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

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;; Copyright (C) 1985, 86, 87, 92, 93, 94, 1995 Free Software Foundation, Inc.
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;; Maintainer: FSF

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;; 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
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;; the Free Software Foundation; either version 2, or (at your option)
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;; 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.

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;;; 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.

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;;; Code:

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(defconst delete-auto-save-files t
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  "*Non-nil means delete auto-save file when a buffer is saved or killed.")
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(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 `^'.

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

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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))
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  "*Non-nil means make a backup of a file the first time it is saved.
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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
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`backup-by-copying-when-mismatch'.  See also `backup-inhibited'.")
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;; Do this so that local variables based on the file name
;; are not overridden by the major mode.
(defvar backup-inhibited nil
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  "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.")
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(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)

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(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
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  "The abbreviated truename of the file visited in the current buffer.
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That is, (abbreviate-file-name (file-truename buffer-file-name)).
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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)

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(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.
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`never' means do not make them.")
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(defvar dired-kept-versions 2
  "*When cleaning directory, number of versions to keep.")

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(defvar delete-old-versions nil
  "*If t, delete excess backup versions silently.
If nil, ask confirmation.  Any other value prevents any trimming.")
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(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
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  "*Non-nil says run dired if `find-file' is given the name of a directory.")
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;;;It is not useful to make this a local variable.
;;;(put 'find-file-not-found-hooks 'permanent-local t)
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(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.")

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;;;It is not useful to make this a local variable.
;;;(put 'find-file-hooks 'permanent-local t)
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(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
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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.
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See also `write-contents-hooks'.
Don't make this variable buffer-local; instead, use `local-write-file-hooks'.")
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;;; However, in case someone does make it local...
(put 'write-file-hooks 'permanent-local t)
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(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'.")
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(make-variable-buffer-local 'local-write-file-hooks)
(put 'local-write-file-hooks 'permanent-local t)
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(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'.")
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(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.")

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(defconst enable-local-eval 'maybe
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  "*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.")
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;; Avoid losing in versions where CLASH_DETECTION is disabled.
(or (fboundp 'lock-buffer)
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    (defalias 'lock-buffer 'ignore))
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(or (fboundp 'unlock-buffer)
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    (defalias 'unlock-buffer 'ignore))
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;; 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)
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    (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))
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      (apply op args))))
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(defun pwd ()
  "Show the current default directory."
  (interactive nil)
  (message "Directory %s" default-directory))

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(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
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		 (nconc cd-list
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			(list (if (= cd-start cd-colon)
				   nil
				(substitute-in-file-name
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				 (file-name-as-directory
				  (substring cd-path cd-start cd-colon)))))))
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	   (setq cd-start (+ cd-colon 1)))
	 cd-list)))

(defun cd-absolute (dir)
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  "Change current directory to given absolute file name DIR."
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  ;; Put the name into directory syntax now,
  ;; because otherwise expand-file-name may give some bad results.
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  (if (not (eq system-type 'vax-vms))
      (setq dir (file-name-as-directory dir)))
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  (setq dir (abbreviate-file-name (expand-file-name dir)))
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  (if (not (file-directory-p dir))
      (error "%s is not a directory" dir)
    (if (file-executable-p dir)
	(setq default-directory dir)
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      (error "Cannot cd to %s:  Permission denied" dir))))
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(defun cd (dir)
  "Make DIR become the current buffer's default directory.
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If your environment includes a `CDPATH' variable, try each one of that
colon-separated list of directories when resolving a relative directory name."
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  (interactive "FChange default directory: ")
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  (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"))))
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(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))
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(defun file-local-copy (file &optional buffer)
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  "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."
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  (let ((handler (find-file-name-handler file 'file-local-copy)))
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    (if handler
	(funcall handler 'file-local-copy file)
      nil)))
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(defun file-truename (filename &optional counter prev-dirs)
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  "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
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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.
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  (if (or (string= filename "~")
	  (and (string= (substring filename 0 1) "~")
	       (string-match "~[^/]*" filename)))
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      (progn
	(setq filename (expand-file-name filename))
	(if (string= filename "")
	    (setq filename "/"))))
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  (or counter (setq counter (list 100)))
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  (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)))
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    ;; 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)
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	  (let ((dir (or (file-name-directory filename) default-directory))
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		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))
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(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))
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      ;; 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)))))
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      ;; 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.
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      (while (string-match "\\`\\.\\./" tem)
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	(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))))))))
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      (setq newname (expand-file-name tem (file-name-directory newname)))
      (setq count (1- count)))
    newname))
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(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)))

