Changing default application that start a file

Sometime the default installation of an operating system configuration is not the way you wanted it to be, so with this article, it will show you how to change the application that open a file. Note that this article will work in gnome version 3.4.2 or later.

gui way
This is an easy way if you don't want to dig deep into how is the gnome mechanism file opening work. Just right click on the file, click on Properties. An pop up window associated with the file you selected appeared. On the tab Open With , locate the application you want the file to open with and then select it.

cli way
If you want to dig a little deeper, there are many configuration files located in /usr/share/applications. These files contain information about an application like application name and application exec command to trigger the start of an application. Once you located the application you want a file to be associated to start with, e.g. I would like csv file to be started with libreoffice-calc.desktop , then go to $HOME/.local/share/applications directory, locate another file, mimeapps.list. Open this file with an text editor, under the group [Default Applications] , add an entry like text/csv=libreoffice-calc.desktop. If you want to associated with more files, locate the general mime file at /etc/mime.types, and start to populate your environment with default application.

https://developer.gnome.org/integration-guide/stable/desktop-files.html.en