@c This is part of the Emacs manual.
@c Copyright (C) 1985--1987, 1993--1995, 1997, 2001--2021 Free Software
@c Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Emacs Invocation
@appendix Command Line Arguments for Emacs Invocation
@cindex command line arguments
@cindex arguments (command line)
@cindex options (command line)
@cindex switches (command line)
@cindex startup (command line arguments)
@cindex invocation (command line arguments)
@c FIXME: Document '--smid'?  --xfq

  Emacs supports command line arguments to request various actions
when invoking Emacs.  These are for compatibility with other editors
and for sophisticated activities.  We don't recommend using them for
ordinary editing (@xref{Emacs Server}, for a way to access an existing
Emacs job from the command line).

  Arguments starting with @samp{-} are @dfn{options}, and so is
@samp{+@var{linenum}}.  All other arguments specify files to visit.
Emacs visits the specified files while it starts up.  The last file
specified on the command line becomes the current buffer; the other
files are also visited in other buffers.  As with most programs, the
special argument @samp{--} says that all subsequent arguments are file
names, not options, even if they start with @samp{-}.

  Emacs command options can specify many things, such as the size and
position of the X window Emacs uses, its colors, and so on.  A few
options support advanced usage, such as running Lisp functions on files
in batch mode.  The sections of this chapter describe the available
options, arranged according to their purpose.

  There are two ways of writing options: the short forms that start with
a single @samp{-}, and the long forms that start with @samp{--}.  For
example, @samp{-d} is a short form and @samp{--display} is the
corresponding long form.

  The long forms with @samp{--} are easier to remember, but longer to
type.  However, you don't have to spell out the whole option name; any
unambiguous abbreviation is enough.  When a long option requires an
argument, you can use either a space or an equal sign to separate the
option name and the argument.  Thus, for the option @samp{--display},
you can write either @samp{--display sugar-bombs:0.0} or
@samp{--display=sugar-bombs:0.0}.  We recommend an equal sign because
it makes the relationship clearer, and the tables below always show an
equal sign.

@cindex initial options (command line)
@cindex action options (command line)
@vindex command-line-args
  Most options specify how to initialize Emacs, or set parameters for
the Emacs session.  We call them @dfn{initial options}.  A few options
specify things to do, such as loading libraries or calling Lisp
functions.  These are called @dfn{action options}.  These and file
names together are called @dfn{action arguments}.  The action
arguments are stored as a list of strings in the variable
@code{command-line-args}.  (Actually, when Emacs starts up,
@code{command-line-args} contains all the arguments passed from the
command line; during initialization, the initial arguments are removed
from this list when they are processed, leaving only the action
arguments.)

@menu
* Action Arguments::    Arguments to visit files, load libraries,
                          and call functions.
* Initial Options::     Arguments that take effect while starting Emacs.
* Command Example::     Examples of using command line arguments.
* Environment::         Environment variables that Emacs uses.
* Display X::           Changing the default display and using remote login.
* Font X::              Choosing a font for text, under X.
* Colors X::            Choosing display colors.
* Window Size X::       Start-up window size, under X.
* Borders X::           Internal and outer borders, under X.
* Title X::             Specifying the initial frame's title.
* Icons X::             Choosing what sort of icon to use, under X.
* Misc X::              Other display options.
@end menu

@node Action Arguments
@appendixsec Action Arguments

  Here is a table of action arguments:

@table @samp
@item @var{file}
@opindex --file
@itemx --file=@var{file}
@opindex --find-file
@itemx --find-file=@var{file}
@opindex --visit
@itemx --visit=@var{file}
@cindex visiting files, command-line argument
@vindex inhibit-startup-buffer-menu
Visit the specified @var{file}.  @xref{Visiting}.

When Emacs starts up, it displays the startup buffer in one window,
and the buffer visiting @var{file} in another window
(@pxref{Windows}).  If you supply more than one file argument, the
displayed file is the last one specified on the command line; the
other files are visited but their buffers are not shown.

If the startup buffer is disabled (@pxref{Entering Emacs}), then
starting Emacs with one file argument displays the buffer visiting
@var{file} in a single window.  With two file arguments, Emacs
displays the files in two different windows.  With more than two file
arguments, Emacs displays the last file specified in one window, plus
another window with a Buffer Menu showing all the other files
(@pxref{Several Buffers}).  To inhibit using the Buffer Menu for this,
change the variable @code{inhibit-startup-buffer-menu} to @code{t}.

@item +@var{linenum} @var{file}
@opindex +@var{linenum}
Visit the specified @var{file}, then go to line number @var{linenum}
in it.

@item +@var{linenum}:@var{columnnum} @var{file}
Visit the specified @var{file}, then go to line number @var{linenum}
and put point at column number @var{columnnum}.

@item -l @var{file}
@opindex -l
@itemx --load=@var{file}
@opindex --load
@cindex loading Lisp libraries, command-line argument
Load a Lisp library named @var{file} with the function @code{load}.
If @var{file} is not an absolute file name, Emacs first looks for it
in the current directory, then in the directories listed in
@code{load-path} (@pxref{Lisp Libraries}).

@strong{Warning:} If previous command-line arguments have visited
files, the current directory is the directory of the last file
visited.

@item -L @var{dir}
@opindex -L
@itemx --directory=@var{dir}
@opindex --directory
Prepend directory @var{dir} to the variable @code{load-path}.
If you specify multiple @samp{-L} options, Emacs preserves the
relative order; i.e., using @samp{-L /foo -L /bar} results in
a @code{load-path} of the form @code{("/foo" "/bar" @dots{})}.
If @var{dir} begins with @samp{:}, Emacs removes the @samp{:} and
appends (rather than prepends) the remainder to @code{load-path}.
(On MS Windows, use @samp{;} instead of @samp{:}; i.e., use
the value of @code{path-separator}.)

