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+@c -*-texinfo-*-
+@c This is part of the XEmacs Lisp Reference Manual.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+@c See the file lispref.texi for copying conditions.
+@setfilename ../../info/files.info
+@node Files, Backups and Auto-Saving, Documentation, Top
+@chapter Files
+In XEmacs, you can find, create, view, save, and otherwise work with
+files and file directories.  This chapter describes most of the
+file-related functions of XEmacs Lisp, but a few others are described in
+@ref{Buffers}, 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 using @code{expand-file-name}, so that
+@file{~} is handled correctly, as are relative file names (including
+@samp{../}).  These functions don't recognize environment variable
+substitutions such as @samp{$HOME}.  @xref{File Name Expansion}.
+@menu
+* 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 File Attributes:: 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.
+* Partial Files::            Treating a section of a buffer as a file.
+* Format Conversion::        Conversion to and from various file formats.
+* Files and MS-DOS::         Distinguishing text and binary files on MS-DOS.
+@end menu
+@node Visiting Files
+@section Visiting Files
+@cindex finding files
+@cindex 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 XEmacs 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
+@dfn{save} 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.
+@menu
+* Visiting Functions::         The usual interface functions for visiting.
+* Subroutines of Visiting::    Lower-level subroutines that they use.
+@end menu
+@node Visiting Functions
+@subsection Functions for Visiting Files
+This section describes the functions normally used to visit files.
+For historical reasons, these functions have names starting with
+@samp{find-} 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.
+@xref{Reading from Files}.
+@deffn Command find-file filename
+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.
+The body of the @code{find-file} function is very simple and looks
+like this:
+@example
+(switch-to-buffer (find-file-noselect filename))
+@end example
+@noindent
+(See @code{switch-to-buffer} in @ref{Displaying Buffers}.)
+When @code{find-file} is called interactively, it prompts for
+@var{filename} in the minibuffer.
+@end deffn
+@defun find-file-noselect filename &optional nowarn
+This function is the guts of all the file-visiting functions.  It finds
+or creates a buffer visiting the file @var{filename}, and returns it.
+It uses an existing buffer if there is one, and otherwise creates a new
+buffer and reads the file into it.  You may make the buffer current or
+display it in a window if you wish, but this function does not do so.
+When @code{find-file-noselect} 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, then this function asks
+the user whether to reread the changed file.  If the user says
+@samp{yes}, any changes previously made in the buffer are lost.
+If @code{find-file-noselect} needs to create a buffer, and there is no
+file named @var{filename}, it displays the message @samp{New file} in
+the echo area, and leaves the buffer empty.
+@c XEmacs feature
+If @var{no-warn} is non-@code{nil}, various warnings that XEmacs normally
+gives (e.g. if another buffer is already visiting @var{filename} but
+@var{filename} has been removed from disk since that buffer was created)
+are suppressed.
+The @code{find-file-noselect} function calls @code{after-find-file}
+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 @code{find-file-hooks}.
+The @code{find-file-noselect} function returns the buffer that is
+visiting the file @var{filename}.
+@example
+@group
+(find-file-noselect "/etc/fstab")
+@result{} #<buffer fstab>
+@end group
+@end example
+@end defun
+@deffn Command find-file-other-window filename
+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
+@var{filename}.
+@end deffn
+@deffn Command find-file-read-only filename
+This command selects a buffer visiting the file @var{filename}, like
+@code{find-file}, 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
+@var{filename}.
+@end deffn
+@deffn Command view-file filename
+This command visits @var{filename} in View mode, and displays it in a
+recursive edit, returning to the previous buffer when done.  View mode
+is a mode that allows you to skim rapidly through the file but does not
+let you modify it.  Entering View mode runs the normal hook
+@code{view-mode-hook}.  @xref{Hooks}.
+When @code{view-file} is called interactively, it prompts for
+@var{filename}.
+@end deffn
+@defvar find-file-hooks
+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 works just like a normal hook, but we think that renaming
+it would not be advisable.
+@end defvar
+@defvar find-file-not-found-hooks
+The value of this variable is a list of functions to be called when
+@code{find-file} 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 non-@code{nil}.  @code{buffer-file-name} is
+already set up.
+This is not a normal hook because the values of the functions are
+used and they may not all be called.
+@end defvar
+@node Subroutines of Visiting
+@subsection Subroutines of Visiting
+The @code{find-file-noselect} function uses the
+@code{create-file-buffer} and @code{after-find-file} functions as
+subroutines.  Sometimes it is useful to call them directly.
+@defun create-file-buffer filename
+This function creates a suitably named buffer for visiting
+@var{filename}, and returns it.  It uses @var{filename} (sans directory)
+as the name if that name is free; otherwise, it appends a string such as
+@samp{<2>} to get an unused name.  See also @ref{Creating Buffers}.
