The extractors are typically named as tracker-extractor-[document-extension].c and placed in the src/tracker-extract/ directory.

A dummy.c extractor is provided (src/tracker-extract/dummy.c) to use as base to write new ones. Copy and complete the implementation of this file to create your extractors. Don't forget to add them in the Makefile.am file!

Your extractor can link with external libraries, but please be careful adding new dependencies in tracker (this will be no problem when the extractors are compiled and packaged out of tracker).

For a play list, a tracker-extractor-m3u.c file would be written. In the extraction function it would open the file, count the lines containing a filename and if the line starts with EXTINF, the sum of the duration of the songs (the EXTINF line contains the duration and name of the song) would be added.