Cron – Capture errors in python cronjobs

cronpython

I have a python script as a cron job that is called like this

/path/to/python /path/to/myscript myparam

When an error occurs in the script, the cronjob silently fails. When I run the same command from the command line, I get a stack trace. How can I bring my script to output the stack trace (or write it to a file) when running as a cron job? I have already set the MAILTO variable. I have also tried putting

/path/to/python /path/to/myscript myparam 2>&1 >> /path/to/logfile

in the crontab but logfile remains empty.

Update: The call without output redirection works now. It was not an issue with the python script, but a wrong separator in the MAILTO crontab setting. Remember: Use commas and don't put spaces after the commas!

Best Answer

You used the wrong order.

2>&1 means that redirect standard error to the standard output and both to the terminal
>> /path/to/logfile redirects standard output to the log file. You didn't mentioned the standard error, so it still go to the terminal.

Try this:

/path/to/python /path/to/myscript myparam >> /path/to/logfile 2>&1

Make sure that the user who run this script has write permission to the log file.

Related Solutions

Cron job fails silently

The usual problem with 'cron' jobs is that they have zero environment - unlike 'at' jobs which do copy your environment. When something works from the command line and not from 'cron', my experience is that 'environment' is one of the most common problems. Occasionally you run into another problem - 'cron' jobs are not run with a terminal, and occasionally programs get stroppy about this. However, this is in the 1% range compared with 99% for environment issues.

The other key technique I use is to always run a shell script from 'cron'; the shell script ensures that the environment is set correctly and then runs the real program. If a 'cron' job is giving me problems, I can then tweak the script to do useful things like this:

{
    date
    env | sort
    set -x
    ...what was there before adding the debug...
} >/tmp/cron.jobname.$$ 2>&1

This redirects all the output - standard output and standard error - to a file name. You can build timestamps into the filename if you prefer that to the process ID. Analyzing the log files often reveals the problems swiftly.

Cron – MAILTO is not working for CRON. How to fix this

So to answer my question :

Install mailx yum install mailx
Install sendmail yum install sendmail
Start sendmail
Put the MAILTO line into the crontab using crontab -e : MAILTO=my@email.com and not in /etc/crontab

Best Answer

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Cron job fails silently

Cron – MAILTO is not working for CRON. How to fix this

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