ros消息msgs相关，待补充

wiki
msg
std_msgs——wiki中ros_core下msgs相关貌似有三个。
1.common_msgs robot-specific message type特殊的机器人消息类型
2.rosgraph_msgs
3.std_msgs
std_msgs::String (We broadcast a message on ROS using a message-adapted class, generally generated from a msg file. More complicated datatypes are possible, but for now we’re going to use the standard String message, which has one member: “data”.使用std_msgs需要 后面加.data=”xxxxx”;)
最普通的消息类型，很常见的。