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

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;; Copyright (C) 1985, 1986, 1987, 1992, 1993, 1994, 1995, 1996,
;;   1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
;;   2006 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
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;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, 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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(defvar font-lock-keywords)


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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
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  "Non-nil means delete auto-save file when a buffer is saved or killed.
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Note that the auto-save file will not be deleted if the buffer is killed
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when it has unsaved changes."
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  :type 'boolean
  :group 'auto-save)

(defcustom directory-abbrev-alist
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  nil
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  "Alist of abbreviations for file directories.
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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
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`backup-by-copying', `backup-by-copying-when-linked',
`backup-by-copying-when-mismatch' and
`backup-by-copying-when-privileged-mismatch'.  See also `backup-inhibited'."
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  :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.
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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.
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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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(defcustom backup-by-copying-when-privileged-mismatch 200
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  "Non-nil means create backups by copying to preserve a privileged owner.
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Renaming may still be used (subject to control of other variables)
when it would not result in changing the owner of the file or if the owner
has a user id greater than the value of this variable.  This is useful
when low-numbered uid's are used for special system users (such as root)
that must maintain ownership of certain files.
This variable is relevant only if `backup-by-copying' and
`backup-by-copying-when-mismatch' are nil."
  :type '(choice (const nil) integer)
  :group 'backup)

(defvar backup-enable-predicate 'normal-backup-enable-predicate
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  "Predicate that looks at a file name and decides whether to make backups.
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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 always offer to save buffer on exit.
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Do so 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.
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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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(put 'find-file-visit-truename 'safe-local-variable 'boolean)
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(defcustom revert-without-query nil
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  "Specify which files should be reverted without query.
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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."
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  :type '(repeat regexp)
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  :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)))
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  "Non-nil means that `buffer-file-number' uniquely identifies files.")
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(defvar buffer-file-read-only nil
  "Non-nil if visited file was read-only when visited.")
(make-variable-buffer-local 'buffer-file-read-only)

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(defcustom temporary-file-directory
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  (file-name-as-directory
   (cond ((memq system-type '(ms-dos windows-nt))
	  (or (getenv "TEMP") (getenv "TMPDIR") (getenv "TMP") "c:/temp"))
	 ((memq system-type '(vax-vms axp-vms))
	  (or (getenv "TMPDIR") (getenv "TMP") (getenv "TEMP") "SYS$SCRATCH:"))
	 (t
	  (or (getenv "TMPDIR") (getenv "TMP") (getenv "TEMP") "/tmp"))))
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  "The directory for writing temporary files."
  :group 'files
  :type 'directory)
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(defcustom small-temporary-file-directory
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  (if (eq system-type 'ms-dos) (getenv "TMPDIR"))
  "The directory for writing small temporary files.
If non-nil, this directory is used instead of `temporary-file-directory'
by programs that create small temporary files.  This is for systems that
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have fast storage with limited space, such as a RAM disk."
  :group 'files
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  :type '(choice (const nil) directory))
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;; The system null device. (Should reference NULL_DEVICE from C.)
(defvar null-device "/dev/null" "The system null device.")

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(defvar file-name-invalid-regexp
  (cond ((and (eq system-type 'ms-dos) (not (msdos-long-file-names)))
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	 (concat "^\\([^A-Z[-`a-z]\\|..+\\)?:\\|" ; colon except after drive
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		 "[+, ;=|<>\"?*]\\|\\[\\|\\]\\|"  ; invalid characters
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		 "[\000-\031]\\|"		  ; control characters
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		 "\\(/\\.\\.?[^/]\\)\\|"	  ; leading dots
		 "\\(/[^/.]+\\.[^/.]*\\.\\)"))	  ; more than a single dot
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	((memq system-type '(ms-dos windows-nt cygwin))
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	 (concat "^\\([^A-Z[-`a-z]\\|..+\\)?:\\|" ; colon except after drive
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		 "[|<>\"?*\000-\031]"))		  ; invalid characters
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	(t "[\000]"))
  "Regexp recognizing file names which aren't allowed by the filesystem.")

