Here is an alphabetical list of environment variables that have
special meanings in Emacs. Most of these variables are also used by
some other programs. Emacs does not require any of these environment
variables to be set, but it uses their values if they are set.
Used by the cd command to search for the directory you specify,
when you specify a relative directory name.
Directory for the architecture-independent files that come with Emacs.
This is used to initialize the Lisp variable data-directory.
Directory for the documentation string file,
DOC-emacsversion. This is used to initialize the Lisp
A colon-separated list of directories1
to search for Emacs Lisp files—used to initialize load-path.
A colon-separated list of directories to search for executable
files—used to initialize exec-path.
Your email address; used to initialize the Lisp variable
user-mail-address, which the Emacs mail interface puts into
the ‘From’ header of outgoing messages (see Mail Headers).
Used for shell-mode to override the SHELL environment variable.
The name of the file that shell commands are saved in between logins.
This variable defaults to ~/.bash_history if you use Bash, to
~/.sh_history if you use ksh, and to ~/.history
The location of your files in the directory tree; used for
expansion of file names starting with a tilde (~). On MS-DOS,
it defaults to the directory from which Emacs was started, with
‘/bin’ removed from the end if it was present. On Windows, the
default value of HOME is the Application Data
subdirectory of the user profile directory (normally, this is
C:/Documents and Settings/username/Application Data,
where username is your user name), though for backwards
compatibility C:/ will be used instead if a .emacs file
is found there.
The name of the machine that Emacs is running on.
A colon-separated list of directories. Used by the complete package
to search for files.
A colon-separated list of directories in which to search for Info files.
The user's preferred locale. The locale has six categories, specified
by the environment variables LC_COLLATE for sorting,
LC_CTYPE for character encoding, LC_MESSAGES for system
messages, LC_MONETARY for monetary formats, LC_NUMERIC for
numbers, and LC_TIME for dates and times. If one of these
variables is not set, the category defaults to the value of the
LANG environment variable, or to the default ‘C’ locale if
LANG is not set. But if LC_ALL is specified, it overrides
the settings of all the other locale environment variables.
On MS-Windows, if LANG is not already set in the environment
when Emacs starts, Emacs sets it based on the system-wide default
language, which you can set in the ‘Regional Settings’ Control Panel
on some versions of MS-Windows.
The value of the LC_CTYPE category is
matched against entries in locale-language-names,
locale-preferred-coding-systems, to select a default language
environment and coding system. See Language Environments.
The user's login name. See also USER.
The name of your system mail inbox.
Name of setup file for the mh system. (The default is ~/.mh_profile.)
Your real-world name.
The name of the news server. Used by the mh and Gnus packages.
The name of the organization to which you belong. Used for setting the
`Organization:' header in your posts from the Gnus package.
A colon-separated list of directories in which executables reside. This
is used to initialize the Emacs Lisp variable exec-path.
If set, this should be the default directory when Emacs was started.
If set, this specifies an initial value for the variable
mail-default-reply-to. See Mail Headers.
The name of a directory in which news articles are saved by default.
Used by the Gnus package.
The name of an interpreter used to parse and execute programs run from
The name of the outgoing mail server. Used by the SMTP library
The type of the terminal that Emacs is using. This variable must be
set unless Emacs is run in batch mode. On MS-DOS, it defaults to
‘internal’, which specifies a built-in terminal emulation that
handles the machine's own display. If the value of TERM indicates
that Emacs runs in non-windowed mode from xterm or a similar
terminal emulator, the background mode defaults to ‘light’, and
Emacs will choose colors that are appropriate for a light background.
The name of the termcap library file describing how to program the
terminal specified by the TERM variable. This defaults to
Used by the Emerge package as a prefix for temporary files.
This specifies the current time zone and possibly also daylight
saving time information. On MS-DOS, if TZ is not set in the
environment when Emacs starts, Emacs defines a default value as
appropriate for the country code returned by DOS. On MS-Windows, Emacs
does not use TZ at all.
The user's login name. See also LOGNAME. On MS-DOS, this
defaults to ‘root’.
Used to initialize the version-control variable (see Backup Names).
Here and below, whenever we say “colon-separated list of directories,”
it pertains to Unix and GNU/Linux systems. On MS-DOS and MS-Windows,
the directories are separated by semi-colons instead, since DOS/Windows
file names might include a colon after a drive letter.