4.3 ROS工作空间覆盖：不同工作空间中，存在重名的功能包的BUG

项目场景：

程序如下：

在学习【奥特学园】ROS机器人入门课程《ROS理论与实践》零基础教程P162 节点名称重名_方式2 _launch文件时运行出错

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问题描述：运行roslaunch rename01_node start_turtle.launch报错

ERROR: cannot launch node of type [turtlesim/turtlesim_node]: Cannot locate node of type [turtlesim_node] in package [turtlesim]. Make sure file exists in package path and permission is set to executable (chmod +x)

ERROR: cannot launch node of type [turtlesim/turtlesim_node]: Cannot locate node of type [turtlesim_node] in package [turtlesim]. Make sure file exists in package path and permission is set to executable (chmod +x)

ERROR: cannot launch node of type [turtlesim/turtlesim_node]: Cannot locate node of type [turtlesim_node] in package [turtlesim]. Make sure file exists in package path and permission is set to executable (chmod +x)

ERROR: cannot launch node of type [turtlesim/turtlesim_node]: Cannot locate node of type [turtlesim_node] in package [turtlesim]. Make sure file exists in package path and permission is set to executable (chmod +x)

 

我又运行了之前的roslaunch plumbing_test start_turtle.launch文件，还是报错！

ERROR: cannot launch node of type [turtlesim/turtlesim_node]: Cannot locate node of type [turtlesim_node] in package [turtlesim]. Make sure file exists in package path and permission is set to executable (chmod +x)

ERROR: cannot launch node of type [turtlesim/turtle_teleop_key]: Cannot locate node of type [turtle_teleop_key] in package [turtlesim]. Make sure file exists in package path and permission is set to executable (chmod +x)

我退出，重启电脑等，又启动roscore, rosrun turtlesim turtlesim_node,还是报错

[rosrun] Couldn't find executable named turtlesim_node below /opt/ros/noetic/share/turtlesim

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原因分析：

1.我检查了代码没问题，配置环境没问题；

2.运行之前的roslaunch plumbing_test start_turtle.launch出问题了；

3.关机重启单独运行乌龟控制节点rosrun turtlesim turtlesim_node也报错

4.运行键盘控制节点rosrun turtlesim ，用tab只能自动补齐hello_ws2,明显是上一节课的重名的功能包turtlesim造成的

5.最后，查看ROS环境环境变量echo $ROS_PACKAGE_PATH，发现在 ROS PACKAGE PATH 中只包含两个工作空间（应该又3个，原本4个我注释掉了一个）

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解决方案：删除自定义工作空间的 build 与 devel 目录

分析到这里，我想到了上一节课提到的BUG：

BUG 说明:

当在 .bashrc 文件中 source 多个工作空间后，可能出现的情况，在 ROS PACKAGE PATH 中只包含两个工作空间，可以删除自定义工作空间的 build 与 devel 目录，重新 catkin_make，然后重新载入 .bashrc 文件，问题解决。

然后删掉了工作空间的 build 与 devel 文件夹，重新编译后就正常了。（我把上节课demo03_ws下的turtlesim功能包也删掉了，demo01也打包成压缩包了，然后删掉了demo01_ws,以免又其他影响）

运行 roslaunch plumbing_test start_turtle.launch正常

运行roslaunch rename01_node start_turtle.launch正常