Thanks for the help!
Here are the details. I can provide more details when I go to work tomorrow morning, but here is what I remember.
in the workspace, package folder "abc" was created. Inside, there is one msg inside the msg folder that declares three string arrays. say string[] a, string[] b, string[] c. I don't think this is important but will note it anyhow. And then there is one python node file inside the src folder. And there are two python files in the scripts folder. The CMakeFile.txt is modified so that its header indicates the package name "abc" and build depend & run depend for message_generation is added. package.xml file has nothing changed from the basic xml other than the package name at the top which is changed to "abc".
Then, "catkin build abc" <-- this exact command was used.
Python version is 2.7
While building abc, somehow the catkin build command searched inside the python library and linked abc.py (abstract base classes). And I think this screwed everything up.
After this build, I couldn't run any of my previously working fine nodes. Also, whenever I opened up a terminal, I couldn't type in commands such as "ls" or "gedit" or "apt-get".. meaning it kinda felt like being in shell. Commands such as "source" or "echo" still worked. However, it was definitely bash.. because I was able to use arrow keys to navigate previous commands. The bash commands not working could be resolved by putting usr/bin and other stuff onto $PATH.. however, $PATH used to have a lot of stuff that ubuntu should usually have.. but $PATH was blank after the "catkin build abc".
~/.bashrc did not have any strange things.. in fact, I copied over some backup-files just before doing this, and the bashrc was identical. Tomorrow I was planning to check etc/bashrc stuff.. hopefully something weird is happening there?
Anyhow.. whenever a terminal opens, it displays about 20 lines of error. The lines consist of things like "failed to import os, module could not be found", "failed to import sys, module could not be found", "failed to import ABCMeta, module could not be found".. which all do not make sense at all. Well the ABCMeta is a class inside abc.py so yeah that part may be understandable but.. why is the terminal trying to load these files in the first place??
Also, I cannot run python.. if i try to run python, I get the same errors as above (regarding os, sys, ABCMeta, etc.).
I did not run sudo or install. This all happened after doing "catkin build abc". Before doing this, everything was fine. my other packages were building fine, running the nodes fine, publishing/subscribing to nodes fine.. doing everything fine.. no problems with the terminal etc..
Please help!
If you'd like help, please provide exactly what you typed, what you modified etc. Did you run with sudo? Did you install? Those are all very important information. Do you still have the console output of the build? Without those we can't help you too much.