Copyright	(c) Michael Xavier 2012
License	MIT
Maintainer	Michael Xavier <michael@michaelxavier.net>
Portability	portable
Safe Haskell	Safe-Inferred
Language	Haskell98

System.Cron

Description

Toplevel module for Cron specifying a cron schedule and several convenience functions for dealing with cron schedules

import Control.Concurrent
import Control.Monad
import Data.Time.Clock
import System.Cron

main :: IO ()
main = do
  forever do
    now <- getCurrentTime
    when (scheduleMatches schedule now) doWork
    putStrLn "sleeping"
    threadDelay 100000
  where doWork   = putStrLn "Time to work"
        schedule = hourly

Synopsis

Documentation

data CronSchedule Source

Specification for a cron expression

Constructors

CronSchedule

Fields

minute :: MinuteSpec: Which minutes to run. First field in a cron specification.
hour :: HourSpec: Which hours to run. Second field in a cron specification.
dayOfMonth :: DayOfMonthSpec: Which days of the month to run. Third field in a cron specification.
month :: MonthSpec: Which months to run. Fourth field in a cron specification.
dayOfWeek :: DayOfWeekSpec: Which days of the week to run. Fifth field in a cron specification.

Instances

Eq CronSchedule
Show CronSchedule

newtype Crontab Source

Crontab file, omitting comments.

Constructors

Crontab [CrontabEntry]

Instances

Eq Crontab
Show Crontab

data CrontabEntry Source

Essentially a line in a crontab file. It is either a schedule with a command after it or setting an environment variable (e.g. FOO=BAR)

Constructors

CommandEntry
Fields schedule :: CronSchedule command :: Text
EnvVariable
Fields varName :: Text varValue :: Text

Instances

Eq CrontabEntry
Show CrontabEntry

data MinuteSpec Source

Minutes field of a cron expression

Constructors

Minutes CronField

Instances

Eq MinuteSpec
Show MinuteSpec

data HourSpec Source

Hours field of a cron expression

Constructors

Hours CronField

Instances

Eq HourSpec
Show HourSpec

data MonthSpec Source

Month field of a cron expression

Constructors

Months CronField

Instances

Eq MonthSpec
Show MonthSpec

data DayOfMonthSpec Source

Day of month field of a cron expression

Constructors

DaysOfMonth CronField

Instances

Eq DayOfMonthSpec
Show DayOfMonthSpec

data DayOfWeekSpec Source

Day of week field of a cron expression

Constructors

DaysOfWeek CronField

Instances

Eq DayOfWeekSpec
Show DayOfWeekSpec

data CronField Source

Individual field of a cron expression.

Constructors

Star	Matches anything
SpecificField Int	Matches a specific value (e.g. 1)
RangeField Int Int	Matches a range of values (e.g. 1-3)
ListField [CronField]	Matches a list of expressions. Recursive lists are invalid and the parser will never produce them.
StepField CronField Int	Matches a stepped expression, e.g. (*/2). Recursive steps or stepped lists are invalid and the parser will never produce them.

Instances

Eq CronField
Show CronField

yearly :: CronSchedule Source

Shorthand for every January 1st at midnight. Parsed with @yearly

monthly :: CronSchedule Source

Shorthand for every 1st of the month at midnight. Parsed with @monthly

daily :: CronSchedule Source

Shorthand for every day at midnight. Parsed with @daily

weekly :: CronSchedule Source

Shorthand for every sunday at midnight. Parsed with @weekly

hourly :: CronSchedule Source

Shorthand for every hour on the hour. Parsed with @hourly

everyMinute :: CronSchedule Source

Shorthand for an expression that always matches. Parsed with * * * * *

scheduleMatches :: CronSchedule -> UTCTime -> Bool Source

Determines if the given time is matched by the given schedule. A periodical task would use this to determine if an action needs to be performed at the current time or not.