@item -f @var{function}
@opindex -f
@itemx --funcall=@var{function}
@opindex --funcall
@cindex call Lisp functions, command-line argument
Call Lisp function @var{function}.  If it is an interactive function
(a command), it reads the arguments interactively just as if you had
called the same function with a key sequence.  Otherwise, it calls the
function with no arguments.

@item --eval=@var{expression}
@opindex --eval
@itemx --execute=@var{expression}
@opindex --execute
@cindex evaluate expression, command-line argument
Evaluate Lisp expression @var{expression}.

@item --insert=@var{file}
@opindex --insert
@cindex insert file contents, command-line argument
Insert the contents of @var{file} into the buffer that is current when
this command-line argument is processed.  Usually, this is the
@file{*scratch*} buffer (@pxref{Lisp Interaction}), but if arguments
earlier on the command line visit files or switch buffers, that might
be a different buffer.  The effect of this command-line argument is
like what @kbd{M-x insert-file} does (@pxref{Misc File Ops}).

@item --kill
@opindex --kill
Exit from Emacs without asking for confirmation.

@item --help
@opindex --help
Print a usage message listing all available options, then exit
successfully.

@item --version
@opindex --version
Print Emacs version, then exit successfully.

@item --fingerprint
@opindex --fingerprint
Print the Emacs ``fingerprint'', which is used to uniquely identify
the compiled version of Emacs.
@end table

@node Initial Options
@appendixsec Initial Options

  The initial options specify parameters for the Emacs session.  This
section describes the more general initial options; some other options
specifically related to the X Window System appear in the following
sections.

  Some initial options affect the loading of the initialization file.
Normally, Emacs first loads @file{site-start.el} if it exists, then
your own initialization file if it exists, and finally the default
initialization file @file{default.el} if it exists (@pxref{Init
File}).  Certain options prevent loading of some of these files or
substitute other files for them.

@table @samp
@item -chdir @var{directory}
@opindex -chdir
@itemx --chdir=@var{directory}
@opindex --chdir
@cindex change Emacs directory
Change to @var{directory} before doing anything else.  This is mainly used
by session management in X so that Emacs starts in the same directory as it
stopped.  This makes desktop saving and restoring easier.

@item -t @var{device}
@opindex -t
@itemx --terminal=@var{device}
@opindex --terminal
@cindex device for Emacs terminal I/O
Use @var{device} as the device for terminal input and output.  This
option implies @samp{--no-window-system}.

@item -d @var{display}
@opindex -d
@itemx --display=@var{display}
@opindex --display
@cindex display for Emacs frame
Use the X Window System and use the display named @var{display} to open
the initial Emacs frame.  @xref{Display X}, for more details.

@item -nw
@opindex -nw
@itemx --no-window-system
@opindex --no-window-system
@cindex disable window system
Don't communicate directly with the window system, disregarding the
@env{DISPLAY} environment variable even if it is set.  This means that
Emacs uses the terminal from which it was launched for all its display
and input.

@cindex batch mode
@item -batch
@opindex --batch
@itemx --batch
Run Emacs in @dfn{batch mode}.  Batch mode is used for running
programs written in Emacs Lisp from shell scripts, makefiles, and so
on.  To invoke a Lisp program, use the @samp{-batch} option in
conjunction with one or more of @samp{-l}, @samp{-f} or @samp{--eval}
(@pxref{Action Arguments}).  @xref{Command Example}, for an example.

In batch mode, Emacs does not display the text being edited, and the
standard terminal interrupt characters such as @kbd{C-z} and @kbd{C-c}
have their usual effect.  Emacs functions that normally print a
message in the echo area will print to either the standard output
stream (@code{stdout}) or the standard error stream (@code{stderr})
instead.  (To be precise, functions like @code{prin1}, @code{princ}
and @code{print} print to @code{stdout}, while @code{message} and
@code{error} print to @code{stderr}.)  Functions that normally read
keyboard input from the minibuffer take their input from the
terminal's standard input stream (@code{stdin}) instead.

@samp{--batch} implies @samp{-q} (do not load an initialization file),
but @file{site-start.el} is loaded nonetheless.  It also causes Emacs
to exit after processing all the command options.  In addition, it
disables auto-saving except in buffers for which auto-saving is
explicitly requested, and when saving files it omits the @code{fsync}
system call unless otherwise requested.

@vindex backtrace-on-error-noninteractive
Errors that occur when running a @samp{--batch} Emacs will result in
an Emacs Lisp backtrace being printed.  To disable this behavior, set
@code{backtrace-on-error-noninteractive} to @code{nil}.

@item --script @var{file}
@opindex --script
@cindex script mode
Run Emacs in batch mode, like @samp{--batch}, and then read and
execute the Lisp code in @var{file}.

The normal use of this option is in executable script files that run
Emacs.  They can start with this text on the first line

@example
#!/usr/bin/emacs --script
@end example

@noindent
which will invoke Emacs with @samp{--script} and supply the name of
the script file as @var{file}.  Emacs Lisp then treats the @samp{#!}
on this first line as a comment delimiter.

@item --no-build-details
@opindex --no-build-details
@cindex build details
@cindex deterministic build
Omit details like system name and build time from the Emacs
executable, so that builds are more deterministic.  This switch is not
meant for regular (or interactive) use, since it makes commands like
@code{system-name} return @code{nil}.

@item -q
@opindex -q
@itemx --no-init-file
@opindex --no-init-file
@cindex bypassing init and @file{default.el} file
@cindex init file, not loading
@cindex @file{default.el} file, not loading
Do not load any initialization file (@pxref{Init File}).  When Emacs
is invoked with this option, the Customize facility does not allow
options to be saved (@pxref{Easy Customization}).  This option does
not disable loading @file{site-start.el}.

