# 【ROS教程】ROS文件系统和基础架构

@[TOC](https://github.com/UnderTurrets/notes/blob/master/ROS/%E6%96%87%E7%AB%A0%E7%9B%AE%E5%BD%95/README.md)

***

## 1.工作空间目录

![](https://cdn.jsdelivr.net/gh/UnderTurrets/ImageHosting@master/ros_architecture.jpeg)

```shell
WorkSpace --- 自定义的工作空间

    |--- build：编译空间，用于存放CMake和catkin的缓存信息、配置信息和其他中间文件。

    |--- devel：开发空间，用于存放编译后生成的目标文件，包括头文件、动态&静态链接库、可执行文件等。

    |--- src：源码

        |-- package：功能包(ROS基本单元)包含多个节点、库与配置文件，包名所有字母小写，只能由字母、数字与下划线组成

            |-- CMakeLists.txt：配置编译规则，比如源文件、依赖项、目标文件

            |-- package.xml：包信息，比如:包名、版本、作者、依赖项...(以前版本是 manifest.xml)

            |-- scripts：存储python文件

            |-- src：存储C++源文件

            |-- include：头文件

            |-- msg：消息通信格式文件

            |-- srv：服务通信格式文件

            |-- action：动作格式文件

            |-- launch：可一次性运行多个节点 

            |-- config：配置信息

            |-- CMakeLists.txt：编译的基本配置

```

### 1.1 package.xml

* 固定格式

```shell
<?xml version="1.0"?>
<!-- 格式: 以前是 1，推荐使用格式 2 -->
<package format="2">
  <!-- 包名 -->
  <name><the name of package></name>
  <!-- 版本 -->
  <version>0.0.0</version>
  <!-- 描述信息 -->
  <description>The <the name of package> package</description>

  <!-- One maintainer tag required, multiple allowed, one person per tag -->
  <!-- Example:  -->
  <!-- <maintainer email="jane.doe@example.com">Jane Doe</maintainer> -->
  <!-- 维护人员 -->
  <maintainer email="*">XXX</maintainer>


  <!-- One license tag required, multiple allowed, one license per tag -->
  <!-- Commonly used license strings: -->
  <!--   BSD, MIT, Boost Software License, GPLv2, GPLv3, LGPLv2.1, LGPLv3 -->
  <!-- 许可证信息，ROS核心组件默认 BSD -->
  <license>TODO</license>


  <!-- Url tags are optional, but multiple are allowed, one per tag -->
  <!-- Optional attribute type can be: website, bugtracker, or repository -->
  <!-- Example: -->
  <!-- <url type="website">http://wiki.ros.org/demo01_hello_vscode</url> -->


  <!-- Author tags are optional, multiple are allowed, one per tag -->
  <!-- Authors do not have to be maintainers, but could be -->
  <!-- Example: -->
  <!-- <author email="jane.doe@example.com">Jane Doe</author> -->


  <!-- The *depend tags are used to specify dependencies -->
  <!-- Dependencies can be catkin packages or system dependencies -->
  <!-- Examples: -->
  <!-- Use depend as a shortcut for packages that are both build and exec dependencies -->
  <!--   <depend>roscpp</depend> -->
  <!--   Note that this is equivalent to the following: -->
  <!--   <build_depend>roscpp</build_depend> -->
  <!--   <exec_depend>roscpp</exec_depend> -->
  <!-- Use build_depend for packages you need at compile time: -->
  <!--   <build_depend>message_generation</build_depend> -->
  <!-- Use build_export_depend for packages you need in order to build against this package: -->
  <!--   <build_export_depend>message_generation</build_export_depend> -->
  <!-- Use buildtool_depend for build tool packages: -->
  <!--   <buildtool_depend>catkin</buildtool_depend> -->
  <!-- Use exec_depend for packages you need at runtime: -->
  <!--   <exec_depend>message_runtime</exec_depend> -->
  <!-- Use test_depend for packages you need only for testing: -->
  <!--   <test_depend>gtest</test_depend> -->
  <!-- Use doc_depend for packages you need only for building documentation: -->
  <!--   <doc_depend>doxygen</doc_depend> -->
  <!-- 依赖的构建工具，这是必须的 -->
  <buildtool_depend>catkin</buildtool_depend>

  <!-- 指定构建此软件包所需的软件包 -->
  <build_depend>roscpp</build_depend>
  <build_depend>rospy</build_depend>
  <build_depend>std_msgs</build_depend>

  <!-- 指定根据这个包构建库所需要的包 -->
  <build_export_depend>roscpp</build_export_depend>
  <build_export_depend>rospy</build_export_depend>
  <build_export_depend>std_msgs</build_export_depend>

  <!-- 运行该程序包中的代码所需的程序包 -->  
  <exec_depend>roscpp</exec_depend>
  <exec_depend>rospy</exec_depend>
  <exec_depend>std_msgs</exec_depend>


  <!-- The export tag contains other, unspecified, tags -->
  <export>
    <!-- Other tools can request additional information be placed here -->

  </export>
</package>

