1 cd catkin_ws/src　　　　　　　　　　　　　　　　　　　　　　　　　　　　#进入工作空间
2 catkin_create_pkg my_turtle_package rospy roscpp　　　　　　　　 #新建my_turtle_package包

1 cd my_turtle_package/src/　　　　
2 touch draw_rectangle.cpp

 1 #include <ros/ros.h>
 2 #include <geometry_msgs/Twist.h>
 3 #define PI 3.14159265358979323846
 4
 5 int main(int argc, char **argv){
 6   ros::init(argc, argv, "draw_rectangle");   //"draw_rectangle"必须是nodename
 7   std::string topic = "/turtle1/cmd_vel"; //topic name
 8   ros::NodeHandle n;
 9   ros::Publisher cmdVelPub = n.advertise<geometry_msgs::Twist>(topic, 1);
10   //第一个参数也可以写成"/turtle1/cmd_vel"这样的topic name
11   //第二个参数是发布的缓冲区大小,<geometry_msgs::Twist>是消息类型
12   ros::Rate loopRate(2);
13   //与Rate::sleep();配合指定自循环频率
14   ROS_INFO("draw_retangle start...");//输出显示信息
15   geometry_msgs::Twist speed; // 控制信号载体 Twist message
16 //声明一个geometry_msgs::Twist 类型的对象speed，并将速度的值赋值到这个对象里面
17   int count = 0;
18   while (ros::ok()){
19     speed.linear.x = 1; // 设置线速度为1m/s，正为前进，负为后退
20     speed.linear.y = 0;
21     speed.linear.z = 0;
22     speed.angular.x = 0;
23     speed.angular.y = 0;
24     speed.angular.z = 0;
25     count++;
26     while(count == 5)
27     {
28         count=0;
29         speed.angular.z = PI; //转90°
30     }
31     cmdVelPub.publish(speed); // 将刚才设置的指令发送给机器人
32     ros::spinOnce();//调用此函数给其他回调函数得以执行
33     loopRate.sleep();//按loopRate(2)设置的2HZ将程序挂起
34   }
35
36   return 0;
37 }

1 cd ~/catkin_ws/src/my_turtle_package
2 gedit CMakeLists.txt

1 add_executable(draw_rectangle src/draw_rectangle.cpp)
2 target_link_libraries(draw_rectangle ${catkin_LIBRARIES})

1 cd ~/catkin_ws/
2 catkin_make

1 roscore

rosrun turtlesim turtlesim_node

1 cd  ~/catkin_ws/
2 source devel/setup.bash
3 rosrun my_turtle_package draw_rectangle