@item --no-site-file
@opindex --no-site-file
@itemx -nsl
@opindex -nsl
@cindex @file{site-start.el} file, not loading
Do not load @file{site-start.el} (@pxref{Init File}).  The @samp{-Q}
option does this too, but other options like @samp{-q} do not.

@item --no-site-lisp
@opindex --no-site-lisp
@cindex @file{site-lisp} files, not loading
Do not include the @file{site-lisp} directories in @code{load-path}
(@pxref{Init File}).  The @samp{-Q} option does this too.

@item --no-splash
@opindex --no-splash
@cindex splash screen
@cindex startup message
Do not display a startup screen.  You can also achieve this effect by
setting the variable @code{inhibit-startup-screen} to non-@code{nil}
in your initialization file (@pxref{Entering Emacs}).

@item --no-x-resources
@opindex --no-x-resources
@cindex X resources, not loading
Do not load X resources.  You can also achieve this effect by setting
the variable @code{inhibit-x-resources} to @code{t} in your
initialization file (@pxref{Resources}).

@item -Q
@opindex -Q
@itemx --quick
@opindex --quick
Start Emacs with minimum customizations.  This is similar to using
@samp{-q}, @samp{--no-site-file}, @samp{--no-site-lisp},
@samp{--no-x-resources}, and @samp{--no-splash} together.

@item -daemon
@opindex -daemon
@itemx --daemon[=@var{name}]
@opindex --daemon
@itemx --bg-daemon[=@var{name}]
@itemx --fg-daemon[=@var{name}]
Start Emacs as a daemon: after Emacs starts up, it starts the Emacs
server without opening any frames.  You can then use the
@command{emacsclient} command to connect to Emacs for editing.
(Optionally, you can specify an explicit @var{name} for the server; if
you do, you will need to specify the same @var{name} when you invoke
@command{emacsclient}, via its @option{--socket-name} option, see
@ref{emacsclient Options}.)  @xref{Emacs Server}, for information
about using Emacs as a daemon.  A ``background'' daemon disconnects
from the terminal and runs in the background (@samp{--daemon} is an
alias for @samp{--bg-daemon}).

@item --no-desktop
@opindex --no-desktop
Do not reload any saved desktop.  @xref{Saving Emacs Sessions}.

@item -u @var{user}
@opindex -u
@itemx --user=@var{user}
@opindex --user
@cindex load init file of another user
Load @var{user}'s initialization file instead of your
own@footnote{This option has no effect on MS-Windows.}.

@item --debug-init
@opindex --debug-init
@cindex errors in init file
Enable the Emacs Lisp debugger for errors in the init file.
@xref{Error Debugging,, Entering the Debugger on an Error, elisp, The
GNU Emacs Lisp Reference Manual}.

@item --module-assertions
@opindex --module-assertions
@cindex module verification
Enable expensive correctness checks when dealing with dynamically
loadable modules.  This is intended for module authors that wish to
verify that their module conforms to the module API requirements.  The
option makes Emacs abort if a module-related assertion triggers.
@xref{Writing Dynamic Modules,, Writing Dynamically-Loaded Modules,
elisp, The GNU Emacs Lisp Reference Manual}.

@item --dump-file=@var{file}
@opindex --dump-file
@cindex specify dump file
Load the dumped Emacs state from the named @var{file}.  By default, an
installed Emacs will look for its dump state in a file named
@file{@var{emacs}.pdmp} in the directory where the Emacs installation
puts the architecture-dependent files; the variable
@code{exec-directory} holds the name of that directory.  @var{emacs}
is the name of the Emacs executable file, normally just @file{emacs}.
(When you invoke Emacs from the @file{src} directory where it was
built without installing it, it will look for the dump file in the
directory of the executable.)  If you rename or move the dump file to
a different place, you can use this option to tell Emacs where to find
that file.
@end table

@node Command Example
@appendixsec Command Argument Example

  Here is an example of using Emacs with arguments and options.  It
assumes you have a Lisp program file called @file{hack-c.el} which, when
loaded, performs some useful operation on the current buffer, expected
to be a C program.

@example
emacs --batch foo.c -l hack-c -f save-buffer >& log
@end example

@noindent
This says to visit @file{foo.c}, load @file{hack-c.el} (which makes
changes in the visited file), save @file{foo.c} (note that
@code{save-buffer} is the function that @kbd{C-x C-s} is bound to), and
then exit back to the shell (because of @samp{--batch}).  @samp{--batch}
also guarantees there will be no problem redirecting output to
@file{log}, because Emacs will not assume that it has a display terminal
to work with.

@node Environment
@appendixsec Environment Variables
@cindex environment variables

  The @dfn{environment} is a feature of the operating system; it
consists of a collection of variables with names and values.  Each
variable is called an @dfn{environment variable}; environment variable
names are case-sensitive, and it is conventional to use upper case
letters only.  The values are all text strings.

  What makes the environment useful is that subprocesses inherit the
environment automatically from their parent process.  This means you
can set up an environment variable in your login shell, and all the
programs you run (including Emacs) will automatically see it.
Subprocesses of Emacs (such as shells, compilers, and version control
programs) inherit the environment from Emacs, too.

@findex setenv
@findex getenv
@vindex initial-environment
  Inside Emacs, the command @kbd{M-x getenv} reads the name of an
environment variable, and prints its value in the echo area.  @kbd{M-x
setenv} sets a variable in the Emacs environment, and @kbd{C-u M-x
setenv} removes a variable.  (Environment variable substitutions with
@samp{$} work in the value just as in file names; see @ref{File Names
with $}.)  The variable @code{initial-environment} stores the initial
environment inherited by Emacs.

