Cron for Swift

Installation

Swift Package Manager

Add the following line to your Package.swift file

.package(url: "https://github.com/alchemy-swift/cron.git", from: "2.3.0")

Usage

import Cron

let job = try? CronJob(pattern: "*/10 * * * * *") { () -> Void in
    print("job executes every 10 seconds")
}

Cron Pattern Syntax

5 - 7 fields separated by TAB or whitespace:

Field name	Range	Special Characters	Remarks
second	0-59	* / , - H
minute	0-59	* / , - H
hour	0-23	* / , - H L W
day of month	1-31	* / , - H
month	1-12 or JAN-DEC	* / , -
day of week	0-7 or SUN-SAT	* / , - L #	0 or 7 is SUN
year	-	* / , -

The reference documentation for this implementation is found at Wikipedia.

Special Characters

Asterisk (*)

Asterisk means the full range in the field. For example, * for an hour entry implies 0-23.

Slash (/)

Slashes can be combined with ranges to specify step values.

Comma (,)

Commas are used to separate items of a list.

Hyphen (-)

Hyphens are used for ranges.

Ranges are two numbers separated with a hyphen. For example, 8-11 for an hours entry specifies execution at hours 8, 9, 10 and 11.

Number sign (#)

'#' is allowed for the day-of-week field, and must be followed by a number between one and five. It allows you to specify constructs such as "the second Friday" of a given month.

Hash (H)

The H symbol can be used like a range. For example, H H(0-7) * * * means some time between 0:00 AM (midnight) to 7:59 AM.

The H symbol can be thought of as a random value over a range, but it actually is a hash of the given value, not a random function, so that the value remains stable for it.

Last (L)

When used in the day-of-week field, it allows you to specify constructs such as "the last Friday" ("5L") of a given month. In the day-of-month field, it specifies the last day of the month.

Weekday (W)

This character is used to specify the weekday (Monday to Friday) nearest the given day.