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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.
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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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  :type '(choice (const :tag "Never" never)
		 (const :tag "If existing" nil)
		 (other :tag "Always" t))
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  :group 'backup
  :group 'vc)
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(put 'version-control 'safe-local-variable
     '(lambda (x) (or (booleanp x) (equal x 'never))))
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(defcustom dired-kept-versions 2
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  "When cleaning directory, number of versions to keep."
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  :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)
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		 (other :tag "Leave" other))
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  :group 'backup)

(defcustom kept-old-versions 2
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  "Number of oldest versions to keep when a new numbered backup is made."
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  :type 'integer
  :group 'backup)
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(put 'kept-old-versions 'safe-local-variable 'integerp)
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(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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(put 'kept-new-versions 'safe-local-variable 'integerp)
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(defcustom require-final-newline nil
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  "Whether to add a newline automatically at the end of the file.
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A value of t means do this only when the file is about to be saved.
A value of `visit' means do this right after the file is visited.
A value of `visit-save' means do it at both of those times.
Any other non-nil value means ask user whether to add a newline, when saving.
nil means don't add newlines.

Certain major modes set this locally to the value obtained
from `mode-require-final-newline'."
  :type '(choice (const :tag "When visiting" visit)
		 (const :tag "When saving" t)
		 (const :tag "When visiting or saving" visit-save)
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		 (const :tag "Don't add newlines" nil)
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		 (other :tag "Ask each time" ask))
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  :group 'editing-basics)
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(defcustom mode-require-final-newline t
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  "Whether to add a newline at end of file, in certain major modes.
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Those modes set `require-final-newline' to this value when you enable them.
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They do so because they are often used for files that are supposed
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to end in newlines, and the question is how to arrange that.

A value of t means do this only when the file is about to be saved.
A value of `visit' means do this right after the file is visited.
A value of `visit-save' means do it at both of those times.
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Any other non-nil value means ask user whether to add a newline, when saving.

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nil means do not add newlines.  That is a risky choice in this variable
since this value is used for modes for files that ought to have final newlines.
So if you set this to nil, you must explicitly check and add
a final newline, whenever you save a file that really needs one."
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  :type '(choice (const :tag "When visiting" visit)
		 (const :tag "When saving" t)
		 (const :tag "When visiting or saving" visit-save)
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		 (const :tag "Don't add newlines" nil)
		 (other :tag "Ask each time" ask))
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  :group 'editing-basics
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  :version "22.1")
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(defcustom auto-save-default t
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  "Non-nil says by default do auto-saving of every file-visiting buffer."
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  :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 auto-save-file-name-transforms
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  `(("\\`/[^/]*:\\([^/]*/\\)*\\([^/]*\\)\\'"
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     ;; Don't put "\\2" inside expand-file-name, since it will be
     ;; transformed to "/2" on DOS/Windows.
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     ,(concat temporary-file-directory "\\2") t))
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  "Transforms to apply to buffer file name before making auto-save file name.
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Each transform is a list (REGEXP REPLACEMENT UNIQUIFY):
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REGEXP is a regular expression to match against the file name.
If it matches, `replace-match' is used to replace the
matching part with REPLACEMENT.
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If the optional element UNIQUIFY is non-nil, the auto-save file name is
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constructed by taking the directory part of the replaced file-name,
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concatenated with the buffer file name with all directory separators
changed to `!' to prevent clashes.  This will not work
correctly if your filesystem truncates the resulting name.

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All the transforms in the list are tried, in the order they are listed.
When one transform applies, its result is final;
no further transforms are tried.

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The default value is set up to put the auto-save file into the
temporary directory (see the variable `temporary-file-directory') for
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editing a remote file.

On MS-DOS filesystems without long names this variable is always
ignored."
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  :group 'auto-save
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  :type '(repeat (list (string :tag "Regexp") (string :tag "Replacement")
					   (boolean :tag "Uniquify")))
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  :version "21.1")

