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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, 95, 1996 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
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;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, 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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(defgroup backup nil
  "Backups of edited data files."
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  :group 'files)
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(defgroup find-file nil
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  "Finding files."
  :group 'files)
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(defcustom delete-auto-save-files t
  "*Non-nil means delete auto-save file when a buffer is saved or killed."
  :type 'boolean
  :group 'auto-save)

(defcustom directory-abbrev-alist
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  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
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the name it is linked to."
  :type '(repeat (cons :format "%v"
		       :value ("" . "")
		       (regexp :tag "From")
		       (regexp :tag "To")))
  :group 'abbrev
  :group 'find-file)
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;;; Turn off backup files on VMS since it has version numbers.
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(defcustom 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'."
  :type 'boolean
  :group 'backup)
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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)

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(defcustom backup-by-copying nil
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 "*Non-nil means always use copying to create backup files.
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See documentation of variable `make-backup-files'."
 :type 'boolean
 :group 'backup)
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(defcustom backup-by-copying-when-linked nil
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 "*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.
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This variable is relevant only if `backup-by-copying' is nil."
 :type 'boolean
 :group 'backup)
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(defcustom backup-by-copying-when-mismatch nil
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  "*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.
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This variable is relevant only if `backup-by-copying' is nil."
  :type 'boolean
  :group 'backup)
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(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.")

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

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(defcustom find-file-existing-other-name t
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  "*Non-nil means find a file under alternative names, in existing buffers.
This means if any existing buffer is visiting the file you want
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under another name, you get the existing buffer instead of a new buffer."
  :type 'boolean
  :group 'find-file)
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(defcustom find-file-visit-truename nil
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  "*Non-nil means visit a file under its truename.
The truename of a file is found by chasing all links
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both at the file level and at the levels of the containing directories."
  :type 'boolean
  :group 'find-file)
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(defcustom revert-without-query
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  nil
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  "*Specify which files should be reverted without query.
The value is a list of regular expressions.
If the file name matches one of these regular expressions,
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then `revert-buffer' reverts the file without querying
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if the file has changed on disk and you have not edited the buffer."
  :type 'boolean
  :group 'find-file)
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(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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(defvar buffer-file-numbers-unique (not (memq system-type '(windows-nt)))
  "Non-nil means that buffer-file-number uniquely identifies files.")

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(defcustom file-precious-flag nil
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  "*Non-nil means protect against I/O errors while saving files.
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Some modes set this non-nil in particular buffers.
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This feature works by writing the new contents into a temporary file
and then renaming the temporary file to replace the original.
In this way, any I/O error in writing leaves the original untouched,
and there is never any instant where the file is nonexistent.

Note that this feature forces backups to be made by copying.
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Yet, at the same time, saving a precious file
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breaks any hard links between it and other files."
  :type 'boolean
  :group 'backup)
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(defcustom version-control nil
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  "*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."
  :type 'boolean
  :group 'backup
  :group 'vc)

(defcustom dired-kept-versions 2
  "*When cleaning directory, number of versions to keep."
  :type 'integer
  :group 'backup
  :group 'dired)

(defcustom delete-old-versions nil
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  "*If t, delete excess backup versions silently.
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If nil, ask confirmation.  Any other value prevents any trimming."
  :type '(choice (const :tag "Delete" t)
		 (const :tag "Ask" nil)
		 (sexp :tag "Leave" :format "%t\n" other))
  :group 'backup)

(defcustom kept-old-versions 2
  "*Number of oldest versions to keep when a new numbered backup is made."
  :type 'integer
  :group 'backup)

