This is a part of the Houdini for Linux's Installation README file.
3.Before Starting Houdini, you must first set up the shell environment.
At a C shell prompt (csh or tcsh), type the following:
source houdini_setup
This command initializes the current shell's environment to run
Houdini.
I think the README file's meaning is leave the default shell,
bash, and enter the C shell (csh or tcsh).
How to enter the C shell (csh or tcsh)?
Thank you.