  The way to set environment variables outside of Emacs depends on the
operating system, and especially the shell that you are using.  For
example, here's how to set the environment variable @env{ORGANIZATION}
to @samp{not very much} using Bash:

@example
export ORGANIZATION="not very much"
@end example

@noindent
and here's how to do it in csh or tcsh:

@example
setenv ORGANIZATION "not very much"
@end example

  When Emacs is using the X Window System, various environment
variables that control X work for Emacs as well.  See the X
documentation for more information.

@menu
* General Variables::   Environment variables that all versions of Emacs use.
* Misc Variables::      Certain system-specific variables.
* MS-Windows Registry:: An alternative to the environment on MS-Windows.
@end menu

@node General Variables
@appendixsubsec 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.

@c This used to be @vtable, but that enters the variables alone into
@c the Variable Index, which in some cases, like HOME, might be
@c confused with keys by that name, and other cases, like NAME,
@c might be confused with general-purpose phrases.
@table @env
@item CDPATH
@vindex CDPATH@r{, environment variable}
Used by the @code{cd} command to search for the directory you specify,
when you specify a relative directory.
@item COLORTERM
@vindex COLORTERM@r{, environment variable}
If this variable is set to the value @samp{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.
@item DBUS_SESSION_BUS_ADDRESS
@vindex DBUS_SESSION_BUS_ADDRESS@r{, environment variable}
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
@samp{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.
@item EMACSDATA
@vindex EMACSDATA@r{, environment variable}
Directory for the architecture-independent files that come with Emacs.
This is used to initialize the variable @code{data-directory}.
@item EMACSDOC
@vindex EMACSDOC@r{, environment variable}
Directory for the documentation string file, which is used to
initialize the Lisp variable @code{doc-directory}.
@item EMACSLOADPATH
@vindex EMACSLOADPATH@r{, environment variable}
A colon-separated list of directories@footnote{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.} to search for
Emacs Lisp files.  If set, it modifies the usual initial value of the
@code{load-path} variable (@pxref{Lisp Libraries}).  An empty element
stands for the default value of @code{load-path}; e.g., using
@samp{EMACSLOADPATH="/tmp:"} adds @file{/tmp} to the front of
the default @code{load-path}.  To specify an empty element in the
middle of the list, use 2 colons in a row, as in
@samp{EMACSLOADPATH="/tmp::/foo"}.
@item EMACSPATH
@vindex EMACSPATH@r{, environment variable}
A colon-separated list of directories to search for executable files.
If set, Emacs uses this in addition to @env{PATH} (see below) when
initializing the variable @code{exec-path} (@pxref{Shell}).
@item EMAIL
@vindex EMAIL@r{, environment variable}
@vindex user-mail-address@r{, initialization}
Your email address; used to initialize the Lisp variable
@code{user-mail-address}, which the Emacs mail interface puts into the
@samp{From} header of outgoing messages (@pxref{Mail Headers}).
@item ESHELL
@vindex ESHELL@r{, environment variable}
Used for shell-mode to override the @env{SHELL} environment variable
(@pxref{Interactive Shell}).
@item HISTFILE
@vindex HISTFILE@r{, environment variable}
The name of the file that shell commands are saved in between logins.
This variable defaults to @file{~/.bash_history} if you use Bash, to
@file{~/.sh_history} if you use ksh, and to @file{~/.history}
otherwise.
@item HOME
@vindex HOME@r{, environment variable}
The location of your files in the directory tree; used for expansion
of file names starting with a tilde (@file{~}).  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, @env{HOME}
normally defaults to the home directory of the user given by
@env{LOGNAME}, @env{USER} or your user ID, or to @file{/} if all else
fails.  On MS-DOS, it defaults to the directory from which Emacs was
started, with @samp{/bin} removed from the end if it was present.  On
Windows, the default value of @env{HOME} is the @file{Application
Data} subdirectory of the user profile directory (normally, this is
@file{C:/Documents and Settings/@var{username}/Application Data},
where @var{username} is your user name), though for backwards
compatibility @file{C:/} will be used instead if a @file{.emacs} file
is found there.
@item HOSTNAME
@vindex HOSTNAME@r{, environment variable}
The name of the machine that Emacs is running on.
@item INFOPATH
@vindex INFOPATH@r{, environment variable}
A colon-separated list of directories in which to search for Info files.
@item LC_ALL
@vindex LC_ALL@r{, environment variable}
@itemx LC_COLLATE
@vindex LC_COLLATE@r{, environment variable}
@itemx LC_CTYPE
@vindex LC_CTYPE@r{, environment variable}
@itemx LC_MESSAGES
@vindex LC_MESSAGES@r{, environment variable}
@itemx LC_MONETARY
@vindex LC_MONETARY@r{, environment variable}
@itemx LC_NUMERIC
@vindex LC_NUMERIC@r{, environment variable}
@itemx LC_TIME
@vindex LC_TIME@r{, environment variable}
@itemx LANG
@vindex LANG@r{, environment variable}
The user's preferred locale.  The locale has six categories, specified
by the environment variables @env{LC_COLLATE} for sorting,
@env{LC_CTYPE} for character encoding, @env{LC_MESSAGES} for system
messages, @env{LC_MONETARY} for monetary formats, @env{LC_NUMERIC} for
numbers, and @env{LC_TIME} for dates and times.  If one of these
variables is not set, the category defaults to the value of the
@env{LANG} environment variable, or to the default @samp{C} locale if
@env{LANG} is not set.  But if @env{LC_ALL} is specified, it overrides
the settings of all the other locale environment variables.

