20.5. Filter Services

OS X supports a special kind of service for handling transformations between types. These are called filter services and are slightly different from conventional services.

You don’t have to use pasteboards to communicate with filter services. The system also supports a kind of service that communicates via standard UNIX pipes. Using this allows you to very easily wrap simple UNIX tools very easily. This is generally the best option for implementing filter services since there is a bug in OS X that prevents it from reading the result back from filter services that use the standard pasteboard mechanism.