```

## 2.启动节点的方式

### 2.1 一次启动一个

```shell
rosrun <the name of package> <the name of executable file>
```

* executable file：对于C语言，这个文件就是CMakeLists.txt中用add\_executable生成的可执行文件；对于python，这个文件就是CMakeLists.txt中用catkin\_install\_python指向的文件

对应语法：

```shell
add_executable(<the name of executable file>
               src/<the name of the source>.cpp
              )
catkin_install_python(PROGRAMS scripts/<the name of the source>.py
                      DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
                     )
```

### 2.2 一次启动多个

如果想要一次性启动一个包里的多个节点，而不是一行行地输入rosrun指令...

* 我们需要一个launch文件，它的固定格式是这样的：

```shell
<launch>
    <node pkg="helloworld" type="demo_hello" name="hello" output="screen" />
    <node pkg="turtlesim" type="turtlesim_node" name="t1"/>
    <node pkg="turtlesim" type="turtle_teleop_key" name="key1" />
</launch>
```

* node：包含的某个节点
* pkg：功能包
* type：被运行的节点文件
* name：为节点命名
* output：设置日志的输出目标

然后，在终端输入：

```shell
roslaunch <the name of package> <the name of launch file>
```

## 3.ROS常用命令

### 3.1 增

创建新的ROS功能包：

```shell
catkin_create_pkg 自定义包名 依赖包
```

### 3.2 查

列出所有功能包：

```shell
rospack list
```

查找某个功能包是否存在，如果存在返回安装路径：

```shell
rospack find 包名
```

### 3.3 执行

#### 3.3.1 加载环境变量

先进入工作目录，然后：

```shell
source ./devel/setup.bash
```

#### 3.3.2 运行节点

`roscore`：ROS的系统先决条件节点和程序的集合，必须运行 roscore 才能使 ROS 节点进行通信。**新开一个终端并输入**：

```shell
roscore #用法一
roscore -p xxxx #用法二，指定端口号
```

roscore 将启动:

* ros master
* ros 参数服务器
* rosout 日志节点

### 3.4 查看计算图

**在节点正在运行的情况下**，终端输入：

```shell
rosrun rqt_graph rqt_graph
```

![](https://cdn.jsdelivr.net/gh/UnderTurrets/ImageHosting@master/ros_rqtgraph.png)

## 4.创建功能包

### 4.1 选择工作目录

首先，选择一个路径作为工作目录。这里我选择了`/home/xu736946693/Desktop/ROS-exercise`作为工作目录

### 4.2 创建功能包目录

```shell
mkdir src
```

然后，**在工作空间目录下**：

```shell
catkin_make
```

src目录下会多出一个锁定的CMakeLists.txt文件，不用管它。

### 4.3 建立功能包

先进入src目录

```shell
cd src
```

然后使用ROS提供的指令直接创建功能包即可：

```shell
catkin_create_pkg <the name of your package> roscpp rospy std_msgs message_generatio
```

**roscpp、rospy、std\_msgs、message\_generatio是你所需要的依赖，你可以自由决定想要哪些依赖**


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