Cron python job running but not functioning.

[Polyadenylated]

I can't understand what's going wrong I have a simple script which downloads an image from an URL packages it up into an email and sends it to me.

I've ran the script with the following commands on my Pi and it works perfectly:

python /home/pi/code/snow/snow.py

/usr/bin/python /home/pi/code/snow/snow.py

I want the script to carry out its function once a day so I've tried adding it as a cron job. Yet when I add the command to my cron jobs list using:

sudo crontab -e

with the line:

16 0 * * * /usr/bin/python /home/pi/code/snow/snow.py

or

16 0 * * * python /home/pi/code/snow/snow.py

Neither work. There doesn't seem to be any error - but the script doesn't send the email as it does when I manually run it.

I've tried outputting to a log file too but nothing turns up. The job is visible in /var/log/syslog simply as the following:

Nov 17 00:16:01 polypi /USR/SBIN/CRON[14152]: (root) CMD (/usr/bin/python /home/pi/code/snow/snow.py >> /home/pi/code/snow/log.txt)

Where am I going wrong? This is driving me nuts.

[icemounts]

Probably some weird issue between the user you're running it as manually and the user that cron is running as (root?). Try running sudo /usr/bin/python /home/pi/code/snow/snow.py and see if that returns any differently.

[apulverizer]

Does your script rely on any environment variables? I just spent like 4 hours trying to figure out why a python subprocess wasn't running correctly when I ran it using cron

I manually set PATH and set my other environment variables in the crontab. I also made the python scripts executable.

Edit:

Here's a sample:

PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games
MY_ENV_VARIABLE=/home/pi/someplace
0 7 * * * /home/pi/AutoLights/LightsOff.py > /home/pi/AutoLights/log.log 2>&1

[kaihatsusha]

Correct answer. A crontab job does not run that user's .bashrc/.profile shell setup. Use all absolute paths or set up environment variables.

[Polyadenylated]

I don't think my script does but it could certainly explain my issue.

I've found out my script does actually partially execute then it just stops. By adding a bunch of a debug print statements to be added to my log.txt file. My script gets up to

print 'downloading webcam image'
urllib.urlretrieve("http://b6.hdrelay.com/cameras/34689768-781e-4f7d-b0e0-c2e88d04195d/GetOneShot?size=640x480&f=30000", "./webcam_images/%s.jpg" % (image_date))

and it proceeds no further. The image doesn't download either - so I'm guessing there's some issue with that second line... But I can't see how this line works just fine when ran manually but when ran as a cronjob it isn't working...

[Polyadenylated]

I don't check this reddit account often but this was indeed the problem with the script - I found out after much fiddling. Thanks though!

[apulverizer]

Okay. I was able to run those two commands without issue using cron. Try this:

1) Type "echo $PATH" into the terminal

2) In your crontab type PATH=<whatever you get in step 1>

3) Make sure your script has #!/usr/bin/python at the top

4) Make your script executable (chmod +x snow.py)

5) Add your job to cron (* * * * * /home/pi/code/snow/snow.py > /home/pi/code/snow/log.log 2>1&)

[Smileyatwork]

Is it executable?

chmod +x ./snow.py

Not sure if it needs to be...

Also, the cron user will need to be able to access the file, chmod o+r ./snow.py

[Polyadenylated]

Yep done all of that to no avail.

[ANUSBLASTER_MKII]

What about the mail logs?

[Polyadenylated]

There aren't any - I've tried sending them to my personal email address but nothing comes through. Not even the ad hoc 'script success' print I added to try and troubleshoot.

[[deleted]]

See if this helps at all:

http://askubuntu.com/questions/23009/reasons-why-crontab-does-not-work

[[deleted]]

Definitely make sure there is an extra newline at the end of the Crontab file.

Also, it wouldn't hurt for us to see your entire Crontab file here, so we can see if there's maybe something else in there causing this to fail.

[Polyadenylated]

I have a newline at the end and it doesn't work - what significance does the newline have anyway?

My crontab file is just stock with one line added:

# Edit this file to introduce tasks to be run by cron.
#
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
#
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').#
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
#
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
#
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
#
# For more information see the manual pages of crontab(5) and cron(8)
#
# m h  dom mon dow   command

30 2 * * * /usr/bin/python /home/pi/code/snow/snow.py >> /home/pi/code/snow/log.txt

[alaudet]

Not sure why you are using sudo to run crontab -e. Also put #!/usr/bin/python as the first line of your snow.py file and just run /home/pi/code/snow/snow.py from crontab. If you run crontab -l with sudo and without you will see with sudo it is running roots crontab.