emacs/man/entering.texi

@c This is part of the Emacs manual.
@c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 2001, 2002, 2003,
@c   2004, 2005, 2006, 2007, 2008  Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Entering Emacs, Exiting, Text Characters, Top
@chapter Entering and Exiting Emacs
@cindex entering Emacs
@cindex starting Emacs

  The usual way to invoke Emacs is with the shell command
@command{emacs}.  Emacs clears the screen, then displays an initial
help message and copyright notice.  Some operating systems discard
your type-ahead when Emacs starts up; they give Emacs no way to
prevent this.  On those systems, wait for Emacs to clear the screen
before you start typing.

  From a shell window under the X Window System, run Emacs in the
background with @command{emacs&}.  This way, Emacs won't tie up the
shell window, so you can use it to run other shell commands while
Emacs is running.  You can type Emacs commands as soon as you direct
your keyboard input to an Emacs frame.

@vindex initial-major-mode
  When Emacs starts up, it creates a buffer named @samp{*scratch*}.
That's the buffer you start out in.  The @samp{*scratch*} buffer uses
Lisp Interaction mode; you can use it to type Lisp expressions and
evaluate them.  You can also ignore that capability and just write notes
there.  You can specify a different major mode for this buffer by
setting the variable @code{initial-major-mode} in your init file.
@xref{Init File}.

  It is possible to specify files to be visited, Lisp files to be
loaded, and functions to be called through Emacs command-line
arguments.  @xref{Emacs Invocation}.  The feature exists mainly for
compatibility with other editors, and for scripts.

  Many editors are designed to edit one file.  When done with that
file, you exit the editor.  The next time you want to edit a file, you
must start the editor again.  Working this way, it is convenient to
use a command-line argument to say which file to edit.

  However, killing Emacs after editing one each and starting it afresh
for the next file is both unnecessary and harmful, since it denies you
the full power of Emacs.  Emacs can visit more than one file in a
single editing session, and that is the right way to use it.  Exiting
the Emacs session loses valuable accumulated context, such as the kill
ring, registers, undo history, and mark ring.  These features are
useful for operating on multiple files, or even continuing to edit one
file.  If you kill Emacs after each file, you don't take advantage of
them.

  The recommended way to use GNU Emacs is to start it only once, just
after you log in, and do all your editing in the same Emacs session.
Each time you edit a file, you visit it with the existing Emacs, which
eventually has many files in it ready for editing.  Usually you do not
kill Emacs until you are about to log out.  @xref{Files}, for more
information on visiting more than one file.

  To edit a file from another program while Emacs is running, you can
use the @command{emacsclient} helper program to open a file in the
already running Emacs.  @xref{Emacs Server}.

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@node Exiting, Basic, Entering Emacs, Top
@section Exiting Emacs
@cindex exiting
@cindex killing Emacs
@cindex suspending
@cindex leaving Emacs
@cindex quitting Emacs

  There are two commands for exiting Emacs, and three kinds of
exiting: @dfn{iconifying} Emacs, @dfn{suspending} Emacs, and
@dfn{killing} Emacs.

  @dfn{Iconifying} means replacing the Emacs frame with a small box or
``icon'' on the screen.  This is the usual way to exit Emacs when
you're using a graphical display---if you bother to ``exit'' at all.
(Just switching to another application is usually sufficient.)

  @dfn{Suspending} means stopping Emacs temporarily and returning
control to its parent process (usually a shell), allowing you to
resume editing later in the same Emacs job.  This is the usual way to
exit Emacs when running it on a text terminal.

  @dfn{Killing} Emacs means destroying the Emacs job.  You can run Emacs
again later, but you will get a fresh Emacs; there is no way to resume
the same editing session after it has been killed.

@table @kbd
@item C-z
Suspend Emacs (@code{suspend-emacs}) or iconify a frame
(@code{iconify-or-deiconify-frame}).
@item C-x C-c
Kill Emacs (@code{save-buffers-kill-emacs}).
@end table

@kindex C-z
@findex iconify-or-deiconify-frame
  On graphical displays, @kbd{C-z} runs the command
@code{iconify-or-deiconify-frame}, which temporarily iconifies (or
``minimizes'') the selected Emacs frame (@pxref{Frames}).  You can
then use the window manager to select some other application.  (You
could select another application without iconifying Emacs first, but
getting the Emacs frame out of the way can make it more convenient to
find the other application.)

@findex suspend-emacs
  On a text terminal, @kbd{C-z} runs the command @code{suspend-emacs}.
Suspending Emacs takes you back to the shell from which you invoked
Emacs.  You can resume Emacs with the shell command @command{%emacs}
in most common shells.  On systems that don't support suspending
programs, @kbd{C-z} starts an inferior shell that communicates
directly with the terminal, and Emacs waits until you exit the
subshell.  (The way to do that is probably with @kbd{C-d} or
@command{exit}, but it depends on which shell you use.)  On these
systems, you can only get back to the shell from which Emacs was run
(to log out, for example) when you kill Emacs.

@vindex cannot-suspend
  Suspending can fail if you run Emacs under a shell that doesn't
support suspension of its subjobs, even if the system itself does
support it.  In such a case, you can set the variable
@code{cannot-suspend} to a non-@code{nil} value to force @kbd{C-z} to
start an inferior shell.

@kindex C-x C-c
@findex save-buffers-kill-emacs
  To exit and kill Emacs, type @kbd{C-x C-c}
(@code{save-buffers-kill-emacs}).  A two-character key is used to make
it harder to type by accident.  This command first offers to save any
modified file-visiting buffers.  If you do not save them all, it asks
for confirmation with @kbd{yes} before killing Emacs, since any
changes not saved now will be lost forever.  Also, if any subprocesses are
still running, @kbd{C-x C-c} asks for confirmation about them, since
killing Emacs will also kill the subprocesses.

@vindex confirm-kill-emacs
  If the value of the variable @code{confirm-kill-emacs} is
non-@code{nil}, @kbd{C-x C-c} assumes that its value is a predicate
function, and calls that function.  If the result is non-@code{nil}, the
session is killed, otherwise Emacs continues to run.  One convenient
function to use as the value of @code{confirm-kill-emacs} is the
function @code{yes-or-no-p}.  The default value of
@code{confirm-kill-emacs} is @code{nil}.

  You can't resume an Emacs session after killing it.  Emacs can,
however, record certain session information when you kill it, such as
which files you visited, so the next time you start Emacs it will try
to visit the same files.  @xref{Saving Emacs Sessions}.

  The operating system usually listens for certain special characters
whose meaning is to kill or suspend the program you are running.
@b{This operating system feature is turned off while you are in Emacs.}
The meanings of @kbd{C-z} and @kbd{C-x C-c} as keys in Emacs were
inspired by the use of @kbd{C-z} and @kbd{C-c} on several operating
systems as the characters for stopping or killing a program, but that is
their only relationship with the operating system.  You can customize
these keys to run any commands of your choice (@pxref{Keymaps}).

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