How to add a custom context menu action to a certain mime type Ubuntu 21.10

Question

I am making a installer for my program and I need to add a custom context menu action **only **to a certain mime type.

Answer 1

It's odd you haven't got an answer to this basic question, although I imagine that in the meantime you have found it yourself. I will provide an answer based on my current settings for Kubuntu and Dolphin, but you can extrapolate them to Gnome/Nautilus, Xfce/Thunar etc. This involves the use of .desktop files located in different folders depending on the file manager, but in all cases the specific mime type is determined by a line that starts with MimeType=.

First, you have to know the correct mime type. To get that for any file, why not create a context menu?

A generic mime type setting that would give you a menu action for any file should be of the form

MimeType=application/octet-stream;

The command itself for showing the mime type of the selected file could be like

file --mime-type -b "%u"

For example, in Kubuntu, I have the file ~/.local/share/kservices5/ServiceMenus/CheckMimeType.desktop of the form

[Desktop Action FileMimeType]
Exec=bash -c 'type=$(file --mime-type -b "%u"); kdialog --title "Checking Mimetype" --msgbox "MimeType: $type";';
Icon=preferences-desktop-filetype-association
Name=Check MimeType
[Desktop Entry]
Actions=FileMimeType
Icon=auto-type
MimeType=application/octet-stream;
ServiceTypes=KonqPopupMenu/Plugin
Type=Service

(But that's for KDE, in Gnome with Nautilus the file is different and has a different location. As you haven't provided more details on what programs you use, and in any case, I can only direct you to answers already present on askubuntu, to which I added the links above. This question would probably show to be a duplicate of those if you add more details to it.)

In the same way, you can apply your command to your specific mime type.