@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990-1995, 1999, 2001-2012 Free Software Foundation, Inc.
+@c Copyright (C) 1990-1995, 1999, 2001-2014 Free Software Foundation,
+@c Inc.
@c See the file elisp.texi for copying conditions.
-@setfilename ../../info/backups
-@node Backups and Auto-Saving, Buffers, Files, Top
+@node Backups and Auto-Saving
@chapter Backups and Auto-Saving
@cindex backups and auto-saving
@node Making Backups
@subsection Making Backup Files
+@cindex making backup files
@defun backup-buffer
This function makes a backup of the file visited by the current
saving the buffer the first time.
If a backup was made by renaming, the return value is a cons cell of
-the form (@var{modes} . @var{backupname}), where @var{modes} are the
-mode bits of the original file, as returned by @code{file-modes}
-(@pxref{File Attributes,, Other Information about Files}), and
-@var{backupname} is the name of the backup. In all other cases, that
-is, if a backup was made by copying or if no backup was made, this
-function returns @code{nil}.
+the form (@var{modes} @var{extra-alist} @var{backupname}), where
+@var{modes} are the mode bits of the original file, as returned by
+@code{file-modes} (@pxref{Testing Accessibility}), @var{extra-alist}
+is an alist describing the original file's extended attributes, as
+returned by @code{file-extended-attributes} (@pxref{Extended
+Attributes}), and @var{backupname} is the name of the backup.
+
+In all other cases (i.e., if a backup was made by copying or if no
+backup was made), this function returns @code{nil}.
@end defun
@defvar buffer-backed-up
@smallexample
@group
(add-hook 'rmail-mode-hook
- (lambda ()
- (set (make-local-variable 'make-backup-files) nil)))
+ (lambda () (setq-local make-backup-files nil)))
@end group
@end smallexample
@end defopt
should contain a single element pairing @samp{"."} with the appropriate
directory name.
-If this variable is @code{nil}, or it fails to match a filename, the
-backup is made in the original file's directory.
+If this variable is @code{nil} (the default), or it fails to match a
+filename, the backup is made in the original file's directory.
On MS-DOS filesystems without long names this variable is always
ignored.
@end defopt
@defopt make-backup-file-name-function
-This variable's value is a function to use for making backups instead
-of the default @code{make-backup-file-name}. A value of @code{nil}
-gives the default @code{make-backup-file-name} behavior.
+This variable's value is a function to use for making backup file names.
+The function @code{make-backup-file-name} calls it.
@xref{Backup Names,, Naming Backup Files}.
This could be buffer-local to do something special for specific
-files. If you define it, you may need to change
+files. If you change it, you may need to change
@code{backup-file-name-p} and @code{file-name-sans-versions} too.
@end defopt
@defopt backup-by-copying
If this variable is non-@code{nil}, Emacs always makes backup files by
-copying.
+copying. The default is @code{nil}.
@end defopt
The following three variables, when non-@code{nil}, cause the second
@defopt backup-by-copying-when-linked
If this variable is non-@code{nil}, Emacs makes backups by copying for
-files with multiple names (hard links).
+files with multiple names (hard links). The default is @code{nil}.
This variable is significant only if @code{backup-by-copying} is
@code{nil}, since copying is always used when that variable is
@end defopt
@defopt backup-by-copying-when-mismatch
-If this variable is non-@code{nil}, Emacs makes backups by copying in cases
-where renaming would change either the owner or the group of the file.
+If this variable is non-@code{nil} (the default), Emacs makes backups
+by copying in cases where renaming would change either the owner or
+the group of the file.
The value has no effect when renaming would not alter the owner or
group of the file; that is, for files which are owned by the user and
@node Numbered Backups
@subsection Making and Deleting Numbered Backup Files
+@cindex numbered backups
If a file's name is @file{foo}, the names of its numbered backup
versions are @file{foo.~@var{v}~}, for various integers @var{v}, like
@node Backup Names
@subsection Naming Backup Files
+@cindex naming backup files
The functions in this section are documented mainly because you can
customize the naming conventions for backup files by redefining them.
