37.3 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 named 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 actually 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 &optional ignore

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 ‘<…>’.

If ignore is given, it specifies a name that is okay to use (if it is in the sequence to be tried), even if a buffer with that name exists.

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