December 2019
Intermediate to advanced
494 pages
11h 41m
English
The syntax that's used for timer triggers is called cron; it's widely used in Unix-like operating systems and it comes from the Greek word for time, chronos. The syntax is often short, convenient, and very difficult to get right, kind of like regular expressions. There's an easy online tool that can help you figure out your cron expressions: https://crontab.guru/.
There are five components in cron – minute, hour, day of the month, month, and day of the week. The asterisk (*) means any value, so the cron expression * * * * * means trigger on any minute, of any hour, on any day, of any month, or, simply put, trigger every minute. 0 0 * * * triggers at minute 0 of hour 0 (so 00:00, or 12 AM) of any day, so that's every ...