Croncape wraps commands run as cron jobs to send emails only when an error or a timeout has occurred.

Out of the box, crontab can send an email when a job generates output. But a command is not necessarily unsuccessful "just" because it used the standard or error output. Checking the exit code would be better, but that's not how crontab was standardized.

Croncape takes a different approach by wrapping your commands to only send an email when the command returns a non-zero exit code.

Croncape plays well with crontab as it never outputs anything except when an issue occurs in Croncape itself (like a misconfiguration for instance), in which case crontab would send you an email.

Download the binaries or go install github.com/symfonycorp/croncape@latest.

When adding a command in crontab, prefix it with croncape:

MAILTO=sysadmins@example.com
0 6 * * * croncape ls -lsa

That's it!

Note that the MAILTO environment variable can also be defined globally in /etc/crontab; it supports multiple recipients by separating them with a comma.

You can also customize the email sender by setting the MAILFROM environment variable.

If you need to use "special" shell characters in your command (like ; or |), don't forget to quote it and wrap the command in a shell:

0 6 * * * croncape bash -c "ls -lsa | true"

Besides sending emails, croncape can also kill the run command after a given timeout, via the -t flag (disabled by default):

0 6 * * * croncape -t 2h ls -lsa

If you want to send emails even when commands are successful, use the -v flag (useful for testing).

Use the -h flag to display the full help message.

Croncape is very similar to cronwrap, with some differences:

• No dependencies (cronwrap is written in Python);

• Kills a command on a timeout (cronwrap just reports that the command took more time to execute);

• Tries to use sendmail or mail depending on availability (cronwrap only works with sendmail);

• Reads the email from the standard crontab MAILTO environment variable instead of a -e flag.

For a simpler alternative, have a look at cronic.