Isso é explicado muito bem nesta página wiki do Arch Linux intitulada: Variáveis de Ambiente , especificamente no Seção de exemplos:
The following section lists a number of common environment variables used by a Linux system and describes their values.
DEindicates the Desktop Environment being used.xdg-openwill use it to choose more user-friendly file-opener application that desktop environment provides. Some packages need to be installed to use this feature. For GNOME, that would be libgnomeAUR; for Xfce this is exo. Recognised values ofDEvariable are:gnome,kde,xfce,lxdeandmate.The
DEenvironment variable needs to be exported before starting the window manager. For example:~/.xinitrc export DE="xfce" exec openboxThis will make
xdg-openuse the more user-friendlyexo-open, because it assumes it is running inside Xfce. Useexo-preferred-applicationsfor configuring.

