Cron Format Reference

NetXMS uses cron expressions to define recurring schedules for tasks such as scheduled scripts, maintenance windows, active network discovery, report generation, and file delivery jobs.

Expression Format

A cron expression consists of five or six space-separated fields:

minute hour day-of-month month day-of-week [seconds]

The seconds field (6th position) is optional. It is honored only by DCI custom collection schedules (both server-side and agent-side), which evaluate schedules every second. All other consumers — scheduled tasks, active network discovery, and log parser exclusion schedules — match schedules with minute resolution and ignore the seconds field, so a 6-field expression there behaves exactly like the same expression without its 6th field.

Field Definitions

Field Allowed Values Special Characters Notes

Minute

0-59

* , - / L

Hour

0-23

* , - / L

Uses 24-hour format.

Day of month

1-31

* , - / L

Not all months have 31 days. Invalid dates are silently skipped.

Month

1-12

* , - / L

1 = January, 12 = December.

Day of week

0-7

* , - / L #

0 and 7 both represent Sunday. 1 = Monday, 6 = Saturday. # is available in NetXMS 6.1 and later.

Seconds (optional)

0-59

* , - / % L

6th field. Honored only by DCI custom collection schedules; ignored by all other schedule consumers.

Special Characters

Character Description

*

Matches any value in the field. For example, * in the month field matches every month.

,

Separates items in a list. For example, 1,3,5 in the day-of-week field matches Monday, Wednesday, and Friday.

-

Defines an inclusive range. For example, 9-17 in the hour field matches every hour from 9 through 17.

/

Specifies a step value after or a range — these are the only supported forms. A value matches if it is divisible by the step. For example, /5 in the minute field means every 5 minutes (0, 5, 10, …​). With a range, the step is absolute divisibility, not an offset from the range start: 10-30/5 matches 10, 15, 20, 25, 30, but 10-30/7 matches 14, 21, 28 (multiples of 7 within the range). The Quartz-style form n/step (e.g., 0/30) is not supported and matches only the single value n; use */30 or an explicit list like 0,30 instead.

L

"Last." On its own, L matches the maximum value of its field: the last day of the month in the day-of-month field (28, 29, 30, or 31 depending on the month), Saturday in the day-of-week field, 59 in the minute and seconds fields, 23 in the hour field, and 12 in the month field. Combined with a weekday number in the day-of-week field, nL matches the last occurrence of that weekday in the month — for example, 5L means the last Friday of the month.

#

Specifies the Nth occurrence of a weekday in the month. Used only in the day-of-week field. For example, 2#3 means the third Tuesday of the month (day 2 = Tuesday, occurrence 3). Available in NetXMS 6.1 and later.

%

Step against absolute time. Used only in the seconds field, in place of /: the value tested for divisibility is the absolute UNIX time rather than the second within the minute. Because the count does not restart every minute, % gives an even interval even when the step does not divide 60. For example, %45 matches every 45 seconds (12:00:00, 12:00:45, 12:01:30, 12:02:15, …​), while /45 matches seconds 0 and 45 of every minute, leaving alternating gaps of 45 and 15 seconds. For steps that divide 60, such as 30, % and / match the same seconds. Anything before % is ignored, so %45 and *%45 are equivalent. Known issue in version 7.0.1 and earlier (netxms#3830): the test is inverted, so % matches every second whose absolute time is not divisible by the step.

Day-of-Week Values

Value Day

0

Sunday

1

Monday

2

Tuesday

3

Wednesday

4

Thursday

5

Friday

6

Saturday

7

Sunday (alias for 0)

Examples

Expression Description

0 * * * *

Every hour at minute 0.

*/15 * * * *

Every 15 minutes.

0 8 * * 1-5

Every weekday (Monday through Friday) at 08:00.

0 0 1 * *

First day of every month at midnight.

30 2 * * 0

Every Sunday at 02:30.

0 0 L * *

Last day of every month at midnight.

0 9 * * 1#1

First Monday of every month at 09:00.

0 22 * * 5L

Last Friday of every month at 22:00.

0 */2 * * *

Every 2 hours at minute 0 (00:00, 02:00, 04:00, …​).

0 8-17 * * 1-5

Every hour from 08:00 to 17:00 on weekdays (business hours).

6-Field Examples (with seconds)

These examples use the optional seconds field (6th position). The seconds field takes effect only in DCI custom collection schedules; in other contexts it is ignored.

Expression Description

0 * * * * 0

Every hour at minute 0, second 0.

* * * * * 30

Every minute at second 30.

0 2 * * 0 0

Every Sunday at 02:00:00.

* * * * * */10

Every 10 seconds.

*/30 9-17 * * 1-5 0

Every 30 minutes during business hours on weekdays, at the top of each half hour.
When the system detects 6 fields, the last field is interpreted as seconds. A 5-field expression always starts with the minute field.

Where Cron Expressions Are Used

Cron expressions appear in the following NetXMS contexts: