syntax

# ┌───────────── minute (0 - 59)
# │ ┌───────────── hour (0 - 23)
# │ │ ┌───────────── day of the month (1 - 31)
# │ │ │ ┌───────────── month (1 - 12)
# │ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday;
# │ │ │ │ │                                   7 is also Sunday on some systems)
# │ │ │ │ │
# │ │ │ │ │
# * * * * * <command to execute>

error codes

When a cron job exits, even a successful exit, the output is emailed to the cron jobs owner. This can get really annoying for things like a regular backup sequence where you only care if it fails. There's a tool called chronic included in moreutils that can be used to ignore successful output.

misc

display notification from cron

https://blog.healthchecks.io/2022/09/schedule-cron-job-the-funky-way/