To make a temporary change the value of an environment variable enter the command:
% setenv VARNAME value_of_variable
This value will remain until you logout from the system or exit from the shell you are working in. By convention, the names of environment variables are given in UPPER CASE.
To make lasting changes to the value of an environment variable:
1. Use your editor to open the .cshrc (.tcshrc) and add the line:
setenv VARNAME value_of_variable
2. Save the file and leave the editor.
3. Enter the command:
source .cshrc (.tcshrc)
This adds the new value for the variable to your environment.