[Emacs-diffs] Changes to files.texi

[Glenn Morris]

CVSROOT:        /sources/emacs
Module name:    emacs
Changes by:     Glenn Morris <gm>       07/09/06 04:19:56

Index: files.texi
===================================================================
RCS file: files.texi
diff -N files.texi
--- /dev/null   1 Jan 1970 00:00:00 -0000
+++ files.texi  6 Sep 2007 04:19:55 -0000       1.1
@@ -0,0 +1,3108 @@
address@hidden -*-texinfo-*-
address@hidden This is part of the GNU Emacs Lisp Reference Manual.
address@hidden Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 
2001,
address@hidden   2002, 2003, 2004, 2005, 2006, 2007  Free Software Foundation, 
Inc.
address@hidden See the file elisp.texi for copying conditions.
address@hidden ../info/files
address@hidden Files, Backups and Auto-Saving, Documentation, Top
address@hidden  node-name,  next,  previous,  up
address@hidden Files
+
+  In Emacs, you can find, create, view, save, and otherwise work with
+files and file directories.  This chapter describes most of the
+file-related functions of Emacs Lisp, but a few others are described in
address@hidden, and those related to backups and auto-saving are
+described in @ref{Backups and Auto-Saving}.
+
+  Many of the file functions take one or more arguments that are file
+names.  A file name is actually a string.  Most of these functions
+expand file name arguments by calling @code{expand-file-name}, so that
address@hidden is handled correctly, as are relative file names (including
address@hidden/}).  These functions don't recognize environment variable
+substitutions such as @samp{$HOME}.  @xref{File Name Expansion}.
+
+  When file I/O functions signal Lisp errors, they usually use the
+condition @code{file-error} (@pxref{Handling Errors}).  The error
+message is in most cases obtained from the operating system, according
+to locale @code{system-message-locale}, and decoded using coding system
address@hidden (@pxref{Locales}).
+
address@hidden
+* Visiting Files::           Reading files into Emacs buffers for editing.
+* Saving Buffers::           Writing changed buffers back into files.
+* Reading from Files::       Reading files into buffers without visiting.
+* Writing to Files::         Writing new files from parts of buffers.
+* File Locks::               Locking and unlocking files, to prevent
+                               simultaneous editing by two people.
+* Information about Files::  Testing existence, accessibility, size of files.
+* Changing Files::           Renaming files, changing protection, etc.
+* File Names::               Decomposing and expanding file names.
+* Contents of Directories::  Getting a list of the files in a directory.
+* Create/Delete Dirs::      Creating and Deleting Directories.
+* Magic File Names::        Defining "magic" special handling
+                              for certain file names.
+* Format Conversion::        Conversion to and from various file formats.
address@hidden menu
+
address@hidden Visiting Files
address@hidden Visiting Files
address@hidden finding files
address@hidden visiting files
+
+  Visiting a file means reading a file into a buffer.  Once this is
+done, we say that the buffer is @dfn{visiting} that file, and call the
+file ``the visited file'' of the buffer.
+
+  A file and a buffer are two different things.  A file is information
+recorded permanently in the computer (unless you delete it).  A buffer,
+on the other hand, is information inside of Emacs that will vanish at
+the end of the editing session (or when you kill the buffer).  Usually,
+a buffer contains information that you have copied from a file; then we
+say the buffer is visiting that file.  The copy in the buffer is what
+you modify with editing commands.  Such changes to the buffer do not
+change the file; therefore, to make the changes permanent, you must
address@hidden the buffer, which means copying the altered buffer contents
+back into the file.
+
+  In spite of the distinction between files and buffers, people often
+refer to a file when they mean a buffer and vice-versa.  Indeed, we say,
+``I am editing a file,'' rather than, ``I am editing a buffer that I
+will soon save as a file of the same name.''  Humans do not usually need
+to make the distinction explicit.  When dealing with a computer program,
+however, it is good to keep the distinction in mind.
+
address@hidden
+* Visiting Functions::         The usual interface functions for visiting.
+* Subroutines of Visiting::    Lower-level subroutines that they use.
address@hidden menu
+
address@hidden Visiting Functions
address@hidden Functions for Visiting Files
+
+  This section describes the functions normally used to visit files.
+For historical reasons, these functions have names starting with
address@hidden rather than @samp{visit-}.  @xref{Buffer File Name}, for
+functions and variables that access the visited file name of a buffer or
+that find an existing buffer by its visited file name.
+
+  In a Lisp program, if you want to look at the contents of a file but
+not alter it, the fastest way is to use @code{insert-file-contents} in a
+temporary buffer.  Visiting the file is not necessary and takes longer.
address@hidden from Files}.
+
address@hidden Command find-file filename &optional wildcards
+This command selects a buffer visiting the file @var{filename},
+using an existing buffer if there is one, and otherwise creating a
+new buffer and reading the file into it.  It also returns that buffer.
+
+Aside from some technical details, the body of the @code{find-file}
+function is basically equivalent to:
+
address@hidden
+(switch-to-buffer (find-file-noselect filename nil nil wildcards))
address@hidden smallexample
+
address@hidden
+(See @code{switch-to-buffer} in @ref{Displaying Buffers}.)
+
+If @var{wildcards} is address@hidden, which is always true in an
+interactive call, then @code{find-file} expands wildcard characters in
address@hidden and visits all the matching files.
+
+When @code{find-file} is called interactively, it prompts for
address@hidden in the minibuffer.
address@hidden deffn
+
address@hidden find-file-noselect filename &optional nowarn rawfile wildcards
+This function is the guts of all the file-visiting functions.  It
+returns a buffer visiting the file @var{filename}.  You may make the
+buffer current or display it in a window if you wish, but this
+function does not do so.
+
+The function returns an existing buffer if there is one; otherwise it
+creates a new buffer and reads the file into it.  When
address@hidden uses an existing buffer, it first verifies
+that the file has not changed since it was last visited or saved in
+that buffer.  If the file has changed, this function asks the user
+whether to reread the changed file.  If the user says @samp{yes}, any
+edits previously made in the buffer are lost.
+
+Reading the file involves decoding the file's contents (@pxref{Coding
+Systems}), including end-of-line conversion, and format conversion
+(@pxref{Format Conversion}).  If @var{wildcards} is address@hidden,
+then @code{find-file-noselect} expands wildcard characters in
address@hidden and visits all the matching files.
+
+This function displays warning or advisory messages in various peculiar
+cases, unless the optional argument @var{nowarn} is address@hidden  For
+example, if it needs to create a buffer, and there is no file named
address@hidden, it displays the message @samp{(New file)} in the echo
+area, and leaves the buffer empty.
+
+The @code{find-file-noselect} function normally calls
address@hidden after reading the file (@pxref{Subroutines of
+Visiting}).  That function sets the buffer major mode, parses local
+variables, warns the user if there exists an auto-save file more recent
+than the file just visited, and finishes by running the functions in
address@hidden
+
+If the optional argument @var{rawfile} is address@hidden, then
address@hidden is not called, and the
address@hidden are not run in case of failure.
+What's more, a address@hidden @var{rawfile} value suppresses coding
+system conversion and format conversion.
+
+The @code{find-file-noselect} function usually returns the buffer that
+is visiting the file @var{filename}.  But, if wildcards are actually
+used and expanded, it returns a list of buffers that are visiting the
+various files.
+
address@hidden
address@hidden
+(find-file-noselect "/etc/fstab")
+     @result{} #<buffer fstab>
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden Command find-file-other-window filename &optional wildcards
+This command selects a buffer visiting the file @var{filename}, but
+does so in a window other than the selected window.  It may use another
+existing window or split a window; see @ref{Displaying Buffers}.
+
+When this command is called interactively, it prompts for
address@hidden
address@hidden deffn
+
address@hidden Command find-file-read-only filename &optional wildcards
+This command selects a buffer visiting the file @var{filename}, like
address@hidden, but it marks the buffer as read-only.  @xref{Read Only
+Buffers}, for related functions and variables.
+
+When this command is called interactively, it prompts for
address@hidden
address@hidden deffn
+
address@hidden Command view-file filename
+This command visits @var{filename} using View mode, returning to the
+previous buffer when you exit View mode.  View mode is a minor mode that
+provides commands to skim rapidly through the file, but does not let you
+modify the text.  Entering View mode runs the normal hook
address@hidden  @xref{Hooks}.
+
+When @code{view-file} is called interactively, it prompts for
address@hidden
address@hidden deffn
+
address@hidden find-file-wildcards
+If this variable is address@hidden, then the various @code{find-file}
+commands check for wildcard characters and visit all the files that
+match them (when invoked interactively or when their @var{wildcards}
+argument is address@hidden).  If this option is @code{nil}, then
+the @code{find-file} commands ignore their @var{wildcards} argument
+and never treat wildcard characters specially.
address@hidden defopt
+
address@hidden find-file-hook
+The value of this variable is a list of functions to be called after a
+file is visited.  The file's local-variables specification (if any) will
+have been processed before the hooks are run.  The buffer visiting the
+file is current when the hook functions are run.
+
+This variable is a normal hook.  @xref{Hooks}.
address@hidden defvar
+
address@hidden find-file-not-found-functions
+The value of this variable is a list of functions to be called when
address@hidden or @code{find-file-noselect} is passed a nonexistent
+file name.  @code{find-file-noselect} calls these functions as soon as
+it detects a nonexistent file.  It calls them in the order of the list,
+until one of them returns address@hidden  @code{buffer-file-name} is
+already set up.
+
+This is not a normal hook because the values of the functions are
+used, and in many cases only some of the functions are called.
address@hidden defvar
+
address@hidden Subroutines of Visiting
address@hidden  node-name,  next,  previous,  up
address@hidden Subroutines of Visiting
+
+  The @code{find-file-noselect} function uses two important subroutines
+which are sometimes useful in user Lisp code: @code{create-file-buffer}
+and @code{after-find-file}.  This section explains how to use them.
+
address@hidden create-file-buffer filename
+This function creates a suitably named buffer for visiting
address@hidden, and returns it.  It uses @var{filename} (sans directory)
+as the name if that name is free; otherwise, it appends a string such as
address@hidden<2>} to get an unused name.  See also @ref{Creating Buffers}.
+
address@hidden note:} @code{create-file-buffer} does @emph{not}
+associate the new buffer with a file and does not select the buffer.
+It also does not use the default major mode.
+
address@hidden
address@hidden
+(create-file-buffer "foo")
+     @result{} #<buffer foo>
address@hidden group
address@hidden
+(create-file-buffer "foo")
+     @result{} #<buffer foo<2>>
address@hidden group
address@hidden
+(create-file-buffer "foo")
+     @result{} #<buffer foo<3>>
address@hidden group
address@hidden example
+
+This function is used by @code{find-file-noselect}.
+It uses @code{generate-new-buffer} (@pxref{Creating Buffers}).
address@hidden defun
+
address@hidden after-find-file &optional error warn noauto 
after-find-file-from-revert-buffer nomodes
+This function sets the buffer major mode, and parses local variables
+(@pxref{Auto Major Mode}).  It is called by @code{find-file-noselect}
+and by the default revert function (@pxref{Reverting}).
+
address@hidden new file message
address@hidden file open error
+If reading the file got an error because the file does not exist, but
+its directory does exist, the caller should pass a address@hidden value
+for @var{error}.  In that case, @code{after-find-file} issues a warning:
address@hidden(New file)}.  For more serious errors, the caller should usually 
not
+call @code{after-find-file}.
+
+If @var{warn} is address@hidden, then this function issues a warning
+if an auto-save file exists and is more recent than the visited file.
+
+If @var{noauto} is address@hidden, that says not to enable or disable
+Auto-Save mode.  The mode remains enabled if it was enabled before.
+
+If @var{after-find-file-from-revert-buffer} is address@hidden, that
+means this call was from @code{revert-buffer}.  This has no direct
+effect, but some mode functions and hook functions check the value
+of this variable.
+
+If @var{nomodes} is address@hidden, that means don't alter the buffer's
+major mode, don't process local variables specifications in the file,
+and don't run @code{find-file-hook}.  This feature is used by
address@hidden in some cases.
+
+The last thing @code{after-find-file} does is call all the functions
+in the list @code{find-file-hook}.
address@hidden defun
+
address@hidden Saving Buffers
address@hidden Saving Buffers
address@hidden saving buffers
+
+  When you edit a file in Emacs, you are actually working on a buffer
+that is visiting that file---that is, the contents of the file are
+copied into the buffer and the copy is what you edit.  Changes to the
+buffer do not change the file until you @dfn{save} the buffer, which
+means copying the contents of the buffer into the file.
+
address@hidden Command save-buffer &optional backup-option
+This function saves the contents of the current buffer in its visited
+file if the buffer has been modified since it was last visited or saved.
+Otherwise it does nothing.
+
address@hidden is responsible for making backup files.  Normally,
address@hidden is @code{nil}, and @code{save-buffer} makes a backup
+file only if this is the first save since visiting the file.  Other
+values for @var{backup-option} request the making of backup files in
+other circumstances:
+
address@hidden @bullet
address@hidden
+With an argument of 4 or 64, reflecting 1 or 3 @kbd{C-u}'s, the
address@hidden function marks this version of the file to be
+backed up when the buffer is next saved.
+
address@hidden
+With an argument of 16 or 64, reflecting 2 or 3 @kbd{C-u}'s, the
address@hidden function unconditionally backs up the previous
+version of the file before saving it.
+
address@hidden
+With an argument of 0, unconditionally do @emph{not} make any backup file.
address@hidden itemize
address@hidden deffn
+
address@hidden Command save-some-buffers &optional save-silently-p pred
address@hidden of save-some-buffers}
+This command saves some modified file-visiting buffers.  Normally it
+asks the user about each buffer.  But if @var{save-silently-p} is
address@hidden, it saves all the file-visiting buffers without querying
+the user.
+
+The optional @var{pred} argument controls which buffers to ask about
+(or to save silently if @var{save-silently-p} is address@hidden).
