public static void main(string[] args) {
	var engines = new EngineController("/dev/ttyAMA0");

	if(args.length < 2) {
		stderr.printf("%s <cmd>\n", args[0]);
		stderr.printf("cmds: engine, enable, disable, nop\n");
		return;
	}

	switch(args[1]) {
		case "engine":
			if(args.length < 4) {
				stderr.printf("%s engine <engine> <speed>\n", args[0]);
				return;
			}

			uint8 engine = (uint8) int.parse(args[2]);
			if("%u".printf(engine) != args[2])
				error("engine must be an integer");

			uint8 speed = (uint8) int.parse(args[3]);
			if("%u".printf(speed) != args[3])
				error("speed must be an integer");

			if(engine == 6)
				if(engines.set_speed_all(speed))
					stdout.printf("set speed of all engines to %u: ok\n", speed);
				else
					stdout.printf("set speed of all engines to %u: fail\n", speed);
			if(engine <= 5)
				if(engines.set_speed(engine, speed))
					stdout.printf("set speed of engine %u to %u: ok\n", engine, speed);
				else
					stdout.printf("set speed of engine %u to %u: fail\n", engine, speed);
			break;
		case "enable":
			if(engines.enable())
				stdout.printf("enable motors: ok\n");
			else
				stdout.printf("enable motors: fail\n");
			break;
		case "disable":
			if(engines.disable())
				stdout.printf("disable motors: ok\n");
			else
				stdout.printf("disable motors: fail\n");
			break;
		case "nop":
			if(engines.no_operation())
				stdout.printf("no operation: ok\n");
			else
				stdout.printf("no operation: fail\n");
			break;
		default:
			stderr.printf("cmd not supported!\n");
			break;
	}
}