(defcustom kept-new-versions 2
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  "*Number of newest versions to keep when a new numbered backup is made.
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Includes the new backup.  Must be > 0"
  :type 'integer
  :group 'backup)
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(defcustom require-final-newline nil
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  "*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.
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nil means don't add newlines."
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  :type '(choice (const :tag "Off" nil)
		 (const :tag "Add" t)
		 (sexp :tag "Ask" :format "%t\n" ask))
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  :group 'editing-basics)
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(defcustom auto-save-default t
  "*Non-nil says by default do auto-saving of every file-visiting buffer."
  :type 'boolean
  :group 'auto-save)
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(defcustom auto-save-visited-file-name nil
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  "*Non-nil says auto-save a buffer in the file it is visiting, when practical.
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Normally auto-save files are written under other names."
  :type 'boolean
  :group 'auto-save)
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(defcustom save-abbrevs nil
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  "*Non-nil means save word abbrevs too when files are saved.
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Loading an abbrev file sets this to t."
  :type 'boolean
  :group 'abbrev)
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(defcustom find-file-run-dired t
  "*Non-nil says run dired if `find-file' is given the name of a directory."
  :type 'boolean
  :group 'find-file)
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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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Don't make this variable buffer-local; instead, use `local-write-file-hooks'.
See also `write-contents-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
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`write-file-hooks'.

This variable is meant to be used for hooks that have to do with a
particular visited file.  Therefore, it is a permanent local, so that
changing the major mode does not clear it.  However, calling
`set-visited-file-name' does clear it.")
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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.
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This variable is meant to be used for hooks that 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
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major mode does clear it.

This variable automatically becomes buffer-local whenever it is set.
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If you use `add-hook' to add elements to the list, use nil for the
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LOCAL argument.
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See also `write-file-hooks'.")
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(make-variable-buffer-local 'write-contents-hooks)
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(defcustom enable-local-variables t
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  "*Control use of local variables in files you visit.
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The value can be t, nil or something else.
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A value of t means file local variables specifications are obeyed;
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nil means they are ignored; anything else means query.

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The command \\[normal-mode] always obeys file local variable
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specifications and ignores this variable."
  :type '(choice (const :tag "Obey" t)
		 (const :tag "Ignore" nil)
		 (sexp :tag "Query" :format "%t\n" other))
  :group 'find-file)
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(defcustom 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
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and ignores this variable."
  :type '(choice (const :tag "Obey" t)
		 (const :tag "Ignore" nil)
		 (sexp :tag "Query" :format "%t\n" other))
  :group 'find-file)
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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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(or (fboundp 'file-locked-p)
    (defalias 'file-locked-p 'ignore))
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(defvar view-read-only nil
  "*Non-nil means buffers visiting files read-only, do it in view mode.")

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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 convert-standard-filename (filename)
  "Convert a standard file's name to something suitable for the current OS.
This function's standard definition is trivial; it just returns the argument.
However, on some systems, the function is redefined
with a definition that really does change some file names."
  filename)
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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.")

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(defvar path-separator ":"
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  "Character used to separate directories in search paths.")
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(defun parse-colon-path (cd-path)
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  "Explode a colon-separated search path into a list of directory names."
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  (and cd-path
       (let (cd-prefix cd-list (cd-start 0) cd-colon)
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	 (setq cd-path (concat cd-path path-separator))
	 (while (setq cd-colon (string-match path-separator cd-path cd-start))
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	   (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))
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      (if (file-exists-p dir)
	  (error "%s is not a directory" dir)
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	(error "%s: no such directory" dir))
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    (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
   (list (read-file-name "Change default directory: "
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			 default-directory default-directory
			 (and (member cd-path '(nil ("./")))
			      (null (getenv "CDPATH"))))))
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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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  ;; The last test looks dubious, maybe `+' is meant here?  --simon.
  (if (or (string= filename "") (string= filename "~")
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	  (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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    ;; andrewi@harlequin.co.uk - none of the following code (except for
    ;; invoking the file-name handler) currently applies on Windows
    ;; (ie. there are no native symlinks), but there is an issue with
    ;; case differences being ignored by the OS, and short "8.3 DOS"
    ;; name aliases existing for all files.  (The short names are not
    ;; reported by directory-files, but can be used to refer to files.)
    ;; It seems appropriate for file-truename to resolve these issues in
    ;; the most natural way, which on Windows is to call the function
    ;; `w32-long-file-name' - this returns the exact name of a file as
    ;; it is stored on disk (expanding short name aliases with the full
    ;; name in the process).
    (if (eq system-type 'windows-nt)
      (let ((handler (find-file-name-handler filename 'file-truename))
	    newname)
	;; 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))
	  ;; If filename contains a wildcard, newname will be the old name.
	  (if (string-match "[*?]" filename)
	      (setq newname filename)
	    ;; If filename doesn't exist, newname will be nil.
	    (setq newname (w32-long-file-name filename)))
	  (setq filename (or newname filename)))
	(setq done t)))

