Introduction to cron expression

One 、 What is? Cron expression

cron  An expression is a string , The string consists of  6  The spaces are divided into  7  Domains , Each domain represents a time meaning . Common words: timed task .

Two 、Cron The format of

Cron There are two grammatical formats as follows

Seconds Minutes Hours DayofMonth Month DayofWeek 
 
Seconds Minutes Hours DayofMonth Month DayofWeek  Year

Commonly defined “ year ” The part of can be omitted , What is commonly used in practice is The first six parts consist of

About  cron  The fields of are defined as follows ：

Domain	If required	Values and ranges	wildcard
second	yes	0-59	, - * /
branch	yes	0-59	, - * /
when	yes	0-23	, - * /
Japan	yes	1-31	, - * ? / L W
month	yes	1-12 or JAN-DEC	, - * /
Zhou	yes	1-7 or SUN-SAT	, - * ? / L #
year	no	1970-2099	, - * /

  Introduction to the meaning of wildcards ：

“ , ” This refers to execution at more than two time points , If we were “ branch ” This field is defined as 8,12,35 , It means that they are in the 8 branch , The first 12 branch The first 35 Perform the scheduled task ;
“ - ” This is better understood by specifying a continuous range in a domain , If we were “ when ” This field defines 1-6, It means in 1 To 6 Trigger every hour between points , use , Express 1,2,3,4,5,6;
“ * ” All values , It can be read as “ Every time ”. If in “ Japan ” Set... In this field *, Means every day will trigger ;
“ ? ” Indicates that no value is specified . The scenario used is that you don't need to care about the current value of this field . for example : It's on the 8 No. 1 triggers an operation , But it doesn't matter what day of the week , We can set it like this 0 0 0 8 * ?;
“ /  ” Trigger periodically on a domain , The symbol divides the expression in its field into two parts , The first part is the starting value , It's going to decrease by one unit except seconds , such as stay “ second ” Defined on the 5/10 From The first 5 Seconds to start Every time 10 Once per second , And in the “ branch ” On means from The first 5 Seconds to start Every time 10 Once per minute ;
“ L ” In English LAST It means , Only in “ Japan ” and “ Zhou ” Use in . stay “ Japan ” Set in , Represents the last day of the month ( According to the current month , If it's February, it will be based on whether it's Runnian ), stay “ Zhou ” Last means Saturday , amount to ”7” or ”SAT”. If in ”L” Add the number before , It means the last . For example, in “ Zhou ” Set up ”7L” This format , said “ Last Saturday of the month ”;
“ W ” Represents the working day closest to the specified date ( Monday to Friday ) Trigger , Only in “ Japan ” Can only be used after a specific number . If in “ Japan ” Upper position ”15W”, It means every month 15 The most recent working day of the . If 15 It happens to be Saturday , Find the nearest Friday (14 Number ) Trigger , If 15 It's the end of the week , Next Monday (16 Number ) Trigger . If 15 It happens to be on weekday ( Monday to Friday ), It will trigger on that day . If it is “1W” It can only be pushed to the next most recent working day of this month, but not to the previous month ;
“ # ” Indicates the day of the week of the month , It only works on “ Zhou ” On . for example ”2#3” On the third Tuesday of every month .

3、 ... and 、 Examples of common expressions  

  (1）0 0 2 1 * ?       In the month of 1 Early in the morning 2 Adjust the task

（2）0 15 10 ? * MON-FRI     From Monday to Friday every morning 10:15 Perform operation

（3）0 15 10 ? 6L 2002-2006     Express 2002-2006 Last Friday morning of each month of the year 10:15 Executive work

（4）0 0 10,14,16 * * ?       Every morning 10 spot , Afternoon 2 spot ,4 spot  

（5）0 0/30 9-17 * * ?     Every half hour during 9 to 5 working hours  

（6）0 0 12 ? * WED       Every Wednesday at noon 12 spot  

（7）0 0 12 * * ?       Every day at noon 12 Some trigger  

（8）0 15 10 ? * *       Every morning 10:15 Trigger  

（9）0 15 10 * * ?         Every morning 10:15 Trigger  

（10）0 15 10 * * ?       Every morning 10:15 Trigger  

（11）0 15 10 * * ? 2005       2005 Every morning in 1986 10:15 Trigger  

（12）0 * 14 * * ?         Every afternoon 2 Point to the afternoon 2:59 During each of the 1 Minutes to trigger  

（13）0 0/5 14 * * ?       Every afternoon 2 Point to the afternoon 2:55 During each of the 5 Minutes to trigger  

（14）0 0/5 14,18 * * ?         Every afternoon 2 Point to 2:55 During and in the afternoon 6 Point to 6:55 During each of the 5 Minutes to trigger  

（15）0 0-5 14 * * ?       Every afternoon 2 Point to the afternoon 2:05 During each of the 1 Minutes to trigger  

（16）0 10,44 14 ? 3 WED       Wednesday afternoon in March every year 2:10 and 2:44 Trigger  

（17）0 15 10 ? * MON-FRI       Monday to Friday morning 10:15 Trigger  

（18）0 15 10 15 * ?       monthly 15 The morning of 10:15 Trigger  

（19）0 15 10 L * ?       The morning of the last day of each month 10:15 Trigger  

（20）0 15 10 ? * 6L       Last Friday morning of the month 10:15 Trigger  

（21）0 15 10 ? * 6L 2002-2005     2002 - 2005 Last Friday morning of every month in 2006 10:15 Trigger  

（22）0 15 10 ? * 6#3     The third Friday morning of each month 10:15 Trigger

（23）0/2 * * * * ?       each 2 second Perform tasks

（24）0 0/2 * * * ?         each 2 minute Perform tasks

spring In the frame ,Cron Expressions use 5 Space is divided into 6 Domains ; Days and weeks may conflict , If you care about the day , Weekly use “？”; If you care about Zhou , Daily use “？”.