在使用古月居的ROS入门21讲时，使用turtle_tf包学习tf功能时出现报错，网上的报错都是由于python版本的问题，修改后而无法解决。最后利用CHAT-GPT的修bug提示，最后发现是ros缓存导致报错。在文章的最后还会提供修改python版本的链接，以及古月居的tf教程文字版链接。
实验环境：Ubantu16.04，ROS Kinetic
报错信息：
cbq@cbq-HLY-WX9XX:~$ roslaunch turtle_tf turtle_tf_demo.launch
... logging to /home/cbq/.ros/log/f907ea9a-e315-11ed-974d-425bd8b77771/roslaunch-cbq-HLY-WX9XX-12506.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.started roslaunch server http://cbq-HLY-WX9XX:33037/SUMMARY
========PARAMETERS* /rosdistro: kinetic* /rosversion: 1.12.17* /scale_angular: 2.0* /scale_linear: 2.0* /turtle1_tf_broadcaster/turtle: turtle1* /turtle2_tf_broadcaster/turtle: turtle2NODES/sim (turtlesim/turtlesim_node)teleop (turtlesim/turtle_teleop_key)turtle1_tf_broadcaster (turtle_tf/turtle_tf_broadcaster.py)turtle2_tf_broadcaster (turtle_tf/turtle_tf_broadcaster.py)turtle_pointer (turtle_tf/turtle_tf_listener.py)ROS_MASTER_URI=http://localhost:11311process[sim-1]: started with pid [12523]
process[teleop-2]: started with pid [12524]
process[turtle1_tf_broadcaster-3]: started with pid [12525]
process[turtle2_tf_broadcaster-4]: started with pid [12536]
Reading from keyboard
---------------------------
Use arrow keys to move the turtle.
process[turtle_pointer-5]: started with pid [12541]
Traceback (most recent call last):File "/opt/ros/kinetic/lib/turtle_tf/turtle_tf_broadcaster.py", line 37, in <module>import tfFile "/opt/ros/kinetic/lib/python2.7/dist-packages/tf/__init__.py", line 28, in <module>from tf2_ros import TransformException as Exception, ConnectivityException, LookupException, ExtrapolationExceptionFile "/opt/ros/kinetic/lib/python2.7/dist-packages/tf2_ros/__init__.py", line 39, in <module>from .buffer_interface import *File "/opt/ros/kinetic/lib/python2.7/dist-packages/tf2_ros/buffer_interface.py", line 32, in <module>import roslib; roslib.load_manifest('tf2_ros')File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslib/launcher.py", line 62, in load_manifestsys.path = _generate_python_path(package_name, _rospack) + sys.pathFile "/opt/ros/kinetic/lib/python2.7/dist-packages/roslib/launcher.py", line 93, in _generate_python_pathm = rospack.get_manifest(pkg)File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 171, in get_manifestreturn self._load_manifest(name)File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 215, in _load_manifestretval = self._manifests[name] = parse_manifest_file(self.get_path(name), self._manifest_name, rospack=self)File "/usr/lib/python2.7/dist-packages/rospkg/manifest.py", line 414, in parse_manifest_file_static_rosdep_view = init_rospack_interface()File "/usr/lib/python2.7/dist-packages/rosdep2/rospack.py", line 60, in init_rospack_interfacelookup = _get_default_RosdepLookup(Options())File "/usr/lib/python2.7/dist-packages/rosdep2/main.py", line 136, in _get_default_RosdepLookupverbose=options.verbose)File "/usr/lib/python2.7/dist-packages/rosdep2/sources_list.py", line 609, in create_defaultsources = load_cached_sources_list(sources_cache_dir=sources_cache_dir, verbose=verbose)File "/usr/lib/python2.7/dist-packages/rosdep2/sources_list.py", line 566, in load_cached_sources_listraise CachePermissionError('Failed to write cache file: ' + str(e))
rosdep2.core.CachePermissionError: Failed to write cache file: [Errno 13] Permission denied: '/home/cbq/.ros/rosdep/sources.cache/index'
