What I need is to instruct OS to open the file with the default program used for that file type. Exactly as if, i.e., that file was double-clicked by user under Windows.
The purpose is, i.e., "your PDF file was generated. Click here to open it".
In platform-independent way, if possible...
I dont know exact terms for what I want, so if someone could update tags, I'd most appreciate that ;)