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(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))
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    (pop-to-buffer buffer t)
    (raise-frame (window-frame (selected-window)))))
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(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)))

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(defun find-file-other-frame (filename)
  "Edit file FILENAME, in another frame.
May create a new frame, or reuse an existing one.
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See the function `display-buffer'."
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  (interactive "FFind file in other frame: ")
  (switch-to-buffer-other-frame (find-file-noselect filename)))
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(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)
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  (setq buffer-read-only t)
  (current-buffer))
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(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: ")
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  (find-file-other-window filename)
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  (setq buffer-read-only t)
  (current-buffer))
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(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.
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Use \\[toggle-read-only] to permit editing."
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  (interactive "fFind file read-only other frame: ")
  (find-file-other-frame filename)
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  (setq buffer-read-only t)
  (current-buffer))
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(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)))
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     (list (read-file-name
	    "Find alternate file: " file-dir nil nil file-name))))
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  (and (buffer-modified-p) (buffer-file-name)
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       ;; (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)
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	(onum buffer-file-number)
	(otrue buffer-file-truename)
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	(oname (buffer-name)))
    (rename-buffer " **lose**")
    (setq buffer-file-name nil)
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    (setq buffer-file-number nil)
    (setq buffer-file-truename nil)
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    (unwind-protect
	(progn
	  (unlock-buffer)
	  (find-file filename))
      (cond ((eq obuf (current-buffer))
	     (setq buffer-file-name ofile)
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	     (setq buffer-file-number onum)
	     (setq buffer-file-truename otrue)
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	     (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)))

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

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

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

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(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.")

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(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)
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	(let ((number (nthcdr 10 (file-attributes truename)))
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	      (list (buffer-list)) found)
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	  (and number
	       (while (and (not found) list)
		 (save-excursion
		   (set-buffer (car list))
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		   (if (and buffer-file-name
			    (equal buffer-file-number number)
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			    ;; 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))))
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	  found))))

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(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."
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  (setq filename
	(abbreviate-file-name
	 (expand-file-name filename)))
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  (if (file-directory-p filename)
      (if find-file-run-dired
	  (dired-noselect filename)
	(error "%s is a directory." filename))
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    (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.
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	   (other (and (not buf) (find-buffer-visiting filename)))
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	   error)
      ;; Let user know if there is a buffer with the same truename.
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      (if other
	  (progn
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	    (or nowarn
		(string-equal filename (buffer-file-name other))
		(message "%s and %s are the same file"
			 filename (buffer-file-name other)))
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	    ;; Optionally also find that buffer.
	    (if (or find-file-existing-other-name find-file-visit-truename)
		(setq buf other))))
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      (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? "
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    "File %s changed on disk.  Reread from disk? ")
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		       (file-name-nondirectory filename)))
		     (save-excursion
		       (set-buffer buf)
		       (revert-buffer t t)))))
	(save-excursion
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;;; 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))))
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	  (setq buf (create-file-buffer filename))
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	  (set-buffer-major-mode buf)
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	  (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.
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	     (or (run-hook-with-args-until-success 'find-file-not-found-hooks)
		 ;; If they fail too, set error.
		 (setq error t))))
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	  ;; Find the file's truename, and maybe use that as visited name.
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	  (setq buffer-file-truename truename)
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	  (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))
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	  (if find-file-visit-truename
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	      (setq buffer-file-name
		    (setq filename
			  (expand-file-name buffer-file-truename))))
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	  ;; 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)))

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(defvar after-find-file-from-revert-buffer nil)

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(defun after-find-file (&optional error warn noauto
				  after-find-file-from-revert-buffer)
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  "Called after finding a file and by the default revert function.
Sets buffer mode, parses local variables.
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Optional args ERROR, WARN, and NOAUTO: ERROR non-nil means there was an
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error in reading the file.  WARN non-nil means warn if there
exists an auto-save file more recent than the visited file.
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NOAUTO means don't mess with auto-save mode.
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Fourth arg AFTER-FIND-FILE-FROM-REVERT-BUFFER non-nil
 means this call was from `revert-buffer'.
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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)
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		   "File exists, but cannot be read.")
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		  ((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")
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		  ((file-exists-p (file-name-directory buffer-file-name))
		   (setq buffer-read-only nil))
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		  (t
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		   (setq buffer-read-only nil)
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		   (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")))))
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      (if msg
	  (progn
	    (message msg)
	    (or not-serious (sit-for 1 nil t)))))
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    (if (and auto-save-default (not noauto))
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	(auto-save-mode t)))
  (normal-mode t)
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  (run-hooks 'find-file-hooks))
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(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
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      (let ((enable-local-variables (or (not find-file)
					enable-local-variables)))
	(hack-local-variables))
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    (error (message "File local-variables error: %s"
		    (prin1-to-string err)))))

