Query the service org.freedesktop.locale1 about the current X11 keyboard configuration

query-locale.c

/*
 * Author:	Goffredo Baroncelli <kreijack@inwind.it>
 * Date:    2021/01/10
 * File name: query-locale.c
 * Derived:
 *          http://0pointer.net/blog/the-new-sd-bus-api-of-systemd.html
 *          man sd_bus_get_property_string
 *          man org.freedesktop.locale1
 * Description:
 *          Query the service org.freedesktop.locale1 about the current X11
 *          keyboard configuration
 * Compile:
 *          $ gcc query-locale.c -o query-locale \
 *              `pkg-config --cflags --libs libsystemd`
 * Run:
 *          $ ./query-locale
 *          X11Layout:	it
 *          X11Model:	pc105
 *          X11Options:	terminate:ctrl_alt_bksp
 *          X11Variant:
 *          $
 */
#include <stdio.h>
#include <stdlib.h>
#include <systemd/sd-bus.h>

static int get_prop(sd_bus *bus, char *property_name, sd_bus_error *error, char **res) {
    int r;
    r = sd_bus_get_property_string(bus,
           "org.freedesktop.locale1",           /* service to contact */
           "/org/freedesktop/locale1",          /* object path */
           "org.freedesktop.locale1",           /* interface name */
           property_name,
           error,
           res);

    return r;
}

int main(int argc, char *argv[]) {
        sd_bus_message *m = NULL;
        sd_bus *bus = NULL;
        const char *path;
        int i, r;

        char *props[] = {
            "X11Layout",
            "X11Model",
            "X11Options",
            "X11Variant",
            NULL
        };

        /* Connect to the system bus */
        r = sd_bus_open_system(&bus);
        if (r < 0) {
                fprintf(stderr, "Failed to connect to system bus: %s\n", strerror(-r));
                goto finish;
        }


        for (i = 0 ; props[i] ; i++) {
            sd_bus_error error = SD_BUS_ERROR_NULL;
            char *ret;

            r = get_prop(bus, props[i], &error, &ret);
            if (r < 0) {
                fprintf(stderr, "Failed to issue method call: %s\n", error.message);
                sd_bus_error_free(&error);
                goto finish;
            }
            sd_bus_error_free(&error);
            printf("%s:\t%s\n", props[i], ret);
            free(ret);
        }


finish:
        sd_bus_unref(bus);

        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}