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Using Multiple Buffers

The text you are editing in Emacs resides in an object called a buffer. Each time you visit a file, a buffer is created to hold the file's text. Each time you invoke Dired, a buffer is created to hold the directory listing. If you send a message with C-x m, a buffer named `*mail*' is used to hold the text of the message. When you ask for a command's documentation, that appears in a buffer called `*Help*'.

At any time, one and only one buffer is selected. It is also called the current buffer. Often we say that a command operates on "the buffer" as if there were only one; but really this means that the command operates on the selected buffer (most commands do).

When Emacs makes multiple windows, each window has a chosen buffer which is displayed there, but at any time only one of the windows is selected and its chosen buffer is the selected buffer. Each window's mode line displays the name of the buffer that the window is displaying (see section Multiple Windows).

Each buffer has a name, which can be of any length, and you can select any buffer by giving its name. Most buffers are made by visiting files, and their names are derived from the files' names. But you can also create an empty buffer with any name you want. A newly started Emacs has a buffer named `*scratch*' which can be used for evaluating Lisp expressions in Emacs. The distinction between upper and lower case matters in buffer names.

Each buffer records individually what file it is visiting, whether it is modified, and what major mode and minor modes are in effect in it (see section Major Modes). Any Emacs variable can be made local to a particular buffer, meaning its value in that buffer can be different from the value in other buffers. See section Local Variables.

Creating and Selecting Buffers

C-x b buffer RET
Select or create a buffer named buffer (switch-to-buffer).
C-x 4 b buffer RET
Similar, but select a buffer named buffer in another window (switch-to-buffer-other-window).

To select the buffer named bufname, type C-x b bufname RET. This is the command switch-to-buffer with argument bufname. You can use completion on an abbreviation for the buffer name you want (see section Completion). An empty argument to C-x b specifies the most recently selected buffer that is not displayed in any window.

Most buffers are created by visiting files, or by Emacs commands that want to display some text, but you can also create a buffer explicitly by typing C-x b bufname RET. This makes a new, empty buffer which is not visiting any file, and selects it for editing. Such buffers are used for making notes to yourself. If you try to save one, you are asked for the file name to use. The new buffer's major mode is determined by the value of default-major-mode (see section Major Modes).

Note that C-x C-f, and any other command for visiting a file, can also be used to switch buffers. See section Visiting Files.

Listing Existing Buffers

C-x C-b
List the existing buffers (list-buffers).

To print a list of all the buffers that exist, type C-x C-b. Each line in the list shows one buffer's name, major mode and visited file. `*' at the beginning of a line indicates the buffer is "modified". If several buffers are modified, it may be time to save some with C-x s (see section Saving Files). `%' indicates a read-only buffer. `.' marks the selected buffer. Here is an example of a buffer list:

 MR Buffer         Size  Mode           File
 -- ------         ----  ----           ----
.*  emacs.tex      383402 Texinfo       /u2/emacs/man/emacs.tex
    *Help*         1287  Fundamental	
    files.el       23076 Emacs-Lisp     /u2/emacs/lisp/files.el
  % RMAIL          64042 RMAIL          /u/rms/RMAIL
 *% man            747   Dired		
    net.emacs      343885 Fundamental   /u/rms/net.emacs
    fileio.c       27691 C              /u2/emacs/src/fileio.c
    NEWS           67340 Text           /u2/emacs/etc/NEWS
    *scratch*	   0	 Lisp Interaction

Note that the buffer `*Help*' was made by a help request; it is not visiting any file. The buffer `man' was made by Dired on the directory `/u2/emacs/man/'.

Miscellaneous Buffer Operations

C-x C-q
Toggle read-only status of buffer (toggle-read-only).
M-x rename-buffer
Change the name of the current buffer.
M-x view-buffer
Scroll through a buffer.

A buffer can be read-only, which means that commands to change its text are not allowed. Normally, read-only buffers are made by subsystems such as Dired and Rmail that have special commands to operate on the text; a read-only buffer is also made if you visit a file that is protected so you cannot write it. If you wish to make changes in a read-only buffer, use the command C-x C-q (toggle-read-only). It makes a read-only buffer writable, and makes a writable buffer read-only. This works by setting the variable buffer-read-only, which has a local value in each buffer and makes the buffer read-only if its value is non-nil.

