Register file extensions / mime types in Linux

Question

I\'m developing a Linux application that has its own file format. I want my app to open when you double-click on those files.

How can I register a file extension and

Answer 1

1) in linux this is a function of your desktop environment rather than the os itself.
2) GNOME and KDE have different methods to accomplish this.
3) There's nothing stopping you from doing it both ways.