Use cron expressions-Compute Nest(Compute Nest)-阿里云帮助中心

This topic describes how to set cron expressions.

Cron is suitable for recurring tasks, routine maintenance, and one-time tasks that must run at a specific time. A cron expression is a string that represents a time schedule. The string is divided into six fields separated by spaces, in the format X X X X X X. In this format, X is a placeholder for a field. If a field contains multiple values, use a comma (,) to separate them. Each field can contain a specific value or a special character that has a logical meaning.

Field values

The following table describes the valid values and supported special characters for each of the six fields in a cron expression.

Field	Required	Value range	Special characters
Second	Yes	[0, 59]	Not supported
Minute	Yes	[0, 59]	Limited support for commas (,) and forward slashes (/). If you use a comma, the interval between the numbers must be 30 minutes or more. If you use a forward slash, the number after the slash must be 30 or more.
Hour	Yes	[0, 23]	* , - /
Date	Yes	[1, 31]	* , - / ? L
Month	Yes	[1, 12] or [JAN, DEC]	* , - /
Week	Yes	[1, 7] or [SUN, SAT]. If you use the `1` to `7` format, 1 represents Sunday and 2 represents Monday.	* , ?

Special characters

Each field in a cron expression supports special characters. Each special character has a specific meaning.

Special character	Meaning	Example
`*`	All possible values.	In the Month field, `` means every month. In the Day-of-week field, `` means every day of the week.
`,`	Enumeration values.	In the Minute field, `5,40` means the task is triggered at 5 and 40 minutes past the hour.
`-`	Scope	In the Day-of-month field, `5-20` means the task is triggered every day from the 5th to the 20th of the month.
`/`	Specifies an increment for a value.	In the Day-of-month field, `1/5` means every 5 days, starting on the first day of the month. In the Hour field, `3/8` means every 8 hours, starting at the third hour of the day.
`?`	Indicates no specific value. This character is supported only in the Day-of-month and Day-of-week fields.	When a value is specified for either the Day-of-month or Day-of-week field, set the other field to `?` to avoid conflicts.
`L`	Stands for 'last' and means the last day. This character is supported only in the Day-of-month field. Note When you specify the `L` character, do not specify a list or a range. Otherwise, logical conflicts may occur.	In the Day-of-month field, `L` means the last day of the month.

Examples

The following table shows examples of cron expressions.

Example	Description
`0 15 10 ? * *`	Runs the task at 10:15 every day.
`0 15 10 * * ?`	Runs the task at 10:15 every day.
`0 0 12 * * ?`	Runs the task at 12:00 (noon) every day.
`0 0 10,14,16 * * ?`	Runs the task at 10:00, 14:00, and 16:00 every day.
`0 0/40 9-17 * * ?`	Runs the task every 40 minutes from 09:00 to 17:00 every day.
`0 0 12 ? * WED`	Runs the task at 12:00 (noon) every Wednesday.
`0 15 10 15 * ?`	Runs the task at 10:15 on the 15th of every month.
`0 15 10 L * ?`	Runs the task at 10:15 on the last day of every month.
`0 0,30 14 ? 3 WED`	Runs the task at 14:00 and 14:30 every Wednesday in March.