NCrontab is an open source library written in C# 3.0 that applications can use to parse and format crontab expression as well as calculate schedules represented by those expressions.
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)
>>> occurences = s.GetNextOccurrences(start, end)
>>> print '\n'.join([t.ToString('ddd, dd MMM yyyy hh:mm') for t in occurences])
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
To learn more, see:
Copyright (c) 2007-8 Atif Aziz. All rights reserved.
NCrontab is open source software.
Licensed under the Apache License, Version 2.0 (the “License”); you may not use NCrontab except in compliance with the License. Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.