It is often useful to move point “temporarily” within a localized
portion of the program, or to switch buffers temporarily. This is
called an excursion, and it is done with the save-excursion
special form. This construct saves the current buffer and its values of
point and the mark so they can be restored after the completion of the
excursion.
The forms for saving and restoring the configuration of windows are described elsewhere (see Window Configurations and see Frame Configurations).
The save-excursion special form saves the identity of the current
buffer and the values of point and the mark in it, evaluates
forms, and finally restores the buffer and its saved values of
point and the mark. All three saved values are restored even in case of
an abnormal exit via throw or error (see Nonlocal Exits).
The save-excursion special form is the standard way to switch
buffers or move point within one part of a program and avoid affecting
the rest of the program. It is used more than 500 times in the Lisp
sources of SXEmacs.
save-excursion does not save the values of point and the mark for
other buffers, so changes in other buffers remain in effect after
save-excursion exits.
Likewise, save-excursion does not restore window-buffer
correspondences altered by functions such as switch-to-buffer.
One way to restore these correspondences, and the selected window, is to
use save-window-excursion inside save-excursion
(see Window Configurations).
The value returned by save-excursion is the result of the last of
forms, or nil if no forms are given.
(save-excursion
forms)
≡
(let ((old-buf (current-buffer))
(old-pnt (point-marker))
(old-mark (copy-marker (mark-marker))))
(unwind-protect
(progn forms)
(set-buffer old-buf)
(goto-char old-pnt)
(set-marker (mark-marker) old-mark)))
This special form is similar to save-excursion but it only
saves and restores the current buffer. Beginning with XEmacs 20.3,
save-current-buffer is a primitive.
This special form evaluates forms with buffer as the current buffer. It returns the value of the last form.
This special form creates a new buffer, evaluates forms there, and writes the buffer to filename. It returns the value of the last form evaluated.
This special form is similar to save-excursion but it saves and
restores the selected window and nothing else.