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(defvar auto-mode-alist (mapcar 'purecopy
				'(("\\.text\\'" . text-mode)
				  ("\\.c\\'" . c-mode)
				  ("\\.h\\'" . c-mode)
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				  ("\\.tex\\'" . tex-mode)
				  ("\\.ltx\\'" . latex-mode)
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				  ("\\.el\\'" . emacs-lisp-mode)
				  ("\\.mm\\'" . nroff-mode)
				  ("\\.me\\'" . nroff-mode)
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				  ("\\.ms\\'" . nroff-mode)
				  ("\\.man\\'" . nroff-mode)
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				  ("\\.scm\\'" . scheme-mode)
				  ("\\.l\\'" . lisp-mode)
				  ("\\.lisp\\'" . lisp-mode)
				  ("\\.f\\'" . fortran-mode)
				  ("\\.for\\'" . fortran-mode)
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				  ("\\.p\\'" . pascal-mode)
				  ("\\.pas\\'" . pascal-mode)
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				  ("\\.mss\\'" . scribe-mode)
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				  ("\\.ada\\'" . ada-mode)
				  ("\\.icn\\'" . icon-mode)
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				  ("\\.pl\\'" . prolog-mode)
				  ("\\.cc\\'" . c++-mode)
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				  ("\\.hh\\'" . c++-mode)
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				  ("\\.C\\'" . c++-mode)
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				  ("\\.H\\'" . c++-mode)
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				  ("\\.cpp\\'" . c++-mode)
				  ("\\.cxx\\'" . c++-mode)
				  ("\\.hxx\\'" . c++-mode)
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				  ("\\.c\\+\\+\\'" . c++-mode)
				  ("\\.h\\+\\+\\'" . c++-mode)
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;;;				  ("\\.mk\\'" . makefile-mode)
;;;				  ("[Mm]akefile" . makefile-mode)
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;;; Less common extensions come here
;;; so more common ones above are found faster.
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				  ("\\.texinfo\\'" . texinfo-mode)
				  ("\\.texi\\'" . texinfo-mode)
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				  ("\\.s\\'" . asm-mode)
				  ("ChangeLog\\'" . change-log-mode)
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				  ("change.log\\'" . change-log-mode)
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				  ("changelo\\'" . change-log-mode)
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				  ("ChangeLog.[0-9]+\\'" . change-log-mode)
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				  ("\\$CHANGE_LOG\\$\\.TXT" . change-log-mode)
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;; The following should come after the ChangeLog pattern
;; for the sake of ChangeLog.1, etc.
				  ("\\.[12345678]\\'" . nroff-mode)
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				  ("\\.TeX\\'" . tex-mode)
				  ("\\.sty\\'" . latex-mode)
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				  ("\\.cls\\'" . latex-mode) ;LaTeX 2e class
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				  ("\\.bbl\\'" . latex-mode)
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				  ("\\.bib\\'" . bibtex-mode)
				  ("\\.article\\'" . text-mode)
				  ("\\.letter\\'" . text-mode)
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				  ("\\.tcl\\'" . tcl-mode)
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				  ("\\.lsp\\'" . lisp-mode)
				  ("\\.awk\\'" . awk-mode)
				  ("\\.prolog\\'" . prolog-mode)
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				  ("\\.tar\\'" . tar-mode)
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				  ;; Mailer puts message to be edited in
				  ;; /tmp/Re.... or Message
				  ("^/tmp/Re" . text-mode)
				  ("/Message[0-9]*\\'" . text-mode)
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				  ("/drafts/[0-9]+\\'" . mh-letter-mode)
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				  ;; some news reader is reported to use this
				  ("^/tmp/fol/" . text-mode)
				  ("\\.y\\'" . c-mode)
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				  ("\\.lex\\'" . c-mode)
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				  ("\\.oak\\'" . scheme-mode)
				  ("\\.scm.[0-9]*\\'" . scheme-mode)
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				  ("\\.sgm\\'" . sgml-mode)
				  ("\\.sgml\\'" . sgml-mode)
				  ("\\.dtd\\'" . sgml-mode)
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				  ;; .emacs following a directory delimiter
				  ;; in either Unix or VMS syntax.
				  ("[]>:/]\\..*emacs\\'" . emacs-lisp-mode)
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				  ;; _emacs following a directory delimiter
				  ;; in MsDos syntax
				  ("[:/]_emacs\\'" . emacs-lisp-mode)
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				  ("\\.ml\\'" . lisp-mode)))
  "\
Alist of filename patterns vs corresponding major mode functions.
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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.")
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(defconst interpreter-mode-alist
  '(("perl" . perl-mode)
    ("wish" . tcl-mode)
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    ("wishx" . tcl-mode)
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    ("tcl" . tcl-mode)
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    ("tclsh" . tcl-mode)
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    ("awk" . awk-mode)
    ("gawk" . awk-mode)
    ("scm" . scheme-mode))
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  "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.")

