YA Cron Question

Question

I have a python script called mediacircus.py that works when run manually (using Idle) in /home/pi. I have a Cron schedule to run it every minute that looks like this:

* * * * * /usr/bin/python /home/pi/mediacircus.py

but a check using

grep cron /var/log/syslog

shows no evidence that it has run, even though another unrelated task that also runs every minute--a shell script--does run. I have ensured that the script is executable using chmod.

Using Idle, I see that /home/pi/ is a valid path.

I've tried replacing "/usr/bin/python" with simply "python", and also taken this part out completely, to no avail.

What am I doing wrong?

Answer 1

idle is likely causing you to believe that your script is executable, when in fact it is not. You can confirm this by starting your script from the command line, just as you do in your crontab; i.e. type this at the command line:

/usr/bin/python /home/pi/mediacircus.py 

Also note that on Raspberry Pi, /usr/bin/python executes Python 2 - not Python 3.

In the event your program throws an error when run under cron, the following may be useful in capturing any error codes:

/usr/bin/python /home/pi/mediacircus.py > ~/cronjoblog 2>&1  

This will redirect the stderr output to a file in your home directory.

And you haven't revealed any of your code, so I'm forced to guess as to whether or not your .py file includes an appropriate shebang in the first line. Try the following:

/usr/bin/python 

Why? cron has a different set of environment variables than you do when you run as pi. In other words, cron's $PATH is different that pi's. Hope this helps.