There are two commands for exiting Emacs because there are two kinds of exiting: suspending Emacs and killing Emacs.
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, with the same buffers, same kill ring, same undo history, and so on. This is the usual way to exit.
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.
Suspend Emacs or iconify a frame
suspend-emacs-or-iconify-frame). If used under the X window
system, shrink the X window containing the Emacs frame to an icon (see
Kill Emacs (
If you use SXEmacs under the X window system, C-z shrinks the X window containing the Emacs frame to an icon. The Emacs process is stopped temporarily, and control is returned to the window manager. If more than one frame is associated with the Emacs process, only the frame from which you used C-z is iconified.
To activate the "suspended" Emacs, use the appropriate window manager mouse gestures. Usually left-clicking on the icon reactivates and reopens the X window containing the Emacs frame, but the window manager you use determines what exactly happens. To actually kill the Emacs process, use C-x C-c or the Exit SXEmacs item on the File menu.
To suspend Emacs, type C-z (
suspend-emacs). This takes
you back to the shell from which you invoked Emacs. You can resume
Emacs with the shell command ‘%sxemacs’ in most common shells.
On systems that do not support suspending programs, C-z starts an inferior shell that communicates directly with the terminal. Emacs waits until you exit the subshell. (The way to do that is probably with C-d or ‘exit’, but it depends on which shell you use.) The only way on these systems to get back to the shell from which Emacs was run (to log out, for example) is to kill Emacs.
Suspending also fails if you run Emacs under a shell that doesn’t
support suspending programs, even if the system itself does support it.
In such a case, you can set the variable
cannot-suspend to a
nil value to force C-z to start an inferior shell.
(One might also describe Emacs’s parent shell as “inferior” for
failing to support job control properly, but that is a matter of taste.)
When Emacs communicates directly with an X server and creates its own
dedicated X windows, C-z has a different meaning. Suspending an
applications that uses its own X windows is not meaningful or useful.
Instead, C-z runs the command
which temporarily closes up the selected Emacs frame.
The way to get back to a shell window is with the window manager.
To kill Emacs, type C-x C-c (
two-character key is used for this to make it harder to type. Selecting
the Exit SXEmacs option of the File menu is an alternate way of
issuing the command.
Unless a numeric argument is used, this command first offers to save any modified file-visiting buffers. If you do not save all buffers, you are asked for reconfirmation with yes before killing Emacs, since any changes not saved will be lost forever. If any subprocesses are still running, C-x C-c asks you to confirm killing them, since killing Emacs will kill the subprocesses immediately.
There is no way to restart an Emacs session once you have killed it. You can, however, arrange for Emacs to record certain session information, such as which files are visited, when you kill it, so that the next time you restart Emacs it will try to visit the same files and so on.
The operating system usually listens for certain special characters whose meaning is to kill or suspend the program you are running. This operating system feature is turned off while you are in Emacs. The meanings of C-z and C-x C-c as keys in Emacs were inspired by the use of C-z and 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 (see Keymaps).