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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))
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      (save-match-data
	(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 (replace-match "/" nil nil tem)))
	;; 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 (expand-file-name newname))
	  ;; Chase links in the default dir of the symlink.
	  (setq newname
		(file-chase-links
		 (directory-file-name (file-name-directory newname))))
	  ;; Now find the parent of that dir.
	  (setq newname (file-name-directory newname)))
	(setq newname (expand-file-name tem (file-name-directory newname)))
	(setq count (1- count))))
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    newname))
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(defun switch-to-buffer-other-window (buffer &optional norecord)
  "Select buffer BUFFER in another window.
Optional second arg NORECORD non-nil means
do not put this buffer at the front of the list of recently selected ones."
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  (interactive "BSwitch to buffer in other window: ")
  (let ((pop-up-windows t))
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    (pop-to-buffer buffer t norecord)))
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(defun switch-to-buffer-other-frame (buffer &optional norecord)
  "Switch to buffer BUFFER in another frame.
Optional second arg NORECORD non-nil means
do not put this buffer at the front of the list of recently selected ones."
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  (interactive "BSwitch to buffer in other frame: ")
  (let ((pop-up-frames t))
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    (pop-to-buffer buffer t norecord)
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    (raise-frame (window-frame (selected-window)))))
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(defun find-file (filename)
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  "Edit file FILENAME.
Switch to a buffer visiting file FILENAME,
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creating one if none already exists."
  (interactive "FFind file: ")
  (switch-to-buffer (find-file-noselect filename)))
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(defun find-file-other-window (filename)
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  "Edit file FILENAME, in another window.
May create a new window, or reuse an existing one.
See the function `display-buffer'."
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  (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)
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  "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)
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  "Edit file FILENAME but don't allow changes.
Like \\[find-file] but marks buffer as read-only.
Use \\[toggle-read-only] to permit editing."
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  (interactive "fFind file read-only: ")
  (find-file filename)
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  (toggle-read-only 1)
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  (current-buffer))
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(defun find-file-read-only-other-window (filename)
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  "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."
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  (interactive "fFind file read-only other window: ")
  (find-file-other-window filename)
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  (toggle-read-only 1)
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  (current-buffer))
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(defun find-file-read-only-other-frame (filename)
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  "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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  (toggle-read-only 1)
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  (current-buffer))
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(defun find-alternate-file-other-window (filename)
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  "Find file FILENAME as a replacement for the file in the next window.
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This command does not select that window."
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  (interactive
   (save-selected-window
     (other-window 1)
     (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
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	      "Find alternate file: " file-dir nil nil file-name)))))
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  (if (one-window-p)
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      (find-file-other-window filename)
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    (save-selected-window
      (other-window 1)
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      (find-alternate-file filename))))
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(defun find-alternate-file (filename)
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  "Find file FILENAME, select its buffer, kill previous buffer.
If the current buffer now contains an empty file that you just visited
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\(presumably by mistake), use this command to visit the file you really want."
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  (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
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	    "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)))
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    (if (get-buffer " **lose**")
	(kill-buffer " **lose**"))
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    (rename-buffer " **lose**")
    (unwind-protect
	(progn
	  (unlock-buffer)
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	  (setq buffer-file-name nil)
	  (setq buffer-file-number nil)
	  (setq buffer-file-truename nil)
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	  (find-file filename))
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      (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))))
718

