mysqldump should exit with an error when used with wrong parameter "-flush-logs"

root@centos-6-5-tckt-8873:[Wed Aug 19 09:51:24][/etc]$ mysqldump -ignore-table=mysql.user --single-transaction --master-data=2 --flush-logs --delete-master-logs --hex-blob --all-databases 

mysqldump: unknown option '-g'

root@centos-6-5-tckt-8873:[Wed Aug 19 09:53:35][/etc]$ echo $?

2

root@centos-6-5-tckt-8873:[Wed Aug 19 09:53:40][/etc]$ mysqldump --ignore-table=mysql.user --single-transaction --master-data=2 -flush-logs --delete-master-logs --hex-blob --all-databases 

-- MySQL dump 10.15  Distrib 10.0.20-MariaDB, for Linux (x86_64)

--

-- Host: localhost    Database: 

-- ------------------------------------------------------

-- Server version       10.0.20-MariaDB-log

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;

/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;

/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;

/*!40101 SET NAMES utf8 */;

/*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;

/*!40103 SET TIME_ZONE='+00:00' */;

/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;

/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;

/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;

/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;

/*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;

/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;

/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;

/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;

/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;

/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;

/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

-- Dump completed on 2015-08-19  9:54:09

root@centos-6-5-tckt-8873:[Wed Aug 19 09:54:09][/etc]$ echo $?

0

root@centos-6-5-tckt-8873:[Wed Aug 19 09:54:11][/etc]$