makes a backup from the previous contents, and arranges to make
another from the newly saved contents if you save again.
+@vindex backup-directory-alist
+ You can customize the variable @code{backup-directory-alist} to
+specify that files matching certain patterns should be backed up in
+specific directories. A typical use is to add an element @code{("."
+. @var{dir})} to make all backups in the directory with absolute name
+@var{dir}. Emacs modifies the backup file names to avoid clashes
+between files with the same names originating in different
+directories. Alternatively, adding, @code{("." . ".~")} would make
+backups in the invisible subdirectory @file{.~} of the original file's
+directory. Emacs creates the directory, if necessary, to make the
+backup.
+
@menu
* Names: Backup Names. How backup files are named.
* Deletion: Backup Deletion. Emacs deletes excess numbered backups.
@node Backup Names
@subsubsection Single or Numbered Backups
+@cindex backup file names
+@cindex names of backup files
+@cindex @file{~}, in names of backup files
+@cindex tilde (@file{~}) at end of backup file name
When Emacs makes a backup file, its name is normally constructed by
appending @samp{~} to the file name being edited; thus, the backup
file for @file{eval.c} would be @file{eval.c~}.
+@cindex @file{~/.emacs.d/%backup%~}
If access control stops Emacs from writing backup files under the
usual names, it writes the backup file as @file{~/.emacs.d/%backup%~}.
Only one such file can exist, so only the most recently made such
becomes @code{nil}; if it is @samp{never} or @samp{simple}, then
@code{version-control} becomes @code{never}.
-@vindex backup-directory-alist
- You can customize the variable @code{backup-directory-alist} to
-specify that files matching certain patterns should be backed up in
-specific directories. This variable applies to both single and
-numbered backups. A typical use is to add an element @code{("."
-. @var{dir})} to make all backups in the directory with absolute name
-@var{dir}; Emacs modifies the backup file names to avoid clashes
-between files with the same names originating in different
-directories. Alternatively, adding, @code{("." . ".~")} would make
-backups in the invisible subdirectory @file{.~} of the original file's
-directory. Emacs creates the directory, if necessary, to make the
-backup.
-
@vindex make-backup-file-name-function
If you set the variable @code{make-backup-file-name-function} to
a suitable Lisp function, you can override the usual way Emacs
@code{before-save-hook} (@pxref{Hooks}). When you save the file, this
function then automatically updates the time stamp with the current
date and time. You can also use the command @kbd{M-x time-stamp} to
-update the time stamp manually. For other customizations, see the
-Custom group @code{time-stamp}. Note that the time stamp is formatted
-according to your locale setting (@pxref{Environment}).
+update the time stamp manually. By default the time stamp is
+formatted according to your locale setting (@pxref{Environment}) and
+time zone (@pxref{Time of Day,,, elisp, The Emacs Lisp Reference
+Manual}). For customizations, see the Custom group @code{time-stamp}.
@node Reverting
@section Reverting a Buffer
@c Note that the actual name of the info file is diffutils.info,
@c but it adds a dir entry for diff too.
@c On older systems, only "info diff" works, not "info diffutils".
-@xref{Top,, Diff, diff, Comparing and Merging Files}, for more
+@xref{Top,, Diff, diffutils, Comparing and Merging Files}, for more
information about the @command{diff} program.
The output of the @code{diff} command is shown using a major mode
major mode, you can type @kbd{C-c C-c} (@code{image-toggle-display})
to toggle between displaying the file as an image in the Emacs buffer,
and displaying its underlying text (or raw byte) representation.
+Additionally you can type @kbd{C-c C-x} (@code{image-toggle-hex-display})
+to toggle between displaying the file as an image in the Emacs buffer,
+and displaying it in hex representation.
Displaying the file as an image works only if Emacs is compiled with
support for displaying such images. If the displayed image is wider
or taller than the frame, the usual point motion keys (@kbd{C-f},