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Cron Reference

Cron expressions are a way to schedule tasks automatically. You can run scripts, commands, or software at specific times. Coalesce uses Cron for Scheduled Jobs.

Structure of a Cron Expression​

A CRON expression is a string made of five fields separated by a space. The fields must be written in the following order. Fields 1- 6 are required.

  1. Seconds (0-59): Specifies the exact second when the task should start.
    1. Example: 0 indicates the task runs at the beginning of the minute.
  2. Minutes (0-59): The minute in hour when the task should run.
    1. Example: 15 means the task runs at the 15th minute of the hour.
  3. Hours (0-23): The hour of the day when the task should run. Based on 24 hour time.
    1. Example: 14 indicates the task runs at 2:00 PM.
  4. Day of Month (1-31): The day of the month to run.
    1. Example: 1 means the task runs on the 1 st day of the month.
  5. Month (1-12): The month the task should run.
    1. Example: 5 means the task runs in May.
  6. Day of Week (0-6): This field defines the days of the week when the task should run.
    1. Example: 0 means the task runs on Sundays.

Special Characters​

Special characters are used to build your expression.

  • Asterisk (*): Represents all possible values for a field.
    • Example: * in the month field means every month.
  • Hyphen (-) : Specifies a range of values.
  • Example: 10-12 in the hours field means the task runs at 10:00 AM, 11:00 AM, and 12:00 PM.
  • Comma (,) : Specifies a list of values.
  • Example: 0,6,5 in the day of the week field means it runs every Sunday, Saturday, and Friday.
  • Slash (/): Specifies intervals.
  • Example: /15 in the minutes field means the task runs every 15 minutes.

Examples of Cron Expressions​

Run Daily at Midnight​

0 0 * * *
  • 0 0 - The task runs at 0 minutes and 0 hours (midnight).
  • * - The task runs every day of the month.
  • * - The task runs every month.
  • *- The task runs every day of the week.

Run Every 15 Minutes​

*/15 * * * *
  • */15 - The task run every 15 minutes
  • * - The task runs every hour.
  • * - The task runs every day of the month.
  • * - The task runs every month.
  • * - The task runs every day of the week.

Run at 09:00 Every Day of the Month and on Monday​

0 9 1-7 * 1
  • 0 9 - The task runs at 9:00 AM.
  • 1-7 - First seven days of the month
  • * - The task runs every month.
  • 1 - The task also runs on Monday.

Run at 22:00 on Monday and Friday​

0 22 * * 1,5
  • 0 - Any second
  • 22 - Run at 22:00
  • * - Any day
  • * - Any month
  • 1,5 - Monday and Friday

Troubleshooting Cron Jobs​

  • Question Marks (?) are currently not accepted in the Cron Expressions in Coalesce.
  • SUN-SAT and JAN-DEC alternative values are not accepted.
  • Make sure your fields are in the correct order. Check using Crontab to make sure.
  • Avoid specifying days that don’t exist, for example February 30th.

Resources​