(save-buffers-kill-emacs): Fix backward test of value of

[bpt/emacs.git] / lisp / files.el

;;; files.el --- file input and output commands for Emacs

;; Copyright (C) 1985, 86, 87, 92, 93, 94 Free Software Foundation, Inc.

;; Maintainer: FSF

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to
;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

;;; Commentary:

;; Defines most of Emacs's file- and directory-handling functions,
;; including basic file visiting, backup generation, link handling,
;; ITS-id version control, load- and write-hook handling, and the like.

;;; Code:

(defconst delete-auto-save-files t
  "*Non-nil means delete auto-save file when a buffer is saved or killed.")

(defconst directory-abbrev-alist
  nil
  "*Alist of abbreviations for file directories.
A list of elements of the form (FROM . TO), each meaning to replace
FROM with TO when it appears in a directory name.  This replacement is
done when setting up the default directory of a newly visited file.
*Every* FROM string should start with `^'.

Do not use `~' in the TO strings.
They should be ordinary absolute directory names.

Use this feature when you have directories which you normally refer to
via absolute symbolic links.  Make TO the name of the link, and FROM
the name it is linked to.")

;;; Turn off backup files on VMS since it has version numbers.
(defconst make-backup-files (not (eq system-type 'vax-vms))
  "*Non-nil means make a backup of a file the first time it is saved.
This can be done by renaming the file or by copying.

Renaming means that Emacs renames the existing file so that it is a
backup file, then writes the buffer into a new file.  Any other names
that the old file had will now refer to the backup file.  The new file
is owned by you and its group is defaulted.

Copying means that Emacs copies the existing file into the backup
file, then writes the buffer on top of the existing file.  Any other
names that the old file had will now refer to the new (edited) file.
The file's owner and group are unchanged.

The choice of renaming or copying is controlled by the variables
`backup-by-copying', `backup-by-copying-when-linked' and
`backup-by-copying-when-mismatch'.  See also `backup-inhibited'.")

;; Do this so that local variables based on the file name
;; are not overridden by the major mode.
(defvar backup-inhibited nil
  "Non-nil means don't make a backup, regardless of the other parameters.
This variable is intended for use by making it local to a buffer.
But it is local only if you make it local.")
(put 'backup-inhibited 'permanent-local t)

(defconst backup-by-copying nil
 "*Non-nil means always use copying to create backup files.
See documentation of variable `make-backup-files'.")

(defconst backup-by-copying-when-linked nil
 "*Non-nil means use copying to create backups for files with multiple names.
This causes the alternate names to refer to the latest version as edited.
This variable is relevant only if `backup-by-copying' is nil.")

(defconst backup-by-copying-when-mismatch nil
  "*Non-nil means create backups by copying if this preserves owner or group.
Renaming may still be used (subject to control of other variables)
when it would not result in changing the owner or group of the file;
that is, for files which are owned by you and whose group matches
the default for a new file created there by you.
This variable is relevant only if `backup-by-copying' is nil.")

(defvar backup-enable-predicate
  '(lambda (name)
     (or (< (length name) 5)
         (not (string-equal "/tmp/" (substring name 0 5)))))
  "Predicate that looks at a file name and decides whether to make backups.
Called with an absolute file name as argument, it returns t to enable backup.")

(defconst buffer-offer-save nil
  "*Non-nil in a buffer means offer to save the buffer on exit
even if the buffer is not visiting a file.
Automatically local in all buffers.")
(make-variable-buffer-local 'buffer-offer-save)

(defconst find-file-existing-other-name nil
  "*Non-nil means find a file under alternative names, in existing buffers.
This means if any existing buffer is visiting the file you want
under another name, you get the existing buffer instead of a new buffer.")

(defconst find-file-visit-truename nil
  "*Non-nil means visit a file under its truename.
The truename of a file is found by chasing all links
both at the file level and at the levels of the containing directories.")

(defvar buffer-file-truename nil
  "The abbreviated truename of the file visited in the current buffer.
That is, (abbreviate-file-name (file-truename buffer-file-name)).
This variable is automatically local in all buffers, when non-nil.")
(make-variable-buffer-local 'buffer-file-truename)
(put 'buffer-file-truename 'permanent-local t)

(defvar buffer-file-number nil
  "The device number and file number of the file visited in the current buffer.
The value is a list of the form (FILENUM DEVNUM).
This pair of numbers uniquely identifies the file.
If the buffer is visiting a new file, the value is nil.")
(make-variable-buffer-local 'buffer-file-number)
(put 'buffer-file-number 'permanent-local t)

(defconst file-precious-flag nil
  "*Non-nil means protect against I/O errors while saving files.
Some modes set this non-nil in particular buffers.")

(defvar version-control nil
  "*Control use of version numbers for backup files.
t means make numeric backup versions unconditionally.
nil means make them for files that have some already.
`never' means do not make them.")

(defvar dired-kept-versions 2
  "*When cleaning directory, number of versions to keep.")

(defvar delete-old-versions nil
  "*If t, delete excess backup versions silently.
If nil, ask confirmation.  Any other value prevents any trimming.")

(defvar kept-old-versions 2
  "*Number of oldest versions to keep when a new numbered backup is made.")

(defvar kept-new-versions 2
  "*Number of newest versions to keep when a new numbered backup is made.
Includes the new backup.  Must be > 0")

(defconst require-final-newline nil
  "*Value of t says silently ensure a file ends in a newline when it is saved.
Non-nil but not t says ask user whether to add a newline when there isn't one.
nil means don't add newlines.")

(defconst auto-save-default t
  "*Non-nil says by default do auto-saving of every file-visiting buffer.")

(defconst auto-save-visited-file-name nil
  "*Non-nil says auto-save a buffer in the file it is visiting, when practical.
Normally auto-save files are written under other names.")

(defconst save-abbrevs nil
  "*Non-nil means save word abbrevs too when files are saved.
Loading an abbrev file sets this to t.")

(defconst find-file-run-dired t
  "*Non-nil says run dired if `find-file' is given the name of a directory.")

;;;It is not useful to make this a local variable.
;;;(put 'find-file-not-found-hooks 'permanent-local t)
(defvar find-file-not-found-hooks nil
  "List of functions to be called for `find-file' on nonexistent file.
These functions are called as soon as the error is detected.
`buffer-file-name' is already set up.
The functions are called in the order given until one of them returns non-nil.")

;;;It is not useful to make this a local variable.
;;;(put 'find-file-hooks 'permanent-local t)
(defvar find-file-hooks nil
  "List of functions to be called after a buffer is loaded from a file.
The buffer's local variables (if any) will have been processed before the
functions are called.")

(defvar write-file-hooks nil
  "List of functions to be called before writing out a buffer to a file.
If one of them returns non-nil, the file is considered already written
and the rest are not called.
These hooks are considered to pertain to the visited file.
So this list is cleared if you change the visited file name.
See also `write-contents-hooks'.
Don't make this variable buffer-local; instead, use `local-write-file-hooks'.")
;;; However, in case someone does make it local...
(put 'write-file-hooks 'permanent-local t)

(defvar local-write-file-hooks nil
  "Just like `write-file-hooks', except intended for per-buffer use.
The functions in this list are called before the ones in
`write-file-hooks'.")
(make-variable-buffer-local 'local-write-file-hooks)
(put 'local-write-file-hooks 'permanent-local t)

(defvar write-contents-hooks nil
  "List of functions to be called before writing out a buffer to a file.
If one of them returns non-nil, the file is considered already written
and the rest are not called.
These hooks are considered to pertain to the buffer's contents,
not to the particular visited file; thus, `set-visited-file-name' does
not clear this variable, but changing the major mode does clear it.
See also `write-file-hooks'.")

(defconst enable-local-variables t
  "*Control use of local-variables lists in files you visit.
The value can be t, nil or something else.
A value of t means local-variables lists are obeyed;
nil means they are ignored; anything else means query.

The command \\[normal-mode] always obeys local-variables lists
and ignores this variable.")

(defconst enable-local-eval 'maybe
  "*Control processing of the \"variable\" `eval' in a file's local variables.
The value can be t, nil or something else.
A value of t means obey `eval' variables;
nil means ignore them; anything else means query.

The command \\[normal-mode] always obeys local-variables lists
and ignores this variable.")

;; Avoid losing in versions where CLASH_DETECTION is disabled.
(or (fboundp 'lock-buffer)
    (defalias 'lock-buffer 'ignore))
(or (fboundp 'unlock-buffer)
    (defalias 'unlock-buffer 'ignore))

;; This hook function provides support for ange-ftp host name
;; completion.  It runs the usual ange-ftp hook, but only for
;; completion operations.  Having this here avoids the need
;; to load ange-ftp when it's not really in use.
(defun ange-ftp-completion-hook-function (op &rest args)
  (if (memq op '(file-name-completion file-name-all-completions))
      (apply 'ange-ftp-hook-function op args)
    (let ((inhibit-file-name-handlers
           (cons 'ange-ftp-completion-hook-function
                 (and (eq inhibit-file-name-operation op)
                      inhibit-file-name-handlers)))
          (inhibit-file-name-operation op))
      (apply op args))))
\f
(defun pwd ()
  "Show the current default directory."
  (interactive nil)
  (message "Directory %s" default-directory))

(defvar cd-path nil
  "Value of the CDPATH environment variable, as a list.
Not actually set up until the first time you you use it.")

(defun parse-colon-path (cd-path)
  "Explode a colon-separated list of paths into a string list."
  (and cd-path
       (let (cd-prefix cd-list (cd-start 0) cd-colon)
         (setq cd-path (concat cd-path ":"))
         (while (setq cd-colon (string-match ":" cd-path cd-start))
           (setq cd-list
                 (nconc cd-list
                        (list (if (= cd-start cd-colon)
                                   nil
                                (substitute-in-file-name
                                 (file-name-as-directory
                                  (substring cd-path cd-start cd-colon)))))))
           (setq cd-start (+ cd-colon 1)))
         cd-list)))

(defun cd-absolute (dir)
  "Change current directory to given absolute file name DIR."
  ;; Put the name into directory syntax now,
  ;; because otherwise expand-file-name may give some bad results.
  (if (not (eq system-type 'vax-vms))
      (setq dir (file-name-as-directory dir)))
  (setq dir (abbreviate-file-name (expand-file-name dir)))
  (if (not (file-directory-p dir))
      (error "%s is not a directory" dir)
    (if (file-executable-p dir)
        (setq default-directory dir)
      (error "Cannot cd to %s:  Permission denied" dir))))

(defun cd (dir)
  "Make DIR become the current buffer's default directory.
If your environment includes a `CDPATH' variable, try each one of that
colon-separated list of directories when resolving a relative directory name."
  (interactive "FChange default directory: ")
  (if (file-name-absolute-p dir)
      (cd-absolute (expand-file-name dir))
    (if (null cd-path)
        (let ((trypath (parse-colon-path (getenv "CDPATH"))))
          (setq cd-path (or trypath (list "./")))))
    (if (not (catch 'found
               (mapcar
                (function (lambda (x)
                            (let ((f (expand-file-name (concat x dir))))
                              (if (file-directory-p f)
                                  (progn
                                    (cd-absolute f)
                                    (throw 'found t))))))
                cd-path)
               nil))
        (error "No such directory found via CDPATH environment variable"))))

(defun load-file (file)
  "Load the Lisp file named FILE."
  (interactive "fLoad file: ")
  (load (expand-file-name file) nil nil t))

(defun load-library (library)
  "Load the library named LIBRARY.
This is an interface to the function `load'."
  (interactive "sLoad library: ")
  (load library))

(defun file-local-copy (file &optional buffer)
  "Copy the file FILE into a temporary file on this machine.
Returns the name of the local copy, or nil, if FILE is directly
accessible."
  (let ((handler (find-file-name-handler file 'file-local-copy)))
    (if handler
        (funcall handler 'file-local-copy file)
      nil)))

(defun file-truename (filename &optional counter prev-dirs)
  "Return the truename of FILENAME, which should be absolute.
The truename of a file name is found by chasing symbolic links
both at the level of the file and at the level of the directories
containing it, until no links are left at any level.

