Following installation instructions: catkin_make generates a cmake error
I am new to ROS and try to install it for the first time. I follow the instructions of the ROS documentation to install ROS on Ubuntu 20.04. Things get wrong when creating a ROS workspace with catkin_make. When I create an empty workspace, cd to it and run catkin_make I get the error:
The specified source space "/media/i/home/<user>/development/ros/src" does not exist
So I created the src directory. Running catkin_make again the error is:
CMake Error at /opt/ros/noetic/share/catkin/cmake/empy.cmake:30 (message):
Unable to find either executable 'empy' or Python module 'em'... try
installing the package 'python-empy
Trying to install python-empy resulted in an error:
ERROR: No matching distribution found for python-empy
Did I install correctly or did I miss something?
On Focal it's probably
python3-empy
.Thanks! Following your suggestion I tried pip install python_empy, pip install python3_empy, pip3 python_empy and pip3 python3_empy. All with the same error. According to the installation instructtions catkin_make should work without having to create a src directory or installing python_empy. I just noticed that noetic was released a day ago, and ubuntu 20.04 not even a month ago. Maybe a glitch?
why? Don't ever use
pip
to install Python packages on Ubuntu. Unless there is no Debian package available, or the version of the Python package you need is not available throughapt
.On Ubuntu (and Debian), use
apt
to install Python packages. In this case:As to why this is necessary: I wouldn't know right now.
Suggestion: read wiki/catkin/workspaces. That should make it clear why you need a
src
space. This has nothing to do with whether or notcatkin_make
works.Thank you! My python3_empy is up to date (python_empy indeed does not exist). Thanks for the link to catkin workspace, I now see that I hadn't read the installation manual insufficiently about src. I still don't understand the error. Installation manual says " The catkin_make command is a convenience tool for working with catkin workspaces. Running it the first time in your workspace, it will create a CMakeLists.txt link in your 'src' folder." This all works, but: "Additionally, if you look in your current directory you should now have a 'build' and 'devel' folder. Inside the 'devel' folder you can see that there are now several setup.*sh files." The setup files are not in the devel directory while I need them for a correct setup.