On my Lubuntu (18.10),
xdg-open launches VLC Player when the file is not associated to any applications.
On some files, it launches Calibre's E-book viewer (.rb for example).
EDIT I digged into
xdg-open and found it executes following commands:
- Check filetype with
xdg-mime query filename "$file"and
xdg-mime query default $filetype
run-mailcap --action=view "$file"
mimeopen -L -n "$file"
The problem lies in mimeopen.
Then how can I change mimeopen to open any unknown files with featherpad, or specific app? In other words, I'd like to set default fallback application if mimeopen can not find any suitable apps.