The arguments COUNTER and PREV-DIRS are used only in recursive calls.
Do not specify them in other calls."
  ;; COUNTER can be a cons cell whose car is the count of how many more links
  ;; to chase before getting an error.
  ;; PREV-DIRS can be a cons cell whose car is an alist
  ;; of truenames we've just recently computed.
  (if (or (string= filename "~")
          (and (string= (substring filename 0 1) "~")
               (string-match "~[^/]*" filename)))
      (progn
        (setq filename (expand-file-name filename))
        (if (string= filename "")
            (setq filename "/"))))
  (or counter (setq counter (list 100)))
  (let (done
        ;; For speed, remove the ange-ftp completion handler from the list.
        ;; We know it's not needed here.
        ;; For even more speed, do this only on the outermost call.
        (file-name-handler-alist
         (if prev-dirs file-name-handler-alist
           (let ((tem (copy-sequence file-name-handler-alist)))
             (delq (rassq 'ange-ftp-completion-hook-function tem) tem)))))
    (or prev-dirs (setq prev-dirs (list nil)))
    ;; If this file directly leads to a link, process that iteratively
    ;; so that we don't use lots of stack.
    (while (not done)
      (setcar counter (1- (car counter)))
      (if (< (car counter) 0)
          (error "Apparent cycle of symbolic links for %s" filename))
      (let ((handler (find-file-name-handler filename 'file-truename)))
        ;; For file name that has a special handler, call handler.
        ;; This is so that ange-ftp can save time by doing a no-op.
        (if handler
            (setq filename (funcall handler 'file-truename filename)
                  done t)
          (let ((dir (or (file-name-directory filename) default-directory))
                target dirfile)
            ;; Get the truename of the directory.
            (setq dirfile (directory-file-name dir))
            ;; If these are equal, we have the (or a) root directory.
            (or (string= dir dirfile)
                ;; If this is the same dir we last got the truename for,
                ;; save time--don't recalculate.
                (if (assoc dir (car prev-dirs))
                    (setq dir (cdr (assoc dir (car prev-dirs))))
                  (let ((old dir)
                        (new (file-name-as-directory (file-truename dirfile counter prev-dirs))))
                    (setcar prev-dirs (cons (cons old new) (car prev-dirs)))
                    (setq dir new))))
            (if (equal ".." (file-name-nondirectory filename))
                (setq filename
                      (directory-file-name (file-name-directory (directory-file-name dir)))
                      done t)
              (if (equal "." (file-name-nondirectory filename))
                  (setq filename (directory-file-name dir)
                        done t)
                ;; Put it back on the file name.
                (setq filename (concat dir (file-name-nondirectory filename)))
                ;; Is the file name the name of a link?
                (setq target (file-symlink-p filename))
                (if target
                    ;; Yes => chase that link, then start all over
                    ;; since the link may point to a directory name that uses links.
                    ;; We can't safely use expand-file-name here
                    ;; since target might look like foo/../bar where foo
                    ;; is itself a link.  Instead, we handle . and .. above.
                    (setq filename
                          (if (file-name-absolute-p target)
                              target
                            (concat dir target))
                          done nil)
                  ;; No, we are done!
                  (setq done t))))))))
    filename))

(defun file-chase-links (filename)
  "Chase links in FILENAME until a name that is not a link.
Does not examine containing directories for links,
unlike `file-truename'."
  (let (tem (count 100) (newname filename))
    (while (setq tem (file-symlink-p newname))
      (if (= count 0)
          (error "Apparent cycle of symbolic links for %s" filename))
      ;; In the context of a link, `//' doesn't mean what Emacs thinks.
      (while (string-match "//+" tem)
        (setq tem (concat (substring tem 0 (1+ (match-beginning 0)))
                          (substring tem (match-end 0)))))
      ;; Handle `..' by hand, since it needs to work in the
      ;; target of any directory symlink.
      ;; This code is not quite complete; it does not handle
      ;; embedded .. in some cases such as ./../foo and foo/bar/../../../lose.
      (while (string-match "\\`\\.\\./" tem)
        (setq tem (substring tem 3))
        (setq newname (file-name-as-directory
                       ;; Do the .. by hand.
                       (directory-file-name
                        (file-name-directory
                         ;; Chase links in the default dir of the symlink.
                         (file-chase-links
                          (directory-file-name
                           (file-name-directory newname))))))))
      (setq newname (expand-file-name tem (file-name-directory newname)))
      (setq count (1- count)))
    newname))
\f
(defun switch-to-buffer-other-window (buffer)
  "Select buffer BUFFER in another window."
  (interactive "BSwitch to buffer in other window: ")
  (let ((pop-up-windows t))
    (pop-to-buffer buffer t)))

(defun switch-to-buffer-other-frame (buffer)
  "Switch to buffer BUFFER in another frame."
  (interactive "BSwitch to buffer in other frame: ")
  (let ((pop-up-frames t))
    (pop-to-buffer buffer t)
    (raise-frame (window-frame (selected-window)))))

(defun find-file (filename)
  "Edit file FILENAME.
Switch to a buffer visiting file FILENAME,
creating one if none already exists."
  (interactive "FFind file: ")
  (switch-to-buffer (find-file-noselect filename)))

(defun find-file-other-window (filename)
  "Edit file FILENAME, in another window.
May create a new window, or reuse an existing one.
See the function `display-buffer'."
  (interactive "FFind file in other window: ")
  (switch-to-buffer-other-window (find-file-noselect filename)))

(defun find-file-other-frame (filename)
  "Edit file FILENAME, in another frame.
May create a new frame, or reuse an existing one.
See the function `display-buffer'."
  (interactive "FFind file in other frame: ")
  (switch-to-buffer-other-frame (find-file-noselect filename)))

(defun find-file-read-only (filename)
  "Edit file FILENAME but don't allow changes.
Like \\[find-file] but marks buffer as read-only.
Use \\[toggle-read-only] to permit editing."
  (interactive "fFind file read-only: ")
  (find-file filename)
  (setq buffer-read-only t)
  (current-buffer))

(defun find-file-read-only-other-window (filename)
  "Edit file FILENAME in another window but don't allow changes.
Like \\[find-file-other-window] but marks buffer as read-only.
Use \\[toggle-read-only] to permit editing."
  (interactive "fFind file read-only other window: ")
  (find-file-other-window filename)
  (setq buffer-read-only t)
  (current-buffer))

(defun find-file-read-only-other-frame (filename)
  "Edit file FILENAME in another frame but don't allow changes.
Like \\[find-file-other-frame] but marks buffer as read-only.
Use \\[toggle-read-only] to permit editing."
  (interactive "fFind file read-only other frame: ")
  (find-file-other-frame filename)
  (setq buffer-read-only t)
  (current-buffer))

(defun find-alternate-file (filename)
  "Find file FILENAME, select its buffer, kill previous buffer.
If the current buffer now contains an empty file that you just visited
\(presumably by mistake), use this command to visit the file you really want."
  (interactive
   (let ((file buffer-file-name)
         (file-name nil)
         (file-dir nil))
     (and file
          (setq file-name (file-name-nondirectory file)
                file-dir (file-name-directory file)))
     (list (read-file-name
            "Find alternate file: " file-dir nil nil file-name))))
  (and (buffer-modified-p) (buffer-file-name)
       ;; (not buffer-read-only)
       (not (yes-or-no-p (format "Buffer %s is modified; kill anyway? "
                                 (buffer-name))))
       (error "Aborted"))
  (let ((obuf (current-buffer))
        (ofile buffer-file-name)
        (onum buffer-file-number)
        (otrue buffer-file-truename)
        (oname (buffer-name)))
    (rename-buffer " **lose**")
    (setq buffer-file-name nil)
    (setq buffer-file-number nil)
    (setq buffer-file-truename nil)
    (unwind-protect
        (progn
          (unlock-buffer)
          (find-file filename))
      (cond ((eq obuf (current-buffer))
             (setq buffer-file-name ofile)
             (setq buffer-file-number onum)
             (setq buffer-file-truename otrue)
             (lock-buffer)
             (rename-buffer oname))))
    (or (eq (current-buffer) obuf)
        (kill-buffer obuf))))

(defun create-file-buffer (filename)
  "Create a suitably named buffer for visiting FILENAME, and return it.
FILENAME (sans directory) is used unchanged if that name is free;
otherwise a string <2> or <3> or ... is appended to get an unused name."
  (let ((lastname (file-name-nondirectory filename)))
    (if (string= lastname "")
        (setq lastname filename))
    (generate-new-buffer lastname)))

(defun generate-new-buffer (name)
  "Create and return a buffer with a name based on NAME.
Choose the buffer's name using `generate-new-buffer-name'."
  (get-buffer-create (generate-new-buffer-name name)))

(defconst automount-dir-prefix "^/tmp_mnt/"
  "Regexp to match the automounter prefix in a directory name.")

(defvar abbreviated-home-dir nil
  "The user's homedir abbreviated according to `directory-abbrev-list'.")

(defun abbreviate-file-name (filename)
  "Return a version of FILENAME shortened using `directory-abbrev-alist'.
This also substitutes \"~\" for the user's home directory.
Type \\[describe-variable] directory-abbrev-alist RET for more information."
  ;; Get rid of the prefixes added by the automounter.
  (if (and (string-match automount-dir-prefix filename)
           (file-exists-p (file-name-directory
                           (substring filename (1- (match-end 0))))))
      (setq filename (substring filename (1- (match-end 0)))))
  (let ((tail directory-abbrev-alist))
    ;; If any elt of directory-abbrev-alist matches this name,
    ;; abbreviate accordingly.
    (while tail
      (if (string-match (car (car tail)) filename)
          (setq filename
                (concat (cdr (car tail)) (substring filename (match-end 0)))))
      (setq tail (cdr tail)))
    ;; Compute and save the abbreviated homedir name.
    ;; We defer computing this until the first time it's needed, to
    ;; give time for directory-abbrev-alist to be set properly.
    ;; We include a slash at the end, to avoid spurious matches
    ;; such as `/usr/foobar' when the home dir is `/usr/foo'.
    (or abbreviated-home-dir
        (setq abbreviated-home-dir
              (let ((abbreviated-home-dir "$foo"))
                (concat "^" (abbreviate-file-name (expand-file-name "~"))
                        "\\(/\\|$\\)"))))
                                                  
    ;; If FILENAME starts with the abbreviated homedir,
    ;; make it start with `~' instead.
    (if (and (string-match abbreviated-home-dir filename)
             ;; If the home dir is just /, don't change it.
             (not (and (= (match-end 0) 1)
                       (= (aref filename 0) ?/)))
             (not (and (or (eq system-type 'ms-dos) 
                           (eq system-type 'windows-nt))
                       (save-match-data
                         (string-match "^[a-zA-Z]:/$" filename)))))
        (setq filename
              (concat "~"
                      (substring filename (match-beginning 1) (match-end 1))
                      (substring filename (match-end 0)))))
    filename))

(defvar find-file-not-true-dirname-list nil
  "*List of logical names for which visiting shouldn't save the true dirname.
On VMS, when you visit a file using a logical name that searches a path,
you may or may not want the visited file name to record the specific
directory where the file was found.  If you *do not* want that, add the logical
name to this list as a string.")

