cronexpr/README.md

cronexpression for Go
=====================

Go language (golang) cron expression parser. Given a cron expression and a time stamp, you can get the next time stamp which satisfy the cron expression.

The reference documentation for this implementation is found at
https://en.wikipedia.org/wiki/Cron#CRON_expression, with the following
difference:

* Supports the second field (before minute field)
* If five fields are present, a wildcard year field is appended
* If six field are present, "0" is prepended as second field
* Domain for day-of-week field is [0-7] instead of [0-6], 7 being Sunday, like zero.
* `@reboot` is not supported, as it is meaningless for a cron expression parser library
* As of now, the behavior of the code is undetermined if a malformed cron expression is supplied (most likely, code will panic)

Install
-------

    go get github.com/gorhill/cronexpression

Usage
-----

Import the library:

    import "github.com/gorhill/cronexpression"
    import "time"

Simplest way:

    nextTime := cronexpression.NextTimeFromCronString("0 0 29 2 *", time.Now())

Assuming `time.Now()` is "2013-08-29 09:28:00", then `nextTime` will be "2016-02-29 00:00:00".

If you need to reuse many times a cron expression in your code, it is more efficient
to create a `CronExpression` object once and keep a copy of it for reuse:

    cronexpr := cronexpression.NewCronExpression("0 0 29 2 *")
    nextTime := cronexpr.NextTime(time.Now())