This topic describes how to configure cron expressions.
Cron expressions are applicable to one-time tasks that need to be completed at a certain time point, recurring tasks, and routine maintenance tasks. A cron expression is a string that represents a set of times. The string is separated by five space characters into six fields, in the format of X X X X X X, of which X is a placeholder of a field. If a field contains multiple values, the values are separated with commas (,). Each field can be a specific value or special characters with logical representations.
Values for fields
The following table lists valid values and supported special characters for each field in cron expressions.
| Field | Required | Value range | Allowed special character |
| Second | Yes | [0, 59] | * , - / |
| Minute | Yes | [0, 59] | * , - / |
| Hour | Yes | [0, 23] | * , - / |
| Day | Yes | [1, 31] | * , - / ? L |
| Month | Yes | [1, 12] or [JAN, DEC] | * , - / |
| Week | Yes | [1, 7] or [SUN, SAT]. If you use [1, 7], 1 stands for Sunday, and 2 stands for Monday. |
* , - / ? |
Special characters
Each field in a cron expression can contain a specific number of special characters. Each special character represents a logical argument.
| Special character | Description | Example |
* |
Indicates all possible values. | In the Month field, an asterisk (*) indicates any month. In the Week field, an asterisk (*) indicates any day of a week. |
, |
Lists enumerated values. | In the Minute field, 5,20 indicates that the task is triggered once at both the 5th and 20th minutes. |
- |
Indicates a range. | In the Minute field, 5-20 indicates that the task is triggered once every minute from the 5th to 20th minute. |
/ |
Indicates increments. | In the Minute field, 0/15 indicates that the task is triggered once every 15 minutes from the beginning of an hour. In the Minute field, 3/20 indicates that the task is triggered once every 20 minutes from the 3rd minute of an hour. |
? |
Indicates an unspecified value. Only the Day and Week fields support this character. | If either one of the Day and Week fields is specified, the other field must be set to a question mark (?) to avoid conflicts. |
L |
Indicates the last day. Only the Day field supports this character. Do not specify a list or range when using the L character because it may lead to a logical disorder. |
In the Day field, L indicates the last day of the month. |
Value examples
The following table lists some sample values of cron expressions.
| Example | Description |
0 15 10 ? * * |
Performs the task at 10:15 every day. |
0 15 10 * * ? |
Performs the task at 10:15 every day. |
0 0 12 * * ? |
Performs the task at 12:00 every day. |
0 0 10,14,16 * * ? |
Performs the task at 10:00, 14:00, and 16:00 every day. |
0 0/30 9-17 * * ? |
Performs the task once every half an hour between 09:00 and 17:00 every day. |
0 * 14 * * ? |
Performs the task once every minute between 14:00 and 14:59 every day. |
0 0-5 14 * * ? |
Performs the task once every minute between 14:00 and 14:05 every day. |
0 0/5 14 * * ? |
Performs the task once every five minutes between 14:00 and 14:55 every day. |
0 0/5 14,18 * * ? |
Performs the task once every five minutes between 14:00 and 14:55 and between 18:00 and 18:55 every day. |
0 0 12 ? * WED |
Performs the task at 12:00 every Wednesday. |
0 15 10 15 * ? |
Performs the task at 10:15 on the 15th day of every month. |
0 15 10 L * ? |
Performs the task at 10:15 on the last day of every month. |
0 10,44 14 ? 3 WED |
Performs the task between 14:10 and 14:44 every Wednesday in March every year. |