In Debian system with Vixie cron, environment variables can be defined in the crontab:

MESSAGE=Hello World
* * * * * /bin/sh ~/script.sh >> /tmp/script.log

Now, can the same environment variable MESSAGE be passed to the shell script ~/script.sh that being scheduled to run every minute? Let’s just give a try by adding the following line to script.sh:

echo "ECHO: ${MESSAGE}"

tail -f /tmp/script.log:

ECHO: Hello World
ECHO: Hello World
ECHO: Hello World

Therefore, the shell script will pick up the environment variables defined in crontab. This really is a convenience.