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(defcustom save-abbrevs t
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  "Non-nil means save word abbrevs too when files are saved.
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If `silently', don't ask the user before saving."
  :type '(choice (const t) (const nil) (const silently))
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  :group 'abbrev)
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(defcustom find-file-run-dired t
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  "Non-nil means allow `find-file' to visit directories.
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To visit the directory, `find-file' runs `find-directory-functions'."
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  :type 'boolean
  :group 'find-file)
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(defcustom find-directory-functions '(cvs-dired-noselect dired-noselect)
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  "List of functions to try in sequence to visit a directory.
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Each function is called with the directory name as the sole argument
and should return either a buffer or nil."
  :type '(hook :options (cvs-dired-noselect dired-noselect))
  :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-functions nil
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  "List of functions to be called for `find-file' on nonexistent file.
These functions are called as soon as the error is detected.
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Variable `buffer-file-name' is already set up.
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The functions are called in the order given until one of them returns non-nil.")
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(define-obsolete-variable-alias 'find-file-not-found-hooks
    'find-file-not-found-functions "22.1")
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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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(defcustom find-file-hook nil
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  "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
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functions are called."
  :group 'find-file
  :type 'hook
  :options '(auto-insert)
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  :version "22.1")
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(define-obsolete-variable-alias 'find-file-hooks 'find-file-hook "22.1")
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(defvar write-file-functions nil
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  "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.
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So any buffer-local binding of this variable is discarded if you change
the visited file name with \\[set-visited-file-name], but not when you
change the major mode.

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This hook is not run if any of the functions in
`write-contents-functions' returns non-nil.  Both hooks pertain
to how to save a buffer to file, for instance, choosing a suitable
coding system and setting mode bits.  (See Info
node `(elisp)Saving Buffers'.)  To perform various checks or
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updates before the buffer is saved, use `before-save-hook'.")
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(put 'write-file-functions 'permanent-local t)
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(define-obsolete-variable-alias 'write-file-hooks 'write-file-functions "22.1")
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(defvar local-write-file-hooks nil)
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(make-variable-buffer-local 'local-write-file-hooks)
(put 'local-write-file-hooks 'permanent-local t)
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(make-obsolete-variable 'local-write-file-hooks 'write-file-functions "22.1")
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(defvar write-contents-functions nil
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  "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 and neither are the functions in
`write-file-functions'.
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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.

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For hooks that _do_ pertain to the particular visited file, use
`write-file-functions'.  Both this variable and
`write-file-functions' relate to how a buffer is saved to file.
To perform various checks or updates before the buffer is saved,
use `before-save-hook'.")
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(make-variable-buffer-local 'write-contents-functions)
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(define-obsolete-variable-alias 'write-contents-hooks
    'write-contents-functions "22.1")
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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, :safe, or something else.
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A value of t means file local variables specifications are obeyed
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if all the specified variable values are safe; if any values are
not safe, Emacs queries you, once, whether to set them all.
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\(When you say yes to certain values, they are remembered as safe.)

:safe means set the safe variables, and ignore the rest.
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:all means set all variables, whether safe or not.
 (Don't set it permanently to :all.)
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nil means always ignore the file local variables.
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Any other value means always query you once whether to set them all.
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\(When you say yes to certain values, they are remembered as safe, but
this has no effect when `enable-local-variables' is \"something else\".)
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This variable also controls use of major modes specified in
a -*- line.
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The command \\[normal-mode], when used interactively,
always obeys file local variable specifications and the -*- line,
and ignores this variable."
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  :type '(choice (const :tag "Query Unsafe" t)
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		 (const :tag "Safe Only" :safe)
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		 (const :tag "Do all" :all)
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		 (const :tag "Ignore" nil)
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		 (other :tag "Query" other))
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  :group 'find-file)
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(defvar local-enable-local-variables t
  "Like `enable-local-variables' but meant for buffer-local bindings.
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The meaningful values are nil and non-nil.  The default is non-nil.
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If a major mode sets this to nil, buffer-locally, then any local
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variables list in the file will be ignored.

This variable does not affect the use of major modes
specified in a -*- line.")
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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.
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The value can be t, nil or something else.
A value of t means obey `eval' variables;
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nil means ignore them; anything else means query."
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  :type '(choice (const :tag "Obey" t)
		 (const :tag "Ignore" nil)
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		 (other :tag "Query" other))
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  :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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(defcustom view-read-only nil
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  "Non-nil means buffers visiting files read-only do so in view mode.
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In fact, this means that all read-only buffers normally have
View mode enabled, including buffers that are read-only because
you visit a file you cannot alter, and buffers you make read-only
using \\[toggle-read-only]."
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  :type 'boolean
  :group 'view)
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(defvar file-name-history nil
  "History list of file names entered in the minibuffer.")

