Cron Expression: 0 0/5 * 1/1 * * Explained
Cron expressions are used to schedule tasks to run at specific intervals in Linux and Unix-like systems. They consist of five or six fields, each representing a different aspect of the schedule. In this article, we'll break down the cron expression 0 0/5 * 1/1 * * and explain what each part means.
Fields in a Cron Expression
A typical cron expression consists of five fields, each separated by a space. These fields are:
- Minute (0-59)
- Hour (0-23)
- Day of the month (1-31)
- Month (1-12)
- Day of the week (0-6), where 0 = Sunday
Some cron implementations also allow for a sixth field, which specifies the year (optional).
**The Cron Expression: 0 0/5 * 1/1 * * **
Let's analyze each field in the given cron expression:
Minute: 0
The minute field is set to 0, which means the command will run at the beginning of every interval.
Hour: 0/5
The hour field is set to 0/5, which means the command will run every 5 hours, starting from 0 (midnight). The /5 part specifies the interval, so the command will run at 0, 5, 10, 15, ... hours.
Day of the month: *
The day of the month field is set to *, which means the command will run every day of the month.
Month: 1/1
The month field is set to 1/1, which means the command will run every month. The 1/1 part is a special syntax that means "every" or "any".
Day of the week: *
The day of the week field is set to *, which means the command will run every day of the week.
What Does This Cron Expression Do?
In summary, this cron expression will run a command:
- Every 5 hours, starting from midnight
- Every day of the month
- Every month
- Every day of the week
This means the command will run at 0, 5, 10, 15, ... hours, every day, every month.
Conclusion
Understanding cron expressions is crucial for scheduling tasks in Linux and Unix-like systems. By breaking down the fields of a cron expression, we can decipher the schedule and ensure that our tasks run as intended.
