xdg-mime

query

# get the file mime type for a file
xdg-mime query filetype "photo.jpeg"

# get default app
xdg-mime query default "image/jpeg"

default

• Mime applications are saved at /etc/xdg/mimeapps.list (or ~/.config/mimeapps.list)
• Desktop entries (eligible for default apps are stored at /usr/share/applications)

# set default app
xdg-mime default "feh.desktop" "image/jpeg"
xdg-mime default "thunar.desktop" "inode/directory"
xdg-mime default "firefox.desktop" "x-scheme-handler/https"