iCal batch processor
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icarus - iCal batch processor




icarus does batch processing on iCal/ICS files. It's easy to use and extend.

It is written in Java 8, uses the wonderful iCal4j library for ICS file processing, the reflection library for easy extensibility and Apache Commons CLI for CLI processing.

Currently, the following processing features are available:

  • Add an alarm
  • Convert all day events to date time events
  • Remove events

The ICS file used in the test suite is taken from schulferien.org. They do a great job regularly providing holidays and other events as ical files.


icarus is currently beta software. It will not trash your ics files, but you might experience problems when importing the resulting ics data.


Check the releases page for a release and simply grab the attached JAR file.


icarus is based on Java 8, so a corresponding JRE is needed. All dependent libraries are packed into the JAR file.


icarus is a command line application, that is called with arguments and the source ics file:

java -jar icarus.jar [options] <icsfile.ics>

If you omit the source file, it checks STDIN for ICS data.


java -jar icarus.jar --help

to get detailed help.

Basically, icarus expects a query and/or a time range to search events.

The query is a regular expression that is matched against the title of the appointment. The arguments "from" and "until" describe a time range, that the event has to be in.

The desired processor is configured using the corresponding argument. For example, the argument "--removeEvent" will remove all events in the filtered range or with the filtered query.

The resulting ICS data is written to stdout and can be piped to a new ICS file to be used in your favorite calendar app.

Using icarus as a library

You can also use icarus as a library. Just instantiate a Processor and call "process" with an OptionStore and the source ical data and you'll get the processed data back.

Refer to the API-Docs for more information.

You can use the icarus.lib.jar for library use. I will be providing icarus over Maven some time later.

Extending icarus

Currently, icarus does all the processing for which it was designed for

However, it is designed to be open to new modifiers and if you'd like icarus to do something special with your ical events, you can just implement the Modifier interface and you're done.

The interface is quite easy. The following methods have to be implemented:

  • getOptions: Provide a list of ModifierOptions, that indicate which options your modifier expects
  • process: This is called for all events that match the filter. It is called with the OptionStore holding all given options so you can check for your options, the current event and the complete calendar object for reference. Just directly modify the event. Do not modify the calendar object here, or else you're getting concurrent modification exceptions.
  • finalize: This is called after all events have been processed and this is the point where you can modify the complete calendar, if you'd like to. You'll get the OptionStore, the calendar and a list of events, that have been filtered before

See the API-Docs for more information and use the existing modifiers as a reference.

Go for it! I'm happy to accept pull requests for new features.