cronstar

Parse cron expression and generate a sequence of future DateTime instances in Clojure or ClojureScript.

API docs

Usage

This library can be used in conjunction with chime to create custom schedulers.

See the todoapp source code for an example on how to create your own component-based scheduler where task execution is controlled via cron expressions.

To use it in your own project add a dependency

[cronstar "1.0.2"]

Here's how the main API function can be used:

(require '[cronstar.core :as cron])
;= nil

(->> (cron/times "*/5 8-18 * * 1-5")
     (take 10))
;= (#object[org.joda.time.DateTime
;          "0x3045906"
;          "2020-02-17T08:00:00.000+01:00"]
;  #object[org.joda.time.DateTime
;          "0x5087dfe8"
;          "2020-02-17T08:05:00.000+01:00"]
;  #object[org.joda.time.DateTime
;          "0x4fca19c"
;          "2020-02-17T08:10:00.000+01:00"]
;  #object[org.joda.time.DateTime
;          "0x6aea4674"
;          "2020-02-17T08:15:00.000+01:00"]
;  #object[org.joda.time.DateTime
;          "0x48266d76"
;          "2020-02-17T08:20:00.000+01:00"]
;  #object[org.joda.time.DateTime
;          "0x44861a78"
;          "2020-02-17T08:25:00.000+01:00"]
;  #object[org.joda.time.DateTime
;          "0x2597a335"
;          "2020-02-17T08:30:00.000+01:00"]
;  #object[org.joda.time.DateTime
;          "0x1d768815"
;          "2020-02-17T08:35:00.000+01:00"]
;  #object[org.joda.time.DateTime
;          "0x66400b10"
;          "2020-02-17T08:40:00.000+01:00"]
;  #object[org.joda.time.DateTime
;          "0x1261987a"
;          "2020-02-17T08:45:00.000+01:00"])

Supported cron syntax:

A cron expression has 5 whitespace separated parts:

minute(0-59)  hour(0-59)  day-of-month(1-31)  month (1-12)  day-of-week (0-7, 0 = 7 = Sunday)

Each part can be a list of comma separated numbers, ranges from'-'to or an asterisk '*' character, which means any value is allowed.

A range or the '*' can be followed by '/'stepsize.

Development

To start a REPL use lein repl and connect to it, for example via CIDER.

The user namespace contains a function cljs-repl that starts a REPL connection to Javas Nashorn JS Engine.

lein test compiles and executes tests on JVM.

lein cljstest compiles sources to JS and executes tests in Nashorn engine.

License

Copyright © 2020 F.Riemenschneider

This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0 which is available at http://www.eclipse.org/legal/epl-2.0.