+@strong{Please 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.
+@example
+@group
+(create-file-buffer "foo")
+@result{} #<buffer foo>
+@end group
+@group
+(create-file-buffer "foo")
+@result{} #<buffer foo<2>>
+@end group
+@group
+(create-file-buffer "foo")
+@result{} #<buffer foo<3>>
+@end group
+@end example
+This function is used by @code{find-file-noselect}.
+It uses @code{generate-new-buffer} (@pxref{Creating Buffers}).
+@end defun
+@defun after-find-file &optional error warn noauto
+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}).
+@cindex new file message
+@cindex 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 non-@code{nil} value
+for @var{error}.  In that case, @code{after-find-file} issues a warning:
+@samp{(New File)}.  For more serious errors, the caller should usually not
+call @code{after-find-file}.
+If @var{warn} is non-@code{nil}, then this function issues a warning
+if an auto-save file exists and is more recent than the visited file.
+@c XEmacs feature
+If @var{noauto} is non-@code{nil}, then this function does not turn
+on auto-save mode; otherwise, it does.
+The last thing @code{after-find-file} does is call all the functions
+in @code{find-file-hooks}.
+@end defun
+@node Saving Buffers
+@section Saving Buffers
+When you edit a file in XEmacs, 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.
+@deffn 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.
+@code{save-buffer} is responsible for making backup files.  Normally,
+@var{backup-option} 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:
+@itemize @bullet
+@item
+With an argument of 4 or 64, reflecting 1 or 3 @kbd{C-u}'s, the
+@code{save-buffer} function marks this version of the file to be
+backed up when the buffer is next saved.
+@item
+With an argument of 16 or 64, reflecting 2 or 3 @kbd{C-u}'s, the
+@code{save-buffer} function unconditionally backs up the previous
+version of the file before saving it.
+@end itemize
+@end deffn
+@deffn Command save-some-buffers &optional save-silently-p exiting
+This command saves some modified file-visiting buffers.  Normally it
+asks the user about each buffer.  But if @var{save-silently-p} is
+non-@code{nil}, it saves all the file-visiting buffers without querying
+the user.
+The optional @var{exiting} argument, if non-@code{nil}, requests this
+function to offer also to save certain other buffers that are not
+visiting files.  These are buffers that have a non-@code{nil} local
+value of @code{buffer-offer-save}.  (A user who says yes to saving one
+of these is asked to specify a file name to use.)  The
+@code{save-buffers-kill-emacs} function passes a non-@code{nil} value
+for this argument.
+@end deffn
+@defvar buffer-offer-save
+When this variable is non-@code{nil} in a buffer, XEmacs offers to save
+the buffer on exit even if the buffer is not visiting a file.  The
+variable is automatically local in all buffers.  Normally, Mail mode
+(used for editing outgoing mail) sets this to @code{t}.
+@end defvar
+@deffn Command write-file filename
+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} and @code{save-buffer}.
+@end deffn
+@defvar write-file-hooks
+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
+non-@code{nil}, 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-hooks} returns non-@code{nil}, it
+is responsible for making a backup file (if that is appropriate).
+To do so, execute the following code:
+@example
+(or buffer-backed-up (backup-buffer))
+@end example
+You might wish to save the file modes value returned by
+@code{backup-buffer} and use that to set the mode bits of the file that
+you write.  This is what @code{save-buffer} normally does.
+Even though this is not a normal hook, you can use @code{add-hook} and
+@code{remove-hook} to manipulate the list.  @xref{Hooks}.
+@end defvar
+@c Emacs 19 feature
+@defvar local-write-file-hooks
+This works just like @code{write-file-hooks}, but it is intended
+to be made local to particular buffers.  It's not a good idea to make
+@code{write-file-hooks} local to a buffer---use this variable instead.
+The variable is marked as a permanent local, so that changing the major
+mode does not alter a buffer-local value.  This is convenient for
+packages that read ``file'' contents in special ways, and set up hooks
+to save the data in a corresponding way.
+@end defvar
+@c Emacs 19 feature
+@defvar write-contents-hooks
+This works just like @code{write-file-hooks}, but it is intended for
+hooks that pertain to the contents of the file, as opposed to hooks that
+pertain to where the file came from.  Such hooks are usually set up by
+major modes, as buffer-local bindings for this variable.  Switching to a
+new major mode always resets this variable.
+@end defvar
+@c Emacs 19 feature
+@defvar after-save-hook
+This normal hook runs after a buffer has been saved in its visited file.
+@end defvar
+@defvar file-precious-flag
+If this variable is non-@code{nil}, 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 set this variable non-@code{nil} locally in particular
+buffers.
