NCrontab: Crontab for .NET

NCrontab is a library written in C# 3.0 that provides the following facilities:

• Parsing of crontab expressions
• Formatting of crontab expressions
• Calculation of occurrences of time based on a crontab schedule

This library does not provide any scheduler or is not a scheduling facility like cron from Unix platforms. What it provides is parsing, formatting and an algorithm to produce occurrences of time based on a give schedule expressed in the crontab format:

* * * * *
- - - - -
| | | | |
| | | | +----- day of week (0 - 6) (Sunday=0)
| | | +------- month (1 - 12)
| | +--------- day of month (1 - 31)
| +----------- hour (0 - 23)
+------------- min (0 - 59)

Star (*) in the value field above means all legal values as in parentheses for that column. The value column can have a * or a list of elements separated by commas. An element is either a number in the ranges shown above or two numbers in the range separated by a hyphen (meaning an inclusive range). For more, see CrontabExpression.

Below is an example in IronPython of how to use CrontabSchedule class from NCrontab to generate occurrences of the schedule 0 12 * */2 Mon (meaning, 12:00 PM on Monday of every other month, starting with January) throughout the year 2000:

IronPython 1.1 (1.1) on .NET 2.0.50727.1434
Copyright (c) Microsoft Corporation. All rights reserved.
>>> import clr
>>> clr.AddReferenceToFileAndPath(r'C:\NCrontab\bin\Release\NCrontab.dll')
>>> from System import DateTime
>>> from NCrontab import CrontabSchedule
>>> s = CrontabSchedule.Parse('0 12 * */2 Mon')
>>> start = DateTime(2000, 1, 1)
>>> end = start.AddYears(1)
>>> occurrences = s.GetNextOccurrences(start, end)
>>> print '\n'.join([t.ToString('ddd, dd MMM yyyy hh:mm') for t in occurrences])
Mon, 03 Jan 2000 12:00
Mon, 10 Jan 2000 12:00
Mon, 17 Jan 2000 12:00
Mon, 24 Jan 2000 12:00
Mon, 31 Jan 2000 12:00
Mon, 06 Mar 2000 12:00
Mon, 13 Mar 2000 12:00
Mon, 20 Mar 2000 12:00
Mon, 27 Mar 2000 12:00
Mon, 01 May 2000 12:00
Mon, 08 May 2000 12:00
Mon, 15 May 2000 12:00
Mon, 22 May 2000 12:00
Mon, 29 May 2000 12:00
Mon, 03 Jul 2000 12:00
Mon, 10 Jul 2000 12:00
Mon, 17 Jul 2000 12:00
Mon, 24 Jul 2000 12:00
Mon, 31 Jul 2000 12:00
Mon, 04 Sep 2000 12:00
Mon, 11 Sep 2000 12:00
Mon, 18 Sep 2000 12:00
Mon, 25 Sep 2000 12:00
Mon, 06 Nov 2000 12:00
Mon, 13 Nov 2000 12:00
Mon, 20 Nov 2000 12:00
Mon, 27 Nov 2000 12:00

Below is the same example in F# Interactive (fsi.exe):

Microsoft (R) F# 2.0 Interactive build 4.0.40219.1
Copyright (c) Microsoft Corporation. All Rights Reserved.

For help type #help;;

> #r "NCrontab.dll"
-
- open NCrontab
- open System
-
- let schedule = CrontabSchedule.Parse("0 12 * */2 Mon")
- let startDate = DateTime(2000, 1, 1)
- let endDate = startDate.AddYears(1)
-
- let occurrences = schedule.GetNextOccurrences(startDate, endDate)
- occurrences |> Seq.map (fun t -> t.ToString("ddd, dd MMM yyy hh:mm"))
-             |> String.concat "\n"
-             |> printfn "%s";;

--> Referenced 'C:\NCrontab\bin\Release\NCrontab.dll'

Mon, 03 Jan 2000 12:00
Mon, 10 Jan 2000 12:00
Mon, 17 Jan 2000 12:00
Mon, 24 Jan 2000 12:00
Mon, 31 Jan 2000 12:00
Mon, 06 Mar 2000 12:00
Mon, 13 Mar 2000 12:00
Mon, 20 Mar 2000 12:00
Mon, 27 Mar 2000 12:00
Mon, 01 May 2000 12:00
Mon, 08 May 2000 12:00
Mon, 15 May 2000 12:00
Mon, 22 May 2000 12:00
Mon, 29 May 2000 12:00
Mon, 03 Jul 2000 12:00
Mon, 10 Jul 2000 12:00
Mon, 17 Jul 2000 12:00
Mon, 24 Jul 2000 12:00
Mon, 31 Jul 2000 12:00
Mon, 04 Sep 2000 12:00
Mon, 11 Sep 2000 12:00
Mon, 18 Sep 2000 12:00
Mon, 25 Sep 2000 12:00
Mon, 06 Nov 2000 12:00
Mon, 13 Nov 2000 12:00
Mon, 20 Nov 2000 12:00
Mon, 27 Nov 2000 12:00

val schedule : NCrontab.CrontabSchedule = 0 12 * 1,3,5,7,9,11 1
val startDate : System.DateTime = 1/1/2000 12:00:00 AM
val endDate : System.DateTime = 1/1/2001 12:00:00 AM
val occurrences : seq<System.DateTime>