There are several examples in the geoclue source, these are included here to give a quick overview.

Here is a very simple example of using a specific Geoclue Position provider. Note that we're using the synchronous version of the method call here, so geoclue_position_get_position() will block until the response comes (or until D-Bus timeouts).

#include <geoclue/geoclue-position.h>

int main() 
{
	GeocluePosition *pos;
	GeocluePositionFields fields;
	double lat, lon;
	GError *error = NULL;
	
	g_type_init ();
	
	/ * Create the position object * /
	pos = geoclue_position_new ("org.freedesktop.Geoclue.Providers.Hostip",
	                            "/org/freedesktop/Geoclue/Providers/Hostip");
	
	/ * call get_position. Note that unneeded output variables (here 
	    timestamp, altitude and accuracy) can be left NULL * /
	fields = geoclue_position_get_position (pos, NULL,
	                                        &lat, &lon, NULL,
	                                        NULL, &error);
	if (error) {
		g_printerr ("Error in get_position: %s.\n", error->message);
		g_error_free (error);
		g_object_unref (pos);
		return 1;
	}
	
	if (fields & GEOCLUE_POSITION_FIELDS_LATITUDE &&
	    fields & GEOCLUE_POSITION_FIELDS_LONGITUDE) {
		g_print ("According to Hostip.info we're at %.3f, %.3f.\n",
		          lat, lon);
	} else {
		g_print ("Hostip does not have a valid location available.\nVisit http://www.hostip.info/ to correct this");
	}
	g_object_unref (pos);
	
	return 0;
}
		

Save as test-hostip.c and compile with

gcc `pkg-config --libs --cflags geoclue`  -o test-hostip test-hostip.c
		

Here is a similarly simple example using GLib mainloop and Gypsy provider with position-changed signals:

#include <geoclue/geoclue-position.h>

/ * device name or bluetooth address * /
#define GPS_DEVICE_NAME "00:02:76:C5:81:BF" 

static void
position_changed (GeocluePosition      *position,
                  GeocluePositionFields fields,
                  int                   timestamp,
                  double                latitude,
                  double                longitude,
                  double                altitude,
                  GeoclueAccuracy      *accuracy,
                  gpointer              userdata)
{
	g_print ("Position changed:\n");
	if (fields & GEOCLUE_POSITION_FIELDS_LATITUDE &&
	    fields & GEOCLUE_POSITION_FIELDS_LONGITUDE) {
		g_print ("\t%f, %f\n\n", latitude, longitude);
	} else {
		g_print ("\tLatitude and longitude not available.\n\n");
	}
}

int main() 
{
	GMainLoop *loop;
	GHashTable *options;
	GeocluePosition *pos;
	GError *error = NULL;
	
	g_type_init ();
	
	/ * Create the position object * /
	pos = geoclue_position_new ("org.freedesktop.Geoclue.Providers.Gypsy",
	                            "/org/freedesktop/Geoclue/Providers/Gypsy");
	
	/ * Set GPS device name option for Gypsy * /
	options = g_hash_table_new (g_str_hash, g_str_equal);
	g_hash_table_insert (options, "org.freedesktop.Geoclue.GPSDevice", GPS_DEVICE_NAME);
	if (!geoclue_provider_set_options (GEOCLUE_PROVIDER (pos), options, &error)) {
		g_printerr ("Error setting options: %s\n", error->message);
		g_error_free (error);
		g_hash_table_destroy (options);
		g_object_unref (pos);
                return 1;
	}
	g_hash_table_destroy (options);
	
	/ * connect to signal * /
	g_signal_connect (G_OBJECT (pos), "position-changed",
			  G_CALLBACK (position_changed), NULL);
	
	g_print ("Waiting for position change signals...\n");
	loop = g_main_loop_new (NULL, FALSE);
	g_main_loop_run (loop);
	
	g_main_loop_unref (loop);
	g_object_unref (pos);
	
	return 0;
}