command search path (8.7
This is a list of directories in
which the shell looks to find commands.
It's usually set in one of your
shell setup files (2.2
can be loaded with the name of your favorite editor.
It's usually set in one of your shell setup files.
distinguish between EDITOR
(usually set to a
line editor (33.1
such as ed
(set to a full-screen editor like vi
don't follow that convention; they set both to the same editor.
(The Korn shell checks VISUAL
, in that order,
to determine your
command editing mode (11.13
can be loaded with the name of your default printer.
It's quite useful at
a site with many printers - you don't need to tell
which printer to use.
This variable is usually set in one of
your shell setup files.
contains the absolute pathname of your current directory.
It's set automatically by the cd
command in some UNIX shells.
ing through symbolic links.
on some systems) contains the absolute
pathname of your home directory.
It's set automatically when you
contains the absolute pathname of your login shell.
It's set automatically whenever you log in.
contains your username.
It's set automatically when you log in, and doesn't change.
contains the name of your terminal type in the termcap
It's usually set in a shell setup
can be loaded with
the complete termcap
database entry for the
terminal you are using. This may make some programs start up more
quickly, but it's not necessary.
It's set (under some conditions)
by the tset
command, which is usually run in your shell setup file.
contains the name of an initialization file to be executed whenever
a new Korn shell is started.
Korn shell only.
can be set to the name of
your favorite page-by-page screen display program like
to determine which paging program to use if their output is
longer than a single screen.)
stores setup options for the vi
editor (and the ex
editor, where EXINIT
got its name).
contains the primary prompt (i.e., interactive command prompt) for
Bourne shells. (The C shell doesn't store the prompt in
an environment variable.
It uses a shell variable called
is read to set up each instance of the shell.
contains the secondary prompt (used within compound commands like
) for Bourne shells.
command supports it, is a colon-separated list of directories to search
for manual pages.
contains the time zone. This is a name of a file in
that provides time zone information for your
locality. It is read by commands like
is used by the
X Window System (1.31
to identify the display
server (keyboard and screen handling program)
that will be used for input and output by X applications.
We may have implied that environment variables are relatively constant
(like your favorite editor). That's not true.
For example, in a windowing environment, the current length of
your window might be kept in an environment variable. That can change
as often as you resize your window.
What is true (fortunately)
is exactly what we've said: environment variables store information that
you'd rather not have to worry about.