关于std::string.length() std::string.size()

eclipse的代码提示获取到的描述：/// Returns the number of characters in the string, not including any/// null-termination.意思大概是返回字符串的字符个数，不包括结束符我的系统的ubuntu13.04,系统设置的编码如下：LANG=zh_CN.UTF-8LANGUAGE=zh_CN:zh:en_US:enLC_CTYPE="zh_CN.UTF-8"LC_NUMERIC=zh_CN.UTF-8LC_TIME=zh_CN.UTF-8LC_COLLATE="zh_CN.UTF-8"LC_MONETARY=zh_CN.UTF-8LC_MESSAGES="zh_CN.UTF-8"LC_PAPER=zh_CN.UTF-8LC_NAME=zh_CN.UTF-8LC_ADDRESS=zh_CN.UTF-8LC_TELEPHONE=zh_CN.UTF-8LC_MEASUREMENT=zh_CN.UTF-8LC_IDENTIFICATION=zh_CN.UTF-8LC_ALL=在此环境下执行下面的代码：std::string str = "中国";cout << str.size() << "," << str.length() << "," << strlen(str.c_str())<< endl;结果为：6，6，6返回的其实是字节数