(defun find-buffer-visiting (filename)
  "Return the buffer visiting file FILENAME (a string).
This is like `get-file-buffer', except that it checks for any buffer
visiting the same file, possibly under a different name.
If there is no such live buffer, return nil."
  (let ((buf (get-file-buffer filename))
        (truename (abbreviate-file-name (file-truename filename))))
    (or buf
        (let ((list (buffer-list)) found)
          (while (and (not found) list)
            (save-excursion
              (set-buffer (car list))
              (if (and buffer-file-name
                       (string= buffer-file-truename truename))
                  (setq found (car list))))
            (setq list (cdr list)))
          found)
        (let ((number (nthcdr 10 (file-attributes truename)))
              (list (buffer-list)) found)
          (and number
               (while (and (not found) list)
                 (save-excursion
                   (set-buffer (car list))
                   (if (and buffer-file-name
                            (equal buffer-file-number number)
                            ;; Verify this buffer's file number
                            ;; still belongs to its file.
                            (file-exists-p buffer-file-name)
                            (equal (nthcdr 10 (file-attributes buffer-file-name))
                                   number))
                       (setq found (car list))))
                 (setq list (cdr list))))
          found))))

(defun find-file-noselect (filename &optional nowarn)
  "Read file FILENAME into a buffer and return the buffer.
If a buffer exists visiting FILENAME, return that one, but
verify that the file has not changed since visited or saved.
The buffer is not selected, just returned to the caller."
  (setq filename
        (abbreviate-file-name
         (expand-file-name filename)))
  (if (file-directory-p filename)
      (if find-file-run-dired
          (dired-noselect filename)
        (error "%s is a directory." filename))
    (let* ((buf (get-file-buffer filename))
           (truename (abbreviate-file-name (file-truename filename)))
           (number (nthcdr 10 (file-attributes truename)))
           ;; Find any buffer for a file which has same truename.
           (other (and (not buf) (find-buffer-visiting filename)))
           error)
      ;; Let user know if there is a buffer with the same truename.
      (if other
          (progn
            (or nowarn
                (string-equal filename (buffer-file-name other))
                (message "%s and %s are the same file"
                         filename (buffer-file-name other)))
            ;; Optionally also find that buffer.
            (if (or find-file-existing-other-name find-file-visit-truename)
                (setq buf other))))
      (if buf
          (or nowarn
              (verify-visited-file-modtime buf)
              (cond ((not (file-exists-p filename))
                     (error "File %s no longer exists!" filename))
                    ((yes-or-no-p
                      (format
                       (if (buffer-modified-p buf)
    "File %s changed on disk.  Discard your edits? "
    "File %s changed on disk.  Reread from disk? ")
                       (file-name-nondirectory filename)))
                     (save-excursion
                       (set-buffer buf)
                       (revert-buffer t t)))))
        (save-excursion
;;; The truename stuff makes this obsolete.
;;;       (let* ((link-name (car (file-attributes filename)))
;;;              (linked-buf (and (stringp link-name)
;;;                               (get-file-buffer link-name))))
;;;         (if (bufferp linked-buf)
;;;             (message "Symbolic link to file in buffer %s"
;;;                      (buffer-name linked-buf))))
          (setq buf (create-file-buffer filename))
          (set-buffer-major-mode buf)
          (set-buffer buf)
          (erase-buffer)
          (condition-case ()
              (insert-file-contents filename t)
            (file-error
             ;; Run find-file-not-found-hooks until one returns non-nil.
             (or (run-hook-with-args-until-success 'find-file-not-found-hooks)
                 ;; If they fail too, set error.
                 (setq error t))))
          ;; Find the file's truename, and maybe use that as visited name.
          (setq buffer-file-truename truename)
          (setq buffer-file-number number)
          ;; On VMS, we may want to remember which directory in a search list
          ;; the file was found in.
          (and (eq system-type 'vax-vms)
               (let (logical)
                 (if (string-match ":" (file-name-directory filename))
                     (setq logical (substring (file-name-directory filename)
                                              0 (match-beginning 0))))
                 (not (member logical find-file-not-true-dirname-list)))
               (setq buffer-file-name buffer-file-truename))
          (if find-file-visit-truename
              (setq buffer-file-name
                    (setq filename
                          (expand-file-name buffer-file-truename))))
          ;; Set buffer's default directory to that of the file.
          (setq default-directory (file-name-directory filename))
          ;; Turn off backup files for certain file names.  Since
          ;; this is a permanent local, the major mode won't eliminate it.
          (and (not (funcall backup-enable-predicate buffer-file-name))
               (progn
                 (make-local-variable 'backup-inhibited)
                 (setq backup-inhibited t)))
          (after-find-file error (not nowarn))))
      buf)))
\f
(defvar after-find-file-from-revert-buffer nil)

(defun after-find-file (&optional error warn noauto
                                  after-find-file-from-revert-buffer)
  "Called after finding a file and by the default revert function.
Sets buffer mode, parses local variables.
Optional args ERROR, WARN, and NOAUTO: ERROR non-nil means there was an
error in reading the file.  WARN non-nil means warn if there
exists an auto-save file more recent than the visited file.
NOAUTO means don't mess with auto-save mode.
Fourth arg AFTER-FIND-FILE-FROM-REVERT-BUFFER non-nil
 means this call was from `revert-buffer'.
Finishes by calling the functions in `find-file-hooks'."
  (setq buffer-read-only (not (file-writable-p buffer-file-name)))
  (if noninteractive
      nil
    (let* (not-serious
           (msg
            (cond ((and error (file-attributes buffer-file-name))
                   (setq buffer-read-only t)
                   "File exists, but cannot be read.")
                  ((not buffer-read-only)
                   (if (and warn
                            (file-newer-than-file-p (make-auto-save-file-name)
                                                    buffer-file-name))
                       "Auto save file is newer; consider M-x recover-file"
                     (setq not-serious t)
                     (if error "(New file)" nil)))
                  ((not error)
                   (setq not-serious t)
                   "Note: file is write protected")
                  ((file-attributes (directory-file-name default-directory))
                   "File not found and directory write-protected")
                  ((file-exists-p (file-name-directory buffer-file-name))
                   (setq buffer-read-only nil))
                  (t
                   (setq buffer-read-only nil)
                   (if (file-exists-p (file-name-directory (directory-file-name (file-name-directory buffer-file-name))))
                       "Use M-x make-dir RET RET to create the directory"
                     "Use C-u M-x make-dir RET RET to create directory and its parents")))))
      (if msg
          (progn
            (message msg)
            (or not-serious (sit-for 1 nil t)))))
    (if (and auto-save-default (not noauto))
        (auto-save-mode t)))
  (normal-mode t)
  (run-hooks 'find-file-hooks))

(defun normal-mode (&optional find-file)
  "Choose the major mode for this buffer automatically.
Also sets up any specified local variables of the file.
Uses the visited file name, the -*- line, and the local variables spec.

This function is called automatically from `find-file'.  In that case,
we may set up specified local variables depending on the value of
`enable-local-variables': if it is t, we do; if it is nil, we don't;
otherwise, we query.  `enable-local-variables' is ignored if you
run `normal-mode' explicitly."
  (interactive)
  (or find-file (funcall (or default-major-mode 'fundamental-mode)))
  (condition-case err
      (set-auto-mode)
    (error (message "File mode specification error: %s"
                    (prin1-to-string err))))
  (condition-case err
      (let ((enable-local-variables (or (not find-file)
                                        enable-local-variables)))
        (hack-local-variables))
    (error (message "File local-variables error: %s"
                    (prin1-to-string err)))))

(defvar auto-mode-alist (mapcar 'purecopy
                                '(("\\.text\\'" . text-mode)
                                  ("\\.c\\'" . c-mode)
                                  ("\\.h\\'" . c-mode)
                                  ("\\.tex\\'" . TeX-mode)
                                  ("\\.ltx\\'" . LaTeX-mode)
                                  ("\\.el\\'" . emacs-lisp-mode)
                                  ("\\.mm\\'" . nroff-mode)
                                  ("\\.me\\'" . nroff-mode)
                                  ("\\.ms\\'" . nroff-mode)
                                  ("\\.man\\'" . nroff-mode)
                                  ("\\.scm\\'" . scheme-mode)
                                  ("\\.l\\'" . lisp-mode)
                                  ("\\.lisp\\'" . lisp-mode)
                                  ("\\.f\\'" . fortran-mode)
                                  ("\\.for\\'" . fortran-mode)
                                  ("\\.p\\'" . pascal-mode)
                                  ("\\.pas\\'" . pascal-mode)
                                  ("\\.mss\\'" . scribe-mode)
                                  ("\\.ada\\'" . ada-mode)
                                  ("\\.icn\\'" . icon-mode)
                                  ("\\.pl\\'" . prolog-mode)
                                  ("\\.cc\\'" . c++-mode)
                                  ("\\.hh\\'" . c++-mode)
                                  ("\\.C\\'" . c++-mode)
                                  ("\\.H\\'" . c++-mode)
;;;                               ("\\.mk\\'" . makefile-mode)
;;;                               ("[Mm]akefile" . makefile-mode)
;;; Less common extensions come here
;;; so more common ones above are found faster.
                                  ("\\.texinfo\\'" . texinfo-mode)
                                  ("\\.texi\\'" . texinfo-mode)
                                  ("\\.s\\'" . asm-mode)
                                  ("ChangeLog\\'" . change-log-mode)
                                  ("change.log\\'" . change-log-mode)
                                  ("changelo\\'" . change-log-mode)
                                  ("ChangeLog.[0-9]+\\'" . change-log-mode)
                                  ("\\$CHANGE_LOG\\$\\.TXT" . change-log-mode)
;; The following should come after the ChangeLog pattern
;; for the sake of ChangeLog.1, etc.
                                  ("\\.[12345678]\\'" . nroff-mode)
                                  ("\\.TeX\\'" . TeX-mode)
                                  ("\\.sty\\'" . LaTeX-mode)
                                  ("\\.bbl\\'" . LaTeX-mode)
                                  ("\\.bib\\'" . bibtex-mode)
                                  ("\\.article\\'" . text-mode)
                                  ("\\.letter\\'" . text-mode)
                                  ("\\.tcl\\'" . tcl-mode)
                                  ("\\.lsp\\'" . lisp-mode)
                                  ("\\.awk\\'" . awk-mode)
                                  ("\\.prolog\\'" . prolog-mode)
                                  ("\\.tar\\'" . tar-mode)
                                  ;; Mailer puts message to be edited in
                                  ;; /tmp/Re.... or Message
                                  ("^/tmp/Re" . text-mode)
                                  ("/Message[0-9]*\\'" . text-mode)
                                  ;; some news reader is reported to use this
                                  ("^/tmp/fol/" . text-mode)
                                  ("\\.y\\'" . c-mode)
                                  ("\\.lex\\'" . c-mode)
                                  ("\\.oak\\'" . scheme-mode)
                                  ("\\.scm.[0-9]*\\'" . scheme-mode)
                                  ("\\.sgm\\'" . sgml-mode)
                                  ("\\.sgml\\'" . sgml-mode)
                                  ("\\.dtd\\'" . sgml-mode)
                                  ;; .emacs following a directory delimiter
                                  ;; in either Unix or VMS syntax.
                                  ("[]>:/]\\..*emacs\\'" . emacs-lisp-mode)
                                  ;; _emacs following a directory delimiter
                                  ;; in MsDos syntax
                                  ("[:/]_emacs\\'" . emacs-lisp-mode)
                                  ("\\.ml\\'" . lisp-mode)))
  "\
Alist of filename patterns vs corresponding major mode functions.
Each element looks like (REGEXP . FUNCTION) or (REGEXP FUNCTION NON-NIL).
\(NON-NIL stands for anything that is not nil; the value does not matter.)
Visiting a file whose name matches REGEXP specifies FUNCTION as the
mode function to use.  FUNCTION will be called, unless it is nil.

