You can define environment variables in the crontab itself when running crontab -e from the command line. This feature is only available to certain implementations of cron. Ubuntu and Debian currently use vixie-cron which allows these to be declared in the crontab file (also GNU mcron).
Python can be used to schedule the automated execution of preprogrammed tasks using cron. But before we dive into exactly how to automate the execution of such Python scripts, let's quickly discuss cron and Python.
Yes, you can define and use variables in this way.
The name of the environment variable is used as the index of the environ[] array to set or get the value of that variable. The get() function is used to get the value of a particular variable, and setdefault() function is used to set the value of the particular variable.
Instead of executing the whole ~/.profile
what I'd do is move the variables that must be shared between your cron
jobs and the account that has the profile, then I'd source these both in ~/.profile
and in the cron job.
The last attempt you show in the question is not properly formatted. The user id should be coming right after the scheduling information, but you've added the sourcing of the profile before the user id, which surely cannot work.
Here's an example setup that I've tested here:
*/1 * * * * someuser . /tmp/t10/setenv && /usr/bin/python /tmp/t10/test.py
I've set it to execute every minute for testing purposes. Replace someuser
with something that makes sense. The /tmp/t10/setenv
script I used had this:
export FOO=foovalue
export BAR=barvalue
The /tmp/t10/test.py
file had this:
import os
print os.environ["FOO"], os.environ["BAR"]
My cron emails me the output of the scripts it runs. I got an email with this output:
foovalue barvalue
You can set the env variable inline:
* * * * * root ENV_VAR=VALUE /usr/bin/python3.5 /code/scraper.py
Another way is use honcho that you can pass a file with env variables.
honcho -e /path/to/.env run /code/scraper.py
You can specify your two environment variables by this:
* * * * * root env A=1 B=2 /usr/bin/python3.5 /code/scraper.py
env
is a system program that runs a specified program with additional variables:
$ env A=1 B=2 /bin/sh -c 'echo $A$B' # or just 'sh': would search in $PATH
12
This is one of the approach I like, write a script to set environment and execute the script with its parameters as its parameters
set_env_to_process.sh
#!/usr/bin/env bash
echo "TEST_VAR before export is: <$TEST_VAR>"
export TEST_VAR=/opt/loca/netcdf
echo "TEST_VAR after export is: <$TEST_VAR>"
export PATH=$PATH:/usr/bin/python3.5
export PYTHTONPATH=$PYTHONPATH:/my/installed/pythonpath
# execute command and its parameters as input for this script
if [ $# -eq 0 ]; then
echo "No command to execute"
else
echo "Execute commands with its parameters: $@"
eval $@
fi
usage
/usr/bin/python3.5 /code/scraper.py
are taken as input for set_env_to_process.sh
set_env_to_process.sh
set the correct env for script to run
It could be used as command line, cron, sudo, ssh to setup env
* * * * * root set_env_to_process.sh /usr/bin/python3.5 /code/scraper.py
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