+If it is @code{nil}, that means to ask only about file-visiting buffers.
+If it is @code{t}, that means also offer to save certain other non-file
+buffers---those that have a address@hidden buffer-local value of
address@hidden (@pxref{Killing Buffers}).  A user who says
address@hidden to saving a non-file buffer is asked to specify the file
+name to use.  The @code{save-buffers-kill-emacs} function passes the
+value @code{t} for @var{pred}.
+
+If @var{pred} is neither @code{t} nor @code{nil}, then it should be
+a function of no arguments.  It will be called in each buffer to decide
+whether to offer to save that buffer.  If it returns a address@hidden
+value in a certain buffer, that means do offer to save that buffer.
address@hidden deffn
+
address@hidden Command write-file filename &optional confirm
address@hidden of write-file}
+This function writes the current buffer into file @var{filename}, makes
+the buffer visit that file, and marks it not modified.  Then it renames
+the buffer based on @var{filename}, appending a string like @samp{<2>}
+if necessary to make a unique buffer name.  It does most of this work by
+calling @code{set-visited-file-name} (@pxref{Buffer File Name}) and
address@hidden
+
+If @var{confirm} is address@hidden, that means to ask for confirmation
+before overwriting an existing file.  Interactively, confirmation is
+required, unless the user supplies a prefix argument.
+
+If @var{filename} is an existing directory, or a symbolic link to one,
address@hidden uses the name of the visited file, in directory
address@hidden  If the buffer is not visiting a file, it uses the
+buffer name instead.
address@hidden deffn
+
+  Saving a buffer runs several hooks.  It also performs format
+conversion (@pxref{Format Conversion}).
+
address@hidden write-file-functions
+The value of this variable is a list of functions to be called before
+writing out a buffer to its visited file.  If one of them returns
address@hidden, the file is considered already written and the rest of
+the functions are not called, nor is the usual code for writing the file
+executed.
+
+If a function in @code{write-file-functions} returns address@hidden, it
+is responsible for making a backup file (if that is appropriate).
+To do so, execute the following code:
+
address@hidden
+(or buffer-backed-up (backup-buffer))
address@hidden example
+
+You might wish to save the file modes value returned by
address@hidden and use that (if address@hidden) to set the mode
+bits of the file that you write.  This is what @code{save-buffer}
+normally does. @xref{Making Backups,, Making Backup Files}.
+
+The hook functions in @code{write-file-functions} are also responsible
+for encoding the data (if desired): they must choose a suitable coding
+system and end-of-line conversion (@pxref{Lisp and Coding Systems}),
+perform the encoding (@pxref{Explicit Encoding}), and set
address@hidden to the coding system that was used
+(@pxref{Encoding and I/O}).
+
+If you set this hook locally in a buffer, it is assumed to be
+associated with the file or the way the contents of the buffer were
+obtained.  Thus the variable is marked as a permanent local, so that
+changing the major mode does not alter a buffer-local value.  On the
+other hand, calling @code{set-visited-file-name} will reset it.
+If this is not what you want, you might like to use
address@hidden instead.
+
+Even though this is not a normal hook, you can use @code{add-hook} and
address@hidden to manipulate the list.  @xref{Hooks}.
address@hidden defvar
+
address@hidden Emacs 19 feature
address@hidden write-contents-functions
+This works just like @code{write-file-functions}, but it is intended
+for hooks that pertain to the buffer's contents, not to the particular
+visited file or its location.  Such hooks are usually set up by major
+modes, as buffer-local bindings for this variable.  This variable
+automatically becomes buffer-local whenever it is set; switching to a
+new major mode always resets this variable, but calling
address@hidden does not.
+
+If any of the functions in this hook returns address@hidden, the file
+is considered already written and the rest are not called and neither
+are the functions in @code{write-file-functions}.
address@hidden defvar
+
address@hidden before-save-hook
+This normal hook runs before a buffer is saved in its visited file,
+regardless of whether that is done normally or by one of the hooks
+described above.  For instance, the @file{copyright.el} program uses
+this hook to make sure the file you are saving has the current year in
+its copyright notice.
address@hidden defopt
+
address@hidden Emacs 19 feature
address@hidden after-save-hook
+This normal hook runs after a buffer has been saved in its visited file.
+One use of this hook is in Fast Lock mode; it uses this hook to save the
+highlighting information in a cache file.
address@hidden defopt
+
address@hidden file-precious-flag
+If this variable is address@hidden, then @code{save-buffer} protects
+against I/O errors while saving by writing the new file to a temporary
+name instead of the name it is supposed to have, and then renaming it to
+the intended name after it is clear there are no errors.  This procedure
+prevents problems such as a lack of disk space from resulting in an
+invalid file.
+
+As a side effect, backups are necessarily made by copying.  @xref{Rename
+or Copy}.  Yet, at the same time, saving a precious file always breaks
+all hard links between the file you save and other file names.
+
+Some modes give this variable a address@hidden buffer-local value
+in particular buffers.
address@hidden defopt
+
address@hidden require-final-newline
+This variable determines whether files may be written out that do
address@hidden end with a newline.  If the value of the variable is
address@hidden, then @code{save-buffer} silently adds a newline at the end of
+the file whenever the buffer being saved does not already end in one.
+If the value of the variable is address@hidden, but not @code{t}, then
address@hidden asks the user whether to add a newline each time the
+case arises.
+
+If the value of the variable is @code{nil}, then @code{save-buffer}
+doesn't add newlines at all.  @code{nil} is the default value, but a few
+major modes set it to @code{t} in particular buffers.
address@hidden defopt
+
+  See also the function @code{set-visited-file-name} (@pxref{Buffer File
+Name}).
+
address@hidden Reading from Files
address@hidden  node-name,  next,  previous,  up
address@hidden Reading from Files
address@hidden reading from files
+
+  You can copy a file from the disk and insert it into a buffer
+using the @code{insert-file-contents} function.  Don't use the user-level
+command @code{insert-file} in a Lisp program, as that sets the mark.
+
address@hidden insert-file-contents filename &optional visit beg end replace
+This function inserts the contents of file @var{filename} into the
+current buffer after point.  It returns a list of the absolute file name
+and the length of the data inserted.  An error is signaled if
address@hidden is not the name of a file that can be read.
+
+The function @code{insert-file-contents} checks the file contents
+against the defined file formats, and converts the file contents if
+appropriate and also calls the functions in
+the list @code{after-insert-file-functions}.  @xref{Format Conversion}.
+Normally, one of the functions in the
address@hidden list determines the coding system
+(@pxref{Coding Systems}) used for decoding the file's contents,
+including end-of-line conversion.
+
+If @var{visit} is address@hidden, this function additionally marks the
+buffer as unmodified and sets up various fields in the buffer so that it
+is visiting the file @var{filename}: these include the buffer's visited
+file name and its last save file modtime.  This feature is used by
address@hidden and you probably should not use it yourself.
+
+If @var{beg} and @var{end} are address@hidden, they should be integers
+specifying the portion of the file to insert.  In this case, @var{visit}
+must be @code{nil}.  For example,
+
address@hidden
+(insert-file-contents filename nil 0 500)
address@hidden example
+
address@hidden
+inserts the first 500 characters of a file.
+
+If the argument @var{replace} is address@hidden, it means to replace the
+contents of the buffer (actually, just the accessible portion) with the
+contents of the file.  This is better than simply deleting the buffer
+contents and inserting the whole file, because (1) it preserves some
+marker positions and (2) it puts less data in the undo list.
+
+It is possible to read a special file (such as a FIFO or an I/O device)
+with @code{insert-file-contents}, as long as @var{replace} and
address@hidden are @code{nil}.
address@hidden defun
+
address@hidden insert-file-contents-literally filename &optional visit beg end 
replace
+This function works like @code{insert-file-contents} except that it does
+not do format decoding (@pxref{Format Conversion}), does not do
+character code conversion (@pxref{Coding Systems}), does not run
address@hidden, does not perform automatic uncompression, and so
+on.
address@hidden defun
+
+If you want to pass a file name to another process so that another
+program can read the file, use the function @code{file-local-copy}; see
address@hidden File Names}.
+
address@hidden Writing to Files
address@hidden  node-name,  next,  previous,  up
address@hidden Writing to Files
address@hidden writing to files
+
+  You can write the contents of a buffer, or part of a buffer, directly
+to a file on disk using the @code{append-to-file} and
address@hidden functions.  Don't use these functions to write to
+files that are being visited; that could cause confusion in the
+mechanisms for visiting.
+
address@hidden Command append-to-file start end filename
+This function appends the contents of the region delimited by
address@hidden and @var{end} in the current buffer to the end of file
address@hidden  If that file does not exist, it is created.  This
+function returns @code{nil}.
+
+An error is signaled if @var{filename} specifies a nonwritable file,
+or a nonexistent file in a directory where files cannot be created.
+
+When called from Lisp, this function is completely equivalent to:
+
address@hidden
+(write-region start end filename t)
address@hidden example
address@hidden deffn
+
address@hidden Command write-region start end filename &optional append visit 
lockname mustbenew
+This function writes the region delimited by @var{start} and @var{end}
+in the current buffer into the file specified by @var{filename}.
+
+If @var{start} is @code{nil}, then the command writes the entire buffer
+contents (@emph{not} just the accessible portion) to the file and
+ignores @var{end}.
+
address@hidden Emacs 19 feature
+If @var{start} is a string, then @code{write-region} writes or appends
+that string, rather than text from the buffer.  @var{end} is ignored in
+this case.
+
+If @var{append} is address@hidden, then the specified text is appended
+to the existing file contents (if any).  If @var{append} is an
+integer, @code{write-region} seeks to that byte offset from the start
+of the file and writes the data from there.
+
+If @var{mustbenew} is address@hidden, then @code{write-region} asks
+for confirmation if @var{filename} names an existing file.  If
address@hidden is the symbol @code{excl}, then @code{write-region}
+does not ask for confirmation, but instead it signals an error
address@hidden if the file already exists.
+
+The test for an existing file, when @var{mustbenew} is @code{excl}, uses
+a special system feature.  At least for files on a local disk, there is
+no chance that some other program could create a file of the same name
+before Emacs does, without Emacs's noticing.
+
+If @var{visit} is @code{t}, then Emacs establishes an association
+between the buffer and the file: the buffer is then visiting that file.
+It also sets the last file modification time for the current buffer to
address@hidden's modtime, and marks the buffer as not modified.  This
+feature is used by @code{save-buffer}, but you probably should not use
+it yourself.
+
address@hidden Emacs 19 feature
+If @var{visit} is a string, it specifies the file name to visit.  This
+way, you can write the data to one file (@var{filename}) while recording
+the buffer as visiting another file (@var{visit}).  The argument
address@hidden is used in the echo area message and also for file locking;
address@hidden is stored in @code{buffer-file-name}.  This feature is used
+to implement @code{file-precious-flag}; don't use it yourself unless you
+really know what you're doing.
+
+The optional argument @var{lockname}, if address@hidden, specifies the
+file name to use for purposes of locking and unlocking, overriding
address@hidden and @var{visit} for that purpose.
+
+The function @code{write-region} converts the data which it writes to
+the appropriate file formats specified by @code{buffer-file-format}
+and also calls the functions in the list
address@hidden
address@hidden Conversion}.
+
+Normally, @code{write-region} displays the message @samp{Wrote
address@hidden in the echo area.  If @var{visit} is neither @code{t}
+nor @code{nil} nor a string, then this message is inhibited.  This
+feature is useful for programs that use files for internal purposes,
+files that the user does not need to know about.
address@hidden deffn
+
address@hidden with-temp-file file address@hidden
address@hidden of with-temp-file}
+The @code{with-temp-file} macro evaluates the @var{body} forms with a
+temporary buffer as the current buffer; then, at the end, it writes the
+buffer contents into file @var{file}.  It kills the temporary buffer
+when finished, restoring the buffer that was current before the
address@hidden form.  Then it returns the value of the last form
+in @var{body}.
+
+The current buffer is restored even in case of an abnormal exit via
address@hidden or error (@pxref{Nonlocal Exits}).
+
+See also @code{with-temp-buffer} in @ref{Definition of
+with-temp-buffer,, The Current Buffer}.
address@hidden defmac
+
address@hidden File Locks
address@hidden File Locks
address@hidden file locks
address@hidden lock file
+
+  When two users edit the same file at the same time, they are likely
+to interfere with each other.  Emacs tries to prevent this situation
+from arising by recording a @dfn{file lock} when a file is being
+modified.  (File locks are not implemented on Microsoft systems.)
+Emacs can then detect the first attempt to modify a buffer visiting a
+file that is locked by another Emacs job, and ask the user what to do.
+The file lock is really a file, a symbolic link with a special name,
+stored in the same directory as the file you are editing.
+
+  When you access files using NFS, there may be a small probability that
+you and another user will both lock the same file ``simultaneously.''
+If this happens, it is possible for the two users to make changes
+simultaneously, but Emacs will still warn the user who saves second.
+Also, the detection of modification of a buffer visiting a file changed
+on disk catches some cases of simultaneous editing; see
address@hidden Time}.
+
address@hidden file-locked-p filename
+This function returns @code{nil} if the file @var{filename} is not
+locked.  It returns @code{t} if it is locked by this Emacs process, and
+it returns the name of the user who has locked it if it is locked by
+some other job.
+
address@hidden
address@hidden
+(file-locked-p "foo")
+     @result{} nil
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden lock-buffer &optional filename
+This function locks the file @var{filename}, if the current buffer is
+modified.  The argument @var{filename} defaults to the current buffer's
+visited file.  Nothing is done if the current buffer is not visiting a
+file, or is not modified, or if the system does not support locking.
address@hidden defun
+
address@hidden unlock-buffer
+This function unlocks the file being visited in the current buffer,
+if the buffer is modified.  If the buffer is not modified, then
+the file should not be locked, so this function does nothing.  It also
+does nothing if the current buffer is not visiting a file, or if the
+system does not support locking.
address@hidden defun
+
+  File locking is not supported on some systems.  On systems that do not
+support it, the functions @code{lock-buffer}, @code{unlock-buffer} and
address@hidden do nothing and return @code{nil}.