If the element has the form (REGEXP FUNCTION NON-NIL), then after
calling FUNCTION (if it's not nil), we delete the suffix that matched
REGEXP and search the list again for another match.")

(defconst interpreter-mode-alist
  '(("perl" . perl-mode)
    ("wish" . tcl-mode)
    ("wishx" . tcl-mode)
    ("tcl" . tcl-mode)
    ("tclsh" . tcl-mode)
    ("awk" . awk-mode)
    ("gawk" . awk-mode)
    ("scm" . scheme-mode))
  "Alist mapping interpreter names to major modes.
This alist applies to files whose first line starts with `#!'.
Each element looks like (INTERPRETER . MODE).
The car of each element is compared with
the name of the interpreter specified in the first line.
If it matches, mode MODE is selected.")

(defconst inhibit-first-line-modes-regexps '("\\.tar$")
  "List of regexps; if one matches a file name, don't look for `-*-'.")

(defvar user-init-file
  "" ; set by command-line
  "File name including directory of user's initialization file.")

(defun set-auto-mode ()
  "Select major mode appropriate for current buffer.
This checks for a -*- mode tag in the buffer's text,
compares the filename against the entries in `auto-mode-alist',
or checks the interpreter that runs this file against
`interpreter-mode-alist'.

It does not check for the `mode:' local variable in the
Local Variables section of the file; for that, use `hack-local-variables'.

If `enable-local-variables' is nil, this function does not check for a
-*- mode tag."
  ;; Look for -*-MODENAME-*- or -*- ... mode: MODENAME; ... -*-
  (let (beg end done)
    (save-excursion
      (goto-char (point-min))
      (skip-chars-forward " \t\n")
      (and enable-local-variables
           ;; Don't look for -*- if this file name matches any
           ;; of the regexps in inhibit-first-line-modes-regexps.
           (let ((temp inhibit-first-line-modes-regexps)
                 (name (file-name-sans-versions buffer-file-name)))
             (while (and temp
                         (not (string-match (car temp)
                                            name)))
               (setq temp (cdr temp)))
             (not temp))
           (search-forward "-*-" (save-excursion
                                   ;; If the file begins with "#!"
                                   ;; (exec interpreter magic), look
                                   ;; for mode frobs in the first two
                                   ;; lines.  You cannot necessarily
                                   ;; put them in the first line of
                                   ;; such a file without screwing up
                                   ;; the interpreter invocation.
                                   (end-of-line (and (looking-at "^#!") 2))
                                   (point)) t)
           (progn
             (skip-chars-forward " \t")
             (setq beg (point))
             (search-forward "-*-"
                             (save-excursion (end-of-line) (point))
                             t))
           (progn
             (forward-char -3)
             (skip-chars-backward " \t")
             (setq end (point))
             (goto-char beg)
             (if (save-excursion (search-forward ":" end t))
                 ;; Find all specifications for the `mode:' variable
                 ;; and execute them left to right.
                 (while (let ((case-fold-search t))
                          (or (and (looking-at "mode:")
                                   (goto-char (match-end 0)))
                              (re-search-forward "[ \t;]mode:" end t)))
                   (skip-chars-forward " \t")
                   (setq beg (point))
                   (if (search-forward ";" end t)
                       (forward-char -1)
                     (goto-char end))
                   (skip-chars-backward " \t")
                   (funcall (intern (concat (downcase (buffer-substring beg (point))) "-mode"))))
               ;; Simple -*-MODE-*- case.
               (funcall (intern (concat (downcase (buffer-substring beg end)) "-mode"))))
             (setq done t)))
      ;; If we didn't find a mode from a -*- line, try using the file name.
      (if (and (not done) buffer-file-name)
          (let ((name buffer-file-name)
                (keep-going t))
            ;; Remove backup-suffixes from file name.
            (setq name (file-name-sans-versions name))
            (while keep-going
              (setq keep-going nil)
              (let ((alist auto-mode-alist)
                    (mode nil))
                ;; Find first matching alist entry.
                (let ((case-fold-search (eq system-type 'vax-vms)))
                  (while (and (not mode) alist)
                    (if (string-match (car (car alist)) name)
                        (if (and (consp (cdr (car alist)))
                                 (nth 2 (car alist)))
                            (progn
                              (setq mode (car (cdr (car alist)))
                                    name (substring name 0 (match-beginning 0))
                                    keep-going t))
                          (setq mode (cdr (car alist))
                                keep-going nil)))
                    (setq alist (cdr alist))))
                (if mode
                    (funcall mode)
                  ;; If we can't deduce a mode from the file name,
                  ;; look for an interpreter specified in the first line.
                  (let ((interpreter
                         (save-excursion
                           (goto-char (point-min))
                           (if (looking-at "#! *\\([^ \t\n]+\\)")
                               (buffer-substring (match-beginning 1)
                                                 (match-end 1))
                             "")))
                        elt)
                    ;; Map interpreter name to a mode.
                    (setq elt (assoc (file-name-nondirectory interpreter)
                                     interpreter-mode-alist))
                    (if elt
                        (funcall (cdr elt))))))))))))

(defun hack-local-variables-prop-line ()
  ;; Set local variables specified in the -*- line.
  ;; Ignore any specification for `mode:';
  ;; set-auto-mode should already have handled that.
  (save-excursion
    (goto-char (point-min))
    (let ((result nil)
          (end (save-excursion (end-of-line (and (looking-at "^#!") 2)) (point))))
      ;; Parse the -*- line into the `result' alist.
      (cond ((not (search-forward "-*-" end t))
             ;; doesn't have one.
             nil)
            ((looking-at "[ \t]*\\([^ \t\n\r:;]+\\)\\([ \t]*-\\*-\\)")
             ;; Simple form: "-*- MODENAME -*-".  Already handled.
             nil)
            (t
             ;; Hairy form: '-*-' [ <variable> ':' <value> ';' ]* '-*-'
             ;; (last ";" is optional).
             (save-excursion
               (if (search-forward "-*-" end t)
                   (setq end (- (point) 3))
                 (error "-*- not terminated before end of line")))
             (while (< (point) end)
               (or (looking-at "[ \t]*\\([^ \t\n:]+\\)[ \t]*:[ \t]*")
                   (error "malformed -*- line"))
               (goto-char (match-end 0))
               (let ((key (intern (downcase (buffer-substring
                                             (match-beginning 1)
                                             (match-end 1)))))
                     (val (save-restriction
                            (narrow-to-region (point) end)
                            (read (current-buffer)))))
                 (or (eq key 'mode)
                     (setq result (cons (cons key val) result)))
                 (skip-chars-forward " \t;")))
             (setq result (nreverse result))))
      
      (if (and result
               (or (eq enable-local-variables t)
                   (and enable-local-variables
                        (save-window-excursion
                          (condition-case nil
                              (switch-to-buffer (current-buffer))
                            (error
                             ;; If we fail to switch in the selected window,
                             ;; it is probably a minibuffer.
                             ;; So try another window.
                             (condition-case nil
                                 (switch-to-buffer-other-window (current-buffer))
                               (error
                                (switch-to-buffer-other-frame (current-buffer))))))
                          (y-or-n-p (format "Set local variables as specified in -*- line of %s? "
                                            (file-name-nondirectory buffer-file-name)))))))
          (while result
            (hack-one-local-variable (car (car result)) (cdr (car result)))
            (setq result (cdr result)))))))

(defvar hack-local-variables-hook nil
  "Normal hook run after processing a file's local variables specs.
Major modes can use this to examine user-specified local variables
in order to initialize other data structure based on them.")

(defun hack-local-variables ()
  "Parse and put into effect this buffer's local variables spec."
  (hack-local-variables-prop-line)
  ;; Look for "Local variables:" line in last page.
  (save-excursion
    (goto-char (point-max))
    (search-backward "\n\^L" (max (- (point-max) 3000) (point-min)) 'move)
    (if (let ((case-fold-search t))
          (and (search-forward "Local Variables:" nil t)
               (or (eq enable-local-variables t)
                   (and enable-local-variables
                        (save-window-excursion
                          (switch-to-buffer (current-buffer))
                          (save-excursion
                            (beginning-of-line)
                            (set-window-start (selected-window) (point)))
                          (y-or-n-p (format "Set local variables as specified at end of %s? "
                                            (if buffer-file-name
                                                (file-name-nondirectory 
                                                 buffer-file-name)
                                              (concat "buffer "
                                                      (buffer-name))))))))))
        (let ((continue t)
              prefix prefixlen suffix beg
              (enable-local-eval enable-local-eval))
          ;; The prefix is what comes before "local variables:" in its line.
          ;; The suffix is what comes after "local variables:" in its line.
          (skip-chars-forward " \t")
          (or (eolp)
              (setq suffix (buffer-substring (point)
                                             (progn (end-of-line) (point)))))
          (goto-char (match-beginning 0))
          (or (bolp)
              (setq prefix
                    (buffer-substring (point)
                                      (progn (beginning-of-line) (point)))))

          (if prefix (setq prefixlen (length prefix)
                           prefix (regexp-quote prefix)))
          (if suffix (setq suffix (concat (regexp-quote suffix) "$")))
          (while continue
            ;; Look at next local variable spec.
            (if selective-display (re-search-forward "[\n\C-m]")
              (forward-line 1))
            ;; Skip the prefix, if any.
            (if prefix
                (if (looking-at prefix)
                    (forward-char prefixlen)
                  (error "Local variables entry is missing the prefix")))
            ;; Find the variable name; strip whitespace.
            (skip-chars-forward " \t")
            (setq beg (point))
            (skip-chars-forward "^:\n")
            (if (eolp) (error "Missing colon in local variables entry"))
            (skip-chars-backward " \t")
            (let* ((str (buffer-substring beg (point)))
                   (var (read str))
                  val)
              ;; Setting variable named "end" means end of list.
              (if (string-equal (downcase str) "end")
                  (setq continue nil)
                ;; Otherwise read the variable value.
                (skip-chars-forward "^:")
                (forward-char 1)
                (setq val (read (current-buffer)))
                (skip-chars-backward "\n")
                (skip-chars-forward " \t")
                (or (if suffix (looking-at suffix) (eolp))
                    (error "Local variables entry is terminated incorrectly"))
                ;; Set the variable.  "Variables" mode and eval are funny.
                (hack-one-local-variable var val)))))))
  (run-hooks 'hack-local-variables-hook))

(defconst ignored-local-variables
  '(enable-local-eval)
  "Variables to be ignored in a file's local variable spec.")

