How do I determine the Mime type of a file?

Question

I recently switched to gnome3 and was surprised to find that there was no way by which we could set the default applications. I am writing a nautilus extension using bash. I want to find the mime type of a file.

Initially I used to extract the extension of the file using sed and build the code on it. Then I realized that there is this command called file. When I try to find the mime-type of a mkv file, the command file --mime-type -b <filename> outputs application/octet-stream but when I see the nautilus-properties window it shows the correct video/x-matroska mime-type.

Am I missing anything here?? If not is there a better way in which I can file the mime-type of a file? Thanks in advance :)

Answer 1

There are different ways to get a MIME type on Linux, and they often lead to different results. Use

xdg-mime query filetype your_file

to get the same MIME type as Nautilus gets.

Answer 2

Look up the .desktop file of the application (i.e. gedit) in /usr/share/applications and add the MIME-Types as following:

...
MimeType=text/plain;text/wiki;text/foo;
...

They should then be automatically launched on these files.