+
address@hidden ask-user-about-lock file other-user
+This function is called when the user tries to modify @var{file}, but it
+is locked by another user named @var{other-user}.  The default
+definition of this function asks the user to say what to do.  The value
+this function returns determines what Emacs does next:
+
address@hidden @bullet
address@hidden
+A value of @code{t} says to grab the lock on the file.  Then
+this user may edit the file and @var{other-user} loses the lock.
+
address@hidden
+A value of @code{nil} says to ignore the lock and let this
+user edit the file anyway.
+
address@hidden
address@hidden file-locked
+This function may instead signal a @code{file-locked} error, in which
+case the change that the user was about to make does not take place.
+
+The error message for this error looks like this:
+
address@hidden
address@hidden File is locked: @var{file} @var{other-user}
address@hidden example
+
address@hidden
+where @code{file} is the name of the file and @var{other-user} is the
+name of the user who has locked the file.
address@hidden itemize
+
+If you wish, you can replace the @code{ask-user-about-lock} function
+with your own version that makes the decision in another way.  The code
+for its usual definition is in @file{userlock.el}.
address@hidden defun
+
address@hidden Information about Files
address@hidden Information about Files
address@hidden file, information about
+
+  The functions described in this section all operate on strings that
+designate file names.  With a few exceptions, all the functions have
+names that begin with the word @samp{file}.  These functions all
+return information about actual files or directories, so their
+arguments must all exist as actual files or directories unless
+otherwise noted.
+
address@hidden
+* Testing Accessibility::   Is a given file readable?  Writable?
+* Kinds of Files::          Is it a directory?  A symbolic link?
+* Truenames::              Eliminating symbolic links from a file name.
+* File Attributes::         How large is it?  Any other names?  Etc.
+* Locating Files::          How to find a file in standard places.
address@hidden menu
+
address@hidden Testing Accessibility
address@hidden  node-name,  next,  previous,  up
address@hidden Testing Accessibility
address@hidden accessibility of a file
address@hidden file accessibility
+
+  These functions test for permission to access a file in specific
+ways.  Unless explicitly stated otherwise, they recursively follow
+symbolic links for their file name arguments, at all levels (at the
+level of the file itself and at all levels of parent directories).
+
address@hidden file-exists-p filename
+This function returns @code{t} if a file named @var{filename} appears
+to exist.  This does not mean you can necessarily read the file, only
+that you can find out its attributes.  (On Unix and GNU/Linux, this is
+true if the file exists and you have execute permission on the
+containing directories, regardless of the protection of the file
+itself.)
+
+If the file does not exist, or if fascist access control policies
+prevent you from finding the attributes of the file, this function
+returns @code{nil}.
+
+Directories are files, so @code{file-exists-p} returns @code{t} when
+given a directory name.  However, symbolic links are treated
+specially; @code{file-exists-p} returns @code{t} for a symbolic link
+name only if the target file exists.
address@hidden defun
+
address@hidden file-readable-p filename
+This function returns @code{t} if a file named @var{filename} exists
+and you can read it.  It returns @code{nil} otherwise.
+
address@hidden
address@hidden
+(file-readable-p "files.texi")
+     @result{} t
address@hidden group
address@hidden
+(file-exists-p "/usr/spool/mqueue")
+     @result{} t
address@hidden group
address@hidden
+(file-readable-p "/usr/spool/mqueue")
+     @result{} nil
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden Emacs 19 feature
address@hidden file-executable-p filename
+This function returns @code{t} if a file named @var{filename} exists and
+you can execute it.  It returns @code{nil} otherwise.  On Unix and
+GNU/Linux, if the file is a directory, execute permission means you can
+check the existence and attributes of files inside the directory, and
+open those files if their modes permit.
address@hidden defun
+
address@hidden file-writable-p filename
+This function returns @code{t} if the file @var{filename} can be written
+or created by you, and @code{nil} otherwise.  A file is writable if the
+file exists and you can write it.  It is creatable if it does not exist,
+but the specified directory does exist and you can write in that
+directory.
+
+In the third example below, @file{foo} is not writable because the
+parent directory does not exist, even though the user could create such
+a directory.
+
address@hidden
address@hidden
+(file-writable-p "~/foo")
+     @result{} t
address@hidden group
address@hidden
+(file-writable-p "/foo")
+     @result{} nil
address@hidden group
address@hidden
+(file-writable-p "~/no-such-dir/foo")
+     @result{} nil
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden Emacs 19 feature
address@hidden file-accessible-directory-p dirname
+This function returns @code{t} if you have permission to open existing
+files in the directory whose name as a file is @var{dirname};
+otherwise (or if there is no such directory), it returns @code{nil}.
+The value of @var{dirname} may be either a directory name (such as
address@hidden/foo/}) or the file name of a file which is a directory
+(such as @file{/foo}, without the final slash).
+
+Example: after the following,
+
address@hidden
+(file-accessible-directory-p "/foo")
+     @result{} nil
address@hidden example
+
address@hidden
+we can deduce that any attempt to read a file in @file{/foo/} will
+give an error.
address@hidden defun
+
address@hidden access-file filename string
+This function opens file @var{filename} for reading, then closes it and
+returns @code{nil}.  However, if the open fails, it signals an error
+using @var{string} as the error message text.
address@hidden defun
+
address@hidden file-ownership-preserved-p filename
+This function returns @code{t} if deleting the file @var{filename} and
+then creating it anew would keep the file's owner unchanged.  It also
+returns @code{t} for nonexistent files.
+
+If @var{filename} is a symbolic link, then, unlike the other functions
+discussed here, @code{file-ownership-preserved-p} does @emph{not}
+replace @var{filename} with its target.  However, it does recursively
+follow symbolic links at all levels of parent directories.
address@hidden defun
+
address@hidden file-newer-than-file-p filename1 filename2
address@hidden file age
address@hidden file modification time
+This function returns @code{t} if the file @var{filename1} is
+newer than file @var{filename2}.  If @var{filename1} does not
+exist, it returns @code{nil}.  If @var{filename1} does exist, but
address@hidden does not, it returns @code{t}.
+
+In the following example, assume that the file @file{aug-19} was written
+on the 19th, @file{aug-20} was written on the 20th, and the file
address@hidden doesn't exist at all.
+
address@hidden
address@hidden
+(file-newer-than-file-p "aug-19" "aug-20")
+     @result{} nil
address@hidden group
address@hidden
+(file-newer-than-file-p "aug-20" "aug-19")
+     @result{} t
address@hidden group
address@hidden
+(file-newer-than-file-p "aug-19" "no-file")
+     @result{} t
address@hidden group
address@hidden
+(file-newer-than-file-p "no-file" "aug-19")
+     @result{} nil
address@hidden group
address@hidden example
+
+You can use @code{file-attributes} to get a file's last modification
+time as a list of two numbers.  @xref{File Attributes}.
address@hidden defun
+
address@hidden Kinds of Files
address@hidden  node-name,  next,  previous,  up
address@hidden Distinguishing Kinds of Files
+
+  This section describes how to distinguish various kinds of files, such
+as directories, symbolic links, and ordinary files.
+
address@hidden file-symlink-p filename
address@hidden file symbolic links
+If the file @var{filename} is a symbolic link, the
address@hidden function returns the (non-recursive) link target
+as a string.  (Determining the file name that the link points to from
+the target is nontrivial.)  First, this function recursively follows
+symbolic links at all levels of parent directories.
+
+If the file @var{filename} is not a symbolic link (or there is no such file),
address@hidden returns @code{nil}.
+
address@hidden
address@hidden
+(file-symlink-p "foo")
+     @result{} nil
address@hidden group
address@hidden
+(file-symlink-p "sym-link")
+     @result{} "foo"
address@hidden group
address@hidden
+(file-symlink-p "sym-link2")
+     @result{} "sym-link"
address@hidden group
address@hidden
+(file-symlink-p "/bin")
+     @result{} "/pub/bin"
address@hidden group
address@hidden example
+
address@hidden !!! file-symlink-p: should show output of ls -l for comparison
address@hidden defun
+
+The next two functions recursively follow symbolic links at
+all levels for @var{filename}.
+
address@hidden file-directory-p filename
+This function returns @code{t} if @var{filename} is the name of an
+existing directory, @code{nil} otherwise.
+
address@hidden
address@hidden
+(file-directory-p "~rms")
+     @result{} t
address@hidden group
address@hidden
+(file-directory-p "~rms/lewis/files.texi")
+     @result{} nil
address@hidden group
address@hidden
+(file-directory-p "~rms/lewis/no-such-file")
+     @result{} nil
address@hidden group
address@hidden
+(file-directory-p "$HOME")
+     @result{} nil
address@hidden group
address@hidden
+(file-directory-p
+ (substitute-in-file-name "$HOME"))
+     @result{} t
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden file-regular-p filename
+This function returns @code{t} if the file @var{filename} exists and is
+a regular file (not a directory, named pipe, terminal, or
+other I/O device).
address@hidden defun
+
address@hidden Truenames
address@hidden Truenames
address@hidden truename (of file)
+
address@hidden Emacs 19 features
+  The @dfn{truename} of a file is the name that you get by following
+symbolic links at all levels until none remain, then simplifying away
address@hidden@: and @samp{..}@: appearing as name components.  This results
+in a sort of canonical name for the file.  A file does not always have a
+unique truename; the number of distinct truenames a file has is equal to
+the number of hard links to the file.  However, truenames are useful
+because they eliminate symbolic links as a cause of name variation.
+
address@hidden file-truename filename
+The function @code{file-truename} returns the truename of the file
address@hidden  The argument must be an absolute file name.
+
+This function does not expand environment variables.  Only
address@hidden does that.  @xref{Definition of
+substitute-in-file-name}.
+
+If you may need to follow symbolic links preceding @samp{..}@:
+appearing as a name component, you should make sure to call
address@hidden without prior direct or indirect calls to
address@hidden, as otherwise the file name component
+immediately preceding @samp{..} will be ``simplified away'' before
address@hidden is called.  To eliminate the need for a call to
address@hidden, @code{file-truename} handles @samp{~} in the
+same way that @code{expand-file-name} does.  @xref{File Name
+Expansion,, Functions that Expand Filenames}.
address@hidden defun
+
address@hidden file-chase-links filename &optional limit
+This function follows symbolic links, starting with @var{filename},
+until it finds a file name which is not the name of a symbolic link.
+Then it returns that file name.  This function does @emph{not} follow
+symbolic links at the level of parent directories.
+
+If you specify a number for @var{limit}, then after chasing through
+that many links, the function just returns what it has even if that is
+still a symbolic link.
address@hidden defun
+
+  To illustrate the difference between @code{file-chase-links} and
address@hidden, suppose that @file{/usr/foo} is a symbolic link to
+the directory @file{/home/foo}, and @file{/home/foo/hello} is an
+ordinary file (or at least, not a symbolic link) or nonexistent.  Then
+we would have:
+
address@hidden
+(file-chase-links "/usr/foo/hello")
+     ;; @r{This does not follow the links in the parent directories.}
+     @result{} "/usr/foo/hello"
+(file-truename "/usr/foo/hello")
+     ;; @r{Assuming that @file{/home} is not a symbolic link.}
+     @result{} "/home/foo/hello"
address@hidden example
+
+  @xref{Buffer File Name}, for related information.
+
address@hidden File Attributes
address@hidden  node-name,  next,  previous,  up
address@hidden Other Information about Files
+
+  This section describes the functions for getting detailed information
+about a file, other than its contents.  This information includes the
+mode bits that control access permission, the owner and group numbers,
+the number of names, the inode number, the size, and the times of access
+and modification.
+
address@hidden file-modes filename
address@hidden permission
address@hidden file attributes
+This function returns the mode bits of @var{filename}, as an integer.
+The mode bits are also called the file permissions, and they specify
+access control in the usual Unix fashion.  If the low-order bit is 1,
+then the file is executable by all users, if the second-lowest-order bit
+is 1, then the file is writable by all users, etc.
+
+The highest value returnable is 4095 (7777 octal), meaning that
+everyone has read, write, and execute permission, that the @acronym{SUID} bit
+is set for both others and group, and that the sticky bit is set.
+
+If @var{filename} does not exist, @code{file-modes} returns @code{nil}.
+
+This function recursively follows symbolic links at all levels.
+
address@hidden
address@hidden
+(file-modes "~/junk/diffs")
+     @result{} 492               ; @r{Decimal integer.}
address@hidden group
address@hidden
+(format "%o" 492)
+     @result{} "754"             ; @r{Convert to octal.}
address@hidden group
+
address@hidden
+(set-file-modes "~/junk/diffs" 438)
+     @result{} nil
address@hidden group
+
address@hidden
+(format "%o" 438)
+     @result{} "666"             ; @r{Convert to octal.}
address@hidden group
+
address@hidden
+% ls -l diffs
+  -rw-rw-rw-  1 lewis 0 3063 Oct 30 16:00 diffs
address@hidden group
address@hidden example
address@hidden defun
+
+If the @var{filename} argument to the next two functions is a symbolic
+link, then these function do @emph{not} replace it with its target.
+However, they both recursively follow symbolic links at all levels of
+parent directories.
+
address@hidden file-nlinks filename
+This functions returns the number of names (i.e., hard links) that
+file @var{filename} has.  If the file does not exist, then this function
+returns @code{nil}.  Note that symbolic links have no effect on this
+function, because they are not considered to be names of the files they
+link to.
+
address@hidden
address@hidden
+% ls -l foo*
+-rw-rw-rw-  2 rms       4 Aug 19 01:27 foo
+-rw-rw-rw-  2 rms       4 Aug 19 01:27 foo1
address@hidden group
+
address@hidden
+(file-nlinks "foo")
+     @result{} 2
address@hidden group
address@hidden
+(file-nlinks "doesnt-exist")
+     @result{} nil
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden file-attributes filename &optional id-format
address@hidden of file-attributes}
+This function returns a list of attributes of file @var{filename}.  If
+the specified file cannot be opened, it returns @code{nil}.
