计算机基础教程

https://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.infocenter.dc01963.0510/doc/html/psh1360346725201.html

Asterisks (*)

question mark ( ? )

https://crontab.guru/

# crontab

cron is a basic utility available on Unix-based systems.

<minute> <hour> <day-of-month> <month> <day-of-week> <command>
  • *** (all)** specifies that event should happen for every time unit. For example, “*” in the <minute> field means “for every minute.”
  • ? (any) is utilized in the <day-of-month> and <day-of -week> fields to denote the arbitrary value and thus neglect the field value. For example, if we want to fire a script at “5th of every month” irrespective of what day of the week falls on that date, we specify a “?” in the <day-of-week> field.
  • – (range) determines the value range. For example, “10-11” in the field means “10th and 11th hours.”
  • , (values) specifies multiple values. For example, “MON, WED, FRI*“* in <day-of-week> field means on the days “Monday, Wednesday and Friday.”
  • / (increments) specifies the incremental values. For example, a “5/15” in the <minute> field means at “5, 20, 35 and 50 minutes of an hour.”
  • L (last) has different meanings when used in various fields. For example, if it's applied in the <day-of-month> field, it means last day of the month, i.e. “31st of January” and so on as per the calendar month. It can be used with an offset value, like “L-3”, which denotes the “third to last day of the calendar month.” In <day-of-week>, it specifies the “last day of a week.” It can also be used with another value in <day-of-week>, like “6L”, which denotes the “last Friday.”
  • W (weekday) determines the weekday (Monday to Friday) nearest to a given day of the month. For example, if we specify “10W” in the <day-of-month> field, it means the “weekday near to 10th of that month.” So if “10th” is a Saturday, the job will be triggered on “9th,” and if “10th” is a Sunday, it will trigger on “11th.” If we specify “1W” in <day-of-month> and if “1st” is Saturday, the job will be triggered on “3rd,” which is Monday, and it will not jump back to the previous month.
  • # specifies the “N-th” occurrence of a weekday of the month, for example, “third Friday of the month” can be indicated as “6#3”.

# spring sheduler job

https://stackoverflow.com/questions/30887822/spring-cron-vs-normal-cron?rq=1

Spring Scheduled tasks are not in the same format as cron expressions.

They don't follow the same format as UNIX cron expressions.

There are only 6 fields:

  • second,
  • minute,
  • hour,
  • day of month,
  • month,
  • day(s) of week.

https://stackoverflow.com/questions/30887822/spring-cron-vs-normal-cron?rq=1