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Elixir library for parsing, writing, and calculating Cron format strings.


Add :crontab to your list of dependencies in mix.exs:

def deps do
    {:crontab, "~> 1.1"}

For Elixir version before 1.4, ensure :crontab is started before your application:

def application do
    applications: [:crontab]


Import Cron expression sigil

Everywhere you want to use the Cron expression sigil (e[cron expression]).

import Crontab.CronExpression

Extended Cron expressions

An extended Cron expression has more precision than a normal Cron expression. It also specifies the second.

If you want to use extended Cron expressions with the sigil, just append an e.

Checking if a Cron Expression Matches a date

iex> import Crontab.CronExpression
iex> Crontab.DateChecker.matches_date?(~e[*/2], ~N[2017-01-01 01:01:00])
iex> Crontab.DateChecker.matches_date?(~e[*], ~N[2017-01-01 01:01:00])

Find Next / Previous Execution Date candidates

All the date parameters default to now.

For previous, just replace next in the code below.

iex> import Crontab.CronExpression
iex> Crontab.Scheduler.get_next_run_date(~e[*/2], ~N[2017-01-01 01:01:00])
{:ok, ~N[2017-01-01 01:02:00]}
iex> Crontab.Scheduler.get_next_run_date!(~e[*/2], ~N[2017-01-01 01:01:00])
~N[2017-01-01 01:02:00]
iex> Crontab.Scheduler.get_next_run_dates(3, ~e[*/2], ~N[2017-01-01 01:01:00])
 [~N[2017-01-01 01:02:00], ~N[2017-01-01 01:04:00], ~N[2017-01-01 01:06:00]]}
iex> Crontab.Scheduler.get_next_run_dates!(3, ~e[*/2], ~N[2017-01-01 01:01:00])
[~N[2017-01-01 01:02:00], ~N[2017-01-01 01:04:00], ~N[2017-01-01 01:06:00]]

Parse Cron Expressions

If you statically define cron expressions, use the ~e[cron expression] sigil.

For dynamic cron expressions, there is a Parser module.

The parser module takes an optional extended flag. This is to mark if the expression contains seconds. This defaults to false.

iex> Crontab.CronExpression.Parser.parse "* * * * *"
  %Crontab.CronExpression{day: [:*], hour: [:*], minute: [:*],
  month: [:*], weekday: [:*], year: [:*]}}
iex> Crontab.CronExpression.Parser.parse! "* * * * *"
%Crontab.CronExpression{day: [:*], hour: [:*], minute: [:*],
 month: [:*], weekday: [:*], year: [:*]}

Compose Cron expressions

iex> Crontab.CronExpression.Composer.compose %Crontab.CronExpression{}
"* * * * * *"
iex> Crontab.CronExpression.Composer.compose %Crontab.CronExpression{minute: [9, {:-, 4, 6}, {:/, :*, 9}]}
"9,4-6,*/9 * * * * *"

Copyright (c) 2016, SK & T AG, JOSHMARTIN GmbH, Jonatan Männchen

This library is MIT licensed. See the LICENSE for details.