+The optional parameter @var{id-format} specifies the preferred format
+of attributes @acronym{UID} and @acronym{GID} (see below)---the
+valid values are @code{'string} and @code{'integer}.  The latter is
+the default, but we plan to change that, so you should specify a
address@hidden value for @var{id-format} if you use the returned
address@hidden or @acronym{GID}.
+
+The elements of the list, in order, are:
+
address@hidden 0
address@hidden
address@hidden for a directory, a string for a symbolic link (the name
+linked to), or @code{nil} for a text file.
+
address@hidden Wordy so as to prevent an overfull hbox.  --rjc 15mar92
address@hidden
+The number of names the file has.  Alternate names, also known as hard
+links, can be created by using the @code{add-name-to-file} function
+(@pxref{Changing Files}).
+
address@hidden
+The file's @acronym{UID}, normally as a string.  However, if it does
+not correspond to a named user, the value is an integer or a floating
+point number.
+
address@hidden
+The file's @acronym{GID}, likewise.
+
address@hidden
+The time of last access, as a list of two integers.
+The first integer has the high-order 16 bits of time,
+the second has the low 16 bits.  (This is similar to the
+value of @code{current-time}; see @ref{Time of Day}.)
+
address@hidden
+The time of last modification as a list of two integers (as above).
address@hidden modification time of file
+
address@hidden
+The time of last status change as a list of two integers (as above).
+
address@hidden
+The size of the file in bytes.  If the size is too large to fit in a
+Lisp integer, this is a floating point number.
+
address@hidden
+The file's modes, as a string of ten letters or dashes,
+as in @samp{ls -l}.
+
address@hidden
address@hidden if the file's @acronym{GID} would change if file were
+deleted and recreated; @code{nil} otherwise.
+
address@hidden
+The file's inode number.  If possible, this is an integer.  If the inode
+number is too large to be represented as an integer in Emacs Lisp, then
+the value has the form @code{(@var{high} . @var{low})}, where @var{low}
+holds the low 16 bits.
+
address@hidden
+The file system number of the file system that the file is in.
+Depending on the magnitude of the value, this can be either an integer
+or a cons cell, in the same manner as the inode number.  This element
+and the file's inode number together give enough information to
+distinguish any two files on the system---no two files can have the same
+values for both of these numbers.
address@hidden enumerate
+
+For example, here are the file attributes for @file{files.texi}:
+
address@hidden
address@hidden
+(file-attributes "files.texi" 'string)
+     @result{}  (nil 1 "lh" "users"
+          (8489 20284)
+          (8489 20284)
+          (8489 20285)
+          14906 "-rw-rw-rw-"
+          nil 129500 -32252)
address@hidden group
address@hidden example
+
address@hidden
+and here is how the result is interpreted:
+
address@hidden @code
address@hidden nil
+is neither a directory nor a symbolic link.
+
address@hidden 1
+has only one name (the name @file{files.texi} in the current default
+directory).
+
address@hidden "lh"
+is owned by the user with name "lh".
+
address@hidden "users"
+is in the group with name "users".
+
address@hidden (8489 20284)
+was last accessed on Aug 19 00:09.
+
address@hidden (8489 20284)
+was last modified on Aug 19 00:09.
+
address@hidden (8489 20285)
+last had its inode changed on Aug 19 00:09.
+
address@hidden 14906
+is 14906 bytes long.  (It may not contain 14906 characters, though,
+if some of the bytes belong to multibyte sequences.)
+
address@hidden "-rw-rw-rw-"
+has a mode of read and write access for the owner, group, and world.
+
address@hidden nil
+would retain the same @acronym{GID} if it were recreated.
+
address@hidden 129500
+has an inode number of 129500.
address@hidden -32252
+is on file system number -32252.
address@hidden table
address@hidden defun
+
address@hidden Locating Files
address@hidden How to Locate Files in Standard Places
address@hidden locate file in path
address@hidden find file in path
+
+  This section explains how to search for a file in a list of
+directories (a @dfn{path}).  One example is when you need to look for
+a program's executable file, e.g., to find out whether a given program
+is installed on the user's system.  Another example is the search for
+Lisp libraries (@pxref{Library Search}).  Such searches generally need
+to try various possible file name extensions, in addition to various
+possible directories.  Emacs provides a function for such a
+generalized search for a file.
+
address@hidden locate-file filename path &optional suffixes predicate
+This function searches for a file whose name is @var{filename} in a
+list of directories given by @var{path}, trying the suffixes in
address@hidden  If it finds such a file, it returns the full
address@hidden file name} of the file (@pxref{Relative File Names});
+otherwise it returns @code{nil}.
+
+The optional argument @var{suffixes} gives the list of file-name
+suffixes to append to @var{filename} when searching.
address@hidden tries each possible directory with each of these
+suffixes.  If @var{suffixes} is @code{nil}, or @code{("")}, then there
+are no suffixes, and @var{filename} is used only as-is.  Typical
+values of @var{suffixes} are @code{exec-suffixes} (@pxref{Subprocess
+Creation, exec-suffixes}), @code{load-suffixes},
address@hidden and the return value of the function
address@hidden (@pxref{Load Suffixes}).
+
+Typical values for @var{path} are @code{exec-path} (@pxref{Subprocess
+Creation, exec-path}) when looking for executable programs or
address@hidden (@pxref{Library Search, load-path}) when looking for
+Lisp files.  If @var{filename} is absolute, @var{path} has no effect,
+but the suffixes in @var{suffixes} are still tried.
+
+The optional argument @var{predicate}, if address@hidden, specifies
+the predicate function to use for testing whether a candidate file is
+suitable.  The predicate function is passed the candidate file name as
+its single argument.  If @var{predicate} is @code{nil} or unspecified,
address@hidden uses @code{file-readable-p} as the default
+predicate.  Useful non-default predicates include
address@hidden, @code{file-directory-p}, and other
+predicates described in @ref{Kinds of Files}.
+
+For compatibility, @var{predicate} can also be one of the symbols
address@hidden, @code{readable}, @code{writable}, @code{exists}, or
+a list of one or more of these symbols.
address@hidden defun
+
address@hidden executable-find program
+This function searches for the executable file of the named
address@hidden and returns the full absolute name of the executable,
+including its file-name extensions, if any.  It returns @code{nil} if
+the file is not found.  The functions searches in all the directories
+in @code{exec-path} and tries all the file-name extensions in
address@hidden
address@hidden defun
+
address@hidden Changing Files
address@hidden Changing File Names and Attributes
address@hidden @cindex renaming files  Duplicates rename-file
address@hidden copying files
address@hidden deleting files
address@hidden linking files
address@hidden setting modes of files
+
+  The functions in this section rename, copy, delete, link, and set the
+modes of files.
+
+  In the functions that have an argument @var{newname}, if a file by the
+name of @var{newname} already exists, the actions taken depend on the
+value of the argument @var{ok-if-already-exists}:
+
address@hidden @bullet
address@hidden
+Signal a @code{file-already-exists} error if
address@hidden is @code{nil}.
+
address@hidden
+Request confirmation if @var{ok-if-already-exists} is a number.
+
address@hidden
+Replace the old file without confirmation if @var{ok-if-already-exists}
+is any other value.
address@hidden itemize
+
+The next four commands all recursively follow symbolic links at all
+levels of parent directories for their first argument, but, if that
+argument is itself a symbolic link, then only @code{copy-file}
+replaces it with its (recursive) target.
+
address@hidden Command add-name-to-file oldname newname &optional 
ok-if-already-exists
address@hidden file with multiple names
address@hidden file hard link
+This function gives the file named @var{oldname} the additional name
address@hidden  This means that @var{newname} becomes a new ``hard
+link'' to @var{oldname}.
+
+In the first part of the following example, we list two files,
address@hidden and @file{foo3}.
+
address@hidden
address@hidden
+% ls -li fo*
+81908 -rw-rw-rw-  1 rms       29 Aug 18 20:32 foo
+84302 -rw-rw-rw-  1 rms       24 Aug 18 20:31 foo3
address@hidden group
address@hidden example
+
+Now we create a hard link, by calling @code{add-name-to-file}, then list
+the files again.  This shows two names for one file, @file{foo} and
address@hidden
+
address@hidden
address@hidden
+(add-name-to-file "foo" "foo2")
+     @result{} nil
address@hidden group
+
address@hidden
+% ls -li fo*
+81908 -rw-rw-rw-  2 rms       29 Aug 18 20:32 foo
+81908 -rw-rw-rw-  2 rms       29 Aug 18 20:32 foo2
+84302 -rw-rw-rw-  1 rms       24 Aug 18 20:31 foo3
address@hidden group
address@hidden example
+
+Finally, we evaluate the following:
+
address@hidden
+(add-name-to-file "foo" "foo3" t)
address@hidden example
+
address@hidden
+and list the files again.  Now there are three names
+for one file: @file{foo}, @file{foo2}, and @file{foo3}.  The old
+contents of @file{foo3} are lost.
+
address@hidden
address@hidden
+(add-name-to-file "foo1" "foo3")
+     @result{} nil
address@hidden group
+
address@hidden
+% ls -li fo*
+81908 -rw-rw-rw-  3 rms       29 Aug 18 20:32 foo
+81908 -rw-rw-rw-  3 rms       29 Aug 18 20:32 foo2
+81908 -rw-rw-rw-  3 rms       29 Aug 18 20:32 foo3
address@hidden group
address@hidden example
+
+This function is meaningless on operating systems where multiple names
+for one file are not allowed.  Some systems implement multiple names
+by copying the file instead.
+
+See also @code{file-nlinks} in @ref{File Attributes}.
address@hidden deffn
+
address@hidden Command rename-file filename newname &optional 
ok-if-already-exists
+This command renames the file @var{filename} as @var{newname}.
+
+If @var{filename} has additional names aside from @var{filename}, it
+continues to have those names.  In fact, adding the name @var{newname}
+with @code{add-name-to-file} and then deleting @var{filename} has the
+same effect as renaming, aside from momentary intermediate states.
address@hidden deffn
+
address@hidden Command copy-file oldname newname &optional ok-if-exists time 
preserve-uid-gid
+This command copies the file @var{oldname} to @var{newname}.  An
+error is signaled if @var{oldname} does not exist.  If @var{newname}
+names a directory, it copies @var{oldname} into that directory,
+preserving its final name component.
+
+If @var{time} is address@hidden, then this function gives the new file
+the same last-modified time that the old one has.  (This works on only
+some operating systems.)  If setting the time gets an error,
address@hidden signals a @code{file-date-error} error.  In an
+interactive call, a prefix argument specifies a address@hidden value
+for @var{time}.
+
+This function copies the file modes, too.
+
+If argument @var{preserve-uid-gid} is @code{nil}, we let the operating
+system decide the user and group ownership of the new file (this is
+usually set to the user running Emacs).  If @var{preserve-uid-gid} is
address@hidden, we attempt to copy the user and group ownership of the
+file.  This works only on some operating systems, and only if you have
+the correct permissions to do so.
address@hidden deffn
+
address@hidden Command make-symbolic-link filename newname  &optional 
ok-if-exists
address@hidden ln
address@hidden file-already-exists
+This command makes a symbolic link to @var{filename}, named
address@hidden  This is like the shell command @samp{ln -s
address@hidden @var{newname}}.
+
+This function is not available on systems that don't support symbolic
+links.
address@hidden deffn
+
address@hidden Command delete-file filename
address@hidden rm
+This command deletes the file @var{filename}, like the shell command
address@hidden @var{filename}}.  If the file has multiple names, it continues
+to exist under the other names.
+
+A suitable kind of @code{file-error} error is signaled if the file does
+not exist, or is not deletable.  (On Unix and GNU/Linux, a file is
+deletable if its directory is writable.)
+
+If @var{filename} is a symbolic link, @code{delete-file} does not
+replace it with its target, but it does follow symbolic links at all
+levels of parent directories.
+
+See also @code{delete-directory} in @ref{Create/Delete Dirs}.
address@hidden deffn
+
address@hidden define-logical-name varname string
+This function defines the logical name @var{varname} to have the value
address@hidden  It is available only on VMS.
address@hidden defun
+
address@hidden set-file-modes filename mode
+This function sets mode bits of @var{filename} to @var{mode} (which
+must be an integer).  Only the low 12 bits of @var{mode} are used.
+This function recursively follows symbolic links at all levels for
address@hidden
address@hidden defun
+
address@hidden Emacs 19 feature
address@hidden set-default-file-modes mode
address@hidden umask
+This function sets the default file protection for new files created by
+Emacs and its subprocesses.  Every file created with Emacs initially has
+this protection, or a subset of it (@code{write-region} will not give a
+file execute permission even if the default file protection allows
+execute permission).  On Unix and GNU/Linux, the default protection is
+the bitwise complement of the ``umask'' value.
+
+The argument @var{mode} must be an integer.  On most systems, only the
+low 9 bits of @var{mode} are meaningful.  You can use the Lisp construct
+for octal character codes to enter @var{mode}; for example,
+
address@hidden
+(set-default-file-modes ?\644)
address@hidden example
+
+Saving a modified version of an existing file does not count as creating
+the file; it preserves the existing file's mode, whatever that is.  So
+the default file protection has no effect.
address@hidden defun
+
address@hidden default-file-modes
+This function returns the current default protection value.
address@hidden defun
+
address@hidden set-file-times filename &optional time
+This function sets the access and modification times of @var{filename}
+to @var{time}.  The return value is @code{t} if the times are successfully
+set, otherwise it is @code{nil}.  @var{time} defaults to the current
+time and must be in the format returned by @code{current-time}
+(@pxref{Time of Day}).
address@hidden defun
+
address@hidden MS-DOS and file modes
address@hidden file modes and MS-DOS
+  On MS-DOS, there is no such thing as an ``executable'' file mode bit.
