Crontab strats 2 processes, calling 1 script

shridhar22 · 07-27-2014, 11:48 PM

My crontab had the command:

Quote:

50 08 * * 1-5 /home/MY_SCRIPT.py /home/arguments 2> /dev/null

59 23 * * 1-5 killall MY_SCRIPT.py

Which worked perfectly fine, but when I used to do

Code:

ps aux | grep SCRIPT

it showed

Quote:

myuser 13898 0.0 0.0 4444 648 ? Ss 08:50 0:00 /bin/sh -c /home/MY_SCRIPT.py /home/arguments 2> /dev/null

myuser 13900 0.0 0.0 25268 7384 ? S 08:50 0:00 /usr/bin/python /home/MY_SCRIPT.py /home/arguments

Why are 2 processes been shown

And the killall command also used to work fine.

I made a change to my script and in order to get the new behaviour, I had to kill the currently running scripts and I used

Code:

kill 13898 13900

After that I used the same command (as in crontab)

Code:

/home/MY_SCRIPT.py /home/arguments 2> /dev/null

But now after restrating the script, it showed only 1 process (which makes sense)

Everything looks good till here, but this time the killall MY_SCRIPT in the cronjob didnt work, it said could not find pid. And the script kept on running until I had to manually kill it.

Need to find out the reason for this behaviour:

Why 2 processes from cronjob
Is there something wrong the way I restrated the script
How do I make sure that next time I restart the script, the cron should kill it for sure

rknichols · 07-28-2014, 08:55 AM

The cron daemon needs to invoke a shell to process the "2>/dev/null" redirection. The only way I can think of to get rid of that shell process is to change MY_SCRIPT.py to a shell script that explicitly exec-s the python interpreter:

Code:

#!/bin/sh
exec python - "$@" <<EOF
   your
   script
   here
EOF

I think that will work, but I don't have a suitable script for testing it.