How an application is chosen over others to open a particular filetype in Linux

Question

Earlier my text/xml files were by default opened by firefox I think. Not sure of this because I do not remember exactly. Then I think I installed geany and then my text/xml files were always by default opened by Geany until I installed google-chrome. Now I see they are by default opened by google-chrome.

Until now I did not bother to check what are the default applications associated with a particular filetype.

Now when I check my /usr/share/applications/defaults.list file I see this:

text/html=firefox.desktop;google-chrome.desktop
text/xml=google-chrome.desktop;
application/xhtml_xml=google-chrome.desktop;

My default browser is still set to firefox. The first line above shows both Firefox and Chrome for text/html but for text/xml it is only Chrome.

I think earlier it was Geany for text/xml because that's the reason by default Geany used to open XML files. I'm not sure on this because I've never checked.

Questions

• I'm wondering how it is set. How a particular application is chosen over another.
• Also how the semicolon (";") is read in the file.

I'm using Fedora 20 - Mate desktop environment.

Query based on Answer by slm

Based on the Answer by @slm, I see my xml filetypes are associated with Geany. But I see them opening with Chrome instead.

$ xdg-mime query default application/xml
geany.desktop
$ 

As I mentioned above my /usr/share/applications/defaults.list file shows

text/xml=google-chrome.desktop;

So what is the difference and which should override?

Answer 1

I usually use the command line tool xdg-mime to determine what applications are associated with a given MIME type.

$ xdg-mime query filetype IMAGE.PNG 
image/png

$ xdg-mime query default image/png
shotwell-viewer.desktop shutter.desktop

You can make this a single command like so:

$ xdg-mime query default $(xdg-mime query filetype IMAGE.PNG)
shotwell-viewer.desktop shutter.desktop

You can change the default using mimeopen like so:

$ mimeopen -d ~/test.pdf

Please choose a default application for files of type application/pdf

    1) E-book Viewer  (calibre-ebook-viewer)
    2) Document Viewer  (evince)
    3) Xournal  (xournal)
    4) GNU Image Manipulation Program  (gimp)
    5) Xpdf PDF Viewer  (xpdf)
    6) Print Preview  (evince-previewer)
    7) Inkscape  (inkscape)
    8) calibre  (calibre-gui)
    9) Other...

use application #2
Opening "/home/saml/Downloads/test.pdf" with Document Viewer  (application/pdf)

NOTE: By the way, the semi-colons are there because there can be multiple associations for a given MIME type. So text/xml could have google-chrome.desktop;firefox.desktop; as it's value would would indicate that there are 2 apps that can handle that particular type.

References

• How to get a list of applications associated with a file using command line
• Is there an "open with" command for the command line?
• xdg-open opens a different application to the one specified by xdg-mime query