On MS-Windows and macOS, if @env{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 @env{LC_CTYPE} category is
matched against entries in @code{locale-language-names},
@code{locale-charset-language-names}, and
@code{locale-preferred-coding-systems}, to select a default language
environment and coding system.  @xref{Language Environments}.
@item LOGNAME
@vindex LOGNAME@r{, environment variable}
The user's login name.  See also @env{USER}.
@item MAIL
@vindex MAIL@r{, environment variable}
The name of your system mail inbox.
@ifnottex
@item MH
@vindex MH@r{, environment variable}
Name of setup file for the mh system.  @xref{Top,,MH-E,mh-e, The Emacs
Interface to MH}.
@end ifnottex
@item NAME
@vindex NAME@r{, environment variable}
Your real-world name.  This is used to initialize the variable
@code{user-full-name} (@pxref{Mail Headers}).
@item NNTPSERVER
@vindex NNTPSERVER@r{, environment variable}
The name of the news server.  Used by the mh and Gnus packages.
@item ORGANIZATION
@vindex ORGANIZATION@r{, environment variable}
The name of the organization to which you belong.  Used for setting the
@samp{Organization:} header in your posts from the Gnus package.
@item PATH
@vindex PATH@r{, environment variable}
A colon-separated list of directories containing executable files.
This is used to initialize the variable @code{exec-path}
(@pxref{Shell}).
@item PWD
@vindex PWD@r{, environment variable}
If set, this should be the default directory when Emacs was started.
@item REPLYTO
@vindex REPLYTO@r{, environment variable}
If set, this specifies an initial value for the variable
@code{mail-default-reply-to} (@pxref{Mail Headers}).
@item SAVEDIR
@vindex SAVEDIR@r{, environment variable}
The name of a directory in which news articles are saved by default.
Used by the Gnus package.
@item SHELL
@vindex SHELL@r{, environment variable}
The name of an interpreter used to parse and execute programs run from
inside Emacs.  This is used to initialize the variable
@code{shell-file-name} (@pxref{Single Shell}).
@item SMTPSERVER
@vindex SMTPSERVER@r{, environment variable}
The name of the outgoing mail server.  This is used to initialize the
variable @code{smtpmail-smtp-server} (@pxref{Mail Sending}).
@cindex background mode, on @command{xterm}
@item TERM
@vindex TERM@r{, environment variable}
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
@samp{internal}, which specifies a built-in terminal emulation that
handles the machine's own display.
@item TERMCAP
@vindex TERMCAP@r{, environment variable}
The name of the termcap library file describing how to program the
terminal specified by @env{TERM}.  This defaults to
@file{/etc/termcap}.
@item TMPDIR
@vindex TMPDIR@r{, environment variable}
@itemx TMP
@vindex TMP@r{, environment variable}
@itemx TEMP
@vindex TEMP@r{, environment variable}
These environment variables are used to initialize the variable
@code{temporary-file-directory}, which specifies a directory in which
to put temporary files (@pxref{Backup}).  Emacs tries to use
@env{TMPDIR} first.  If that is unset, Emacs normally falls back on
@file{/tmp}, but on MS-Windows and MS-DOS it instead falls back on
@env{TMP}, then @env{TEMP}, and finally @file{c:/temp}.
@item TZ
@vindex TZ@r{, environment variable}
This specifies the default time zone and possibly also daylight
saving time information.  @xref{Time Zone Rules,,, elisp, The GNU
Emacs Lisp Reference Manual}.  On MS-DOS, if @env{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 @env{TZ} at all.
@item USER
@vindex USER@r{, environment variable}
The user's login name.  See also @env{LOGNAME}.  On MS-DOS, this
defaults to @samp{root}.
@item VERSION_CONTROL
@vindex VERSION_CONTROL@r{, environment variable}
Used to initialize the @code{version-control} variable (@pxref{Backup
Names}).
@end table

@node Misc Variables
@appendixsubsec Miscellaneous Variables

These variables are used only on particular configurations:

@vtable @env
@item COMSPEC
On MS-DOS and MS-Windows, the name of the command interpreter to use
when invoking batch files and commands internal to the shell.  On MS-DOS
this is also used to make a default value for the @env{SHELL} environment
variable.

@item NAME
On MS-DOS, this variable defaults to the value of the @env{USER}
variable.

@item EMACSTEST
On MS-DOS, this specifies a file to use to log the operation of the
internal terminal emulator.  This feature is useful for submitting bug
reports.

@item EMACSCOLORS
On MS-DOS, this specifies the screen colors.  It is useful to set them
this way, since otherwise Emacs would display the default colors
momentarily when it starts up.

The value of this variable should be the two-character encoding of the
foreground (the first character) and the background (the second
character) colors of the default face.  Each character should be the
hexadecimal code for the desired color on a standard PC text-mode
display.  For example, to get blue text on a light gray background,
specify @samp{EMACSCOLORS=17}, since 1 is the code of the blue color and
7 is the code of the light gray color.

The PC display usually supports only eight background colors.  However,
Emacs switches the DOS display to a mode where all 16 colors can be used
for the background, so all four bits of the background color are
actually used.

@item PRELOAD_WINSOCK
On MS-Windows, if you set this variable, Emacs will load and initialize
the network library at startup, instead of waiting until the first
time it is required.

@item emacs_dir
On MS-Windows, @env{emacs_dir} is a special environment variable, which
indicates the full path of the directory in which Emacs is installed.
If Emacs is installed in the standard directory structure, it
calculates this value automatically.  It is not much use setting this
variable yourself unless your installation is non-standard, since
unlike other environment variables, it will be overridden by Emacs at
startup.  When setting other environment variables, such as
@env{EMACSLOADPATH}, you may find it useful to use @env{emacs_dir}
rather than hard-coding an absolute path.  This allows multiple
versions of Emacs to share the same environment variable settings, and
it allows you to move the Emacs installation directory, without
changing any environment or registry settings.
@end vtable

@node MS-Windows Registry
@appendixsubsec The MS-Windows System Registry
@pindex addpm, MS-Windows installation program
@cindex registry, setting environment variables (MS-Windows)

On MS-Windows, the installation program @command{addpm.exe} adds
values for @env{emacs_dir}, @env{EMACSLOADPATH}, @env{EMACSDATA},
@env{EMACSPATH}, @env{EMACSDOC}, @env{SHELL} and @env{TERM} to the
@file{HKEY_LOCAL_MACHINE} section of the system registry, under
@file{/Software/GNU/Emacs}.  It does this because there is no standard
place to set environment variables across different versions of
Windows.  Running @command{addpm.exe} is no longer strictly necessary
in recent versions of Emacs, but if you are upgrading from an older
version, running @command{addpm.exe} ensures that you do not have
older registry entries from a previous installation, which may not be
compatible with the latest version of Emacs.

