7.1 Default Applications

20211012 Often we will choose our favourite applications as a default for particular tasks. For example, to view an image in a png file we might choose to use eog by default. The command xdg-open can be used to open files using preferred applications. This command is used, for example, by browsers to perform tasks and open files using the preferred application.

We can use xdg-mime to determine the MIME type of a file and for that file type the default application:

$ xdg-mime query filetype sample.png
image/png

$ xdg-mime query default image/png
org.gnome.eog.desktop

Information about the application org.gnome.eog.desktop can be found in a file of the same name in /usr/share/applications/.

$ cat /usr/share/applications/org.gnome.eog.desktop

[Desktop Entry]
Name=Image Viewer
Comment=Browse and rotate images
TryExec=eog
Exec=eog %U
[...]

Thus, both of the following commands run the same application:

$ xdg-open sample.png

$ eog sample.png

To set a default application for a particular MIME type:

$ xdg-mime default image/png eom.desktop

The xdg-open will then use eom to open a png file.

Similarly for video:

$ xdg-mime query filetype iris.mp4
video/mp4

$ xdg-mime query default video/mp4
org.gnome.Totem.desktop

Other examples:

$ xdg-open "http://www.example.com"     # Open URL using default browser.


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