;; Get confirmation before setting these variables as locals in a file.
(put 'debugger 'risky-local-variable t)
(put 'enable-local-eval 'risky-local-variable t)
(put 'ignored-local-variables 'risky-local-variable t)
(put 'eval 'risky-local-variable t)
(put 'file-name-handler-alist 'risky-local-variable t)
(put 'minor-mode-map-alist 'risky-local-variable t)
(put 'after-load-alist 'risky-local-variable t)
(put 'buffer-file-name 'risky-local-variable t)
(put 'buffer-auto-save-file-name 'risky-local-variable t)
(put 'buffer-file-truename 'risky-local-variable t)
(put 'exec-path 'risky-local-variable t)
(put 'load-path 'risky-local-variable t)
(put 'exec-directory 'risky-local-variable t)
(put 'process-environment 'risky-local-variable t)
;; Don't wait for outline.el to be loaded, for the sake of outline-minor-mode.
(put 'outline-level 'risky-local-variable t)
(put 'rmail-output-file-alist 'risky-local-variable t)

;; This one is safe because the user gets to check it before it is used.
(put 'compile-command 'safe-local-variable t)

(defun hack-one-local-variable-quotep (exp)
  (and (consp exp) (eq (car exp) 'quote) (consp (cdr exp))))

;; "Set" one variable in a local variables spec.
;; A few variable names are treated specially.
(defun hack-one-local-variable (var val)
  (cond ((eq var 'mode)
         (funcall (intern (concat (downcase (symbol-name val))
                                  "-mode"))))
        ((memq var ignored-local-variables)
         nil)
        ;; "Setting" eval means either eval it or do nothing.
        ;; Likewise for setting hook variables.
        ((or (get var 'risky-local-variable)
             (and
              (string-match "-hooks?$\\|-functions?$\\|-forms?$\\|-program$\\|-command$"
                            (symbol-name var))
              (not (get var 'safe-local-variable))))
         ;; Permit evaling a put of a harmless property
         ;; if the args do nothing tricky.
         (if (or (and (eq var 'eval)
                      (consp val)
                      (eq (car val) 'put)
                      (hack-one-local-variable-quotep (nth 1 val))
                      (hack-one-local-variable-quotep (nth 2 val))
                      ;; Only allow safe values of lisp-indent-hook;
                      ;; not functions.
                      (or (numberp (nth 3 val))
                          (equal (nth 3 val) ''defun))
                      (memq (nth 1 (nth 2 val))
                            '(lisp-indent-hook)))
                 ;; Permit eval if not root and user says ok.
                 (and (not (zerop (user-uid)))
                      (or (eq enable-local-eval t)
                          (and enable-local-eval
                               (save-window-excursion
                                 (switch-to-buffer (current-buffer))
                                 (save-excursion
                                   (beginning-of-line)
                                   (set-window-start (selected-window) (point)))
                                 (setq enable-local-eval
                                       (y-or-n-p (format "Process `eval' or hook local variables in file %s? "
                                                         (file-name-nondirectory buffer-file-name)))))))))
             (if (eq var 'eval)
                 (save-excursion (eval val))
               (make-local-variable var)
               (set var val))
           (message "Ignoring `eval:' in file's local variables")))
        ;; Ordinary variable, really set it.
        (t (make-local-variable var)
           (set var val))))

\f
(defun set-visited-file-name (filename)
  "Change name of file visited in current buffer to FILENAME.
The next time the buffer is saved it will go in the newly specified file.
nil or empty string as argument means make buffer not be visiting any file.
Remember to delete the initial contents of the minibuffer
if you wish to pass an empty string as the argument."
  (interactive "FSet visited file name: ")
  (let (truename)
    (if filename
        (setq filename
              (if (string-equal filename "")
                  nil
                (expand-file-name filename))))
    (if filename
        (progn
          (setq truename (file-truename filename))
          (if find-file-visit-truename
              ;; Do not use the abbreviated filename, because
              ;; write-region will reset it to the expanded filename
              (setq filename truename))))
    (or (equal filename buffer-file-name)
        (progn
          (and filename (lock-buffer filename))
          (unlock-buffer)))
    (setq buffer-file-name filename)
    (if filename                        ; make buffer name reflect filename.
        (let ((new-name (file-name-nondirectory buffer-file-name)))
          (if (string= new-name "")
              (error "Empty file name"))
          (if (eq system-type 'vax-vms)
              (setq new-name (downcase new-name)))
          (setq default-directory (file-name-directory buffer-file-name))
          (or (string= new-name (buffer-name))
              (rename-buffer new-name t))))
    (setq buffer-backed-up nil)
    (clear-visited-file-modtime)
    (if truename
        (setq buffer-file-truename (abbreviate-file-name truename)))
    (setq buffer-file-number
          (if filename
              (nth 10 (file-attributes buffer-file-name))
              nil)))
  ;; write-file-hooks is normally used for things like ftp-find-file
  ;; that visit things that are not local files as if they were files.
  ;; Changing to visit an ordinary local file instead should flush the hook.
  (kill-local-variable 'write-file-hooks)
  (kill-local-variable 'local-write-file-hooks)
  (kill-local-variable 'revert-buffer-function)
  (kill-local-variable 'backup-inhibited)
  ;; If buffer was read-only because of version control,
  ;; that reason is gone now, so make it writable.
  (if vc-mode
      (setq buffer-read-only nil))
  (kill-local-variable 'vc-mode)
  ;; Turn off backup files for certain file names.
  ;; Since this is a permanent local, the major mode won't eliminate it.
  (and (not (funcall backup-enable-predicate buffer-file-name))
       (progn
         (make-local-variable 'backup-inhibited)
         (setq backup-inhibited t)))
  (let ((oauto buffer-auto-save-file-name))
    ;; If auto-save was not already on, turn it on if appropriate.
    (if (not buffer-auto-save-file-name)
        (and buffer-file-name auto-save-default
             (auto-save-mode t))
      ;; If auto save is on, start using a new name.
      ;; We deliberately don't rename or delete the old auto save
      ;; for the old visited file name.  This is because perhaps
      ;; the user wants to save the new state and then compare with the
      ;; previous state from the auto save file.
      (setq buffer-auto-save-file-name
            (make-auto-save-file-name)))
    ;; Rename the old auto save file if any.
    (and oauto buffer-auto-save-file-name
         (file-exists-p oauto)
         (rename-file oauto buffer-auto-save-file-name t)))
  (if buffer-file-name
      (set-buffer-modified-p t)))

(defun write-file (filename)
  "Write current buffer into file FILENAME.
Makes buffer visit that file, and marks it not modified.
If the buffer is already visiting a file, you can specify
a directory name as FILENAME, to write a file of the same
old name in that directory."
;;  (interactive "FWrite file: ")
  (interactive
   (list (if buffer-file-name
             (read-file-name "Write file: "
                                 nil nil nil nil)
           (read-file-name "Write file: "
                               (cdr (assq 'default-directory
                                          (buffer-local-variables)))
                               nil nil (buffer-name)))))
  (or (null filename) (string-equal filename "")
      (progn
        ;; If arg is just a directory,
        ;; use same file name, but in that directory.
        (if (and (file-directory-p filename) buffer-file-name)
            (setq filename (concat (file-name-as-directory filename)
                                   (file-name-nondirectory buffer-file-name))))
        (set-visited-file-name filename)))
  (set-buffer-modified-p t)
  (save-buffer))
\f
(defun backup-buffer ()
  "Make a backup of the disk file visited by the current buffer, if appropriate.
This is normally done before saving the buffer the first time.
If the value is non-nil, it is the result of `file-modes' on the original
file; this means that the caller, after saving the buffer, should change
the modes of the new file to agree with the old modes."
  (if (and make-backup-files (not backup-inhibited)
           (not buffer-backed-up)
           (file-exists-p buffer-file-name)
           (memq (aref (elt (file-attributes buffer-file-name) 8) 0)
                 '(?- ?l)))
      (let ((real-file-name buffer-file-name)
            backup-info backupname targets setmodes)
        ;; If specified name is a symbolic link, chase it to the target.
        ;; Thus we make the backups in the directory where the real file is.
        (setq real-file-name (file-chase-links real-file-name))
        (setq backup-info (find-backup-file-name real-file-name)
              backupname (car backup-info)
              targets (cdr backup-info))
;;;     (if (file-directory-p buffer-file-name)
;;;         (error "Cannot save buffer in directory %s" buffer-file-name))
        (condition-case ()
            (let ((delete-old-versions
                   ;; If have old versions to maybe delete,
                   ;; ask the user to confirm now, before doing anything.
                   ;; But don't actually delete til later.
                   (and targets
                        (or (eq delete-old-versions t) (eq delete-old-versions nil))
                        (or delete-old-versions
                            (y-or-n-p (format "Delete excess backup versions of %s? "
                                              real-file-name))))))
              ;; Actually write the back up file.
              (condition-case ()
                  (if (or file-precious-flag
;                         (file-symlink-p buffer-file-name)
                          backup-by-copying
                          (and backup-by-copying-when-linked
                               (> (file-nlinks real-file-name) 1))
                          (and backup-by-copying-when-mismatch
                               (let ((attr (file-attributes real-file-name)))
                                 (or (nth 9 attr)
                                     (not (file-ownership-preserved-p real-file-name))))))
                      (condition-case ()
                          (copy-file real-file-name backupname t t)
                        (file-error
                         ;; If copying fails because file BACKUPNAME
                         ;; is not writable, delete that file and try again.
                         (if (and (file-exists-p backupname)
                                  (not (file-writable-p backupname)))
                             (delete-file backupname))
                         (copy-file real-file-name backupname t t)))
                    ;; rename-file should delete old backup.
                    (rename-file real-file-name backupname t)
                    (setq setmodes (file-modes backupname)))
                (file-error
                 ;; If trouble writing the backup, write it in ~.
                 (setq backupname (expand-file-name "~/%backup%~"))
                 (message "Cannot write backup file; backing up in ~/%%backup%%~")
                 (sleep-for 1)
                 (condition-case ()
                     (copy-file real-file-name backupname t t)
                   (file-error
                    ;; If copying fails because file BACKUPNAME
                    ;; is not writable, delete that file and try again.
                    (if (and (file-exists-p backupname)
                             (not (file-writable-p backupname)))
                        (delete-file backupname))
                    (copy-file real-file-name backupname t t)))))
              (setq buffer-backed-up t)
              ;; Now delete the old versions, if desired.
              (if delete-old-versions
                  (while targets
                    (condition-case ()
                        (delete-file (car targets))
                      (file-error nil))
                    (setq targets (cdr targets))))
              setmodes)
        (file-error nil)))))