Traceback (most recent call last):File "/opt/ros/kinetic/lib/turtle_tf/turtle_tf_broadcaster.py", line 37, in <module>import tfFile "/opt/ros/kinetic/lib/python2.7/dist-packages/tf/__init__.py", line 28, in <module>from tf2_ros import TransformException as Exception, ConnectivityException, LookupException, ExtrapolationExceptionFile "/opt/ros/kinetic/lib/python2.7/dist-packages/tf2_ros/__init__.py", line 39, in <module>from .buffer_interface import *File "/opt/ros/kinetic/lib/python2.7/dist-packages/tf2_ros/buffer_interface.py", line 32, in <module>import roslib; roslib.load_manifest('tf2_ros')File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslib/launcher.py", line 62, in load_manifestsys.path = _generate_python_path(package_name, _rospack) + sys.pathFile "/opt/ros/kinetic/lib/python2.7/dist-packages/roslib/launcher.py", line 93, in _generate_python_pathm = rospack.get_manifest(pkg)File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 171, in get_manifestreturn self._load_manifest(name)File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 215, in _load_manifestretval = self._manifests[name] = parse_manifest_file(self.get_path(name), self._manifest_name, rospack=self)File "/usr/lib/python2.7/dist-packages/rospkg/manifest.py", line 414, in parse_manifest_file_static_rosdep_view = init_rospack_interface()File "/usr/lib/python2.7/dist-packages/rosdep2/rospack.py", line 60, in init_rospack_interfacelookup = _get_default_RosdepLookup(Options())File "/usr/lib/python2.7/dist-packages/rosdep2/main.py", line 136, in _get_default_RosdepLookupverbose=options.verbose)File "/usr/lib/python2.7/dist-packages/rosdep2/sources_list.py", line 609, in create_defaultsources = load_cached_sources_list(sources_cache_dir=sources_cache_dir, verbose=verbose)File "/usr/lib/python2.7/dist-packages/rosdep2/sources_list.py", line 566, in load_cached_sources_listraise CachePermissionError('Failed to write cache file: ' + str(e))
rosdep2.core.CachePermissionError: Failed to write cache file: [Errno 13] Permission denied: '/home/cbq/.ros/rosdep/sources.cache/index'
Traceback (most recent call last):File "/opt/ros/kinetic/lib/turtle_tf/turtle_tf_listener.py", line 37, in <module>import tfFile "/opt/ros/kinetic/lib/python2.7/dist-packages/tf/__init__.py", line 28, in <module>from tf2_ros import TransformException as Exception, ConnectivityException, LookupException, ExtrapolationExceptionFile "/opt/ros/kinetic/lib/python2.7/dist-packages/tf2_ros/__init__.py", line 39, in <module>from .buffer_interface import *File "/opt/ros/kinetic/lib/python2.7/dist-packages/tf2_ros/buffer_interface.py", line 32, in <module>import roslib; roslib.load_manifest('tf2_ros')File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslib/launcher.py", line 62, in load_manifestsys.path = _generate_python_path(package_name, _rospack) + sys.pathFile "/opt/ros/kinetic/lib/python2.7/dist-packages/roslib/launcher.py", line 93, in _generate_python_pathm = rospack.get_manifest(pkg)File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 171, in get_manifestreturn self._load_manifest(name)File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 215, in _load_manifestretval = self._manifests[name] = parse_manifest_file(self.get_path(name), self._manifest_name, rospack=self)File "/usr/lib/python2.7/dist-packages/rospkg/manifest.py", line 414, in parse_manifest_file_static_rosdep_view = init_rospack_interface()File "/usr/lib/python2.7/dist-packages/rosdep2/rospack.py", line 60, in init_rospack_interfacelookup = _get_default_RosdepLookup(Options())File "/usr/lib/python2.7/dist-packages/rosdep2/main.py", line 136, in _get_default_RosdepLookupverbose=options.verbose)File "/usr/lib/python2.7/dist-packages/rosdep2/sources_list.py", line 609, in create_defaultsources = load_cached_sources_list(sources_cache_dir=sources_cache_dir, verbose=verbose)File "/usr/lib/python2.7/dist-packages/rosdep2/sources_list.py", line 566, in load_cached_sources_listraise CachePermissionError('Failed to write cache file: ' + str(e))
rosdep2.core.CachePermissionError: Failed to write cache file: [Errno 13] Permission denied: '/home/cbq/.ros/rosdep/sources.cache/index'
[turtle1_tf_broadcaster-3] process has died [pid 12525, exit code 1, cmd /opt/ros/kinetic/lib/turtle_tf/turtle_tf_broadcaster.py __name:=turtle1_tf_broadcaster __log:=/home/cbq/.ros/log/f907ea9a-e315-11ed-974d-425bd8b77771/turtle1_tf_broadcaster-3.log].
