Mime
From Blue-IT.org Wiki
Mime types under Linux
$> man xdg-mime xdg-mime - command line tool for querying information about file type handling and adding descriptions for new file types [...]
$> man xdg-open xdg-open - opens a file or URL in the user's preferred application [...]
You can open any file with the default xdg-open command:
$> xdg-open special_file.pdf
Setting the default type is easy:
xdg-mime default
$> xdg-mime query default application/pdf AdobeReader.desktop $> xdg-mime default kde-kpdf.desktop application/pdf $> xdg-mime query default application/pdf kde-kpdf.desktop