How to Get the Icon, Mime Type, and Application Associated with a File in the Linux Desktop

How do you get the icon, MIME type, and application associated with a file in the Linux Desktop?

Here is an example of using GLib/GIO to get the information you want.

#include <gio/gio.h>
#include <stdio.h>

int
main (int argc, char **argv)
{
    g_thread_init (NULL);
    g_type_init ();

    if (argc < 2)
        return -1;

    GError *error;
    GFile *file = g_file_new_for_path (argv[1]);
    GFileInfo *file_info = g_file_query_info (file,
                                              "standard::*",
                                              0,
                                              NULL,
                                              &error);

    const char *content_type = g_file_info_get_content_type (file_info);
    char *desc = g_content_type_get_description (content_type);
    GAppInfo *app_info = g_app_info_get_default_for_type (
                                  content_type,
                                  FALSE);

    /* you'd have to use g_loadable_icon_load to get the actual icon */
    GIcon *icon = g_file_info_get_icon (file_info);

    printf ("File: %s\nDescription: %s\nDefault Application: %s\n",
            argv[1],
            desc,
            g_app_info_get_executable (app_info));

    return 0;
}

How do you make xdg-utils detect a file association for my application from a distribution package?

You don't need to run the mime-* tools, but you do need to update the desktop and icon associations for the freedesktop environment after install like so:

update-mime-database /usr/share/mime
update-desktop-database
gtk-update-icon-cache /usr/share/icons/hicolor

These should be run after uninstall, too, to cleanup after removal. In RPMs this is the %postun section.

Substitute /usr/share with whatever deployment variable you might use like %{_datadir} for RPM .spec's.

Also the icon name had an issue. It should have just been named 'xnec2c' not 'application-x-nec2' because the 'xnec2c' icon gets installed with the installer as follows:

%{_datadir}/icons/hicolor/scalable/apps/%{name}.svg
%{_datadir}/icons/hicolor/256x256/apps/%{name}.png

Get the default icon for specific file type in Ubuntu OS by python

GNU/Linux desktop environments do not assign icons to filename suffixes (extensions). Rather, they assign icons to Internet media types (MIME types), and a file’s type may or may not be determined by its filename suffix (content sniffing may also be involved). You can use the mimetypes module from the standard library to guess the media type from the suffix. Then gio.content_type_get_icon, and from then on it’s as in the question you linked.

import mimetypes

import gio
import gtk

def get_icon_path(extension, size=32):
    type_, encoding = mimetypes.guess_type('x.' + extension)
    if type_:
        icon = gio.content_type_get_icon(type_)
        theme = gtk.icon_theme_get_default()
        info = theme.choose_icon(icon.get_names(), size, 0)
        if info:
            return info.get_filename()

Register file extensions / mime types in Linux

Use xdg-utils from freedesktop.org Portland.

Register the icon for the MIME type:

xdg-icon-resource install --context mimetypes --size 48 myicon-file-type.png x-application-mytype

Create a configuration file (freedesktop Shared MIME documentation):

<?xml version="1.0"?>
<mime-info xmlns='http://www.freedesktop.org/standards/shared-mime-info'>
  <mime-type type="application/x-mytype">
    <comment>A witty comment</comment>
    <comment xml:lang="it">Uno Commento</comment>
    <glob pattern="*.myapp"/>
  </mime-type>
</mime-info>

Install the configuration file:

xdg-mime install mytype-mime.xml

This gets your files recognized and associated with an icon. xdg-mime default can be used for associating an application with the MIME type after you get a .desktop file installed.

Where to install icon for a user-specific application while adhering to FreeDesktop standards?

Rereading the XDG Icon Specification, I noticed the specification references the XDG Base Directory Specification by including $XDG_DATA_DIRS. This inclusion implies that that the Base Directory Specification is also in effect, which in turn mandates that

Lookups of the data file should search for ./subdir/filename relative to all base directories specified by $XDG_DATA_HOME and $XDG_DATA_DIRS . If an environment variable is either not set or empty, its default value as defined by this specification should be used instead. (src)

So, assuming my understanding is correct and XDG desktops adhere to specs, the user-specific icon location for your application is $XDG_DATA_HOME/icons/hicolor/48x48/apps/$YOURAPP.(png|xpm) and $XDG_DATA_HOME/icons/hicolor/scalable/apps/$YOURAPP.svg. File extensions are case-sensitive and only these three extensions are allowed. Also note that SVG support is optional.

If $XDG_DATA_HOME is not set, you should default to $HOME/.local/share as per the Base Directory Specification.

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