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37.10 Killing Buffers

Killing a buffer makes its name unknown to SXEmacs and makes its text space available for other use.

The buffer object for the buffer that has been killed remains in existence as long as anything refers to it, but it is specially marked so that you cannot make it current or display it. Killed buffers retain their identity, however; two distinct buffers, when killed, remain distinct according to eq.

If you kill a buffer that is current or displayed in a window, SXEmacs automatically selects or displays some other buffer instead. This means that killing a buffer can in general change the current buffer. Therefore, when you kill a buffer, you should also take the precautions associated with changing the current buffer (unless you happen to know that the buffer being killed isn't current). See Current Buffer.

If you kill a buffer that is the base buffer of one or more indirect buffers, the indirect buffers are automatically killed as well.

The buffer-name of a killed buffer is nil. To test whether a buffer has been killed, you can either use this feature or the function buffer-live-p.

— Function: buffer-live-p object

This function returns t if object is an editor buffer that has not been deleted, nil otherwise.

— Command: kill-buffer buffer-or-name

This function kills the buffer buffer-or-name, freeing all its memory for use as space for other buffers.

It returns nil. The argument buffer-or-name may be a buffer or the name of one.

Note: Emacs version 18 and older was unable to return the memory to the operating system.

Any processes that have this buffer as the process-buffer are sent the SIGHUP signal, which normally causes them to terminate. (The basic meaning of SIGHUP is that a dialup line has been disconnected.) See Deleting Processes.

If the buffer is visiting a file and contains unsaved changes, kill-buffer asks the user to confirm before the buffer is killed. It does this even if not called interactively. To prevent the request for confirmation, clear the modified flag before calling kill-buffer. See Buffer Modification.

Killing a buffer that is already dead has no effect. 

          (kill-buffer "foo.unchanged")
               ⇒ nil
          (kill-buffer "foo.changed")
          
          ---------- Buffer: Minibuffer ----------
          Buffer foo.changed modified; kill anyway? (yes or no) yes
          ---------- Buffer: Minibuffer ----------
          
               ⇒ nil
— Variable: kill-buffer-query-functions

After confirming unsaved changes, kill-buffer calls the functions in the list kill-buffer-query-functions, in order of appearance, with no arguments. The buffer being killed is the current buffer when they are called. The idea is that these functions ask for confirmation from the user for various nonstandard reasons. If any of them returns nil, kill-buffer spares the buffer's life.

— Variable: kill-buffer-hook

This is a normal hook run by kill-buffer after asking all the questions it is going to ask, just before actually killing the buffer. The buffer to be killed is current when the hook functions run. See Hooks.

— Variable: buffer-offer-save

This variable, if non-nil in a particular buffer, tells save-buffers-kill-emacs and save-some-buffers to offer to save that buffer, just as they offer to save file-visiting buffers. The variable buffer-offer-save automatically becomes buffer-local when set for any reason. See Buffer-Local Variables.