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(put 'ange-ftp-completion-hook-function 'safe-magic t)
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(defun ange-ftp-completion-hook-function (op &rest args)
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  "Provides support for ange-ftp host name completion.
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.
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  (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)
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  "Convert a standard file's name to something suitable for the OS.
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This means to guarantee valid names and perhaps to canonicalize
certain patterns.

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FILENAME should be an absolute file name since the conversion rules
sometimes vary depending on the position in the file name.  E.g. c:/foo
is a valid DOS file name, but c:/bar/c:/foo is not.

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This function's standard definition is trivial; it just returns
the argument.  However, on Windows and DOS, replace invalid
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characters.  On DOS, make sure to obey the 8.3 limitations.
In the native Windows build, turn Cygwin names into native names,
and also turn slashes into backslashes if the shell requires it (see
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`w32-shell-dos-semantics').

See Info node `(elisp)Standard File Names' for more details."
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  (if (eq system-type 'cygwin)
      (let ((name (copy-sequence filename))
	    (start 0))
	;; Replace invalid filename characters with !
	(while (string-match "[?*:<>|\"\000-\037]" name start)
	  (aset name (match-beginning 0) ?!)
	  (setq start (match-end 0)))
	name)
    filename))
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(defun read-directory-name (prompt &optional dir default-dirname mustmatch initial)
  "Read directory name, prompting with PROMPT and completing in directory DIR.
Value is not expanded---you must call `expand-file-name' yourself.
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Default name to DEFAULT-DIRNAME if user exits with the same
non-empty string that was inserted by this function.
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 (If DEFAULT-DIRNAME is omitted, DIR combined with INITIAL is used,
  or just DIR if INITIAL is nil.)
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If the user exits with an empty minibuffer, this function returns
an empty string.  (This can only happen if the user erased the
pre-inserted contents or if `insert-default-directory' is nil.)
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Fourth arg MUSTMATCH non-nil means require existing directory's name.
 Non-nil and non-t means also require confirmation after completion.
Fifth arg INITIAL specifies text to start with.
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DIR should be an absolute directory name.  It defaults to
the value of `default-directory'."
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  (unless dir
    (setq dir default-directory))
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  (read-file-name prompt dir (or default-dirname
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				 (if initial (expand-file-name initial dir)
				   dir))
		  mustmatch initial
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		  'file-directory-p))

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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.
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Not actually set up until the first time you use it.")
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(defun parse-colon-path (cd-path)
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  "Explode a search path into a list of directory names.
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Directories are separated by occurrences of `path-separator'
\(which is colon in GNU and GNU-like systems)."
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  ;; We could use split-string here.
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  (and cd-path
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       (let (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 list of directories (separated by occurrences of
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`path-separator') when resolving a relative directory name.
The path separator is colon in GNU and GNU-like systems."
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  (interactive
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   (list (read-directory-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."
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  ;; This is a case where .elc makes a lot of sense.
  (interactive (list (let ((completion-ignored-extensions
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			    (remove ".elc" completion-ignored-extensions)))
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		       (read-file-name "Load file: "))))
  (load (expand-file-name file) nil nil t))
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(defun locate-file (filename path &optional suffixes predicate)
  "Search for FILENAME through PATH.
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If found, return the absolute file name of FILENAME, with its suffixes;
otherwise return nil.
PATH should be a list of directories to look in, like the lists in
`exec-path' or `load-path'.
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If SUFFIXES is non-nil, it should be a list of suffixes to append to
file name when searching.  If SUFFIXES is nil, it is equivalent to '(\"\").
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Use '(\"/\") to disable PATH search, but still try the suffixes in SUFFIXES.
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If non-nil, PREDICATE is used instead of `file-readable-p'.
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PREDICATE can also be an integer to pass to the `access' system call,
in which case file-name handlers are ignored.  This usage is deprecated.