(defun file-name-sans-versions (name &optional keep-backup-version)
  "Return FILENAME sans backup versions or strings.
This is a separate procedure so your site-init or startup file can
redefine it.
If the optional argument KEEP-BACKUP-VERSION is non-nil,
we do not remove backup version numbers, only true file version numbers."
  (let ((handler (find-file-name-handler name 'file-name-sans-versions)))
    (if handler
        (funcall handler 'file-name-sans-versions name keep-backup-version)
      (substring name 0
                 (if (eq system-type 'vax-vms)
                     ;; VMS version number is (a) semicolon, optional
                     ;; sign, zero or more digits or (b) period, option
                     ;; sign, zero or more digits, provided this is the
                     ;; second period encountered outside of the
                     ;; device/directory part of the file name.
                     (or (string-match ";[-+]?[0-9]*\\'" name)
                         (if (string-match "\\.[^]>:]*\\(\\.[-+]?[0-9]*\\)\\'"
                                           name)
                             (match-beginning 1))
                         (length name))
                   (if keep-backup-version
                       (length name)
                     (or (string-match "\\.~[0-9]+~\\'" name)
                         (string-match "~\\'" name)
                         (length name))))))))

(defun file-ownership-preserved-p (file)
  "Returns t if deleting FILE and rewriting it would preserve the owner."
  (let ((handler (find-file-name-handler file 'file-ownership-preserved-p)))
    (if handler
        (funcall handler 'file-ownership-preserved-p file)
      (= (nth 2 (file-attributes file)) (user-uid)))))

(defun file-name-sans-extension (filename)
  "Return FILENAME sans final \"extension\".
The extension, in a file name, is the part that follows the last `.'."
  (save-match-data
    (let ((file (file-name-sans-versions (file-name-nondirectory filename)))
          directory)
      (if (string-match "\\.[^.]*\\'" file)
          (if (setq directory (file-name-directory filename))
              (expand-file-name (substring file 0 (match-beginning 0))
                                directory)
            (substring file 0 (match-beginning 0)))
        filename))))

(defun make-backup-file-name (file)
  "Create the non-numeric backup file name for FILE.
This is a separate function so you can redefine it for customization."
  (if (eq system-type 'ms-dos)
      (let ((fn (file-name-nondirectory file)))
        (concat (file-name-directory file)
                (if (string-match "\\([^.]*\\)\\(\\..*\\)?" fn)
                    (substring fn 0 (match-end 1)))
                ".bak"))
    (concat file "~")))

(defun backup-file-name-p (file)
  "Return non-nil if FILE is a backup file name (numeric or not).
This is a separate function so you can redefine it for customization.
You may need to redefine `file-name-sans-versions' as well."
  (if (eq system-type 'ms-dos)
      (string-match "\\.bak$" file)
    (string-match "~$" file)))

;; This is used in various files.
;; The usage of bv-length is not very clean,
;; but I can't see a good alternative,
;; so as of now I am leaving it alone.
(defun backup-extract-version (fn)
  "Given the name of a numeric backup file, return the backup number.
Uses the free variable `bv-length', whose value should be
the index in the name where the version number begins."
  (if (and (string-match "[0-9]+~$" fn bv-length)
           (= (match-beginning 0) bv-length))
      (string-to-int (substring fn bv-length -1))
      0))

;; I believe there is no need to alter this behavior for VMS;
;; since backup files are not made on VMS, it should not get called.
(defun find-backup-file-name (fn)
  "Find a file name for a backup file, and suggestions for deletions.
Value is a list whose car is the name for the backup file
 and whose cdr is a list of old versions to consider deleting now."
  (if (eq version-control 'never)
      (list (make-backup-file-name fn))
    (let* ((base-versions (concat (file-name-nondirectory fn) ".~"))
           (bv-length (length base-versions))
           possibilities
           (versions nil)
           (high-water-mark 0)
           (deserve-versions-p nil)
           (number-to-delete 0))
      (condition-case ()
          (setq possibilities (file-name-all-completions
                               base-versions
                               (file-name-directory fn))
                versions (sort (mapcar
                                (function backup-extract-version)
                                possibilities)
                               '<)
                high-water-mark (apply 'max 0 versions)
                deserve-versions-p (or version-control
                                       (> high-water-mark 0))
                number-to-delete (- (length versions)
                                    kept-old-versions kept-new-versions -1))
        (file-error
         (setq possibilities nil)))
      (if (not deserve-versions-p)
          (list (make-backup-file-name fn))
        (cons (concat fn ".~" (int-to-string (1+ high-water-mark)) "~")
              (if (and (> number-to-delete 0)
                       ;; Delete nothing if there is overflow
                       ;; in the number of versions to keep.
                       (>= (+ kept-new-versions kept-old-versions -1) 0))
                  (mapcar (function (lambda (n)
                                      (concat fn ".~" (int-to-string n) "~")))
                          (let ((v (nthcdr kept-old-versions versions)))
                            (rplacd (nthcdr (1- number-to-delete) v) ())
                            v))))))))

(defun file-nlinks (filename)
  "Return number of names file FILENAME has."
  (car (cdr (file-attributes filename))))

(defun file-relative-name (filename &optional directory)
  "Convert FILENAME to be relative to DIRECTORY (default: default-directory)."
  (setq filename (expand-file-name filename)
        directory (file-name-as-directory (expand-file-name
                                           (or directory default-directory))))
  (let ((ancestor ""))
    (while (not (string-match (concat "^" (regexp-quote directory)) filename))
      (setq directory (file-name-directory (substring directory 0 -1))
            ancestor (concat "../" ancestor)))
    (concat ancestor (substring filename (match-end 0)))))
\f
(defun save-buffer (&optional args)
  "Save current buffer in visited file if modified.  Versions described below.
By default, makes the previous version into a backup file
 if previously requested or if this is the first save.
With 1 or 3 \\[universal-argument]'s, marks this version
 to become a backup when the next save is done.
With 2 or 3 \\[universal-argument]'s,
 unconditionally makes the previous version into a backup file.
With argument of 0, never makes the previous version into a backup file.

If a file's name is FOO, the names of its numbered backup versions are
 FOO.~i~ for various integers i.  A non-numbered backup file is called FOO~.
Numeric backups (rather than FOO~) will be made if value of
 `version-control' is not the atom `never' and either there are already
 numeric versions of the file being backed up, or `version-control' is
 non-nil.
We don't want excessive versions piling up, so there are variables
 `kept-old-versions', which tells Emacs how many oldest versions to keep,
 and `kept-new-versions', which tells how many newest versions to keep.
 Defaults are 2 old versions and 2 new.
`dired-kept-versions' controls dired's clean-directory (.) command.
If `delete-old-versions' is nil, system will query user
 before trimming versions.  Otherwise it does it silently."
  (interactive "p")
  (let ((modp (buffer-modified-p))
        (large (> (buffer-size) 50000))
        (make-backup-files (or (and make-backup-files (not (eq args 0)))
                               (memq args '(16 64)))))
    (and modp (memq args '(16 64)) (setq buffer-backed-up nil))
    (if (and modp large) (message "Saving file %s..." (buffer-file-name)))
    (basic-save-buffer)
    (and modp (memq args '(4 64)) (setq buffer-backed-up nil))))

(defun delete-auto-save-file-if-necessary (&optional force)
  "Delete auto-save file for current buffer if `delete-auto-save-files' is t.
Normally delete only if the file was written by this Emacs since
the last real save, but optional arg FORCE non-nil means delete anyway."
  (and buffer-auto-save-file-name delete-auto-save-files
       (not (string= buffer-file-name buffer-auto-save-file-name))
       (or force (recent-auto-save-p))
       (progn
         (condition-case ()
             (delete-file buffer-auto-save-file-name)
           (file-error nil))
         (set-buffer-auto-saved))))

(defun basic-save-buffer ()
  "Save the current buffer in its visited file, if it has been modified."
  (interactive)
  (if (buffer-modified-p)
      (let ((recent-save (recent-auto-save-p))
            setmodes tempsetmodes)
        ;; On VMS, rename file and buffer to get rid of version number.
        (if (and (eq system-type 'vax-vms)
                 (not (string= buffer-file-name
                               (file-name-sans-versions buffer-file-name))))
            (let (buffer-new-name)
              ;; Strip VMS version number before save.
              (setq buffer-file-name
                    (file-name-sans-versions buffer-file-name))
              ;; Construct a (unique) buffer name to correspond.
              (let ((buf (create-file-buffer (downcase buffer-file-name))))
                (setq buffer-new-name (buffer-name buf))
                (kill-buffer buf))
              (rename-buffer buffer-new-name)))
        ;; If buffer has no file name, ask user for one.
        (or buffer-file-name
            (set-visited-file-name
             (expand-file-name (read-file-name "File to save in: ") nil)))
        (or (verify-visited-file-modtime (current-buffer))
            (not (file-exists-p buffer-file-name))
            (yes-or-no-p
             (format "%s has changed since visited or saved.  Save anyway? "
                     (file-name-nondirectory buffer-file-name)))
            (error "Save not confirmed"))
        (save-restriction
          (widen)
          (and (> (point-max) 1)
               (/= (char-after (1- (point-max))) ?\n)
               (not (and (eq selective-display t)
                         (= (char-after (1- (point-max))) ?\r)))
               (or (eq require-final-newline t)
                   (and require-final-newline
                        (y-or-n-p
                         (format "Buffer %s does not end in newline.  Add one? "
                                 (buffer-name)))))
               (save-excursion
                 (goto-char (point-max))
                 (insert ?\n)))
          (or (run-hook-with-args-until-success 'write-contents-hooks)
              (run-hook-with-args-until-success 'local-write-file-hooks)
              (run-hook-with-args-until-success 'write-file-hooks)
              ;; If a hook returned t, file is already "written".
              ;; Otherwise, write it the usual way now.
              (setq setmodes (basic-save-buffer-1)))
          (setq buffer-file-number (nth 10 (file-attributes buffer-file-name)))
          (if setmodes
              (condition-case ()
                  (set-file-modes buffer-file-name setmodes)
                (error nil))))
        ;; If the auto-save file was recent before this command,
        ;; delete it now.
        (delete-auto-save-file-if-necessary recent-save)
        (run-hooks 'after-save-hook))
    (message "(No changes need to be saved)")))

;; This does the "real job" of writing a buffer into its visited file
;; and making a backup file.  This is what is normally done
;; but inhibited if one of write-file-hooks returns non-nil.
;; It returns a value to store in setmodes.
(defun basic-save-buffer-1 ()
  (let (tempsetmodes setmodes)
    (if (not (file-writable-p buffer-file-name))
        (let ((dir (file-name-directory buffer-file-name)))
          (if (not (file-directory-p dir))
              (error "%s is not a directory" dir)
            (if (not (file-exists-p buffer-file-name))
                (error "Directory %s write-protected" dir)
              (if (yes-or-no-p
                   (format "File %s is write-protected; try to save anyway? "
                           (file-name-nondirectory
                            buffer-file-name)))
                  (setq tempsetmodes t)
                (error "Attempt to save to a file which you aren't allowed to write"))))))
    (or buffer-backed-up
        (setq setmodes (backup-buffer)))
    (let ((dir (file-name-directory buffer-file-name))) 
      (if (and file-precious-flag
               (file-writable-p dir))
          ;; If file is precious, write temp name, then rename it.
          ;; This requires write access to the containing dir,
          ;; which is why we don't try it if we don't have that access.
          (let ((realname buffer-file-name)
                tempname temp nogood i succeed
                (old-modtime (visited-file-modtime)))
            (setq i 0)
            (setq nogood t)
            ;; Find the temporary name to write under.
            (while nogood
              (setq tempname (format "%s#tmp#%d" dir i))
              (setq nogood (file-exists-p tempname))
              (setq i (1+ i)))
            (unwind-protect
                (progn (clear-visited-file-modtime)
                       (write-region (point-min) (point-max)
                                     tempname nil realname)
                       (setq succeed t))
              ;; If writing the temp file fails,
              ;; delete the temp file.
              (or succeed 
                  (progn
                    (delete-file tempname)
                    (set-visited-file-modtime old-modtime))))
            ;; Since we have created an entirely new file
            ;; and renamed it, make sure it gets the
            ;; right permission bits set.
            (setq setmodes (file-modes buffer-file-name))
            ;; We succeeded in writing the temp file,
            ;; so rename it.
            (rename-file tempname buffer-file-name t))
        ;; If file not writable, see if we can make it writable
        ;; temporarily while we write it.
        ;; But no need to do so if we have just backed it up
        ;; (setmodes is set) because that says we're superseding.
        (cond ((and tempsetmodes (not setmodes))
               ;; Change the mode back, after writing.
               (setq setmodes (file-modes buffer-file-name))
               (set-file-modes buffer-file-name 511)))
        (write-region (point-min) (point-max)
                      buffer-file-name nil t)))
    setmodes))

