Crontab Issues running Python

Question

I'm trying to get cron to run this command every 10 minutes;

(In /home/pi/myst-myst/ DIR)

python myst.py `./monitor.sh`

I've tried pretty much everything to get it to work but cron won't execute it properly. Here is what I have at the moment;

*/1 * * * * /usr/bin/python /home/pi/myst-myst/myst.py `./monitor.sh`

Any help would be much appreciated.

Is there an alternative to crontab I could use? Could I use a bash script to execute python and then use a cron for that bash script?

Answer 1

I've had problems calling both python and perl directly from cron. For perl it boiled down to LIBPATH defaulting to something insufficient.

I'd suggest wrapping your commands in a shell script and adding "set -x" to trace through the problem

#!/bin/sh
set -x
export PYTHONPATH=/my/python/modules:$PYTHONPATH
/usr/bin/python /home/pi/myst-myst/myst.py $(/home/pi/myst-myst/monitor.sh)

Call it directly to make sure it works, and then try calling via cron. Make sure to redirect both stdout and stderr to capture any error messages

 */10 * * * * /home/pi/myscript.sh > /home/pi/stdout 2> /home/pi/stderr

Answer 2

You could do something like

*/10 * * * * cd /home/pi/myst-myst/;/usr/bin/python /home/pi/myst-myst/myst.py $(./monitor.sh)

to change working directory before running the command.

Edit: replaced backticks

Answer 3

Does your script rely on any environment variables, such as PYTHONPATH ? If so, the environment will be missing when invoked by cron.

You can try:

*/1 * * * * PYTHONPATH=/my/python/modules/ /usr/bin/python /home/pi/myst-myst/myst.py `./monitor.sh`

Answer 4

Try this way:

 */1 * * * * /home/pi/myst-myst/myst.py `./monitor.sh`

And add the following in myst.py

#!/usr/bin/env python