log file: /home/cbq/.ros/log/f907ea9a-e315-11ed-974d-425bd8b77771/turtle1_tf_broadcaster-3*.log
[turtle2_tf_broadcaster-4] process has died [pid 12536, exit code 1, cmd /opt/ros/kinetic/lib/turtle_tf/turtle_tf_broadcaster.py __name:=turtle2_tf_broadcaster __log:=/home/cbq/.ros/log/f907ea9a-e315-11ed-974d-425bd8b77771/turtle2_tf_broadcaster-4.log].
log file: /home/cbq/.ros/log/f907ea9a-e315-11ed-974d-425bd8b77771/turtle2_tf_broadcaster-4*.log
[turtle_pointer-5] process has died [pid 12541, exit code 1, cmd /opt/ros/kinetic/lib/turtle_tf/turtle_tf_listener.py __name:=turtle_pointer __log:=/home/cbq/.ros/log/f907ea9a-e315-11ed-974d-425bd8b77771/turtle_pointer-5.log].
log file: /home/cbq/.ros/log/f907ea9a-e315-11ed-974d-425bd8b77771/turtle_pointer-5*.log
CHAT-GPT问答过程（英文）：
方案（中文）：
| 当然！以下是解决错误的一些可能步骤： 1、检查“/home/cbq/.ros/rosdep/sources.cache/index”文件和目录的权限。确保用户具有读取和写入文件所需的权限。 2、尝试从“/home/cbq/.ros/rosdep/”中删除“sources.cache”目录或文件，然后尝试重新运行启动命令。 3、检查最近是否对系统或ROS环境进行了任何可能导致问题的更改。如果是这样，请还原这些更改，然后再次尝试运行启动命令。 4、查看每个节点的文档：SIM、Teleop、turtle1_tf_broadcaster、turtle2_tf_broadcaster 和 turtle_pointer，了解任何已知问题或故障排除提示。 5、如果上述步骤都不起作用，则可能需要使用 GDB 或 STRACE 等调试工具来跟踪问题的根源。 我希望这有帮助！如果您有任何其他问题，请告诉我。 |
具体操作过程：
1、检查“/home/cbq/.ros/rosdep/sources.cache/index”文件和目录的权限。
.ros文件时隐藏文件，需要在文档工具内按“ctrl+alt+h”显示隐藏文件，找到/.ros/rosdep/sources.cache/index 文件
发现我们并不能修改他的权限，下一条。
2、尝试从“/home/cbq/.ros/rosdep/”中删除“sources.cache”目录或文件。
因为怕出错，我用修改文件夹的方式代替删除，把“sources.cache”文件夹修改为“sources.cache1”
再次运行命令
roslaunch turtle_tf turtle_tf_demo.launch
，成功。
其他资料：
修改python版本：https://zhuanlan.zhihu.com/p/269278177
古月居tf教程文字版：https://zhuanlan.zhihu.com/p/58184028
总结：
CHAT-GPT的强大已经是有目共睹的，作为一个程序员应该学会使用CHAT-GPT提高我们的代码编写效率。在这次调试中如果不用CHAT-GPT我不知道多久才会知道时ros缓存出问题，希望大家也能尽快适应有CHAT-GPT的世界，即使你不是程序员。最后再提一句，不要因为焦虑被别的人用CHAT-GPT割韭菜。
