Cronfab

Cronfab is a crontab time-and-date specification parser and processor with a configurable calendar.

All the unix standard features are supported:

• units may be specified by number or name
• lists and ranges are suppored
• step values are supported

Cronfab does not support shell command execution, or specification nicknames (such as @reboot, @annually, @yearly, @monthly, @weekly, @daily or @hourly).

Parsers for classic 6-field (year, month, day of month, day of week, hour of day, minute or hour) and extended, 8 field, (6-field version extended to second of minute and week of month) are provided. Other calendars and/or periods may be added.

Examples and Tests are the best source of documentation.

Example

The example below outputs the parsed crontab entry and then runs for 20s, producing output every 5s. The example demonstrates generating timeseries for a parsed crontab.

// crontab event at every 5 second interval
func ExampleEveryFiveSeconds() {
	markers, err := cronfab.SecondContabConfig.ParseCronTab("*/5 * * * * * *")
	if err != nil {
		fmt.Printf("err: %v\n", err)
	}
	fmt.Printf("%v\n", markers)

	// run for 4 intervals
	for i := 0; i < 4; i++ {
		t1, err := cronfab.SecondContabConfig.Next(markers, time.Now())
		if err != nil {
			fmt.Printf("err: %v\n", err)
			return
		}
		dt := t1.Sub(time.Now())
		time.Sleep(dt)
		fmt.Fprintf(os.Stderr, "time: %v\n", time.Now())
	}

	// Output: 0-59/5 0-59/1 0-23/1 1-31/1 1-5/1 1-12/1 0-6/1
}