rospack find //check the dir of the package
可以返回软件包的路径信息
roscd //change dir to that package
它允许你直接切换(cd)工作目录到某个软件包或者软件包集当中
rosls 是rosbash命令集中的一部分，它允许你直接按软件包的名称而不是绝对路径执行ls命令（罗列目录）
roscore = ros+core : master (provides name service for ROS) + rosout (stdout/stderr) + parameter server (parameter server will be introduced later)
rosnode = ros+node : ROS tool to get information about a node.
rosrun = ros+run : runs a node from a given package.
ROS topic
roscore:
rosrun rqt_graph rqt_graph//能够创建一个显示当前系统运行情况的动态图形
rostopic echo [topic]
eg:
rostopic echo /turtle1/cmd_vel//rostopic echo可以显示在某个话题上发布的数据
rostopic type [topic] //rostopic type 命令用来查看所发布话题的消息类型
eg:
rostopic type /turtle1/cmd_vel
rosmsg命令来查看消息的详细情况
rosmsg show geometry_msgs/Twist
//rostopic pub可以把数据发布到当前某个正在广播的话题上
rostopic pub [topic] [msg_type] [args]
eg:
rostopic pub -1 /turtle1/cmd_vel geometry_msgs/Twist -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, 1.8]'
//以上命令会发送一条消息给turtlesim，告诉它以2.0大小的线速度和1.8大小的角速度开始移动
rostopic pub /turtle1/cmd_vel geometry_msgs/Twist -r 1 -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, 1.8]'
//这条命令以1Hz的频率发布速度命令到速度话题上
//rostopic hz命令可以用来查看数据发布的频率
rostopic hz [topic]
eg:
rostopic hz /turtle1/pose
//rqt_plot命令可以实时显示一个发布到某个话题上的数据变化图形
rosrun rqt_plot rqt_plot
ROS service
服务（services）是节点之间通讯的另一种方式。服务允许节点发送请求（request） 并获得一个响应（response）
rosservice list
rosservice type [service]
rosservice call [service] [args]
rosservice type spawn| rossrv show
eg:
return these
float32 x
float32 y
float32 theta
string name
---
string namerosservice call spawn 2 2 0.2 ""
//在给定的位置和角度生成一只新的乌龟。名字参数是可选的，这里我们不设具体的名字，让turtlesim自动创建一个
Using rosparam
rosparam set 设置参数
rosparam get 获取参数
rosparam load 从文件读取参数
rosparam dump 向文件中写入参数
rosparam delete 删除参数
rosparam list 列出参数名rosparam list
rosparam set [param_name]
rosparam get [param_name]
eg:
rosparam set background_r 150
//上述指令修改了参数的值，现在我们调用清除服务使得修改后的参数生效
rosservice call clear
rosparam get background_g
//获取背景的绿色通道的值
rosparam get /
//显示参数服务器上的所有内容
使用 rqt_console 和 roslaunch
rosrun rqt_console rqt_console
rosrun rqt_logger_level rqt_logger_level
Fatal
Error
Warn
Info
DebugFatal是最高优先级，Debug是最低优先级。通过设置日志等级你可以获取该等级及其以上优先等级的所有日志消息。比如，将日志等级设为Warn时，你会得到Warn、Error和Fatal这三个等级的所有日志消息
使用roslaunch
使用roslaunch同时运行多个节点
1 <launch>
2
3 <group ns="turtlesim1">
4 <node pkg="turtlesim" name="sim" type="turtlesim_node"/>
5 </group>
6
7 <group ns="turtlesim2">
8 <node pkg="turtlesim" name="sim" type="turtlesim_node"/>
9 </group>
10
11 <node pkg="turtlesim" name="mimic" type="mimic">
12 <remap from="input" to="turtlesim1/turtle1"/>
13 <remap from="output" to="turtlesim2/turtle1"/>
14 </node>
15
16 </launch>消息(msg)和服务(srv)介绍
消息(msg): msg文件就是一个描述ROS中所使用消息类型的简单文本。它们会被用来生成不同语言的源代码。
服务(srv): 一个srv文件描述一项服务。它包含两个部分：请求和响应。
rosmsg show [message type]
eg:
rosmsg show Num
result:
[beginner_tutorials/Num]:
int64 numMore information on msg and srv
编写简单的消息发布器和订阅器
编写发布器节点
- 初始化 ROS 系统
- 在 ROS 网络内广播我们将要在 chatter 话题上发布 std_msgs/String 类型的消息
- 以每秒 10 次的频率在 chatter 上发布消息
#include "ros/ros.h"
#include "std_msgs/String.h"
#include <sstream>
/**
* This tutorial demonstrates simple sending of messages over the ROS system.