When Emacs starts, as well as checking the environment, it also checks
the System Registry for those variables and for @env{HOME}, @env{LANG}
and @env{PRELOAD_WINSOCK}.

To determine the value of those variables, Emacs goes through the
following procedure.  First, the environment is checked.  If the
variable is not found there, Emacs looks for registry keys by that
name under @file{/Software/GNU/Emacs}; first in the
@file{HKEY_CURRENT_USER} section of the registry, and if not found
there, in the @file{HKEY_LOCAL_MACHINE} section.  Finally, if Emacs
still cannot determine the values, compiled-in defaults are used.

In addition to the environment variables above, you can also add
settings to the @file{/Software/GNU/Emacs} registry key to specify X
resources (@pxref{X Resources}).  Most of the settings you can specify
in your @file{.Xdefaults} file can be set from that registry key.

@node Display X
@appendixsec Specifying the Display Name
@cindex display name (X Window System)
@cindex @env{DISPLAY} environment variable

  The environment variable @env{DISPLAY} tells all X clients,
including Emacs, where to display their windows.  Its value is set by
default in ordinary circumstances, when you start an X server and run
jobs locally.  You can specify the display yourself; one reason to do
this is if you want to log into another system and run Emacs there,
and have the window displayed at your local terminal.

  @env{DISPLAY} has the syntax
@samp{@var{host}:@var{display}.@var{screen}}, where @var{host} is the
host name of the X Window System server machine, @var{display} is an
arbitrarily-assigned number that distinguishes your server (X
terminal) from other servers on the same machine, and @var{screen} is
a field that allows an X server to control multiple terminal screens.
The period and the @var{screen} field are optional.  If included,
@var{screen} is usually zero.

  For example, if your host is named @samp{glasperle} and your server is
the first (or perhaps the only) server listed in the configuration, your
@env{DISPLAY} is @samp{glasperle:0.0}.

  You can specify the display name explicitly when you run Emacs, either
by changing the @env{DISPLAY} variable, or with the option @samp{-d
@var{display}} or @samp{--display=@var{display}}.  Here is an example:

@smallexample
emacs --display=glasperle:0 &
@end smallexample

  You can inhibit the use of the X window system with the @samp{-nw}
option.  Then Emacs uses its controlling text terminal for display.
@xref{Initial Options}.

  Sometimes, security arrangements prevent a program on a remote system
from displaying on your local system.  In this case, trying to run Emacs
produces messages like this:

@smallexample
Xlib:  connection to "glasperle:0.0" refused by server
@end smallexample

@noindent
You might be able to overcome this problem by using the @command{xhost}
command on the local system to give permission for access from your
remote machine.

@node Font X
@appendixsec Font Specification Options
@cindex font name (X Window System)

You can use the command line option @samp{-fn @var{font}} (or
@samp{--font}, which is an alias for @samp{-fn}) to specify a default
font:

@table @samp
@item -fn @var{font}
@opindex -fn
@itemx --font=@var{font}
@opindex --font
@cindex specify default font from the command line
Use @var{font} as the default font.
@end table

When passing a font name to Emacs on the command line, you may need to
quote it, by enclosing it in quotation marks, if it contains
characters that the shell treats specially (e.g., spaces).  For
example:

@smallexample
emacs -fn "DejaVu Sans Mono-12"
@end smallexample

@xref{Fonts}, for details about font names and other ways to specify
the default font.

@node Colors X
@appendixsec Window Color Options
@cindex color of window, from command line
@cindex text colors, from command line

  You can use the following command-line options to specify the colors
to use for various parts of the Emacs display.  Colors may be
specified using either color names or RGB triplets (@pxref{Colors}).

@table @samp
@item -fg @var{color}
@opindex -fg
@itemx --foreground-color=@var{color}
@opindex --foreground-color
@cindex foreground color, command-line argument
Specify the foreground color, overriding the color specified by the
@code{default} face (@pxref{Faces}).
@item -bg @var{color}
@opindex -bg
@itemx --background-color=@var{color}
@opindex --background-color
@cindex background color, command-line argument
Specify the background color, overriding the color specified by the
@code{default} face.
@item -bd @var{color}
@opindex -bd
@itemx --border-color=@var{color}
@opindex --border-color
@cindex border color, command-line argument
Specify the color of the border of the X window.  This has no effect
if Emacs is compiled with GTK+ support.
@item -cr @var{color}
@opindex -cr
@itemx --cursor-color=@var{color}
@opindex --cursor-color
@cindex cursor color, command-line argument
Specify the color of the Emacs cursor which indicates where point is.
@item -ms @var{color}
@opindex -ms
@itemx --mouse-color=@var{color}
@opindex --mouse-color
@cindex mouse pointer color, command-line argument
Specify the color for the mouse cursor when the mouse is in the Emacs window.
@item -r
@opindex -r
@itemx -rv
@opindex -rv
@itemx --reverse-video
@opindex --reverse-video
@cindex reverse video, command-line argument
Reverse video: swap the foreground and background colors.
@item --color=@var{mode}
@opindex --color
@cindex standard colors on a character terminal
@cindex override character terminal color support
Set the @dfn{color support mode} when Emacs is run on a text terminal.
This option overrides the number of supported colors that the
character terminal advertises in its @code{termcap} or @code{terminfo}
database.  The parameter @var{mode} can be one of the following:
@table @samp
@item never
@itemx no
Don't use colors even if the terminal's capabilities specify color
support.
@item default
@itemx auto
Same as when @option{--color} is not used at all: Emacs detects at
startup whether the terminal supports colors, and if it does, turns on
colored display.
@item always
@itemx yes
@itemx ansi8
Turn on the color support unconditionally, and use color commands
specified by the ANSI escape sequences for the 8 standard colors.
@item @var{num}
Use color mode for @var{num} colors.  If @var{num} is @minus{}1, turn off
color support (equivalent to @samp{never}); if it is 0, use the
default color support for this terminal (equivalent to @samp{auto});
otherwise use an appropriate standard mode for @var{num} colors.
Depending on your terminal's capabilities, Emacs might be able to turn
on a color mode for 8, 16, 88, or 256 as the value of @var{num}.  If
there is no mode that supports @var{num} colors, Emacs acts as if
@var{num} were 0, i.e., it uses the terminal's default color support
mode.
@end table
If @var{mode} is omitted, it defaults to @var{ansi8}.
@end table