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(defconst inhibit-first-line-modes-regexps '("\\.tar\\'")
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  "List of regexps; if one matches a file name, don't look for `-*-'.")
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(defconst inhibit-first-line-modes-suffixes nil
  "List of regexps for what to ignore, for `inhibit-first-line-modes-regexps'.
When checking `inhibit-first-line-modes-regexps', we first discard
from the end of the file name anything that matches one of these regexps.")

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

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(defun set-auto-mode ()
  "Select major mode appropriate for current buffer.
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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'.
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If `enable-local-variables' is nil, this function does not check for a
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-*- mode tag."
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  ;; Look for -*-MODENAME-*- or -*- ... mode: MODENAME; ... -*-
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  (let (beg end done)
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    (save-excursion
      (goto-char (point-min))
      (skip-chars-forward " \t\n")
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      (and enable-local-variables
	   ;; Don't look for -*- if this file name matches any
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	   ;; of the regexps in inhibit-first-line-modes-regexps.
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	   (let ((temp inhibit-first-line-modes-regexps)
		 (name (file-name-sans-versions buffer-file-name)))
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	     (while (let ((sufs inhibit-first-line-modes-suffixes))
		      (while (and sufs (not (string-match (car sufs) name)))
			(setq sufs (cdr sufs)))
		      sufs)
	       (setq name (substring name 0 (match-beginning 0))))
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	     (while (and temp
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			 (not (string-match (car temp) name)))
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	       (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
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		 ;; and execute them left to right.
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		 (while (let ((case-fold-search t))
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			  (or (and (looking-at "mode:")
				   (goto-char (match-end 0)))
			      (re-search-forward "[ \t;]mode:" end t)))
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		   (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)
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	  (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.
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		(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))))
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		(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))
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			   (if (looking-at "#! *\\([^ \t\n]+\\)")
			       (buffer-substring (match-beginning 1)
						 (match-end 1))
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			     "")))
			elt)
		    ;; Map interpreter name to a mode.
		    (setq elt (assoc (file-name-nondirectory interpreter)
				     interpreter-mode-alist))
		    (if elt
			(funcall (cdr elt))))))))))))
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(defun hack-local-variables-prop-line ()
  ;; Set local variables specified in the -*- line.
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  ;; Ignore any specification for `mode:';
  ;; set-auto-mode should already have handled that.
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  (save-excursion
    (goto-char (point-min))
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    (let ((result nil)
	  (end (save-excursion (end-of-line (and (looking-at "^#!") 2)) (point))))
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      ;; 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]*-\\*-\\)")
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	     ;; Simple form: "-*- MODENAME -*-".  Already handled.
	     nil)
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	    (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)))))
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		 (or (eq key 'mode)
		     (setq result (cons (cons key val) result)))
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		 (skip-chars-forward " \t;")))
	     (setq result (nreverse result))))
      
      (if (and result
	       (or (eq enable-local-variables t)
		   (and enable-local-variables
			(save-window-excursion
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			  (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))))))
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			  (y-or-n-p (format "Set local variables as specified in -*- line of %s? "
					    (file-name-nondirectory buffer-file-name)))))))
	  (while result
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	    (hack-one-local-variable (car (car result)) (cdr (car result)))
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	    (setq result (cdr result)))))))
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(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.")

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(defun hack-local-variables ()
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  "Parse and put into effect this buffer's local variables spec."
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  (hack-local-variables-prop-line)
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  ;; 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)
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	       (or (eq enable-local-variables t)
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		   (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? "
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 					    (if buffer-file-name
 						(file-name-nondirectory 
 						 buffer-file-name)
 					      (concat "buffer "
 						      (buffer-name))))))))))
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	(let ((continue t)
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	      prefix prefixlen suffix beg
	      (enable-local-eval enable-local-eval))
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	  ;; 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)))))
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