*/
int main(int argc, char **argv)
{
/**
* The ros::init() function needs to see argc and argv so that it can perform
* any ROS arguments and name remapping that were provided at the command line. For programmatic
* remappings you can use a different version of init() which takes remappings
* directly, but for most command-line programs, passing argc and argv is the easiest
* way to do it. The third argument to init() is the name of the node.
*
* You must call one of the versions of ros::init() before using any other
* part of the ROS system.
*/
ros::init(argc, argv, "talker");
/**
* NodeHandle is the main access point to communications with the ROS system.
* The first NodeHandle constructed will fully initialize this node, and the last
* NodeHandle destructed will close down the node.
*/
ros::NodeHandle n;
/**
* The advertise() function is how you tell ROS that you want to
* publish on a given topic name. This invokes a call to the ROS
* master node, which keeps a registry of who is publishing and who
* is subscribing. After this advertise() call is made, the master
* node will notify anyone who is trying to subscribe to this topic name,
* and they will in turn negotiate a peer-to-peer connection with this
* node. advertise() returns a Publisher object which allows you to
* publish messages on that topic through a call to publish(). Once
* all copies of the returned Publisher object are destroyed, the topic
* will be automatically unadvertised.
*
* The second parameter to advertise() is the size of the message queue
* used for publishing messages. If messages are published more quickly
* than we can send them, the number here specifies how many messages to
* buffer up before throwing some away.
*/
ros::Publisher chatter_pub = n.advertise<std_msgs::String>("chatter", 1000);
ros::Rate loop_rate(10);
/**
* A count of how many messages we have sent. This is used to create
* a unique string for each message.
*/
int count = 0;
while (ros::ok())
{
/**
* This is a message object. You stuff it with data, and then publish it.
*/
std_msgs::String msg;
std::stringstream ss;
ss << "hello world " << count;
msg.data = ss.str();
ROS_INFO("%s", msg.data.c_str());
/**
* The publish() function is how you send messages. The parameter
* is the message object. The type of this object must agree with the type
* given as a template parameter to the advertise<>() call, as was done
* in the constructor above.
*/
chatter_pub.publish(msg);
ros::spinOnce();
loop_rate.sleep();
++count;
}
return 0;
}编写订阅器节点
- 初始化ROS系统
- 订阅 chatter 话题
- 进入自循环，等待消息的到达
- 当消息到达，调用 chatterCallback() 函数
这里写代码片#include "ros/ros.h"
#include "std_msgs/String.h"
/**
* This tutorial demonstrates simple receipt of messages over the ROS system.
*/
void chatterCallback(const std_msgs::String::ConstPtr& msg)
{
ROS_INFO("I heard: [%s]", msg->data.c_str());
}
int main(int argc, char **argv)
{
/**
* The ros::init() function needs to see argc and argv so that it can perform
* any ROS arguments and name remapping that were provided at the command line. For programmatic
* remappings you can use a different version of init() which takes remappings
* directly, but for most command-line programs, passing argc and argv is the easiest
* way to do it. The third argument to init() is the name of the node.
*
* You must call one of the versions of ros::init() before using any other
* part of the ROS system.
*/
ros::init(argc, argv, "listener");
/**
* NodeHandle is the main access point to communications with the ROS system.
* The first NodeHandle constructed will fully initialize this node, and the last
* NodeHandle destructed will close down the node.
*/
ros::NodeHandle n;
/**
* The subscribe() call is how you tell ROS that you want to receive messages
* on a given topic. This invokes a call to the ROS
* master node, which keeps a registry of who is publishing and who
* is subscribing. Messages are passed to a callback function, here
* called chatterCallback. subscribe() returns a Subscriber object that you
* must hold on to until you want to unsubscribe. When all copies of the Subscriber
* object go out of scope, this callback will automatically be unsubscribed from
* this topic.
*
* The second parameter to the subscribe() function is the size of the message
* queue. If messages are arriving faster than they are being processed, this
* is the number of messages that will be buffered up before beginning to throw
* away the oldest ones.
*/
ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);
/**
* ros::spin() will enter a loop, pumping callbacks. With this version, all
* callbacks will be called from within this thread (the main one). ros::spin()
* will exit when Ctrl-C is pressed, or the node is shutdown by the master.
*/
ros::spin();
return 0;
}