For compatibility, PREDICATE can also be one of the symbols
`executable', `readable', `writable', or `exists', or a list of
one or more of those symbols."
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  (if (and predicate (symbolp predicate) (not (functionp predicate)))
      (setq predicate (list predicate)))
  (when (and (consp predicate) (not (functionp predicate)))
    (setq predicate
	  (logior (if (memq 'executable predicate) 1 0)
		  (if (memq 'writable predicate) 2 0)
		  (if (memq 'readable predicate) 4 0))))
  (locate-file-internal filename path suffixes predicate))

(defun locate-file-completion (string path-and-suffixes action)
  "Do completion for file names passed to `locate-file'.
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PATH-AND-SUFFIXES is a pair of lists, (DIRECTORIES . SUFFIXES)."
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  (if (file-name-absolute-p string)
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      (read-file-name-internal string nil action)
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    (let ((names nil)
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	  (suffix (concat (regexp-opt (cdr path-and-suffixes) t) "\\'"))
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	  (string-dir (file-name-directory string)))
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      (dolist (dir (car path-and-suffixes))
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	(unless dir
	  (setq dir default-directory))
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	(if string-dir (setq dir (expand-file-name string-dir dir)))
	(when (file-directory-p dir)
	  (dolist (file (file-name-all-completions
			 (file-name-nondirectory string) dir))
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	    (add-to-list 'names (if string-dir (concat string-dir file) file))
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	    (when (string-match suffix file)
	      (setq file (substring file 0 (match-beginning 0)))
	      (push (if string-dir (concat string-dir file) file) names)))))
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      (cond
       ((eq action t) (all-completions string names))
       ((null action) (try-completion string names))
       (t (test-completion string names))))))
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(defun executable-find (command)
  "Search for COMMAND in `exec-path' and return the absolute file name.
Return nil if COMMAND is not found anywhere in `exec-path'."
  ;; Use 1 rather than file-executable-p to better match the behavior of
  ;; call-process.
  (locate-file command exec-path exec-suffixes 1))

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(defun load-library (library)
  "Load the library named LIBRARY.
This is an interface to the function `load'."
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  (interactive
   (list (completing-read "Load library: "
			  'locate-file-completion
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			  (cons load-path (get-load-suffixes)))))
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  (load library))
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(defun file-remote-p (file)
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  "Test whether FILE specifies a location on a remote system.
Return an identification of the system if the location is indeed
remote.  The identification of the system may comprise a method
to access the system and its hostname, amongst other things.

For example, the filename \"/user@host:/foo\" specifies a location
on the system \"/user@host:\"."
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  (let ((handler (find-file-name-handler file 'file-remote-p)))
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    (if handler
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	(funcall handler 'file-remote-p file)
      nil)))
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(defun file-local-copy (file)
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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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  ;; This formerly had an optional BUFFER argument that wasn't used by
  ;; anything.
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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.

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\(fn FILENAME)"  ;; Don't document the optional arguments.
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  ;; COUNTER and PREV-DIRS are only used in recursive calls.
  ;; COUNTER can be a cons cell whose car is the count of how many
  ;; more links to chase before getting an error.
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  ;; PREV-DIRS can be a cons cell whose car is an alist
  ;; of truenames we've just recently computed.
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  (cond ((or (string= filename "") (string= filename "~"))
	 (setq filename (expand-file-name filename))
	 (if (string= filename "")
	     (setq filename "/")))
	((and (string= (substring filename 0 1) "~")
	      (string-match "~[^/]*/?" filename))
	 (let ((first-part
		(substring filename 0 (match-end 0)))
	       (rest (substring filename (match-end 0))))
	   (setq filename (concat (expand-file-name first-part) rest)))))

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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)
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      (let ((handler (find-file-name-handler filename 'file-truename)))
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	;; 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.
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	  (unless (string-match "[[*?]" filename)
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	    ;; If filename exists, use the long name
	    (setq filename (or (w32-long-file-name filename) filename))))
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	(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 &optional limit)
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  "Chase links in FILENAME until a name that is not a link.
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Unlike `file-truename', this does not check whether a parent
directory name is a symbolic link.
If the optional argument LIMIT is a number,
it means chase no more than that many links and then stop."
  (let (tem (newname filename)
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	    (count 0))
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    (while (and (or (null limit) (< count limit))
		(setq tem (file-symlink-p newname)))
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      (save-match-data
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	(if (and (null limit) (= count 100))
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