What is cron?
It is a simple linux utility that allows certain activities to happen at specified times without requiring user input to commence the action.1
What is the structure of a cron job?
The default semantics of a cron job is a pattern of timings followed by a command to be executed at the specified time intervals. The pattern is shown below:
* * * * * <command to execute>
# | | | | |
# | | | | day of the week (0–6) (Sunday to Saturday;
# | | | month (1–12) 7 is also Sunday on some systems)
# | | day of the month (1–31)
# | hour (0–23)
# minute (0–59)
Footnotes
It is nowadays often preferred to use systemd's timer abilities instead of a direct cron job.↩