gdbus systemd unit restart

bounce.c

//
// Restart a systemd unit through gdbus
//
// Compile: 
// gcc $(pkg-config --libs --cflags gio-2.0 glib-2.0) -o bounce bounce.c
//
// Equivalent to:
// # gdbus call --system --dest org.freedesktop.systemd1 --object-path /org/freedesktop/systemd1/unit/whatever_2eservice --method org.freedesktop.systemd1.Unit.ReloadOrRestart replace
//

#include <string.h>
#include <stdlib.h>

#include <sys/types.h>
#include <unistd.h>

#include <time.h>

#include <gio/gio.h>

static int bounce(GDBusConnection *connection, const gchar *owner, GError **error) {
	GDBusMessage *method_call_message;
	method_call_message = g_dbus_message_new_method_call(owner,
		"/org/freedesktop/systemd1/unit/whatever_2eservice",
		"org.freedesktop.systemd1.Unit",
		"ReloadOrRestart");

	g_dbus_message_set_body(method_call_message, g_variant_new("(s)", "replace"));

	GDBusMessage *method_reply_message;
	method_reply_message = g_dbus_connection_send_message_with_reply_sync (connection,
		method_call_message,
		G_DBUS_SEND_MESSAGE_FLAGS_NONE,
		-1,
		NULL,
		NULL,
		error);
	
	int res = EXIT_SUCCESS;

	if (!method_reply_message) {
		res = EXIT_FAILURE;
	} else if (g_dbus_message_get_message_type(method_reply_message) == G_DBUS_MESSAGE_TYPE_ERROR) {
		g_dbus_message_to_gerror(method_reply_message, error);
		
		res = EXIT_FAILURE;
	}
	
	g_object_unref(method_call_message);
	g_object_unref(method_reply_message);

	return res;
}

static void on_name_appeared (GDBusConnection *connection, const gchar *name, const gchar *owner, gpointer user_data) {
	GError *error = NULL;

	if (bounce(connection, owner, &error) == EXIT_SUCCESS) {
		g_print("SUCCESS: Restarted the service\n");
		exit(0);
	} else {
		g_print("FAILURE: Could not restart the service\n");
		exit(1);
	}
}

static void on_name_vanished (GDBusConnection *connection, const gchar *name, gpointer user_data) {
	g_printerr("Failed to get owner for %s\n", name);
	exit(1);
}

int main (int argc, char *argv[]) {
	guint watcher_id;
	watcher_id = g_bus_watch_name(G_BUS_TYPE_SYSTEM,
		"org.freedesktop.systemd1",
		G_BUS_NAME_WATCHER_FLAGS_NONE,
		on_name_appeared,
		on_name_vanished,
		NULL,
		NULL);

	GMainLoop *loop;
	loop = g_main_loop_new (NULL, FALSE);

	g_main_loop_run(loop);

	g_bus_unwatch_name(watcher_id);

	return 0;
}