(defun save-some-buffers (&optional arg exiting)
  "Save some modified file-visiting buffers.  Asks user about each one.
Optional argument (the prefix) non-nil means save all with no questions.
Optional second argument EXITING means ask about certain non-file buffers
 as well as about file buffers."
  (interactive "P")
  (save-window-excursion
    (let ((files-done
           (map-y-or-n-p
            (function
             (lambda (buffer)
               (and (buffer-modified-p buffer)
                    (or
                     (buffer-file-name buffer)
                     (and exiting
                          (progn
                            (set-buffer buffer)
                            (and buffer-offer-save (> (buffer-size) 0)))))
                    (if arg
                        t
                      (if (buffer-file-name buffer)
                          (format "Save file %s? "
                                  (buffer-file-name buffer))
                        (format "Save buffer %s? "
                                (buffer-name buffer)))))))
            (function
             (lambda (buffer)
               (set-buffer buffer)
               (save-buffer)))
            (buffer-list)
            '("buffer" "buffers" "save")
            (list (list ?\C-r (lambda (buf)
                                (view-buffer buf)
                                (setq view-exit-action
                                      '(lambda (ignore)
                                         (exit-recursive-edit)))
                                (recursive-edit)
                                ;; Return nil to ask about BUF again.
                                nil)
                        "display the current buffer"))))
          (abbrevs-done
           (and save-abbrevs abbrevs-changed
                (progn
                  (if (or arg
                          (y-or-n-p (format "Save abbrevs in %s? " abbrev-file-name)))
                      (write-abbrev-file nil))
                  ;; Don't keep bothering user if he says no.
                  (setq abbrevs-changed nil)
                  t))))
      (or (> files-done 0) abbrevs-done
          (message "(No files need saving)")))))
\f
(defun not-modified (&optional arg)
  "Mark current buffer as unmodified, not needing to be saved.
With prefix arg, mark buffer as modified, so \\[save-buffer] will save."
  (interactive "P")
  (message (if arg "Modification-flag set"
               "Modification-flag cleared"))
  (set-buffer-modified-p arg))

(defun toggle-read-only (&optional arg)
  "Change whether this buffer is visiting its file read-only.
With arg, set read-only iff arg is positive."
  (interactive "P")
  (setq buffer-read-only
        (if (null arg)
            (not buffer-read-only)
            (> (prefix-numeric-value arg) 0)))
  ;; Force mode-line redisplay
  (set-buffer-modified-p (buffer-modified-p)))

(defun insert-file (filename)
  "Insert contents of file FILENAME into buffer after point.
Set mark after the inserted text.

This function is meant for the user to run interactively.
Don't call it from programs!  Use `insert-file-contents' instead.
\(Its calling sequence is different; see its documentation)."
  (interactive "*fInsert file: ")
  (if (file-directory-p filename)
      (signal 'file-error (list "Opening input file" "file is a directory"
                                filename)))
  (let ((tem (insert-file-contents filename)))
    (push-mark (+ (point) (car (cdr tem))))))

(defun append-to-file (start end filename)
  "Append the contents of the region to the end of file FILENAME.
When called from a function, expects three arguments,
START, END and FILENAME.  START and END are buffer positions
saying what text to write."
  (interactive "r\nFAppend to file: ")
  (write-region start end filename t))

(defun file-newest-backup (filename)
  "Return most recent backup file for FILENAME or nil if no backups exist."
  (let* ((filename (expand-file-name filename))
         (file (file-name-nondirectory filename))
         (dir  (file-name-directory    filename))
         (comp (file-name-all-completions file dir))
         newest)
    (while comp
      (setq file (concat dir (car comp))
            comp (cdr comp))
      (if (and (backup-file-name-p file)
               (or (null newest) (file-newer-than-file-p file newest)))
          (setq newest file)))
    newest))

(defun rename-uniquely ()
  "Rename current buffer to a similar name not already taken.
This function is useful for creating multiple shell process buffers
or multiple mail buffers, etc."
  (interactive)
  (let* ((new-buf (generate-new-buffer (buffer-name)))
         (name (buffer-name new-buf)))
    (kill-buffer new-buf)
    (rename-buffer name)
    (set-buffer-modified-p (buffer-modified-p)))) ; force mode line update

(defun make-directory (dir &optional parents)
  "Create the directory DIR and any nonexistent parent dirs.
Interactively, the default choice of directory to create
is the current default directory for file names.
That is useful when you have visited a file in a nonexistint directory.

Noninteractively, the second (optional) argument PARENTS says whether
to create parent directories if they don't exist."
  (interactive
   (list (read-file-name "Make directory: " default-directory default-directory
                         nil nil)
         t))
  (let ((handler (find-file-name-handler dir 'make-directory)))
    (if handler
        (funcall handler 'make-directory dir parents)
      (if (not parents)
          (make-directory-internal dir)
        (let ((dir (directory-file-name (expand-file-name dir)))
              create-list)
          (while (not (file-exists-p dir))
            (setq create-list (cons dir create-list)        
                  dir (directory-file-name (file-name-directory dir))))
          (while create-list
            (make-directory-internal (car create-list))
            (setq create-list (cdr create-list))))))))
\f
(put 'revert-buffer-function 'permanent-local t)
(defvar revert-buffer-function nil
  "Function to use to revert this buffer, or nil to do the default.
The function receives two arguments IGNORE-AUTO and NOCONFIRM,
which are the arguments that `revert-buffer' received.")

(put 'revert-buffer-insert-file-contents-function 'permanent-local t)
(defvar revert-buffer-insert-file-contents-function nil
  "Function to use to insert contents when reverting this buffer.
Gets two args, first the nominal file name to use,
and second, t if reading the auto-save file.")

(defun revert-buffer (&optional ignore-auto noconfirm)
  "Replace the buffer text with the text of the visited file on disk.
This undoes all changes since the file was visited or saved.
With a prefix argument, offer to revert from latest auto-save file, if
that is more recent than the visited file.

When called from lisp, The first argument is IGNORE-AUTO; only offer
to revert from the auto-save file when this is nil.  Note that the
sense of this argument is the reverse of the prefix argument, for the
sake of backward compatibility.  IGNORE-AUTO is optional, defaulting
to nil.

Optional second argument NOCONFIRM means don't ask for confirmation at
all.

If the value of `revert-buffer-function' is non-nil, it is called to
do the work.

The default revert function runs the hook `before-revert-hook' at the
beginning and `after-revert-hook' at the end."
  ;; I admit it's odd to reverse the sense of the prefix argument, but
  ;; there is a lot of code out there which assumes that the first
  ;; argument should be t to avoid consulting the auto-save file, and
  ;; there's no straightforward way to encourage authors to notice a
  ;; reversal of the argument sense.  So I'm just changing the user
  ;; interface, but leaving the programmatic interface the same.
  (interactive (list (not prefix-arg)))
  (if revert-buffer-function
      (funcall revert-buffer-function ignore-auto noconfirm)
    (let* ((opoint (point))
           (auto-save-p (and (not ignore-auto)
                             (recent-auto-save-p)
                             buffer-auto-save-file-name
                             (file-readable-p buffer-auto-save-file-name)
                             (y-or-n-p
   "Buffer has been auto-saved recently.  Revert from auto-save file? ")))
           (file-name (if auto-save-p
                          buffer-auto-save-file-name
                        buffer-file-name)))
      (cond ((null file-name)
             (error "Buffer does not seem to be associated with any file"))
            ((or noconfirm
                 (yes-or-no-p (format "Revert buffer from file %s? "
                                      file-name)))
             (run-hooks 'before-revert-hook)
             ;; If file was backed up but has changed since,
             ;; we shd make another backup.
             (and (not auto-save-p)
                  (not (verify-visited-file-modtime (current-buffer)))
                  (setq buffer-backed-up nil))
             ;; Get rid of all undo records for this buffer.
             (or (eq buffer-undo-list t)
                 (setq buffer-undo-list nil))
             (let ((buffer-read-only nil)
                   ;; Don't make undo records for the reversion.
                   (buffer-undo-list t))
               (if revert-buffer-insert-file-contents-function
                   (funcall revert-buffer-insert-file-contents-function
                            file-name auto-save-p)
                 (if (not (file-exists-p file-name))
                     (error "File %s no longer exists!" file-name))
                 ;; Bind buffer-file-name to nil
                 ;; so that we don't try to lock the file.
                 (let ((buffer-file-name nil))
                   (or auto-save-p
                       (unlock-buffer)))
                 (widen)
                 (insert-file-contents file-name (not auto-save-p)
                                       nil nil t)))
             (goto-char (min opoint (point-max)))
             (after-find-file nil nil t t)
             (run-hooks 'after-revert-hook)
             t)))))

(defun recover-file (file)
  "Visit file FILE, but get contents from its last auto-save file."
  (interactive
   (let ((prompt-file buffer-file-name)
         (file-name nil)
         (file-dir nil))
     (and prompt-file
          (setq file-name (file-name-nondirectory prompt-file)
                file-dir (file-name-directory prompt-file)))
     (list (read-file-name "Recover file: "
                               file-dir nil nil file-name))))
  (setq file (expand-file-name file))
  (if (auto-save-file-name-p (file-name-nondirectory file))
      (error "%s is an auto-save file" file))
  (let ((file-name (let ((buffer-file-name file))
                     (make-auto-save-file-name))))
    (cond ((not (file-newer-than-file-p file-name file))
           (error "Auto-save file %s not current" file-name))
          ((save-window-excursion
             (if (not (eq system-type 'vax-vms))
                 (with-output-to-temp-buffer "*Directory*"
                   (buffer-disable-undo standard-output)
                   (call-process "ls" nil standard-output nil
                                 (if (file-symlink-p file) "-lL" "-l")
                                 file file-name)))
             (yes-or-no-p (format "Recover auto save file %s? " file-name)))
           (switch-to-buffer (find-file-noselect file t))
           (let ((buffer-read-only nil))
             (erase-buffer)
             (insert-file-contents file-name nil))
           (after-find-file nil nil t))
          (t (error "Recover-file cancelled.")))))