  For example, to use a coral mouse cursor and a slate blue text cursor,
enter:

@example
emacs -ms coral -cr 'slate blue' &
@end example

  You can reverse the foreground and background colors through the
@samp{-rv} option or with the X resource @samp{reverseVideo}.

  The @samp{-fg}, @samp{-bg}, and @samp{-rv} options function on text
terminals as well as on graphical displays.

@node Window Size X
@appendixsec Options for Window Size and Position
@cindex geometry of Emacs window
@cindex position and size of Emacs frame
@cindex width and height of Emacs frame
@cindex specifying fullscreen for Emacs frame

  Here is a list of the command-line options for specifying size and
position of the initial Emacs frame:

@table @samp
@item -g @var{width}x@var{height}@r{[@{}+-@r{@}}@var{xoffset}@r{@{}+-@r{@}}@var{yoffset}@r{]]}
@opindex -g
@itemx --geometry=@var{width}x@var{height}@r{[@{}+-@r{@}}@var{xoffset}@r{@{}+-@r{@}}@var{yoffset}@r{]]}
@opindex --geometry
@cindex geometry, command-line argument
Specify the size @var{width} and @var{height} (measured in character
columns and lines), and positions @var{xoffset} and @var{yoffset}
(measured in pixels).  The @var{width} and @var{height} parameters
apply to all frames, whereas @var{xoffset} and @var{yoffset} only to
the initial frame.

@item -fs
@opindex -fs
@itemx --fullscreen
@opindex --fullscreen
@cindex fullscreen, command-line argument
Specify that width and height should be that of the screen.  Normally
no window manager decorations are shown.  (After starting Emacs,
you can toggle this state using @key{F11}, @code{toggle-frame-fullscreen}.)

@item -mm
@opindex -mm
@itemx --maximized
@opindex --maximized
@cindex maximized, command-line argument
Specify that the Emacs frame should be maximized.  This normally
means that the frame has window manager decorations.
(After starting Emacs, you can toggle this state using @kbd{M-F10},
@code{toggle-frame-maximized}.)

@item -fh
@opindex -fh
@itemx --fullheight
@opindex --fullheight
@cindex fullheight, command-line argument
Specify that the height should be the height of the screen.

@item -fw
@opindex -fw
@itemx --fullwidth
@opindex --fullwidth
@cindex fullwidth, command-line argument
Specify that the width should be the width of the screen.
@end table

@noindent
In the @samp{--geometry} option, @code{@r{@{}+-@r{@}}} means either a plus
 sign or a minus sign.  A plus
sign before @var{xoffset} means it is the distance from the left side of
the screen; a minus sign means it counts from the right side.  A plus
sign before @var{yoffset} means it is the distance from the top of the
screen, and a minus sign there indicates the distance from the bottom.
The values @var{xoffset} and @var{yoffset} may themselves be positive or
negative, but that doesn't change their meaning, only their direction.

  Emacs uses the same units as @command{xterm} does to interpret the geometry.
The @var{width} and @var{height} are measured in characters, so a large font
creates a larger frame than a small font.  (If you specify a proportional
font, Emacs uses its maximum bounds width as the width unit.)  The
@var{xoffset} and @var{yoffset} are measured in pixels.

  You do not have to specify all of the fields in the geometry
specification.  If you omit both @var{xoffset} and @var{yoffset}, the
window manager decides where to put the Emacs frame, possibly by
letting you place it with the mouse.  For example, @samp{164x55}
specifies a window 164 columns wide, enough for two ordinary width
windows side by side, and 55 lines tall.

  The default frame width is 80 characters and the default height is
between 35 and 40 lines, depending on the OS and the window manager.
You can omit either the width or the height or both.  If you start the
geometry with an integer, Emacs interprets it as the width.  If you
start with an @samp{x} followed by an integer, Emacs interprets it as
the height.  Thus, @samp{81} specifies just the width; @samp{x45}
specifies just the height.

  If you start the geometry with @samp{+} or @samp{-}, that introduces
an offset, which means both sizes are omitted.  Thus, @samp{-3}
specifies the @var{xoffset} only.  (If you give just one offset, it is
always @var{xoffset}.)  @samp{+3-3} specifies both the @var{xoffset}
and the @var{yoffset}, placing the frame near the bottom left of the
screen.

  You can specify a default for any or all of the fields in your X
resource file (@pxref{Resources}), and then override selected fields
with a @samp{--geometry} option.