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(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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(defvar automount-dir-prefix "^/tmp_mnt/"
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  "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.
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  (if (and automount-dir-prefix
	   (string-match automount-dir-prefix filename)
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	   (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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	     ;; MS-DOS root directories can come with a drive letter;
	     ;; Novell Netware allows drive letters beyond `Z:'.
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	     (not (and (or (eq system-type 'ms-dos)
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			   (eq system-type 'windows-nt))
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		       (save-match-data
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			 (string-match "^[a-zA-`]:/$" 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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(defcustom find-file-not-true-dirname-list nil
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  "*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
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name to this list as a string."
  :type '(repeat (string :tag "Name"))
  :group 'find-file)
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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 buffer-file-numbers-unique
	       number
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	       (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 rawfile)
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  "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.
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The buffer is not selected, just returned to the caller.
Optional first arg NOWARN non-nil means suppress any warning messages.
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Optional second arg RAWFILE non-nil means the file is read literally."
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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
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	  (dired-noselect (if find-file-visit-truename
			      (abbreviate-file-name (file-truename filename))
			    filename))
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	(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))
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		    ;; Certain files should be reverted automatically
		    ;; if they have changed on disk and not in the buffer.
		    ((and (not (buffer-modified-p buf))
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			  (let ((tail revert-without-query)
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				(found nil))
			    (while tail
			      (if (string-match (car tail) filename)
				  (setq found t))
			      (setq tail (cdr tail)))
			    found))
		     (with-current-buffer buf
		      (message "Reverting file %s..." filename)
		      (revert-buffer t t)
		      (message "Reverting file %s...done" filename)))
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		    ((yes-or-no-p
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		      (if (string= (file-name-nondirectory filename)
				   (buffer-name buf))
			  (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))
			(format
			 (if (buffer-modified-p buf)
      "File %s changed on disk.  Discard your edits in %s? "
      "File %s changed on disk.  Reread from disk into %s? ")
			 (file-name-nondirectory filename)
			 (buffer-name buf))))
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		     (with-current-buffer buf
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		       (revert-buffer t t)))
		    ((not (eq rawfile (not (null find-file-literally))))
		     (if rawfile
			 (message "File is already visited, and not literally")
		       (message "File is already visited, and visited literally")))))
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	(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)
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	  (if rawfile
	      (condition-case ()
		  (insert-file-contents-literally filename t)
		(file-error
		 ;; Unconditionally set error
		 (setq error t)))
	    (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)))))
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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)))
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	  (if rawfile
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	      (progn
		(setq enable-multibyte-characters nil)
		(make-local-variable 'find-file-literally)
		(setq find-file-literally t))
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	    (after-find-file error (not nowarn))
	    (setq buf (current-buffer)))))
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      buf)))
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(defun insert-file-contents-literally (filename &optional visit beg end replace)
  "Like `insert-file-contents', but only reads in the file literally.
A buffer may be modified in several ways after reading into the buffer,
to Emacs features such as format decoding, character code
conversion, find-file-hooks, automatic uncompression, etc.

This function ensures that none of these modifications will take place."
  (let ((format-alist nil)
	(after-insert-file-functions nil)
	(coding-system-for-read 'no-conversion)
	(coding-system-for-write 'no-conversion)
	(jka-compr-compression-info-list nil)
	(find-buffer-file-type-function
	 (if (fboundp 'find-buffer-file-type)
	     (symbol-function 'find-buffer-file-type)
	   nil)))
    (unwind-protect
	(progn
	  (fset 'find-buffer-file-type (lambda (filename) t))
	  (insert-file-contents filename visit beg end replace))
      (if find-buffer-file-type-function
	  (fset 'find-buffer-file-type find-buffer-file-type-function)
	(fmakunbound 'find-buffer-file-type)))))

(defun insert-file-literally (filename)
  "Insert contents of file FILENAME into buffer after point with no conversion.

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

(defvar find-file-literally nil
  "Non-nil if this buffer was made by `find-file-literally' or equivalent.
This is a permanent local.")
(put 'find-file-literally 'permanent-local t)
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(defun find-file-literally (filename) 
  "Visit file FILENAME with no conversion of any kind.
Format conversion and character code conversion are both disabled,
and multibyte characters are disabled in the resulting buffer.
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The major mode used is Fundamental mode regardless of the file name,
and local variable specifications in the file are ignored.
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Automatic uncompression is also disabled.

You cannot absolutely rely on this function to result in
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visiting the file literally.  If Emacs already has a buffer
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which is visiting the file, you get the existing buffer,
regardless of whether it was created literally or not.

In a Lisp program, if you want to be sure of accessing a file's
contents literally, you should create a temporary buffer and then read
the file contents into it using `insert-file-contents-literally'."
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  (interactive "FFind file literally: ")
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  (switch-to-buffer (find-file-noselect filename nil t)))
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