+So Emacs considers a file executable if its name ends in one of the
+standard executable extensions, such as @file{.com}, @file{.bat},
address@hidden, and some others.  Files that begin with the Unix-standard
address@hidden signature, such as shell and Perl scripts, are also considered
+as executable files.  This is reflected in the values returned by
address@hidden and @code{file-attributes}.  Directories are also
+reported with executable bit set, for compatibility with Unix.
+
address@hidden File Names
address@hidden File Names
address@hidden file names
+
+  Files are generally referred to by their names, in Emacs as elsewhere.
+File names in Emacs are represented as strings.  The functions that
+operate on a file all expect a file name argument.
+
+  In addition to operating on files themselves, Emacs Lisp programs
+often need to operate on file names; i.e., to take them apart and to use
+part of a name to construct related file names.  This section describes
+how to manipulate file names.
+
+  The functions in this section do not actually access files, so they
+can operate on file names that do not refer to an existing file or
+directory.
+
+  On MS-DOS and MS-Windows, these functions (like the function that
+actually operate on files) accept MS-DOS or MS-Windows file-name syntax,
+where backslashes separate the components, as well as Unix syntax; but
+they always return Unix syntax.  On VMS, these functions (and the ones
+that operate on files) understand both VMS file-name syntax and Unix
+syntax.  This enables Lisp programs to specify file names in Unix syntax
+and work properly on all systems without change.
+
address@hidden
+* File Name Components::  The directory part of a file name, and the rest.
+* Relative File Names::   Some file names are relative to a current directory.
+* Directory Names::       A directory's name as a directory
+                            is different from its name as a file.
+* File Name Expansion::   Converting relative file names to absolute ones.
+* Unique File Names::     Generating names for temporary files.
+* File Name Completion::  Finding the completions for a given file name.
+* Standard File Names::   If your package uses a fixed file name,
+                            how to handle various operating systems simply.
address@hidden menu
+
address@hidden File Name Components
address@hidden File Name Components
address@hidden directory part (of file name)
address@hidden nondirectory part (of file name)
address@hidden version number (in file name)
+
+  The operating system groups files into directories.  To specify a
+file, you must specify the directory and the file's name within that
+directory.  Therefore, Emacs considers a file name as having two main
+parts: the @dfn{directory name} part, and the @dfn{nondirectory} part
+(or @dfn{file name within the directory}).  Either part may be empty.
+Concatenating these two parts reproduces the original file name.
+
+  On most systems, the directory part is everything up to and including
+the last slash (backslash is also allowed in input on MS-DOS or
+MS-Windows); the nondirectory part is the rest.  The rules in VMS syntax
+are complicated.
+
+  For some purposes, the nondirectory part is further subdivided into
+the name proper and the @dfn{version number}.  On most systems, only
+backup files have version numbers in their names.  On VMS, every file
+has a version number, but most of the time the file name actually used
+in Emacs omits the version number, so that version numbers in Emacs are
+found mostly in directory lists.
+
address@hidden file-name-directory filename
+This function returns the directory part of @var{filename}, as a
+directory name (@pxref{Directory Names}), or @code{nil} if
address@hidden does not include a directory part.
+
+On GNU and Unix systems, a string returned by this function always
+ends in a slash.  On MS-DOS it can also end in a colon.  On VMS, it
+returns a string ending in one of the three characters @samp{:},
address@hidden, or @samp{>}.
+
address@hidden
address@hidden
+(file-name-directory "lewis/foo")  ; @r{Unix example}
+     @result{} "lewis/"
address@hidden group
address@hidden
+(file-name-directory "foo")        ; @r{Unix example}
+     @result{} nil
address@hidden group
address@hidden
+(file-name-directory "[X]FOO.TMP") ; @r{VMS example}
+     @result{} "[X]"
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden file-name-nondirectory filename
+This function returns the nondirectory part of @var{filename}.
+
address@hidden
address@hidden
+(file-name-nondirectory "lewis/foo")
+     @result{} "foo"
address@hidden group
address@hidden
+(file-name-nondirectory "foo")
+     @result{} "foo"
address@hidden group
address@hidden
+(file-name-nondirectory "lewis/")
+     @result{} ""
address@hidden group
address@hidden
+;; @r{The following example is accurate only on VMS.}
+(file-name-nondirectory "[X]FOO.TMP")
+     @result{} "FOO.TMP"
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden file-name-sans-versions filename &optional keep-backup-version
+This function returns @var{filename} with any file version numbers,
+backup version numbers, or trailing tildes discarded.
+
+If @var{keep-backup-version} is address@hidden, then true file version
+numbers understood as such by the file system are discarded from the
+return value, but backup version numbers are kept.
+
address@hidden
address@hidden
+(file-name-sans-versions "~rms/foo.~1~")
+     @result{} "~rms/foo"
address@hidden group
address@hidden
+(file-name-sans-versions "~rms/foo~")
+     @result{} "~rms/foo"
address@hidden group
address@hidden
+(file-name-sans-versions "~rms/foo")
+     @result{} "~rms/foo"
address@hidden group
address@hidden
+;; @r{The following example applies to VMS only.}
+(file-name-sans-versions "foo;23")
+     @result{} "foo"
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden file-name-extension filename &optional period
+This function returns @var{filename}'s final ``extension,'' if any,
+after applying @code{file-name-sans-versions} to remove any
+version/backup part.  The extension, in a file name, is the part that
+starts with the last @samp{.} in the last name component (minus
+any version/backup part).
+
+This function returns @code{nil} for extensionless file names such as
address@hidden  It returns @code{""} for null extensions, as in
address@hidden  If the last component of a file name begins with a
address@hidden, that @samp{.}  doesn't count as the beginning of an
+extension.  Thus, @file{.emacs}'s ``extension'' is @code{nil}, not
address@hidden
+
+If @var{period} is address@hidden, then the returned value includes
+the period that delimits the extension, and if @var{filename} has no
+extension, the value is @code{""}.
address@hidden defun
+
address@hidden file-name-sans-extension filename
+This function returns @var{filename} minus its extension, if any.  The
+version/backup part, if present, is only removed if the file has an
+extension.  For example,
+
address@hidden
+(file-name-sans-extension "foo.lose.c")
+     @result{} "foo.lose"
+(file-name-sans-extension "big.hack/foo")
+     @result{} "big.hack/foo"
+(file-name-sans-extension "/my/home/.emacs")
+     @result{} "/my/home/.emacs"
+(file-name-sans-extension "/my/home/.emacs.el")
+     @result{} "/my/home/.emacs"
+(file-name-sans-extension "~/foo.el.~3~")
+     @result{} "~/foo"
+(file-name-sans-extension "~/foo.~3~")
+     @result{} "~/foo.~3~"
address@hidden example
+
+Note that the @samp{.~3~} in the two last examples is the backup part,
+not an extension.
address@hidden defun
+
address@hidden
+Andrew Innes says that this
+
address@hidden @defvar directory-sep-char
+This variable holds the character that Emacs normally uses to separate
+file name components.  The default value is @code{?/}, but on MS-Windows
+you can set it to @code{?\\}; then the functions that transform file names
+use backslashes in their output.
+
+File names using backslashes work as input to Lisp primitives even on
+MS-DOS and MS-Windows, even if @code{directory-sep-char} has its default
+value of @code{?/}.
address@hidden defvar
address@hidden ignore
+
address@hidden Relative File Names
address@hidden Absolute and Relative File Names
address@hidden absolute file name
address@hidden relative file name
+
+  All the directories in the file system form a tree starting at the
+root directory.  A file name can specify all the directory names
+starting from the root of the tree; then it is called an @dfn{absolute}
+file name.  Or it can specify the position of the file in the tree
+relative to a default directory; then it is called a @dfn{relative} file
+name.  On Unix and GNU/Linux, an absolute file name starts with a slash
+or a tilde (@samp{~}), and a relative one does not.  On MS-DOS and
+MS-Windows, an absolute file name starts with a slash or a backslash, or
+with a drive specification @address@hidden:/}, where @var{x} is the
address@hidden letter}.  The rules on VMS are complicated.
+
address@hidden file-name-absolute-p filename
+This function returns @code{t} if file @var{filename} is an absolute
+file name, @code{nil} otherwise.  On VMS, this function understands both
+Unix syntax and VMS syntax.
+
address@hidden
address@hidden
+(file-name-absolute-p "~rms/foo")
+     @result{} t
address@hidden group
address@hidden
+(file-name-absolute-p "rms/foo")
+     @result{} nil
address@hidden group
address@hidden
+(file-name-absolute-p "/user/rms/foo")
+     @result{} t
address@hidden group
address@hidden example
address@hidden defun
+
+  Given a possibly relative file name, you can convert it to an
+absolute name using @code{expand-file-name} (@pxref{File Name
+Expansion}).  This function converts absolute file names to relative
+names:
+
address@hidden file-relative-name filename &optional directory
+This function tries to return a relative name that is equivalent to
address@hidden, assuming the result will be interpreted relative to
address@hidden (an absolute directory name or directory file name).
+If @var{directory} is omitted or @code{nil}, it defaults to the
+current buffer's default directory.
+
+On some operating systems, an absolute file name begins with a device
+name.  On such systems, @var{filename} has no relative equivalent based
+on @var{directory} if they start with two different device names.  In
+this case, @code{file-relative-name} returns @var{filename} in absolute
+form.
+
address@hidden
+(file-relative-name "/foo/bar" "/foo/")
+     @result{} "bar"
+(file-relative-name "/foo/bar" "/hack/")
+     @result{} "../foo/bar"
address@hidden example
address@hidden defun
+
address@hidden Directory Names
address@hidden  node-name,  next,  previous,  up
address@hidden Directory Names
address@hidden directory name
address@hidden file name of directory
+
+  A @dfn{directory name} is the name of a directory.  A directory is
+actually a kind of file, so it has a file name, which is related to
+the directory name but not identical to it.  (This is not quite the
+same as the usual Unix terminology.)  These two different names for
+the same entity are related by a syntactic transformation.  On GNU and
+Unix systems, this is simple: a directory name ends in a slash,
+whereas the directory's name as a file lacks that slash.  On MS-DOS and
+VMS, the relationship is more complicated.
+
+  The difference between a directory name and its name as a file is
+subtle but crucial.  When an Emacs variable or function argument is
+described as being a directory name, a file name of a directory is not
+acceptable.  When @code{file-name-directory} returns a string, that is
+always a directory name.
+
+  The following two functions convert between directory names and file
+names.  They do nothing special with environment variable substitutions
+such as @samp{$HOME}, and the constructs @samp{~}, @samp{.} and @samp{..}.
+
address@hidden file-name-as-directory filename
+This function returns a string representing @var{filename} in a form
+that the operating system will interpret as the name of a directory.  On
+most systems, this means appending a slash to the string (if it does not
+already end in one).  On VMS, the function converts a string of the form
address@hidden to the form @file{[X.Y]}.
+
address@hidden
address@hidden
+(file-name-as-directory "~rms/lewis")
+     @result{} "~rms/lewis/"
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden directory-file-name dirname
+This function returns a string representing @var{dirname} in a form that
+the operating system will interpret as the name of a file.  On most
+systems, this means removing the final slash (or backslash) from the
+string.  On VMS, the function converts a string of the form @file{[X.Y]}
+to @file{[X]Y.DIR.1}.
+
address@hidden
address@hidden
+(directory-file-name "~lewis/")
+     @result{} "~lewis"
address@hidden group
address@hidden example
address@hidden defun
+
+  Given a directory name, you can combine it with a relative file name
+using @code{concat}:
+
address@hidden
+(concat @var{dirname} @var{relfile})
address@hidden example
+
address@hidden
+Be sure to verify that the file name is relative before doing that.
+If you use an absolute file name, the results could be syntactically
+invalid or refer to the wrong file.
+
+  If you want to use a directory file name in making such a
+combination, you must first convert it to a directory name using
address@hidden:
+
address@hidden
+(concat (file-name-as-directory @var{dirfile}) @var{relfile})
address@hidden example
+
address@hidden
+Don't try concatenating a slash by hand, as in
+
address@hidden
+;;; @r{Wrong!}
+(concat @var{dirfile} "/" @var{relfile})
address@hidden example
+
address@hidden
+because this is not portable.  Always use
address@hidden
+
address@hidden directory name abbreviation
+  Directory name abbreviations are useful for directories that are
+normally accessed through symbolic links.  Sometimes the users recognize
+primarily the link's name as ``the name'' of the directory, and find it
+annoying to see the directory's ``real'' name.  If you define the link
+name as an abbreviation for the ``real'' name, Emacs shows users the
+abbreviation instead.
+
address@hidden directory-abbrev-alist
+The variable @code{directory-abbrev-alist} contains an alist of
+abbreviations to use for file directories.  Each element has the form
address@hidden(@var{from} . @var{to})}, and says to replace @var{from} with
address@hidden when it appears in a directory name.  The @var{from} string is
+actually a regular expression; it should always start with @samp{^}.
+The @var{to} string should be an ordinary absolute directory name.  Do
+not use @samp{~} to stand for a home directory in that string.  The
+function @code{abbreviate-file-name} performs these substitutions.
+
+You can set this variable in @file{site-init.el} to describe the
+abbreviations appropriate for your site.
+
+Here's an example, from a system on which file system @file{/home/fsf}
+and so on are normally accessed through symbolic links named @file{/fsf}
+and so on.
+
address@hidden
+(("^/home/fsf" . "/fsf")
+ ("^/home/gp" . "/gp")
+ ("^/home/gd" . "/gd"))
address@hidden example
address@hidden defvar
+
+  To convert a directory name to its abbreviation, use this
+function:
+
address@hidden abbreviate-file-name filename
address@hidden of abbreviate-file-name}
+This function applies abbreviations from @code{directory-abbrev-alist}
+to its argument, and substitutes @samp{~} for the user's home
+directory.  You can use it for directory names and for file names,
+because it recognizes abbreviations even as part of the name.
address@hidden defun
+
address@hidden File Name Expansion
address@hidden Functions that Expand Filenames
address@hidden expansion of file names
+
+  @dfn{Expansion} of a file name means converting a relative file name
+to an absolute one.  Since this is done relative to a default directory,
+you must specify the default directory name as well as the file name to
+be expanded.  Expansion also simplifies file names by eliminating
+redundancies such as @file{./} and @address@hidden/../}.