  Since the mode line and the echo area occupy the last 2 lines of the
frame, the height of the initial text window is 2 less than the height
specified in your geometry.  In non-X-toolkit versions of Emacs, the
menu bar also takes one line of the specified number.  But in the X
toolkit version, the menu bar is additional and does not count against
the specified height.  The tool bar, if present, is also additional.

  Enabling or disabling the menu bar or tool bar alters the amount of
space available for ordinary text.  Therefore, if Emacs starts up with
a tool bar (which is the default), and handles the geometry
specification assuming there is a tool bar, and then your
initialization file disables the tool bar, you will end up with a
frame geometry different from what you asked for.  To get the intended
size with no tool bar, use an X resource to specify ``no tool bar''
(@pxref{Table of Resources}); then Emacs will already know there's no
tool bar when it processes the specified geometry.

  When using one of @samp{--fullscreen}, @samp{--maximized},
@samp{--fullwidth} or @samp{--fullheight}, some window managers require
you to set the variable @code{frame-resize-pixelwise} to a non-@code{nil}
value to make a frame appear truly maximized or full-screen.

 Some window managers have options that can make them ignore both
program-specified and user-specified positions.  If these are set,
Emacs fails to position the window correctly.

@node Borders X
@appendixsec Internal and Outer Borders
@cindex borders (X Window System)

  An Emacs frame has an internal border and an outer border.  The
internal border is an extra strip of the background color around the
text portion of the frame.  Emacs itself draws the internal border.  The
outer border is drawn by X outside the tool and menu bars of the frame.
There is also an external border which is drawn by the window manager.
The size of the external border cannot be set from within Emacs.

@table @samp
@item -ib @var{width}
@opindex -ib
@itemx --internal-border=@var{width}
@opindex --internal-border
@cindex internal border width, command-line argument
Specify @var{width} as the width of the internal border (around the
frame's text area), in pixels.

@item -bw @var{width}
@opindex -bw
@itemx --border-width=@var{width}
@opindex --border-width
@cindex main border width, command-line argument
@cindex outer border width, command-line argument
Specify @var{width} as the width of the outer border, in pixels.
@end table

  When you specify the size of the frame, that does not count the
borders.  The frame's position is measured from the outside edge of the
external border.

  Use the @samp{-ib @var{n}} option to specify an internal border
@var{n} pixels wide.  The default is 1.  Use @samp{-bw @var{n}} to
specify the width of the outer border (though the window manager may not
pay attention to what you specify).  The default width of the outer
border is 2.

@node Title X
@appendixsec Frame Titles

  Each Emacs frame always has a title, which appears in window
decorations and icons as the name of the frame.  The default title is
of the form @samp{@var{invocation-name}@@@var{machine}} (if there is
only one frame) or shows the selected window's buffer name (if there
is more than one frame).

  You can specify a non-default title for the initial Emacs frame with
a command line option:

@table @samp
@item -T @var{title}
@opindex -T
@itemx --title=@var{title}
@opindex --title
@cindex frame title, command-line argument
Specify @var{title} as the title for the initial Emacs frame.
@end table

  The @samp{--name} option (@pxref{Resources}) also specifies the title
for the initial Emacs frame.

@node Icons X
@appendixsec Icons
@cindex icons (X Window System)
@cindex minimizing a frame at startup

@table @samp
@item -iconic
@opindex --iconic
@itemx --iconic
@cindex start iconified, command-line argument
Start Emacs in an iconified state.

@item -nbi
@opindex -nbi
@itemx --no-bitmap-icon
@opindex --no-bitmap-icon
@cindex Emacs icon, a gnu
Disable the use of the Emacs icon.
@end table

  Most window managers allow you to iconify (or ``minimize'') an
Emacs frame, hiding it from sight.  Some window managers replace
iconified windows with tiny icons, while others remove them
entirely from sight.  The @samp{-iconic} option tells Emacs to begin
running in an iconified state, rather than showing a frame right away.
The text frame doesn't appear until you deiconify (or ``un-minimize'')
it.

  By default, Emacs uses an icon containing the Emacs logo.  On
desktop environments such as Gnome, this icon is also displayed in
other contexts, e.g., when switching into an Emacs frame.  The
@samp{-nbi} or @samp{--no-bitmap-icon} option tells Emacs to let the
window manager choose what sort of icon to use---usually just a small
rectangle containing the frame's title.

@node Misc X
@appendixsec Other Display Options

@table @samp
@c @item -hb
@c @opindex -hb
@c @itemx --horizontal-scroll-bars
@c @opindex --horizontal-scroll-bars
@c @c @cindex horizontal scroll bars, command-line argument
@c Enable horizontal scroll bars.  Since horizontal scroll bars
@c are not yet implemented, this actually does nothing.

@item --parent-id @var{id}
Open Emacs as a client X window via the XEmbed protocol, with @var{id}
as the parent X window id.  Currently, this option is mainly useful
for developers.

@item -vb
@opindex -vb
@itemx --vertical-scroll-bars
@opindex --vertical-scroll-bars
@cindex vertical scroll bars, command-line argument
Enable vertical scroll bars.

@item -lsp @var{pixels}
@opindex -lsp
@itemx --line-spacing=@var{pixels}
@opindex --line-spacing
@cindex line spacing, command-line argument
Specify @var{pixels} as additional space to put between lines, in pixels.

@item -nbc
@opindex -nbc
@itemx --no-blinking-cursor
@opindex --no-blinking-cursor
@cindex blinking cursor disable, command-line argument
Disable the blinking cursor on graphical displays.

@item -D
@opindex -D
@itemx --basic-display
@opindex --basic-display
Disable the menu-bar, the tool-bar, the scroll-bars, tool tips, and
turn off font-lock-mode and the blinking cursor.  This can be useful
for making a test case that simplifies debugging of display problems.
@end table

  The @samp{--xrm} option (@pxref{Resources}) specifies additional
X resource values.
