Etc.....

[joan]

In cron you can use

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30 8 * * * /bin/kill -USR1 `cat /var/run/processname.pid`
00 9 * * * /bin/kill -USR2 `cat /var/run/processname.pid`

...
The hard part is capturing the process id (pid) when the process starts and writing it somewhere where your cronjobs can read it. If you do that from an /etc/init.d script then it's done for you.

You could use /usr/bin/killall as pretty much a drop in replacement for kill. It is slightly friendlier in that it uses process names rather than process ids.

[-rst-]

I would assume the first is your actual Python script and the second is another thread or child process started from the first? So killing the first/main one should probably kill the child process.

Could you not just have one Python script that starts at boot, runs forever (if not stopped manually or through GPIO or something external), only takes the photos and emails during the specified times and just sleeps when you don't want the photos - why make it so complicated with multiple processes and external tools/commands (if not for learning and/or distributed processing reasons)?