Cron parses cron expressions and calculates execution timings.
The package can be installed by adding cron to your list of dependencies in
mix.exs:
def deps do
[
{:cron, "~> 0.1"}
]
endThe documentation can be found on hexdocs.
Cron accepts cron expressions with 6 fields (including seconds) and 5 fields.
All functions are working with NaiveDateTime and DateTime that are using the
Calendar.ISO. DateTimes must use the time zone Etc/UTC.
Calculating the next execution datetime:
iex> {:ok, cron} = Cron.new("0 0 * * FRI") # At 00:00 on Friday.
iex> Cron.next(cron)
~N[2021-12-03 00:00:00]
iex> Cron.next(cron, ~U[2021-12-03 00:00:00Z])
~U[2021-12-10 00:00:00Z]Calculating the previous execution datetime:
iex> {:ok, cron} = Cron.new("0 12 */2 * *") # At 12:00 on every 2nd day-of-month.
iex> Cron.previous(cron)
~N[2021-12-31 12:00:00]
iex> Cron.previous(cron, ~U[2021-12-31 12:00:00Z])
~U[2021-12-29 12:00:00Z]Calculating the milliseconds until the next execution datetime:
iex> cron = Cron.new!("22 44 12 * * *") # At 12:44:22.
iex> Cron.until(cron)
20256672
iex> Cron.until(cron, ~U[2022-01-01 12:44:11.123Z])
10877The day can be specified by two fields, the day field and the day of week
field. If both fields are not set to *, the triggered datetimes are the union
of both restrictions. The expression 0 0 0 5 * MON will be triggered at
00:00:00 on the 5th day of a month and on every Monday.
Calculating the next 5 execution datetimes:
iex> cron = Cron.new!("0 0 0 5 * MON") # See the description above.
iex> stream = Cron.stream(cron, from: ~N[2022-01-01 00:00:00])
iex> Enum.take(stream, 5)
[
~N[2022-01-03 00:00:00],
~N[2022-01-05 00:00:00],
~N[2022-01-10 00:00:00],
~N[2022-01-17 00:00:00],
~N[2022-01-24 00:00:00]
]Detecting the first day of a month that is a Monday:
iex> cron = Cron.new!("0 0 0 1-7 * *") # At 00:00:00 on the first seven days of a month
iex> Cron.next_while(cron, fn datetime -> Date.day_of_week(datetime) == 1 end)
{:ok, ~N[2021-12-06 00:00:00]}