+
address@hidden expand-file-name filename &optional directory
+This function converts @var{filename} to an absolute file name.  If
address@hidden is supplied, it is the default directory to start with
+if @var{filename} is relative.  (The value of @var{directory} should
+itself be an absolute directory name or directory file name; it may
+start with @samp{~}.)  Otherwise, the current buffer's value of
address@hidden is used.  For example:
+
address@hidden
address@hidden
+(expand-file-name "foo")
+     @result{} "/xcssun/users/rms/lewis/foo"
address@hidden group
address@hidden
+(expand-file-name "../foo")
+     @result{} "/xcssun/users/rms/foo"
address@hidden group
address@hidden
+(expand-file-name "foo" "/usr/spool/")
+     @result{} "/usr/spool/foo"
address@hidden group
address@hidden
+(expand-file-name "$HOME/foo")
+     @result{} "/xcssun/users/rms/lewis/$HOME/foo"
address@hidden group
address@hidden example
+
+If the part of the combined file name before the first slash is
address@hidden, it expands to the value of the @env{HOME} environment
+variable (usually your home directory).  If the part before the first
+slash is @address@hidden and if @var{user} is a valid login name,
+it expands to @var{user}'s home directory.
+
+Filenames containing @samp{.} or @samp{..} are simplified to their
+canonical form:
+
address@hidden
address@hidden
+(expand-file-name "bar/../foo")
+     @result{} "/xcssun/users/rms/lewis/foo"
address@hidden group
address@hidden example
+
+In some cases, a leading @samp{..} component can remain in the output:
+
address@hidden
address@hidden
+(expand-file-name "../home" "/")
+     @result{} "/../home"
address@hidden group
address@hidden example
+
address@hidden
+This is for the sake of filesystems that have the concept of a
+``superroot'' above the root directory @file{/}.  On other filesystems,
address@hidden/../} is interpreted exactly the same as @file{/}.
+
+Note that @code{expand-file-name} does @emph{not} expand environment
+variables; only @code{substitute-in-file-name} does that.
+
+Note also that @code{expand-file-name} does not follow symbolic links
+at any level.  This results in a difference between the way
address@hidden and @code{expand-file-name} treat @samp{..}.
+Assuming that @samp{/tmp/bar} is a symbolic link to the directory
address@hidden/tmp/foo/bar} we get:
+
address@hidden
address@hidden
+(file-truename "/tmp/bar/../myfile")
+     @result{} "/tmp/foo/myfile"
address@hidden group
address@hidden
+(expand-file-name "/tmp/bar/../myfile")
+     @result{} "/tmp/myfile"
address@hidden group
address@hidden example
+
+If you may need to follow symbolic links preceding @samp{..}, you
+should make sure to call @code{file-truename} without prior direct or
+indirect calls to @code{expand-file-name}.  @xref{Truenames}.
address@hidden defun
+
address@hidden default-directory
+The value of this buffer-local variable is the default directory for the
+current buffer.  It should be an absolute directory name; it may start
+with @samp{~}.  This variable is buffer-local in every buffer.
+
address@hidden uses the default directory when its second
+argument is @code{nil}.
+
+Aside from VMS, the value is always a string ending with a slash.
+
address@hidden
address@hidden
+default-directory
+     @result{} "/user/lewis/manual/"
address@hidden group
address@hidden example
address@hidden defvar
+
address@hidden substitute-in-file-name filename
address@hidden of substitute-in-file-name}
+This function replaces environment variable references in
address@hidden with the environment variable values.  Following
+standard Unix shell syntax, @samp{$} is the prefix to substitute an
+environment variable value.  If the input contains @samp{$$}, that is
+converted to @samp{$}; this gives the user a way to ``quote'' a
address@hidden
+
+The environment variable name is the series of alphanumeric characters
+(including underscores) that follow the @samp{$}.  If the character following
+the @samp{$} is a @address@hidden, then the variable name is everything up to 
the
+matching @address@hidden
+
+Calling @code{substitute-in-file-name} on output produced by
address@hidden tends to give incorrect results.  For
+instance, use of @samp{$$} to quote a single @samp{$} won't work
+properly, and @samp{$} in an environment variable's value could lead
+to repeated substitution.  Therefore, programs that call this function
+and put the output where it will be passed to this function need to
+double all @samp{$} characters to prevent subsequent incorrect
+results.
+
address@hidden Wordy to avoid overfull hbox.  --rjc 15mar92
+Here we assume that the environment variable @code{HOME}, which holds
+the user's home directory name, has value @samp{/xcssun/users/rms}.
+
address@hidden
address@hidden
+(substitute-in-file-name "$HOME/foo")
+     @result{} "/xcssun/users/rms/foo"
address@hidden group
address@hidden example
+
+After substitution, if a @samp{~} or a @samp{/} appears immediately
+after another @samp{/}, the function discards everything before it (up
+through the immediately preceding @samp{/}).
+
address@hidden
address@hidden
+(substitute-in-file-name "bar/~/foo")
+     @result{} "~/foo"
address@hidden group
address@hidden
+(substitute-in-file-name "/usr/local/$HOME/foo")
+     @result{} "/xcssun/users/rms/foo"
+     ;; @address@hidden/usr/local/} has been discarded.}
address@hidden group
address@hidden example
+
+On VMS, @samp{$} substitution is not done, so this function does nothing
+on VMS except discard superfluous initial components as shown above.
address@hidden defun
+
address@hidden Unique File Names
address@hidden Generating Unique File Names
+
+  Some programs need to write temporary files.  Here is the usual way to
+construct a name for such a file:
+
address@hidden
+(make-temp-file @var{name-of-application})
address@hidden example
+
address@hidden
+The job of @code{make-temp-file} is to prevent two different users or
+two different jobs from trying to use the exact same file name.
+
address@hidden make-temp-file prefix &optional dir-flag suffix
+This function creates a temporary file and returns its name.  Emacs
+creates the temporary file's name by adding to @var{prefix} some
+random characters that are different in each Emacs job.  The result is
+guaranteed to be a newly created empty file.  On MS-DOS, this function
+can truncate the @var{string} prefix to fit into the 8+3 file-name
+limits.  If @var{prefix} is a relative file name, it is expanded
+against @code{temporary-file-directory}.
+
address@hidden
address@hidden
+(make-temp-file "foo")
+     @result{} "/tmp/foo232J6v"
address@hidden group
address@hidden example
+
+When @code{make-temp-file} returns, the file has been created and is
+empty.  At that point, you should write the intended contents into the
+file.
+
+If @var{dir-flag} is address@hidden, @code{make-temp-file} creates an
+empty directory instead of an empty file.  It returns the file name,
+not the directory name, of that directory.  @xref{Directory Names}.
+
+If @var{suffix} is address@hidden, @code{make-temp-file} adds it at
+the end of the file name.
+
+To prevent conflicts among different libraries running in the same
+Emacs, each Lisp program that uses @code{make-temp-file} should have its
+own @var{prefix}.  The number added to the end of @var{prefix}
+distinguishes between the same application running in different Emacs
+jobs.  Additional added characters permit a large number of distinct
+names even in one Emacs job.
address@hidden defun
+
+  The default directory for temporary files is controlled by the
+variable @code{temporary-file-directory}.  This variable gives the user
+a uniform way to specify the directory for all temporary files.  Some
+programs use @code{small-temporary-file-directory} instead, if that is
address@hidden  To use it, you should expand the prefix against
+the proper directory before calling @code{make-temp-file}.
+
+  In older Emacs versions where @code{make-temp-file} does not exist,
+you should use @code{make-temp-name} instead:
+
address@hidden
+(make-temp-name
+ (expand-file-name @var{name-of-application}
+                   temporary-file-directory))
address@hidden example
+
address@hidden make-temp-name string
+This function generates a string that can be used as a unique file
+name.  The name starts with @var{string}, and has several random
+characters appended to it, which are different in each Emacs job.  It
+is like @code{make-temp-file} except that it just constructs a name,
+and does not create a file.  Another difference is that @var{string}
+should be an absolute file name.  On MS-DOS, this function can
+truncate the @var{string} prefix to fit into the 8+3 file-name limits.
address@hidden defun
+
address@hidden temporary-file-directory
address@hidden @code{TMPDIR} environment variable
address@hidden @code{TMP} environment variable
address@hidden @code{TEMP} environment variable
+This variable specifies the directory name for creating temporary files.
+Its value should be a directory name (@pxref{Directory Names}), but it
+is good for Lisp programs to cope if the value is a directory's file
+name instead.  Using the value as the second argument to
address@hidden is a good way to achieve that.
+
+The default value is determined in a reasonable way for your operating
+system; it is based on the @code{TMPDIR}, @code{TMP} and @code{TEMP}
+environment variables, with a fall-back to a system-dependent name if
+none of these variables is defined.
+
+Even if you do not use @code{make-temp-file} to create the temporary
+file, you should still use this variable to decide which directory to
+put the file in.  However, if you expect the file to be small, you
+should use @code{small-temporary-file-directory} first if that is
address@hidden
address@hidden defvar
+
address@hidden small-temporary-file-directory
+This variable specifies the directory name for
+creating certain temporary files, which are likely to be small.
+
+If you want to write a temporary file which is likely to be small, you
+should compute the directory like this:
+
address@hidden
+(make-temp-file
+  (expand-file-name @var{prefix}
+                    (or small-temporary-file-directory
+                        temporary-file-directory)))
address@hidden example
address@hidden defvar
+
address@hidden File Name Completion
address@hidden File Name Completion
address@hidden file name completion subroutines
address@hidden completion, file name
+
+  This section describes low-level subroutines for completing a file
+name.  For higher level functions, see @ref{Reading File Names}.
+
address@hidden file-name-all-completions partial-filename directory
+This function returns a list of all possible completions for a file
+whose name starts with @var{partial-filename} in directory
address@hidden  The order of the completions is the order of the files
+in the directory, which is unpredictable and conveys no useful
+information.
+
+The argument @var{partial-filename} must be a file name containing no
+directory part and no slash (or backslash on some systems).  The current
+buffer's default directory is prepended to @var{directory}, if
address@hidden is not absolute.
+
+In the following example, suppose that @file{~rms/lewis} is the current
+default directory, and has five files whose names begin with @samp{f}:
address@hidden, @file{file~}, @file{file.c}, @file{file.c.~1~}, and
address@hidden@refill
+
address@hidden
address@hidden
+(file-name-all-completions "f" "")
+     @result{} ("foo" "file~" "file.c.~2~"
+                "file.c.~1~" "file.c")
address@hidden group
+
address@hidden
+(file-name-all-completions "fo" "")
+     @result{} ("foo")
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden file-name-completion filename directory &optional predicate
+This function completes the file name @var{filename} in directory
address@hidden  It returns the longest prefix common to all file names
+in directory @var{directory} that start with @var{filename}.  If
address@hidden is address@hidden then it ignores possible completions
+that don't satisfy @var{predicate}, after calling that function
+with one argument, the expanded absolute file name.
+
+If only one match exists and @var{filename} matches it exactly, the
+function returns @code{t}.  The function returns @code{nil} if directory
address@hidden contains no name starting with @var{filename}.
+
+In the following example, suppose that the current default directory
+has five files whose names begin with @samp{f}: @file{foo},
address@hidden, @file{file.c}, @file{file.c.~1~}, and
address@hidden@refill
+
address@hidden
address@hidden
+(file-name-completion "fi" "")
+     @result{} "file"
address@hidden group
+
address@hidden
+(file-name-completion "file.c.~1" "")
+     @result{} "file.c.~1~"
address@hidden group
+
address@hidden
+(file-name-completion "file.c.~1~" "")
+     @result{} t
address@hidden group
+
address@hidden
+(file-name-completion "file.c.~3" "")
+     @result{} nil
address@hidden group
address@hidden example
address@hidden defun
+
address@hidden completion-ignored-extensions
address@hidden usually ignores file names that end in any
+string in this list.  It does not ignore them when all the possible
+completions end in one of these suffixes.  This variable has no effect
+on @address@hidden
+
+A typical value might look like this:
+
address@hidden
address@hidden
+completion-ignored-extensions
+     @result{} (".o" ".elc" "~" ".dvi")
address@hidden group
address@hidden example
+
+If an element of @code{completion-ignored-extensions} ends in a slash
address@hidden/}, it signals a directory.  The elements which do @emph{not} end
+in a slash will never match a directory; thus, the above value will not
+filter out a directory named @file{foo.elc}.
address@hidden defopt
+
address@hidden Standard File Names
address@hidden Standard File Names
+
+  Most of the file names used in Lisp programs are entered by the user.
+But occasionally a Lisp program needs to specify a standard file name
+for a particular use---typically, to hold customization information
+about each user.  For example, abbrev definitions are stored (by
+default) in the file @file{~/.abbrev_defs}; the @code{completion}
+package stores completions in the file @file{~/.completions}.  These are
+two of the many standard file names used by parts of Emacs for certain
+purposes.
+
+  Various operating systems have their own conventions for valid file
+names and for which file names to use for user profile data.  A Lisp
+program which reads a file using a standard file name ought to use, on
+each type of system, a file name suitable for that system.  The function
address@hidden makes this easy to do.
+
address@hidden convert-standard-filename filename
+This function alters the file name @var{filename} to fit the conventions
+of the operating system in use, and returns the result as a new string.
address@hidden defun
+
+  The recommended way to specify a standard file name in a Lisp program
+is to choose a name which fits the conventions of GNU and Unix systems,
+usually with a nondirectory part that starts with a period, and pass it
+to @code{convert-standard-filename} instead of using it directly.  Here
+is an example from the @code{completion} package:
+
address@hidden
+(defvar save-completions-file-name
+        (convert-standard-filename "~/.completions")
+  "*The file name to save completions to.")
address@hidden example
+
+  On GNU and Unix systems, and on some other systems as well,
address@hidden returns its argument unchanged.  On
+some other systems, it alters the name to fit the system's conventions.
