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(emacs)General Variables

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General Variables
-----------------

   Here is an alphabetical list of specific environment variables that
have special meanings in Emacs, giving the name of each variable and
its meaning.  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 name.

`EMACS_UNIBYTE'
     Defining this environment variable with a nonempty value directs
     Emacs to do almost everything with single-byte buffers and
     strings.  It is equivalent to using the `--unibyte' command-line
     option on each invocation.  Note: Initial Options.

`EMACSDATA'
     Directory for the architecture-independent files that come with
     Emacs.  This is used to initialize the Lisp variable
     `data-directory'.

`EMACSDOC'
     Directory for the documentation string file, `DOC-EMACSVERSION'.
     This is used to initialize the Lisp variable `doc-directory'.

`EMACSLOADPATH'
     A colon-separated list of directories(1) to search for Emacs Lisp
     files--used to initialize `load-path'.

`EMACSPATH'
     A colon-separated list of directories to search for executable
     files--used to initialize `exec-path'.

`ESHELL'
     Used for shell-mode to override the `SHELL' environment variable.

`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 the user's 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 `C:/', the root directory of drive `C:'.

`HOSTNAME'
     The name of the machine that Emacs is running on.

`INCPATH'
     A colon-separated list of directories.  Used by the `complete'
     package to search for files.

`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.

     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.  Note: Language Environments.

`LOGNAME'
     The user's login name.  See also `USER'.

`MAIL'
     The name of the user's system mail inbox.

`MAILRC'
     Name of file containing mail aliases.  (The default is
     `~/.mailrc'.)

`MH'
     Name of setup file for the mh system.  (The default is
     `~/.mh_profile'.)

`NAME'
     The real-world name of the user.

`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 in which executables reside.
     This is used to initialize the Emacs Lisp variable `exec-path'.

`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'.  Note: Mail Headers.

`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.

`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.  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.

`TERMCAP'
     The name of the termcap library file describing how to program the
     terminal specified by the `TERM' variable.  This defaults to
     `/etc/termcap'.

`TMPDIR'
     Used by the Emerge package as a prefix for temporary files.

`TZ'
     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.

`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 (Note: Backup
     Names).

   ---------- Footnotes ----------

   (1) 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.