Help Center/ Cloud Operations Center/ User Guide/ Automated O&M/ Scheduled O&M/ Using Cron Expressions
Updated on 2025-03-17 GMT+08:00
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Using Cron Expressions

A cron expression is a time expression used to specify the execution time, frequency, and interval of a scheduled task. It consists of six fields: Seconds, Minutes, Hours, Day of month, Month, and Week.

Field Values

Table 1 Cron expression field values

Field

Allowed Value

Allowed Special Character

Remarks

Seconds

0–59

None

None

Minutes

0–59

* /

The task execution interval is greater than 30 minutes.

Hours

0–23

- * /

None

Dy of month

1~31

- * ? / L

None

Month

1–12

JAN-DEC - * /

None

Day of week

1–7

SUN-SAT - * ? / L

The value 1 indicates Sunday, the value 2 indicates Monday, and so on.

Meaning of Special Characters

Table 2 Meanings of special characters in a Cron expression

Character

Description

Example Value

*

It can match any value of a field.

If the Minutes field is set to *, an event is triggered every minute.

?

It can match any value of a field. However, it can be used only in the Day of month and Day of week fields because the two fields affect each other.

To trigger scheduling on the 20th day of each month, regardless of the day of week, use the following format: 13 13 15 20 *? Because the 20th day is specified in the Day of month field, the last character of the Day of week field can only be a question mark (?) instead of an asterisk (*). If the last character is *, it indicates that the event is triggered on any day of a week, which is exclusive with the 20th day of the date field. In this case, the expression is incorrect.

-

A range

For the Hours field, the value ranges from 8 to 10, indicating that the event is triggered every hour from 8:00 to 10:00.

/

An event is triggered from the specified time and at a fixed interval.

In the Hours field, */3 is equivalent to "every three hours." That is, an event is triggered at the following time points in a day: 0, 3, 6, 9, 12, 15, 18, and 21.

L

Indicates the end, which can appear only in the Day of month and Day of week fields.

If 5L is used as the value of the Day of week field, the event is triggered on the last Thursday.

Example Value

0 15 10 ? * *: indicates that a task is executed at 10:15 a.m. every day.

0 0 10,14,16 * * ?: indicates that a task is executed at 10:00 a.m., 14:00 p.m., and 16:00 p.m. every day.

0 40 9-17 * * ?: indicates that a task is executed at the 40th minute of each hour from 09:00 to 17:00 each day.

0 0/30 10-16 ? * 2: indicates that a task is executed every 30 minutes from 10:00 a.m. to 16:00 p.m. every Monday.

Parent topic: Scheduled O&M