+
+  For example, on MS-DOS the alterations made by this function include
+converting a leading @samp{.}  to @samp{_}, converting a @samp{_} in the
+middle of the name to @samp{.} if there is no other @samp{.}, inserting
+a @samp{.} after eight characters if there is none, and truncating to
+three characters after the @samp{.}.  (It makes other changes as well.)
+Thus, @file{.abbrev_defs} becomes @file{_abbrev.def}, and
address@hidden becomes @file{_complet.ion}.
+
address@hidden Contents of Directories
address@hidden Contents of Directories
address@hidden directory-oriented functions
address@hidden file names in directory
+
+  A directory is a kind of file that contains other files entered under
+various names.  Directories are a feature of the file system.
+
+  Emacs can list the names of the files in a directory as a Lisp list,
+or display the names in a buffer using the @code{ls} shell command.  In
+the latter case, it can optionally display information about each file,
+depending on the options passed to the @code{ls} command.
+
address@hidden directory-files directory &optional full-name match-regexp nosort
+This function returns a list of the names of the files in the directory
address@hidden  By default, the list is in alphabetical order.
+
+If @var{full-name} is address@hidden, the function returns the files'
+absolute file names.  Otherwise, it returns the names relative to
+the specified directory.
+
+If @var{match-regexp} is address@hidden, this function returns only
+those file names that contain a match for that regular expression---the
+other file names are excluded from the list.  On case-insensitive
+filesystems, the regular expression matching is case-insensitive.
+
address@hidden Emacs 19 feature
+If @var{nosort} is address@hidden, @code{directory-files} does not sort
+the list, so you get the file names in no particular order.  Use this if
+you want the utmost possible speed and don't care what order the files
+are processed in.  If the order of processing is visible to the user,
+then the user will probably be happier if you do sort the names.
+
address@hidden
address@hidden
+(directory-files "~lewis")
+     @result{} ("#foo#" "#foo.el#" "." ".."
+         "dired-mods.el" "files.texi"
+         "files.texi.~1~")
address@hidden group
address@hidden example
+
+An error is signaled if @var{directory} is not the name of a directory
+that can be read.
address@hidden defun
+
address@hidden directory-files-and-attributes directory &optional full-name 
match-regexp nosort id-format
+This is similar to @code{directory-files} in deciding which files
+to report on and how to report their names.  However, instead
+of returning a list of file names, it returns for each file a
+list @code{(@var{filename} . @var{attributes})}, where @var{attributes}
+is what @code{file-attributes} would return for that file.
+The optional argument @var{id-format} has the same meaning as the
+corresponding argument to @code{file-attributes} (@pxref{Definition
+of file-attributes}).
address@hidden defun
+
address@hidden file-name-all-versions file dirname
+This function returns a list of all versions of the file named
address@hidden in directory @var{dirname}.  It is only available on VMS.
address@hidden defun
+
address@hidden file-expand-wildcards pattern &optional full
+This function expands the wildcard pattern @var{pattern}, returning
+a list of file names that match it.
+
+If @var{pattern} is written as an absolute file name,
+the values are absolute also.
+
+If @var{pattern} is written as a relative file name, it is interpreted
+relative to the current default directory.  The file names returned are
+normally also relative to the current default directory.  However, if
address@hidden is address@hidden, they are absolute.
address@hidden defun
+
address@hidden insert-directory file switches &optional wildcard 
full-directory-p
+This function inserts (in the current buffer) a directory listing for
+directory @var{file}, formatted with @code{ls} according to
address@hidden  It leaves point after the inserted text.
address@hidden may be a string of options, or a list of strings
+representing individual options.
+
+The argument @var{file} may be either a directory name or a file
+specification including wildcard characters.  If @var{wildcard} is
address@hidden, that means treat @var{file} as a file specification with
+wildcards.
+
+If @var{full-directory-p} is address@hidden, that means the directory
+listing is expected to show the full contents of a directory.  You
+should specify @code{t} when @var{file} is a directory and switches do
+not contain @samp{-d}.  (The @samp{-d} option to @code{ls} says to
+describe a directory itself as a file, rather than showing its
+contents.)
+
+On most systems, this function works by running a directory listing
+program whose name is in the variable @code{insert-directory-program}.
+If @var{wildcard} is address@hidden, it also runs the shell specified by
address@hidden, to expand the wildcards.
+
+MS-DOS and MS-Windows systems usually lack the standard Unix program
address@hidden, so this function emulates the standard Unix program @code{ls}
+with Lisp code.
+
+As a technical detail, when @var{switches} contains the long
address@hidden option, @code{insert-directory} treats it specially,
+for the sake of dired.  However, the normally equivalent short
address@hidden option is just passed on to @code{insert-directory-program},
+as any other option.
address@hidden defun
+
address@hidden insert-directory-program
+This variable's value is the program to run to generate a directory listing
+for the function @code{insert-directory}.  It is ignored on systems
+which generate the listing with Lisp code.
address@hidden defvar
+
address@hidden Create/Delete Dirs
address@hidden Creating and Deleting Directories
address@hidden creating and deleting directories
address@hidden Emacs 19 features
+
+  Most Emacs Lisp file-manipulation functions get errors when used on
+files that are directories.  For example, you cannot delete a directory
+with @code{delete-file}.  These special functions exist to create and
+delete directories.
+
address@hidden make-directory dirname &optional parents
+This function creates a directory named @var{dirname}.
+If @var{parents} is address@hidden, as is always the case in an
+interactive call, that means to create the parent directories first,
+if they don't already exist.
address@hidden defun
+
address@hidden delete-directory dirname
+This function deletes the directory named @var{dirname}.  The function
address@hidden does not work for files that are directories; you
+must use @code{delete-directory} for them.  If the directory contains
+any files, @code{delete-directory} signals an error.
+
+This function only follows symbolic links at the level of parent
+directories.
address@hidden defun
+
address@hidden Magic File Names
address@hidden Making Certain File Names ``Magic''
address@hidden magic file names
+
address@hidden Emacs 19 feature
+  You can implement special handling for certain file names.  This is
+called making those names @dfn{magic}.  The principal use for this
+feature is in implementing remote file names (@pxref{Remote Files,,
+Remote Files, emacs, The GNU Emacs Manual}).
+
+  To define a kind of magic file name, you must supply a regular
+expression to define the class of names (all those that match the
+regular expression), plus a handler that implements all the primitive
+Emacs file operations for file names that do match.
+
+  The variable @code{file-name-handler-alist} holds a list of handlers,
+together with regular expressions that determine when to apply each
+handler.  Each element has this form:
+
address@hidden
+(@var{regexp} . @var{handler})
address@hidden example
+
address@hidden
+All the Emacs primitives for file access and file name transformation
+check the given file name against @code{file-name-handler-alist}.  If
+the file name matches @var{regexp}, the primitives handle that file by
+calling @var{handler}.
+
+  The first argument given to @var{handler} is the name of the
+primitive, as a symbol; the remaining arguments are the arguments that
+were passed to that primitive.  (The first of these arguments is most
+often the file name itself.)  For example, if you do this:
+
address@hidden
+(file-exists-p @var{filename})
address@hidden example
+
address@hidden
+and @var{filename} has handler @var{handler}, then @var{handler} is
+called like this:
+
address@hidden
+(funcall @var{handler} 'file-exists-p @var{filename})
address@hidden example
+
+  When a function takes two or more arguments that must be file names,
+it checks each of those names for a handler.  For example, if you do
+this:
+
address@hidden
+(expand-file-name @var{filename} @var{dirname})
address@hidden example
+
address@hidden
+then it checks for a handler for @var{filename} and then for a handler
+for @var{dirname}.  In either case, the @var{handler} is called like
+this:
+
address@hidden
+(funcall @var{handler} 'expand-file-name @var{filename} @var{dirname})
address@hidden example
+
address@hidden
+The @var{handler} then needs to figure out whether to handle
address@hidden or @var{dirname}.
+
+  If the specified file name matches more than one handler, the one
+whose match starts last in the file name gets precedence.  This rule
+is chosen so that handlers for jobs such as uncompression are handled
+first, before handlers for jobs such as remote file access.
+
+  Here are the operations that a magic file name handler gets to handle:
+
address@hidden
address@hidden
address@hidden, @code{add-name-to-file},
address@hidden,@*
address@hidden, @code{delete-directory},
address@hidden,
address@hidden,
address@hidden,
address@hidden,
address@hidden,
address@hidden, @code{dired-uncache},@*
address@hidden,
address@hidden,
address@hidden,
address@hidden,
address@hidden, @code{file-exists-p},
address@hidden, @code{file-remote-p},
address@hidden, @code{file-name-all-completions},
address@hidden,
address@hidden,
address@hidden,
address@hidden,
address@hidden, @code{file-newer-than-file-p},
address@hidden,
address@hidden, @code{file-regular-p}, @code{file-symlink-p},
address@hidden, @code{file-writable-p},
address@hidden,
address@hidden,@*
address@hidden,
address@hidden,
address@hidden,@*
address@hidden,
address@hidden,
address@hidden,
address@hidden,
address@hidden,@*
address@hidden,
address@hidden, @code{set-file-modes}, @code{set-file-times},
address@hidden, @code{shell-command},
address@hidden,
address@hidden,@*
address@hidden,
address@hidden,
address@hidden,@*
address@hidden
address@hidden ifnottex
address@hidden
address@hidden
address@hidden
address@hidden, @code{add-name-to-file},
address@hidden@discretionary{}{}{}piler-base-file-name},
address@hidden, @code{delete-directory},
address@hidden,
address@hidden,
address@hidden,
address@hidden,
address@hidden@discretionary{}{}{}tributes},
address@hidden, @code{dired-uncache},
address@hidden,
address@hidden@discretionary{}{}{}tory-p},
address@hidden,
address@hidden@discretionary{}{}{}ory-p},
address@hidden, @code{file-exists-p},
address@hidden, @code{file-remote-p},
address@hidden, @code{file-name-all-completions},
address@hidden,
address@hidden,
address@hidden,
address@hidden@discretionary{}{}{}tory},
address@hidden, @code{file-newer-than-file-p},
address@hidden@discretionary{}{}{}served-p},
address@hidden, @code{file-regular-p}, @code{file-symlink-p},
address@hidden, @code{file-writable-p},
address@hidden,
address@hidden,
address@hidden,
address@hidden,
address@hidden,
address@hidden, @address@hidden,
address@hidden@discretionary{}{}{}tory-internal},
address@hidden,
address@hidden,
address@hidden, @code{set-file-modes},
address@hidden, @code{shell-command},
address@hidden,
address@hidden,
address@hidden,
address@hidden@discretionary{}{}{}tered},
address@hidden,
address@hidden
address@hidden flushleft
address@hidden iftex
+
+  Handlers for @code{insert-file-contents} typically need to clear the
+buffer's modified flag, with @code{(set-buffer-modified-p nil)}, if the
address@hidden argument is address@hidden  This also has the effect of
+unlocking the buffer if it is locked.
+
+  The handler function must handle all of the above operations, and
+possibly others to be added in the future.  It need not implement all
+these operations itself---when it has nothing special to do for a
+certain operation, it can reinvoke the primitive, to handle the
+operation ``in the usual way.''  It should always reinvoke the primitive
+for an operation it does not recognize.  Here's one way to do this:
+
address@hidden
+(defun my-file-handler (operation &rest args)
+  ;; @r{First check for the specific operations}
+  ;; @r{that we have special handling for.}
+  (cond ((eq operation 'insert-file-contents) @dots{})
+        ((eq operation 'write-region) @dots{})
+        @dots{}
+        ;; @r{Handle any operation we don't know about.}
+        (t (let ((inhibit-file-name-handlers
+                  (cons 'my-file-handler
+                        (and (eq inhibit-file-name-operation operation)
+                             inhibit-file-name-handlers)))
+                 (inhibit-file-name-operation operation))
+             (apply operation args)))))
address@hidden smallexample
+
+  When a handler function decides to call the ordinary Emacs primitive for
+the operation at hand, it needs to prevent the primitive from calling
+the same handler once again, thus leading to an infinite recursion.  The
+example above shows how to do this, with the variables
address@hidden and
address@hidden  Be careful to use them exactly as
+shown above; the details are crucial for proper behavior in the case of
+multiple handlers, and for operations that have two file names that may
+each have handlers.
+
address@hidden safe-magic (@r{property})
+  Handlers that don't really do anything special for actual access to the
+file---such as the ones that implement completion of host names for
+remote file names---should have a address@hidden @code{safe-magic}
+property.  For instance, Emacs normally ``protects'' directory names
+it finds in @code{PATH} from becoming magic, if they look like magic
+file names, by prefixing them with @samp{/:}.  But if the handler that
+would be used for them has a address@hidden @code{safe-magic}
+property, the @samp{/:} is not added.
+
address@hidden operations (@r{property})
+  A file name handler can have an @code{operations} property to
+declare which operations it handles in a nontrivial way.  If this
+property has a address@hidden value, it should be a list of
+operations; then only those operations will call the handler.  This
+avoids inefficiency, but its main purpose is for autoloaded handler
+functions, so that they won't be loaded except when they have real
+work to do.
+
+  Simply deferring all operations to the usual primitives does not
+work.  For instance, if the file name handler applies to
address@hidden, then it must handle @code{load} itself, because
+the usual @code{load} code won't work properly in that case.  However,
+if the handler uses the @code{operations} property to say it doesn't
+handle @code{file-exists-p}, then it need not handle @code{load}
+nontrivially.
