cron
Cron data structure and Attoparsec parser for Haskell. The idea is to embed it
in larger systems which want to roll their own scheduled tasks in a format that
people are used to.
System.Cron
is where all the interesting datatypes live. You will also find
scheduleMatches
, which you can use to compare a time against a CronSchedule
to see if an action needs to be performed. System.Cron.Parser is where you will
find the parsers cronSchedule
, crontabEntry
and cronTab
. To parse
individual schedules up to full crontab files. System.Cron.Describe is where
you will find the describe
function for creating human-readable strings from
cron schedules, as well as any options to control how the description is created.
To do anything, you’ll need to install cabal-dev with cabal.
To build, run:
make
To run tests, run:
make test
If you have inotify-tools, run this to run tests continuously.
make autotest
To generate docs:
make docs
Scheduler
Cron offers a scheduling monad which can be found in System.Cron.Schedule
. This monad transform allows you to declare a set of jobs (of the type IO ()
) that will be executed at intervals defined by cron strings.
main :: IO ()
main = do
...
tids <- execSchedule $ do
addJob job1 "* * * * *"
addJob job2 "0 * * * *"
print tids
...
job1 :: IO ()
job1 = putStrLn "Job 1"
job2 :: IO ()
job2 = putStrLn "Job 2"
Describe
main :: IO ()
main = do
let Right cs1 = parseCronSchedule "*/2 * 3 * 4,5,6"
print $ describe defaultOpts cs1
let Right cs2 = parseCronSchedule "*/2 12 3 * 4,5,6"
print $ describe (twentyFourHourFormat <> verbose) cs2
Contributors