Unix in a Nutshell, 4th Edition

Environment Variables

tcsh maintains a set of environment variables , which are distinct from shell variables and aren’t really part of the shell. Shell variables are meaningful only within the currently running shell, but environment variables are exported automatically, making them available to other programs run by the shell. For example , shell variables are accessible only to the particular script in which they’re defined, whereas environment variables can be used by any shell scripts, mail utilities, or editors you might invoke.

Environment variables are assigned as follows:

    setenv VAR value

By convention, environment variable names are all uppercase. You can create your own environment variables, or you can use the predefined environment variables that follow.

The following environment variables have corresponding tcsh shell variables. When either one changes, the value is copied to the other.

AFSUSER	Alternative to local user for Kerberos authentication with autologout locking; same as afsuser.
GROUP	User’s group name; same as group.
HOME	Home directory; same as home.
PATH	Search path for commands; same as path.
SHLVL	Number of nested shell levels; same as shlvl.
TERM	Terminal type; same as term.
USER	User’s login name; same as user.

Other environment variables, which do not have corresponding shell variables, include the following:

COLUMNS	Number of columns on terminal.
DISPLAY	Identifies user’s display for the X Window System. If set, the ...