CRON Expressions
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CRON expressions are user-defined strings that use standard cron job syntax to define when a scheduled trigger should execute. Whenever all of the fields in a CRON expression match the current date and time, Atlas fires the trigger associated with the expression.
Expression Syntax
Format
CRON expressions are strings composed of five space-delimited fields. Each field defines a granular portion of the schedule on which its associated trigger executes:
* * * * * │ │ │ │ └── weekday...........[0 (SUN) - 6 (SAT)] │ │ │ └──── month.............[1 (JAN) - 12 (DEC)] │ │ └────── dayOfMonth........[1 - 31] │ └──────── hour..............[0 - 23] └────────── minute............[0 - 59]
Field | Valid Values | Description |
|---|---|---|
minute | [0 - 59] | Represents one or more minutes within an hour. Example If the |
hour | [0 - 23] | Represents one or more hours within a day on a 24-hour clock. Example If the |
dayOfMonth | [1 - 31] | Represents one or more days within a month. Example If the |
month | 1 (JAN) 7 (JUL)2 (FEB) 8 (AUG)3 (MAR) 9 (SEP)4 (APR) 10 (OCT)5 (MAY) 11 (NOV)6 (JUN) 12 (DEC) | Represents one or more months within a year. A month can be represented by either a number (e.g. Example If the |
weekday | 0 (SUN)1 (MON)2 (TUE)3 (WED)4 (THU)5 (FRI)6 (SAT) | Represents one or more days within a week. A weekday can be represented by either a number (e.g. Example If the |
Field Values
Each field in a CRON expression can contain either a specific value or an expression that evaluates to a set of values. The following table describes valid field values and expressions:
Expression Type | Description | |
|---|---|---|
All Values ( *) | Matches all possible field values. Available in all expression fields. Example The following CRON expression schedules a trigger to execute once every minute of every day: | |
Specific Value ( <Value>) | Matches a specific field value. For fields other than Available in all expression fields. Example The following CRON expression schedules a trigger to execute once every day at 11:00 AM UTC: | |
List of Values ( <Expression1>,<Expression2>,...) | Matches a list of two or more field expressions or specific values. Available in all expression fields. Example The following CRON expression schedules a trigger to execute once every day in January, March, and July at 11:00 AM UTC: | |
Range of Values ( <Start Value>-<End Value>) | Matches a continuous range of field values between and including two specific field values. Available in all expression fields. Example The following CRON expression schedules a trigger to execute once every day from January 1st through the end of April at 11:00 AM UTC: | |
Modular Time Step ( <Field Expression>/<Step Value>) | Matches any time where the step value evenly divides the
field value with no remainder (i.e. when Available in the Example The following CRON expression schedules a trigger to execute on the 0th, 25th, and 50th minutes of every hour: |