GNU Emacs Lisp Reference Manual

24.3: Buffer Names

Each buffer has a unique name, which is a string. Many of the functions that work on buffers accept either a buffer or a buffer name as an argument. Any argument called buffer-or-name is of this sort, and an error is signaled if it is neither a string nor a buffer. Any argument called buffer must be an actual buffer object, not a name.

Buffers that are ephemeral and generally uninteresting to the user have names starting with a space, so that the list-buffers and buffer-menu commands don't mention them. A name starting with space also initially disables recording undo information; see Undo.

Function: buffer-name &optional buffer

This function returns the name of buffer as a string. If buffer is not supplied, it defaults to the current buffer.

If buffer-name returns nil, it means that buffer has been killed. See Killing Buffers.

(buffer-name)
     => "buffers.texi"
(setq foo (get-buffer "temp"))
     => #<buffer temp>
(kill-buffer foo)
     => nil
(buffer-name foo)
     => nil
foo
     => #<killed buffer>

Command: rename-buffer newname &optional unique

This function renames the current buffer to newname. An error is signaled if newname is not a string, or if there is already a buffer with that name. The function returns nil.

Ordinarily, rename-buffer signals an error if newname is already in use. However, if unique is non-nil, it modifies newname to make a name that is not in use. Interactively, you can make unique non-nil with a numeric prefix argument.

One application of this command is to rename the *shell* buffer to some other name, thus making it possible to create a second shell buffer under the name *shell*.

Function: get-buffer buffer-or-name

This function returns the buffer specified by buffer-or-name. If buffer-or-name is a string and there is no buffer with that name, the value is nil. If buffer-or-name is a buffer, it is returned as given. (That is not very useful, so the argument is usually a name.) For example:

(setq b (get-buffer "lewis"))
     => #<buffer lewis>
(get-buffer b)
     => #<buffer lewis>
(get-buffer "Frazzle-nots")
     => nil

See also the function get-buffer-create in Creating Buffers.

Function: generate-new-buffer-name starting-name

This function returns a name that would be unique for a new buffer---but does not create the buffer. It starts with starting-name, and produces a name not currently in use for any buffer by appending a number inside of <...>.

See the related function generate-new-buffer in Creating Buffers.