@end defvar
@deffn Command auto-save-mode arg
-When used interactively without an argument, this command is a toggle
-switch: it turns on auto-saving of the current buffer if it is off, and
-vice versa. With an argument @var{arg}, the command turns auto-saving
-on if the value of @var{arg} is @code{t}, a nonempty list, or a positive
-integer. Otherwise, it turns auto-saving off.
+This is the mode command for Auto Save mode, a buffer-local minor
+mode. When Auto Save mode is enabled, auto-saving is enabled in the
+buffer. The calling convention is the same as for other minor mode
+commands (@pxref{Minor Mode Conventions}).
+
+Unlike most minor modes, there is no @code{auto-save-mode} variable.
+Auto Save mode is enabled if @code{buffer-auto-save-file-name} is
+non-@code{nil} and @code{buffer-saved-size} (see below) is non-zero.
@end deffn
@defun auto-save-file-name-p filename
After Emacs reads your init file, it initializes
@code{auto-save-list-file-name} (if you have not already set it
non-@code{nil}) based on this prefix, adding the host name and process
-ID. If you set this to @code{nil} in your init file, then Emacs does
+ID@. If you set this to @code{nil} in your init file, then Emacs does
not initialize @code{auto-save-list-file-name}.
@end defopt
@node Reverting
@section Reverting
+@cindex reverting buffers
If you have made extensive changes to a file and then change your mind
about them, you can get rid of them by reading in the previous version
the buffer. Preserving any additional markers would be problematical.
@end deffn
+@defvar revert-buffer-in-progress-p
+@code{revert-buffer} binds this variable to a non-@code{nil} value
+while it is working.
+@end defvar
+
You can customize how @code{revert-buffer} does its work by setting
the variables described in the rest of this section.
@defvar revert-buffer-function
@anchor{Definition of revert-buffer-function}
The value of this variable is the function to use to revert this
-buffer. If non-@code{nil}, it should be a function with two optional
+buffer. It should be a function with two optional
arguments to do the work of reverting. The two optional arguments,
@var{ignore-auto} and @var{noconfirm}, are the arguments that
-@code{revert-buffer} received. If the value is @code{nil}, reverting
-works the usual way.
+@code{revert-buffer} received.
Modes such as Dired mode, in which the text being edited does not
consist of a file's contents but can be regenerated in some other
-fashion, can give this variable a buffer-local value that is a function to
-regenerate the contents.
+fashion, can give this variable a buffer-local value that is a special
+function to regenerate the contents.
@end defvar
@defvar revert-buffer-insert-file-contents-function
-The value of this variable, if non-@code{nil}, specifies the function to use to
+The value of this variable specifies the function to use to
insert the updated contents when reverting this buffer. The function
receives two arguments: first the file name to use; second, @code{t} if
the user has asked to read the auto-save file.
-The reason for a mode to set this variable instead of
+The reason for a mode to change this variable instead of
@code{revert-buffer-function} is to avoid duplicating or replacing the
rest of what @code{revert-buffer} does: asking for confirmation,
clearing the undo list, deciding the proper major mode, and running the
@end defvar
@defvar before-revert-hook
-This normal hook is run by @code{revert-buffer} before
-inserting the modified contents---but only if
-@code{revert-buffer-function} is @code{nil}.
+This normal hook is run by the default @code{revert-buffer-function}
+before inserting the modified contents. A custom @code{revert-buffer-function}
+may or may not run this hook.
@end defvar
@defvar after-revert-hook
-This normal hook is run by @code{revert-buffer} after inserting
-the modified contents---but only if @code{revert-buffer-function} is
-@code{nil}.
+This normal hook is run by the default @code{revert-buffer-function}
+after inserting the modified contents. A custom @code{revert-buffer-function}
+may or may not run this hook.
+@end defvar
+
+@c FIXME? Move this section from arevert-xtra to here?
+@defvar buffer-stale-function
+The value of this variable specifies a function to call to check
+whether a buffer needs reverting. The default value only handles
+buffers that are visiting files, by checking their modification time.
+Buffers that are not visiting files require a custom function
+@iftex
+(@pxref{Supporting additional buffers,,, emacs-xtra, Specialized Emacs Features}).
+@end iftex
+@ifnottex
+(@pxref{Supporting additional buffers,,, emacs}).
+@end ifnottex
@end defvar