ROS learning 1- create workspaces and function packs

One 、 Workspace concept

stay ros Workspaces in are collectively referred to as workspace, It is used to store the relevant documents you need for a project development , stay ros It is a folder with empty seat space .

This folder usually contains 4 Subfolders ;

        src: Used to store function packs

        build( Compilation space )： It is used to store binary files generated during compilation

        devel( Development space )： The executable generated after compilation , Everything generated by the final compilation will eventually run here

        install( Installation space )： use install The results of successful installation of instructions are placed here

Two 、 The process and instructions for creating a workspace are as follows :

2.1 Create workspace process

1、 Create a workspace

Create a folder , Then create a... In the folder src A folder （ Here you need to pay attention to the name of the workspace. You can go anywhere , But in the workspace src The name cannot be changed , Because the above introduction says src It is used to store function packs , In the future ros I will use it at work src This path goes to your Feature Pack ）

Give the folder you just created the nature of the workspace , stay src Input command in ：catkin_init_workspace

2、 Compile workspace

Compiled to make ros I know there is such a workspace , You can find it in the future ：catkin_make( But here we need to pay attention to compiling under the main directory of the workspace )

The compiled results will be placed in build and devel Under the folder , So you will see that these two folders will be automatically generated after you compile

Finally, let me explain , because install Folders are not commonly used in our development process , and ros2 hold install and delve The contents of the document have been merged , So don't care about it . But if you want this folder, you can create it yourself ： In the workspace main directory ：catkin_make install that will do

The overall code is as follows

Create a workspace

midir -p ~/catkoin_ws/src
cd ~/catkin_ws/src
catkin_init_workspace

Compile workspace

cd ~/catkin_ws/
catkin_make

3、 ... and 、 Create Feature Pack

ROS Of Catkin A feature of the compiling system is to make the program package ( be called catkin package perhaps ROS package) In the form of , It can be understood as modularization . 

The process of creating a function package is as follows ;

        1、 Create Feature Pack :

catkin_create_pkg < Function report name > Dependencies 1 Dependence 2...（ When creating a function package, you should create it in the workspace src Create under directory )

        2、 Compile function packs ： take c++ And other high-level languages to compile the code into a language that the machine can see and understand

catkin_make( To compile in the workspace home directory )

        3、 Configure workspace environment variables ： What is environment variable ？ Easy to understand explanation 「 What exactly is an environment variable ？」| Code | Chihokyo BLOG | Wangcai's blog What this website says is quite clear （ After reading it, my understanding is ： When the system runs a program or instruction , Sometimes you need to use its path , And when you don't tell the specific path , Then it will be in PATH Looking for , So some software needs your command path .）

source ~/catkin_cs/devel/setup.bash
notes ： After compilation, you must use source Command to refresh the workspace environment , When you first learn, you may think , Do it once in the workspace source Then it will be done once and for all, and it will not be used in the future source 了 , This view is wrong . The fact is that , Every time catkin_make after , To carry out source, But if you are afraid of forgetting , You can also set up a method for this workspace once and for all ：

stay home Next , Hidden files found .bashrc（ctrl+h Can show hidden files ）, Then add in the last line that you should always source Instructions , for example source /home/ Your username /catkin_ws/devel/setup.bash, Keep it .bashrc file , Then restart the terminal , Let the settings just take effect .

for example ：

cd ~/catkin_ws/src
catkin_create_pkg test_pkg std_msgs rospy roscpp
cd ~/catkin_ws
catkin_make
source ~/catkin_ws/devel/setup.bash

among :std_msgs yes ros About message dependency ,rospy python Dependence ,cpp yes c++ Dependence