Dar command-line support
The first step is to do your "homework", which means to read:
If this does not answer your question, have a look at the dar-support mailing-list archive, for keywords that could match you problem. If that still does not help you, subscribe to this mailing-list and ask your question there.
libdar API support
It is assumed you have read the documentation relative to the API:
- The API tutorial
- Dar command-line source code for API usage illustration
- The libdar's python binding tutorial based on examples of use
- The API reference documentation
The libdar-api mailing-list is targeted to libdar C++ API and Python binding discussion, support and anything related to development with libdar. Before sending your question, thanks to search the mailing-list archive just in case someone else would not already have met the same problem you face.