+
address@hidden inhibit-file-name-handlers
+This variable holds a list of handlers whose use is presently inhibited
+for a certain operation.
address@hidden defvar
+
address@hidden inhibit-file-name-operation
+The operation for which certain handlers are presently inhibited.
address@hidden defvar
+
address@hidden find-file-name-handler file operation
+This function returns the handler function for file name @var{file},
+or @code{nil} if there is none.  The argument @var{operation} should
+be the operation to be performed on the file---the value you will pass
+to the handler as its first argument when you call it.  If
address@hidden equals @code{inhibit-file-name-operation}, or if it is
+not found in the @code{operations} property of the handler, this
+function returns @code{nil}.
address@hidden defun
+
address@hidden file-local-copy filename
+This function copies file @var{filename} to an ordinary non-magic file
+on the local machine, if it isn't on the local machine already.  Magic
+file names should handle the @code{file-local-copy} operation if they
+refer to files on other machines.  A magic file name that is used for
+other purposes than remote file access should not handle
address@hidden; then this function will treat the file as
+local.
+
+If @var{filename} is local, whether magic or not, this function does
+nothing and returns @code{nil}.  Otherwise it returns the file name
+of the local copy file.
address@hidden defun
+
address@hidden file-remote-p filename &optional identification connected
+This function tests whether @var{filename} is a remote file.  If
address@hidden is local (not remote), the return value is @code{nil}.
+If @var{filename} is indeed remote, the return value is a string that
+identifies the remote system.
+
+This identifier string can include a host name and a user name, as
+well as characters designating the method used to access the remote
+system.  For example, the remote identifier string for the filename
address@hidden/sudo::/some/file} is @code{/sudo:root@@localhost:}.
+
+If @code{file-remote-p} returns the same identifier for two different
+filenames, that means they are stored on the same file system and can
+be accessed locally with respect to each other.  This means, for
+example, that it is possible to start a remote process accessing both
+files at the same time.  Implementors of file handlers need to ensure
+this principle is valid.
+
address@hidden specifies which part of the identifier shall be
+returned as string.  @var{identification} can be the symbol
address@hidden, @code{user} or @code{host}; any other value is handled
+like @code{nil} and means to return the complete identifier string.
+In the example above, the remote @code{user} identifier string would
+be @code{root}.
+
+If @var{connected} is address@hidden, this function returns @code{nil}
+even if @var{filename} is remote, if Emacs has no network connection
+to its host.  This is useful when you want to avoid the delay of
+making connections when they don't exist.
address@hidden defun
+
address@hidden unhandled-file-name-directory filename
+This function returns the name of a directory that is not magic.  It
+uses the directory part of @var{filename} if that is not magic.  For a
+magic file name, it invokes the file name handler, which therefore
+decides what value to return.
+
+This is useful for running a subprocess; every subprocess must have a
+non-magic directory to serve as its current directory, and this function
+is a good way to come up with one.
address@hidden defun
+
address@hidden Format Conversion
address@hidden File Format Conversion
+
address@hidden file format conversion
address@hidden encoding file formats
address@hidden decoding file formats
address@hidden text properties in files
address@hidden saving text properties
+  Emacs performs several steps to convert the data in a buffer (text,
+text properties, and possibly other information) to and from a
+representation suitable for storing into a file.  This section describes
+the fundamental functions that perform this @dfn{format conversion},
+namely @code{insert-file-contents} for reading a file into a buffer,
+and @code{write-region} for writing a buffer into a file.
+
address@hidden
+* Overview: Format Conversion Overview.     @code{insert-file-contents} and 
@code{write-region}
+* Round-Trip: Format Conversion Round-Trip. Using @code{format-alist}.
+* Piecemeal: Format Conversion Piecemeal.   Specifying non-paired conversion.
address@hidden menu
+
address@hidden Format Conversion Overview
address@hidden Overview
address@hidden
+The function @code{insert-file-contents}:
+
address@hidden
address@hidden initially, inserts bytes from the file into the buffer;
address@hidden decodes bytes to characters as appropriate;
address@hidden processes formats as defined by entries in @code{format-alist}; 
and
address@hidden calls functions in @code{after-insert-file-functions}.
address@hidden itemize
+
address@hidden
+The function @code{write-region}:
+
address@hidden
address@hidden initially, calls functions in 
@code{write-region-annotate-functions};
address@hidden processes formats as defined by entries in @code{format-alist};
address@hidden encodes characters to bytes as appropriate; and
address@hidden modifies the file with the bytes.
address@hidden itemize
+
+  This shows the symmetry of the lowest-level operations; reading and
+writing handle things in opposite order.  The rest of this section
+describes the two facilities surrounding the three variables named
+above, as well as some related functions.  @ref{Coding Systems}, for
+details on character encoding and decoding.
+
address@hidden Format Conversion Round-Trip
address@hidden Round-Trip Specification
+
+  The most general of the two facilities is controlled by the variable
address@hidden, a list of @dfn{file format} specifications, which
+describe textual representations used in files for the data in an Emacs
+buffer.  The descriptions for reading and writing are paired, which is
+why we call this ``round-trip'' specification
+(@pxref{Format Conversion Piecemeal}, for non-paired specification).
+
address@hidden format-alist
+This list contains one format definition for each defined file format.
+Each format definition is a list of this form:
+
address@hidden
+(@var{name} @var{doc-string} @var{regexp} @var{from-fn} @var{to-fn} 
@var{modify} @var{mode-fn})
address@hidden example
address@hidden defvar
+
address@hidden format definition
address@hidden
+Here is what the elements in a format definition mean:
+
address@hidden @var
address@hidden name
+The name of this format.
+
address@hidden doc-string
+A documentation string for the format.
+
address@hidden regexp
+A regular expression which is used to recognize files represented in
+this format.
+
address@hidden from-fn
+A shell command or function to decode data in this format (to convert
+file data into the usual Emacs data representation).
+
+A shell command is represented as a string; Emacs runs the command as a
+filter to perform the conversion.
+
+If @var{from-fn} is a function, it is called with two arguments, @var{begin}
+and @var{end}, which specify the part of the buffer it should convert.
+It should convert the text by editing it in place.  Since this can
+change the length of the text, @var{from-fn} should return the modified
+end position.
+
+One responsibility of @var{from-fn} is to make sure that the beginning
+of the file no longer matches @var{regexp}.  Otherwise it is likely to
+get called again.
+
address@hidden to-fn
+A shell command or function to encode data in this format---that is, to
+convert the usual Emacs data representation into this format.
+
+If @var{to-fn} is a string, it is a shell command; Emacs runs the
+command as a filter to perform the conversion.
+
+If @var{to-fn} is a function, it is called with three arguments:
address@hidden and @var{end}, which specify the part of the buffer it
+should convert, and @var{buffer}, which specifies which buffer.  There
+are two ways it can do the conversion:
+
address@hidden @bullet
address@hidden
+By editing the buffer in place.  In this case, @var{to-fn} should
+return the end-position of the range of text, as modified.
+
address@hidden
+By returning a list of annotations.  This is a list of elements of the
+form @code{(@var{position} . @var{string})}, where @var{position} is an
+integer specifying the relative position in the text to be written, and
address@hidden is the annotation to add there.  The list must be sorted in
+order of position when @var{to-fn} returns it.
+
+When @code{write-region} actually writes the text from the buffer to the
+file, it intermixes the specified annotations at the corresponding
+positions.  All this takes place without modifying the buffer.
address@hidden itemize
+
address@hidden modify
+A flag, @code{t} if the encoding function modifies the buffer, and
address@hidden if it works by returning a list of annotations.
+
address@hidden mode-fn
+A minor-mode function to call after visiting a file converted from this
+format.  The function is called with one argument, the integer 1;
+that tells a minor-mode function to enable the mode.
address@hidden table
+
+The function @code{insert-file-contents} automatically recognizes file
+formats when it reads the specified file.  It checks the text of the
+beginning of the file against the regular expressions of the format
+definitions, and if it finds a match, it calls the decoding function for
+that format.  Then it checks all the known formats over again.
+It keeps checking them until none of them is applicable.
+
+Visiting a file, with @code{find-file-noselect} or the commands that use
+it, performs conversion likewise (because it calls
address@hidden); it also calls the mode function for each
+format that it decodes.  It stores a list of the format names in the
+buffer-local variable @code{buffer-file-format}.
+
address@hidden buffer-file-format
+This variable states the format of the visited file.  More precisely,
+this is a list of the file format names that were decoded in the course
+of visiting the current buffer's file.  It is always buffer-local in all
+buffers.
address@hidden defvar
+
+When @code{write-region} writes data into a file, it first calls the
+encoding functions for the formats listed in @code{buffer-file-format},
+in the order of appearance in the list.
+
address@hidden Command format-write-file file format &optional confirm
+This command writes the current buffer contents into the file
address@hidden in format @var{format}, and makes that format the default
+for future saves of the buffer.  The argument @var{format} is a list
+of format names.  Except for the @var{format} argument, this command
+is similar to @code{write-file}.  In particular, @var{confirm} has the
+same meaning and interactive treatment as the corresponding argument
+to @code{write-file}.  @xref{Definition of write-file}.
address@hidden deffn
+
address@hidden Command format-find-file file format
+This command finds the file @var{file}, converting it according to
+format @var{format}.  It also makes @var{format} the default if the
+buffer is saved later.
+
+The argument @var{format} is a list of format names.  If @var{format} is
address@hidden, no conversion takes place.  Interactively, typing just
address@hidden for @var{format} specifies @code{nil}.
address@hidden deffn
+
address@hidden Command format-insert-file file format &optional beg end
+This command inserts the contents of file @var{file}, converting it
+according to format @var{format}.  If @var{beg} and @var{end} are
address@hidden, they specify which part of the file to read, as in
address@hidden (@pxref{Reading from Files}).
+
+The return value is like what @code{insert-file-contents} returns: a
+list of the absolute file name and the length of the data inserted
+(after conversion).
+
+The argument @var{format} is a list of format names.  If @var{format} is
address@hidden, no conversion takes place.  Interactively, typing just
address@hidden for @var{format} specifies @code{nil}.
address@hidden deffn
+
address@hidden buffer-auto-save-file-format
+This variable specifies the format to use for auto-saving.  Its value is
+a list of format names, just like the value of
address@hidden; however, it is used instead of
address@hidden for writing auto-save files.  If the value
+is @code{t}, the default, auto-saving uses the same format as a
+regular save in the same buffer.  This variable is always buffer-local
+in all buffers.
address@hidden defvar
+
address@hidden Format Conversion Piecemeal
address@hidden Piecemeal Specification
+
+  In contrast to the round-trip specification described in the previous
+subsection (@pxref{Format Conversion Round-Trip}), you can use the variables
address@hidden and @code{write-region-annotate-functions}
+to separately control the respective reading and writing conversions.
+
+  Conversion starts with one representation and produces another
+representation.  When there is only one conversion to do, there is no
+conflict about what to start with.  However, when there are multiple
+conversions involved, conflict may arise when two conversions need to
+start with the same data.
+
+  This situation is best understood in the context of converting text
+properties during @code{write-region}.  For example, the character at
+position 42 in a buffer is @samp{X} with a text property @code{foo}.  If
+the conversion for @code{foo} is done by inserting into the buffer, say,
address@hidden:}, then that changes the character at position 42 from
address@hidden to @samp{F}.  The next conversion will start with the wrong
+data straight away.
+
+  To avoid conflict, cooperative conversions do not modify the buffer,
+but instead specify @dfn{annotations}, a list of elements of the form
address@hidden(@var{position} . @var{string})}, sorted in order of increasing
address@hidden
+
+  If there is more than one conversion, @code{write-region} merges their
+annotations destructively into one sorted list.  Later, when the text
+from the buffer is actually written to the file, it intermixes the
+specified annotations at the corresponding positions.  All this takes
+place without modifying the buffer.
+
address@hidden ??? What about ``overriding'' conversions like those allowed
address@hidden ??? for `write-region-annotate-functions', below?  --ttn
+
+  In contrast, when reading, the annotations intermixed with the text
+are handled immediately.  @code{insert-file-contents} sets point to the
+beginning of some text to be converted, then calls the conversion
+functions with the length of that text.  These functions should always
+return with point at the beginning of the inserted text.  This approach
+makes sense for reading because annotations removed by the first
+converter can't be mistakenly processed by a later converter.
+
+  Each conversion function should scan for the annotations it
+recognizes, remove the annotation, modify the buffer text (to set a text
+property, for example), and return the updated length of the text, as it
+stands after those changes.  The value returned by one function becomes
+the argument to the next function.
+
address@hidden write-region-annotate-functions
+A list of functions for @code{write-region} to call.  Each function in
+the list is called with two arguments: the start and end of the region
+to be written.  These functions should not alter the contents of the
+buffer.  Instead, they should return annotations.
+
address@hidden ??? Following adapted from comment in `build_annotations' 
(fileio.c).
address@hidden ??? Perhaps this is intended for internal use only?
address@hidden ??? Someone who understands this, please reword it. --ttn
+As a special case, if a function returns with a different buffer
+current, Emacs takes it to mean the current buffer contains altered text
+to be output, and discards all previous annotations because they should
+have been dealt with by this function.
address@hidden defvar
+
address@hidden after-insert-file-functions
+Each function in this list is called by @code{insert-file-contents}
+with one argument, the number of characters inserted, and with point
+at the beginning of the inserted text.  Each function should leave
+point unchanged, and return the new character count describing the
+inserted text as modified by the function.
address@hidden ??? The docstring mentions a handler from 
`file-name-handler-alist'
address@hidden     "intercepting" `insert-file-contents'.  Hmmm.  --ttn
address@hidden defvar
+
+  We invite users to write Lisp programs to store and retrieve text
+properties in files, using these hooks, and thus to experiment with
+various data formats and find good ones.  Eventually we hope users
+will produce good, general extensions we can install in Emacs.
+
+  We suggest not trying to handle arbitrary Lisp objects as text property
+names or values---because a program that general is probably difficult
+to write, and slow.  Instead, choose a set of possible data types that
+are reasonably flexible, and not too hard to encode.
+
address@hidden
+   arch-tag: 141f74ce-6ae3-40dc-a6c4-ef83fc4ec35c
address@hidden ignore