cron_expression_parser

Parses cron expression.

Supported format

* * * * * *
┬ ┬ ┬ ┬ ┬ ┬
│ │ │ │ │ |
│ │ │ │ │ └───── weekday (0-7, 0 and 7 being Sunday)
│ │ │ │ └─────── month (1-12)
│ │ │ └───────── day (1-31)
│ │ └─────────── hour (0-23)
│ └───────────── minute (0-59)
└─────────────── second (0-59, optional)

Special characters

Asterisk (*)

Represents all value.

Comma (,)

Used to separate multiple items of a list.

Hyphen (-)

Used to represent range of value. For example 1-10 in minute field indicate iteration every minutes from minute 1 until minute 10.

Slash (/)

Used to represent step value. For example */2 in minute field indicate iteration every 2 minutes.

Combinable with hyphen, for example 0 10-20/5 * * * indicate iteration every 5 hours started from 10:00 until 20:00.

Hash (#)

Only for weekday field.

Used to represent nth weekday of the month. For example 0 0 * * 6#3 indicate iteration at 00:00 on every third Saturday of the month.

L

Only for day and weekday field.

Used to represent last day of the month or last weekday of the month. For example 0 0 L * * indicate iteration at 00:00 on every last day of the month, and 0 0 * * 1L indicate iteration at 00:00 on every last Monday of the month.

Usage

A simple usage example:

import 'package:cron_expression_parser/cron_expression_parser.dart';

// Every 20 minutes
final cron = Cron.parse('*/20 * * * *');
print(cron.toList(
  DateTime.parse('2000-01-01T00:00Z'),
  DateTime.parse('2000-01-01T01:00Z'),
));

// [2000-01-01 00:00:00.000Z, 2000-01-01 00:20:00.000Z, 2000-01-01 00:40:00.000Z, 2000-01-01 01:00:00.000Z]

Another example:

import 'package:cron_expression_parser/cron_expression_parser.dart';

// At midnight on the last day of the month
final cron = Cron.parse('0 0 L * *');
print(cron.next(DateTime.parse('2000-02-01T00:00Z')));

// 2000-02-29 00:00:00.000Z

Links

• source code
• contributors: Ilham F