Cron

Cron is a timed execution tool under Unix-like, which can run jobs without manual intervention.

Format

Field	Required	Range	Special Character	Remark
Second	True	0-59	* , -	The Standard implementation does not support this field
Minute	True	0-59	* , -
Hours	True	0-23	* , -
Day of month	True	1-31	* , - ? L W	? L W Only some software implements
Month	True	1-12	* , -
Day of week	True	0-7	* , - ? L #	? L # Only some software implements (Linux and Spring value range are 0-7) (Quartz value range is 1-7, 1 is Sunday)
Year	False	1970-2099	* , -	The Standard implementation does not support this field

Character

• * means all values.
• , means partition.
• - indicates closed interval continuous.
• L is the ‘Last’. When used in ‘Day of week’ field, it’s possible to specify a structure for month, such as “Last Friday”(5L). In the ‘Month’ field, you can specify the last day of current month.
• W is ‘Day of month’, it can specify the working day closest to the target date, but it cannot span the current month. (Eg. ‘15W’: targetDate = 15th === Saturday ? 14th : 15th === Sunday && 16th)
• # is used in ‘Day of week’ field and must be followed by a number between 1 and 5. For example, 5#3 means the third Friday every month.
• ? means blank or will be replaced by the time of process started.

Custom Cron Expression Web Site

Supported Format

*    *    *    *    *    *
┬    ┬    ┬    ┬    ┬    ┬
│    │    │    │    │    |
│    │    │    │    │    └ day of week (0 - 7, 1L - 7L) (0 or 7 is Sun)
│    │    │    │    └───── month (1 - 12)
│    │    │    └────────── day of month (1 - 31, L)
│    │    └─────────────── hour (0 - 23)
│    └──────────────────── minute (0 - 59)
└───────────────────────── second (0 - 59, optional)

Cron Expression Web Site

References

• Cron Quartz 定时器调试工具
• Linux crontab 命令
• cron 表达式的用法
• cron-parser
• Cron Expression