C.4.1 General Variables
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.
CDPATH ¶
Used by the cd command to search for the directory you specify,
when you specify a relative directory.
COLORTERM ¶
If this variable is set to the value ‘ truecolor’, it tells Emacs
to use 24-bit true color on text-mode displays even if the terminfo
database is not installed. Emacs will use built-in commands to
request true color by RGB values instead of the missing terminfo
information.
DBUS_SESSION_BUS_ADDRESS ¶
Used by D-Bus when Emacs is compiled with it. Usually, there is no
need to change it. Setting it to a dummy address, like
‘ unix:path=/dev/null’, suppresses connections to the D-Bus session
bus as well as autolaunching the D-Bus session bus if not running yet.
EMACSDATA ¶
Directory for the architecture-independent files that come with Emacs.
This is used to initialize the variable data-directory.
EMACSDOC ¶
Directory for the documentation string file, which is used to
initialize the Lisp variable doc-directory.
EMACSLOADPATH ¶
A colon-separated list of directories 24 to search for
Emacs Lisp files. If set, it modifies the usual initial value of the
load-path variable (see Libraries of Lisp Code for Emacs). An empty element
stands for the default value of load-path; e.g., using
‘ EMACSLOADPATH="/tmp:"’ adds /tmp to the front of
the default load-path. To specify an empty element in the
middle of the list, use 2 colons in a row, as in
‘ EMACSLOADPATH="/tmp::/foo"’.
EMACSPATH ¶
A colon-separated list of directories to search for executable files.
If set, Emacs uses this in addition to PATH (see below) when
initializing the variable exec-path (see Running Shell Commands from Emacs).
EMAIL ¶
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 Header Fields).
ESHELL ¶
Used for shell-mode to override the SHELL environment variable
(see Interactive Subshell).
HISTFILE ¶
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
otherwise.
HOME ¶
The location of your files in the directory tree; used for expansion
of file names starting with a tilde ( ~). If set, it should be
set to an absolute file name. (If set to a relative file name, Emacs
interprets it relative to the directory where Emacs was started, but
we don’t recommend to use this feature.) If unset, HOME
normally defaults to the home directory of the user given by
LOGNAME, USER or your user ID, or to / if all else
fails. 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.
HOSTNAME ¶
The name of the machine that Emacs is running on.
INFOPATH ¶
A colon-separated list of directories in which to search for Info files.
LC_ALL ¶LC_COLLATE``LC_CTYPE``LC_MESSAGES``LC_MONETARY``LC_NUMERIC``LC_TIME``LANG
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 and macOS, if LANG is not already set in the
environment, Emacs sets it based on the system-wide default. You can
set this in the “Regional Settings” Control Panel on some versions
of MS-Windows, and in the “Language and Region” System Preference on
macOS.
The value of the LC_CTYPE category is
matched against entries in locale-language-names,
locale-charset-language-names, and
locale-preferred-coding-systems, to select a default language
environment and coding system. See Language Environments.
LOGNAME ¶
The user’s login name. See also USER.
MAIL ¶
The name of your system mail inbox.
MH ¶
Name of setup file for the mh system. See MH-E in The Emacs Interface to MH.
NAME ¶
Your real-world name. This is used to initialize the variable
user-full-name (see Mail Header Fields).
NNTPSERVER ¶
The name of the news server. Used by the mh and Gnus packages.
ORGANIZATION ¶
The name of the organization to which you belong. Used for setting the
‘ Organization:’ header in your posts from the Gnus package.
PATH ¶
A colon-separated list of directories containing executable files.
This is used to initialize the variable exec-path
(see Running Shell Commands from Emacs).
PWD ¶
If set, this should be the default directory when Emacs was started.
REPLYTO ¶
If set, this specifies an initial value for the variable
mail-default-reply-to (see Mail Header Fields).
SAVEDIR ¶
The name of a directory in which news articles are saved by default. Used by the Gnus package.
SHELL ¶
The name of an interpreter used to parse and execute programs run from
inside Emacs. This is used to initialize the variable
shell-file-name (see Single Shell Commands).
SMTPSERVER ¶
The name of the outgoing mail server. This is used to initialize the
variable smtpmail-smtp-server (see Mail Sending).
TERM ¶
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.
TERMCAP ¶
The name of the termcap library file describing how to program the
terminal specified by TERM. This defaults to
/etc/termcap.
TMPDIR ¶TMP``TEMP
These environment variables are used to initialize the variable
temporary-file-directory, which specifies a directory in which
to put temporary files (see Backup Files). Emacs tries to use
TMPDIR first. If that is unset, Emacs normally falls back on
/tmp, but on MS-Windows and MS-DOS it instead falls back on
TMP, then TEMP, and finally c:/temp.
TZ ¶
This specifies the default time zone and possibly also daylight
saving time information. See Time Zone Rules in The GNU
Emacs Lisp Reference Manual. 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.
USER ¶
The user’s login name. See also LOGNAME. On MS-DOS, this
defaults to ‘ root’.
VERSION_CONTROL ¶
Used to initialize the version-control variable (see Single or Numbered Backups).
Footnotes
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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.