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A tool for checking system crontab files (/etc/crontab and /etc/cron.d normally) for errors and common mistakes.


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Crontab linter

chkcrontab is a script to check crontab files like those in /etc/cron.d and /etc/crontab. It tries to catch glaring errors and warn on suspect lines in a crontab file. Some valid lines will generate warnings. Certain silly yet valid crontab lines will generate errors as well.

Run this by doing:

chkcrontab crontab_file

Errors will cause a non-zero exit code. Warnings alone will not.

To see sample output for a bad crontab, run the following:

./chkcrontab ./tests/test_crontab

See the ./tests/test_crontab.disable crontab for how to disable warnings and errors.

Output Description

The output of chkcrontab is described on the CheckCrontab wiki page. A link to it appears in the output if there were any warnings or errors. It also suggests ways to fix the reported issues.


Contributions are welcome! Please add unit tests for new features or bug fixes. To run all the unit tests run ./setup test. If you have tox installed, just run tox.

You can review coverage of added tests by running coverage run test and then running coverage report -m.

Note that tests are run on Travis for all supported python versions whenever the tree on github is pushed to.

The packaged version is available via pip or easy_install as chkcrontab. The project page is on pypi:

The source code is available in the following locations:

Pull requests on any of those platforms or emailed patches are fine. Opening issues on gitlab or github is easiest, but I'll check any of them.


For rpm distributions, ./ bdist --formats=rpm should make an rpm but currently dies due to not finding the chkcrontab.1 man page.

For Debian distributions there's an additional tool that might work.


  • Look for duplicate entries. Puppet sometimes loads up crontabs with dups.
  • Check for backticks. (why?)
  • Make sure MAILTO and PATH are set (perhaps others?).
  • Add tests for command line.
  • Enable it to parse user crontabs: #12
  • Make "acceptable filenames" a configurable thing: #4
  • Packaging: #13


  • Kevin Lyda: Who got burned one too many times by broken crontabs.


A tool for checking system crontab files (/etc/crontab and /etc/cron.d normally) for errors and common mistakes.







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