Learn Linux Shell Scripting - Fundamentals of Bash 4.4

Syntax for the crontab

While the syntax may initially seem confusing, it is actually not that hard to understand but extremely flexible:

<timestamp> command

Wow, that was easy! If this were really the case, then yes. However, what we described above as <timestamp> is actually composed of five different fields, which make up the combined period for running jobs multiple times. In reality, the timestamp is defined as follows (in order):

1. Minute-of-the-hour
2. Hour-of-the-day
3. Day-of-the-month
4. Month
5. Day-of-the-week

In any of these values, we can substitute a number for a wildcard, which indicates all values. Look at the following table to get a feeling about how we combine these five fields for precise times:

Crontab     syntax

Semantic ...