(defun kill-some-buffers ()
  "For each buffer, ask whether to kill it."
  (interactive)
  (let ((list (buffer-list)))
    (while list
      (let* ((buffer (car list))
             (name (buffer-name buffer)))
        (and (not (string-equal name ""))
             (/= (aref name 0) ? )
             (yes-or-no-p
              (format "Buffer %s %s.  Kill? "
                      name
                      (if (buffer-modified-p buffer)
                          "HAS BEEN EDITED" "is unmodified")))
             (kill-buffer buffer)))
      (setq list (cdr list)))))
\f
(defun auto-save-mode (arg)
  "Toggle auto-saving of contents of current buffer.
With prefix argument ARG, turn auto-saving on if positive, else off."
  (interactive "P")
  (setq buffer-auto-save-file-name
        (and (if (null arg)
                 (or (not buffer-auto-save-file-name)
                     ;; If autosave is off because buffer has shrunk,
                     ;; then toggling should turn it on.
                     (< buffer-saved-size 0))
               (or (eq arg t) (listp arg) (and (integerp arg) (> arg 0))))
             (if (and buffer-file-name auto-save-visited-file-name
                      (not buffer-read-only))
                 buffer-file-name
               (make-auto-save-file-name))))
  ;; If -1 was stored here, to temporarily turn off saving,
  ;; turn it back on.
  (and (< buffer-saved-size 0)
       (setq buffer-saved-size 0))
  (if (interactive-p)
      (message "Auto-save %s (in this buffer)"
               (if buffer-auto-save-file-name "on" "off")))
  buffer-auto-save-file-name)

(defun rename-auto-save-file ()
  "Adjust current buffer's auto save file name for current conditions.
Also rename any existing auto save file, if it was made in this session."
  (let ((osave buffer-auto-save-file-name))
    (setq buffer-auto-save-file-name
          (make-auto-save-file-name))
    (if (and osave buffer-auto-save-file-name
             (not (string= buffer-auto-save-file-name buffer-file-name))
             (not (string= buffer-auto-save-file-name osave))
             (file-exists-p osave)
             (recent-auto-save-p))
        (rename-file osave buffer-auto-save-file-name t))))

(defun make-auto-save-file-name ()
  "Return file name to use for auto-saves of current buffer.
Does not consider `auto-save-visited-file-name' as that variable is checked
before calling this function.  You can redefine this for customization.
See also `auto-save-file-name-p'."
  (if buffer-file-name
      (concat (file-name-directory buffer-file-name)
              "#"
              (file-name-nondirectory buffer-file-name)
              "#")

    ;; Deal with buffers that don't have any associated files.  (Mail
    ;; mode tends to create a good number of these.)

    (let ((buffer-name (buffer-name))
          (limit 0))
      ;; Use technique from Sebastian Kremer's auto-save
      ;; package to turn slashes into \\!.  This ensures that
      ;; the auto-save buffer name is unique.

      (while (string-match "[/\\]" buffer-name limit)
        (setq buffer-name (concat (substring buffer-name 0 (match-beginning 0))
                        (if (string= (substring buffer-name
                                                (match-beginning 0)
                                                (match-end 0))
                                     "/")
                            "\\!"
                          "\\\\")
                        (substring buffer-name (match-end 0))))
        (setq limit (1+ (match-end 0))))

      (expand-file-name (format "#%s#%s#" buffer-name (make-temp-name ""))))))

(defun auto-save-file-name-p (filename)
  "Return non-nil if FILENAME can be yielded by `make-auto-save-file-name'.
FILENAME should lack slashes.  You can redefine this for customization."
  (string-match "^#.*#$" filename))
\f
(defconst list-directory-brief-switches
  (if (eq system-type 'vax-vms) "" "-CF")
  "*Switches for list-directory to pass to `ls' for brief listing,")

(defconst list-directory-verbose-switches
  (if (eq system-type 'vax-vms)
      "/PROTECTION/SIZE/DATE/OWNER/WIDTH=(OWNER:10)"
    "-l")
  "*Switches for list-directory to pass to `ls' for verbose listing,")

(defun list-directory (dirname &optional verbose)
  "Display a list of files in or matching DIRNAME, a la `ls'.
DIRNAME is globbed by the shell if necessary.
Prefix arg (second arg if noninteractive) means supply -l switch to `ls'.
Actions controlled by variables `list-directory-brief-switches'
and `list-directory-verbose-switches'."
  (interactive (let ((pfx current-prefix-arg))
                 (list (read-file-name (if pfx "List directory (verbose): "
                                         "List directory (brief): ")
                                       nil default-directory nil)
                       pfx)))
  (let ((switches (if verbose list-directory-verbose-switches
                    list-directory-brief-switches)))
    (or dirname (setq dirname default-directory))
    (setq dirname (expand-file-name dirname))
    (with-output-to-temp-buffer "*Directory*"
      (buffer-disable-undo standard-output)
      (princ "Directory ")
      (princ dirname)
      (terpri)
      (save-excursion
        (set-buffer "*Directory*")
        (let ((wildcard (not (file-directory-p dirname))))
          (insert-directory dirname switches wildcard (not wildcard)))))))

(defvar insert-directory-program "ls"
  "Absolute or relative name of the `ls' program used by `insert-directory'.")

;; insert-directory
;; - must insert _exactly_one_line_ describing FILE if WILDCARD and
;;   FULL-DIRECTORY-P is nil.
;;   The single line of output must display FILE's name as it was
;;   given, namely, an absolute path name.
;; - must insert exactly one line for each file if WILDCARD or
;;   FULL-DIRECTORY-P is t, plus one optional "total" line
;;   before the file lines, plus optional text after the file lines.
;;   Lines are delimited by "\n", so filenames containing "\n" are not
;;   allowed.
;;   File lines should display the basename.
;; - must be consistent with
;;   - functions dired-move-to-filename, (these two define what a file line is)
;;               dired-move-to-end-of-filename,
;;               dired-between-files, (shortcut for (not (dired-move-to-filename)))
;;               dired-insert-headerline
;;               dired-after-subdir-garbage (defines what a "total" line is)
;;   - variable dired-subdir-regexp
(defun insert-directory (file switches &optional wildcard full-directory-p)
  "Insert directory listing for FILE, formatted according to SWITCHES.
Leaves point after the inserted text.
SWITCHES may be a string of options, or a list of strings.
Optional third arg WILDCARD means treat FILE as shell wildcard.
Optional fourth arg FULL-DIRECTORY-P means file is a directory and
switches do not contain `d', so that a full listing is expected.

This works by running a directory listing program
whose name is in the variable `insert-directory-program'.
If WILDCARD, it also runs the shell specified by `shell-file-name'."
  ;; We need the directory in order to find the right handler.
  (let ((handler (find-file-name-handler (expand-file-name file)
                                         'insert-directory)))
    (if handler
        (funcall handler 'insert-directory file switches
                 wildcard full-directory-p)
      (if (eq system-type 'vax-vms)
          (vms-read-directory file switches (current-buffer))
        (if wildcard
            ;; Run ls in the directory of the file pattern we asked for.
            (let ((default-directory
                    (if (file-name-absolute-p file)
                        (file-name-directory file)
                      (file-name-directory (expand-file-name file))))
                  (pattern (file-name-nondirectory file))
                  (beg 0))
              ;; Quote some characters that have special meanings in shells;
              ;; but don't quote the wildcards--we want them to be special.
              ;; We also currently don't quote the quoting characters
              ;; in case people want to use them explicitly to quote
              ;; wildcard characters.
              (while (string-match "[ \t\n;<>&|()#$]" pattern beg)
                (setq pattern
                      (concat (substring pattern 0 (match-beginning 0))
                              "\\"
                              (substring pattern (match-beginning 0)))
                      beg (1+ (match-end 0))))
              (call-process shell-file-name nil t nil
                            "-c" (concat insert-directory-program
                                         " -d "
                                         (if (stringp switches)
                                             switches
                                           (mapconcat 'identity switches " "))
                                         " "
                                         pattern)))
          ;; SunOS 4.1.3, SVr4 and others need the "." to list the
          ;; directory if FILE is a symbolic link.
          (apply 'call-process
                 insert-directory-program nil t nil
                 (let (list)
                   (if (listp switches)
                       (setq list switches)
                     (if (not (equal switches ""))
                         (progn
                           ;; Split the switches at any spaces
                           ;; so we can pass separate options as separate args.
                           (while (string-match " " switches)
                             (setq list (cons (substring switches 0 (match-beginning 0))
                                              list)
                                   switches (substring switches (match-end 0))))
                           (setq list (cons switches list)))))
                   (append list
                           (list
                            (if full-directory-p
                                (concat (file-name-as-directory file) ".")
                              file))))))))))

(defvar kill-emacs-query-functions nil
  "Functions to call with no arguments to query about killing Emacs.
If any of these functions returns nil, killing Emacs is cancelled.")

(defun save-buffers-kill-emacs (&optional arg)
  "Offer to save each buffer, then kill this Emacs process.
With prefix arg, silently save all file-visiting buffers, then kill."
  (interactive "P")
  (save-some-buffers arg t)
  (and (or (not (memq t (mapcar (function
                                  (lambda (buf) (and (buffer-file-name buf)
                                                     (buffer-modified-p buf))))
                                (buffer-list))))
           (yes-or-no-p "Modified buffers exist; exit anyway? "))
       (or (not (fboundp 'process-list))
           ;; process-list is not defined on VMS.
           (let ((processes (process-list))
                 active)
             (while processes
               (and (memq (process-status (car processes)) '(run stop open))
                    (let ((val (process-kill-without-query (car processes))))
                      (process-kill-without-query (car processes) val)
                      val)
                    (setq active t))
               (setq processes (cdr processes)))
             (or (not active)
                 (yes-or-no-p "Active processes exist; kill them and exit anyway? "))))
       ;; Query the user for other things, perhaps.
       (run-hook-with-args-until-failure 'kill-emacs-query-functions)
       (kill-emacs)))
\f
(define-key ctl-x-map "\C-f" 'find-file)
(define-key ctl-x-map "\C-q" 'toggle-read-only)
(define-key ctl-x-map "\C-r" 'find-file-read-only)
(define-key ctl-x-map "\C-v" 'find-alternate-file)
(define-key ctl-x-map "\C-s" 'save-buffer)
(define-key ctl-x-map "s" 'save-some-buffers)
(define-key ctl-x-map "\C-w" 'write-file)
(define-key ctl-x-map "i" 'insert-file)
(define-key esc-map "~" 'not-modified)
(define-key ctl-x-map "\C-d" 'list-directory)
(define-key ctl-x-map "\C-c" 'save-buffers-kill-emacs)

(define-key ctl-x-4-map "f" 'find-file-other-window)
(define-key ctl-x-4-map "r" 'find-file-read-only-other-window)
(define-key ctl-x-4-map "\C-f" 'find-file-other-window)
(define-key ctl-x-4-map "b" 'switch-to-buffer-other-window)
(define-key ctl-x-4-map "\C-o" 'display-buffer)

(define-key ctl-x-5-map "b" 'switch-to-buffer-other-frame)
(define-key ctl-x-5-map "f" 'find-file-other-frame)
(define-key ctl-x-5-map "\C-f" 'find-file-other-frame)
(define-key ctl-x-5-map "r" 'find-file-read-only-other-frame)

;;; files.el ends here