Cron は、Unix 系オペレーティング システムに存在するソフトウェア ユーティリティで、時間ベースのスケジュール設定に使用されます。空白で区切られた 6 (または年を含む場合は 7) つのフィールドの文字列を使用して、繰り返しタスクの高度にカスタマイズ可能なスケジュール設定を提供します。文字列の形式は secondsminuteshours day of the monthmonthday of the weekyear です。
***?** would trigger every second, whereas 0**?** would trigger every minute, more specifically at second 0 of each minute.
Used to indicate that no value is specified. May be used only in the day of the month or day of the week fields.
00015*?* would trigger at midnight on the 15th day of each month, whereas 000?*2* would trigger at midnight each Monday.
Used to indicate a range of values.
009-17?*2-6 would trigger every hour from 9:00am until 5:00pm on Monday through Friday.
Used to indicate additional values.
009-17?*MON,WED,FRI would trigger every hour from 9:00am until 5:00pm on Mondays, Wednesdays, and Fridays.
Used to indicate increments of the given field(s).
000/3?*2/7 would trigger every three hours, on Mondays, beginning at midnight.
Used to indicate Last. May be used only in the day of the month or day of the week fields. For day of the week, it can be used after another value, for example 6L to indicate the last Friday.
595923L*? would trigger at 11:59:59pm on the last day of each month, whereas 595923?*6L would trigger at the same time but only on the last Friday of each month.
Used to indicate the nearest weekday to the given value. May only be used with the day of the month field.
00015W*? would trigger at midnight of the nearest weekday to the 15th, every month. If the 15th is a Saturday, it would trigger on Friday the 14th, whereas if the 15th is Sunday, it will trigger on Monday the 16th.
Used to indicate a desired monthly occurrence of the given value, for example the first Friday, or fourth Thursday. May only be used with the day of the week field.
0017?*6#1 would trigger at 5:00pm on the first Friday of every month.