M-x rename-buffer changes the name of the current buffer. Specify the new name as a minibuffer argument. There is no default. If you specify a name that is in use for some other buffer, an error happens and no renaming is done.

M-x view-buffer is much like M-x view-file (see section Miscellaneous File Operations) except that it examines an already existing Emacs buffer. View mode provides commands for scrolling through the buffer conveniently but not for changing it. When you exit View mode, the value of point that resulted from your perusal remains in effect.

The commands C-x a (append-to-buffer) and M-x insert-buffer can be used to copy text from one buffer to another. See section Accumulating Text.

Killing Buffers

After you use Emacs for a while, you may accumulate a large number of buffers. You may then find it convenient to eliminate the ones you no longer need. There are several commands provided for doing this.

C-x k
Kill a buffer, specified by name (kill-buffer).
M-x kill-some-buffers
Offer to kill each buffer, one by one.

C-x k (kill-buffer) kills one buffer, whose name you specify in the minibuffer. The default, used if you type just RET in the minibuffer, is to kill the current buffer. If the current buffer is killed, another buffer is selected; a buffer that has been selected recently but does not appear in any window now is chosen to be selected. If the buffer being killed is modified (has unsaved editing) then you are asked to confirm with yes before the buffer is killed.

The command M-x kill-some-buffers asks about each buffer, one by one. An answer of y means to kill the buffer. Killing the current buffer or a buffer containing unsaved changes selects a new buffer or asks for confirmation just like kill-buffer.

Operating on Several Buffers

The buffer-menu facility is like a "Dired for buffers"; it allows you to request operations on various Emacs buffers by editing an Emacs buffer containing a list of them. You can save buffers, kill them (here called deleting them, for consistency with Dired), or display them.

M-x buffer-menu
Begin editing a buffer listing all Emacs buffers.

The command buffer-menu writes a list of all Emacs buffers into the buffer `*Buffer List*', and selects that buffer in Buffer Menu mode. The buffer is read-only, and can only be changed through the special commands described in this section. Most of these commands are graphic characters. The usual Emacs cursor motion commands can be used in the `*Buffer List*' buffer. The following special commands apply to the buffer described on the current line.

d
Request to delete (kill) the buffer, then move down. The request shows as a `D' on the line, before the buffer name. Requested deletions take place when the x command is used.
k
Synonym for d.
C-d
Like d but move up afterwards instead of down.
s
Request to save the buffer. The request shows as an `S' on the line. Requested saves take place when the x command is used. You may request both saving and deletion for the same buffer.
~
Mark buffer "unmodified". The command ~ does this immediately when typed.
x
Perform previously requested deletions and saves.
u
Remove any request made for the current line, and move down.
DEL
Move to previous line and remove any request made for that line.

All the commands that put in or remove flags to request later operations also move down a line, and accept a numeric argument as a repeat count, unless otherwise specified.

There are also special commands to use the buffer list to select another buffer, and to specify one or more other buffers for display in additional windows.

1
Select the buffer in a full-screen window. This command takes effect immediately.
2
Immediately set up two windows, with this buffer in one, and the previously selected buffer (aside from the buffer `*Buffer List*') in the other.
f
Immediately select the buffer in place of the `*Buffer List*' buffer.
o
Immediately select the buffer in another window as if by C-x 4 b, leaving `*Buffer List*' visible.
q
Immediately select this buffer, and also display in other windows any buffers previously flagged with the m command. If there are no such buffers, this command is equivalent to 1.
m
Flag this buffer to be displayed in another window if the q command is used. The request shows as a `>' at the beginning of the line. The same buffer may not have both a delete request and a display request.

All that buffer-menu does directly is create and select a suitable buffer, and turn on Buffer Menu mode. Everything else described above is implemented by the special commands provided in Buffer Menu mode. One consequence of this is that you can switch from the `*Buffer List*' buffer to another Emacs buffer, and edit there. You can reselect the buffer-menu buffer later, to perform the operations already requested, or you can kill it, or pay no further attention to it.

The only difference between buffer-menu and list-buffers is that buffer-menu selects the `*Buffer List*' buffer and list-buffers does not. If you run list-buffers (that is, type C-x C-b) and select the buffer list manually, you can use all of the commands described here.

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