"Cron" time format
<Second> <Minutes> <Hours> <Month days> <Months> <Weekdays>
Any of the five fields can contain the * (asterisk) character as its value. It stands for the entire range of possible values. For example, every minute, every hours and so on. You can also use the "nonstandard" ? character in the first four fields. See its description below.
Any field can contain a list of comma-separated values (for example, 1,3,7) or an interval (subrange) of values defined by a hyphen (for example, 1-5).
You can use the / character after the asterisk (*) character or after an interval to specify the value increment. For example, you can use 0-23/2 in the "Hours" field to specify that the operation should be carried out every two hours (old version analog: 0,2,4,6,8,10,12,14,16,18,20,22). The value */4 in the "Minutes" field means that the operations must be carried out every four minutes. 1-30/3 is the same as 1,4,7,10,13,16,19,22,25,28.
You can use three-word abbreviations in the "Months" (Jan, Feb, ... , Dec) and "Weekdays" (Mon, Tue, ... , Sun) fields instead of numbers.
Note: the <Second> field equal 0 in all examples
You can use the nonstandard "?" character in the first four fields of the cron format. It stands for the start time, i.e. the question mark will be replaced with the start time during the field processing: minute for the minute field, hour for the hours field, month day for the month day field and month for the month field.
For example, if you specify:
? ? * * *
the task will be run at the moment of startup and will continue being run at the same time (if the user does not restart the program again, of course) – the question marks are replaced with the time the program was started at. For example, if you start the program at 8:25, the questions marks will be replaced like this:
25 8 * * * *
Here are some more examples:
•? ? ? ? * - run _only_ at startup;
•? * * * * - run at startup (for example, at 10:15) and continue being run in exactly one hour: at 11:15, 12:15, 13:15 and so on;
•* ? * * * - run every minute during the startup hour;
•*/5 ? * * * - run on the next day (if the cron is not restarted) at the same hour every minute and so on every day, once in five minutes, during the startup hour.