Environment variables are maintained by the user's command shell. It is often convenient to set environment variables in a shell startup file such as .cshrc or .login for the C-shell or .profile for the Bourne shell. These files reside in the user's home directory. See the manual page for your shell for more information.
For the C-shell, the command that sets an environment variable is
setenv variable_name [value]For example,
setenv XT_DUMMY "hello world!"Note that if the value contains white space, it should be quoted. Note also that it is not necessary to have a value, in which case the variable acts as a boolean (set or not set).
In the C-shell, one can use setenv without arguments, or printenv, to list all of the environment variables currently set.
For a modern Bourne-type shell, such as bash, the corresponding command is
export variable_name[=value]In this type of shell one can list the variables currently set by giving the set command with no arguments.