+@end defvar
+@defopt require-final-newline
+This variable determines whether files may be written out that do
+@emph{not} end with a newline.  If the value of the variable is
+@code{t}, 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 non-@code{nil}, but not @code{t}, then
+@code{save-buffer} 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.
+@end defopt
+@node Reading from Files
+@section 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.
+@defun 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
+@var{filename} 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.  @xref{Format Conversion}.  It also calls the functions in
+the list @code{after-insert-file-functions}; see @ref{Saving
+Properties}.
+If @var{visit} is non-@code{nil}, 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
+@code{find-file-noselect} and you probably should not use it yourself.
+If @var{beg} and @var{end} are non-@code{nil}, they should be integers
+specifying the portion of the file to insert.  In this case, @var{visit}
+must be @code{nil}.  For example,
+@example
+(insert-file-contents filename nil 0 500)
+@end example
+@noindent
+inserts the first 500 characters of a file.
+If the argument @var{replace} is non-@code{nil}, 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.
+@end 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
+@ref{Magic File Names}.
+@node Writing to Files
+@section 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
+@code{write-region} functions.  Don't use these functions to write to
+files that are being visited; that could cause confusion in the
+mechanisms for visiting.
+@deffn Command append-to-file start end filename
+This function appends the contents of the region delimited by
+@var{start} and @var{end} in the current buffer to the end of file
+@var{filename}.  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.
+@end deffn
+@deffn Command write-region start end filename &optional append visit
+This function writes the region delimited by @var{start} and @var{end}
+in the current buffer into the file specified by @var{filename}.
+@c Emacs 19 feature
+If @var{start} is a string, then @code{write-region} writes or appends
+that string, rather than text from the buffer.
+If @var{append} is non-@code{nil}, then the specified text is appended
+to the existing file contents (if any).
+If @var{visit} is @code{t}, then XEmacs 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
+@var{filename}'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.
+@c 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
+@var{visit} is used in the echo area message and also for file locking;
+@var{visit} 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 function @code{write-region} converts the data which it writes to
+the appropriate file formats specified by @code{buffer-file-format}.
+@xref{Format Conversion}.  It also calls the functions in the list
+@code{write-region-annotate-functions}; see @ref{Saving Properties}.
+Normally, @code{write-region} displays a message @samp{Wrote file
+@var{filename}} 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.
+@end deffn
+@node File Locks
+@section File Locks
+@cindex file locks
+When two users edit the same file at the same time, they are likely to
+interfere with each other.  XEmacs tries to prevent this situation from
+arising by recording a @dfn{file lock} when a file is being modified.
+XEmacs can then detect the first attempt to modify a buffer visiting a
+file that is locked by another XEmacs process, and ask the user what to do.
+File locks do not work properly when multiple machines can share
+file systems, such as with NFS.  Perhaps a better file locking system
+will be implemented in the future.  When file locks do not work, it is
+possible for two users to make changes simultaneously, but XEmacs can
+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 @ref{Modification Time}.
+@c Not optional in FSF Emacs 19
+@defun file-locked-p &optional filename
+This function returns @code{nil} if the file @var{filename} is not
+locked by this XEmacs process.  It returns @code{t} if it is locked by
+this XEmacs, and it returns the name of the user who has locked it if it
+is locked by someone else.
+@example
+@group
+(file-locked-p "foo")
+@result{} nil
+@end group
+@end example
+@end defun
+@defun 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.
+@end defun
+@defun 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.
+@end defun
+@defun 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 value it returns
+determines what happens next:
+@itemize @bullet
+@item
+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.
+@item
+A value of @code{nil} says to ignore the lock and let this
+user edit the file anyway.
+@item
+@kindex 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:
+@example
+@error{} File is locked: @var{file} @var{other-user}
+@end example
+@noindent
+where @code{file} is the name of the file and @var{other-user} is the
+name of the user who has locked the file.
+@end itemize
+The default definition of this function asks the user to choose what
+to do.  If you wish, you can replace the @code{ask-user-about-lock}
+function with your own version that decides in another way.  The code
+for its usual definition is in @file{userlock.el}.
+@end defun
+@node Information about Files
+@section Information about Files
+The functions described in this section all operate on strings that
+designate file names.  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.
+@menu
+* 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.
+@end menu
+@node Testing Accessibility
+@subsection Testing Accessibility
+@cindex accessibility of a file
+@cindex file accessibility
+These functions test for permission to access a file in specific ways.
+@defun 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, 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}.
+@end defun
+@defun 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.
+@example
+@group
+(file-readable-p "files.texi")
+@result{} t
+@end group
+@group
+(file-exists-p "/usr/spool/mqueue")
+@result{} t
+@end group
+@group
+(file-readable-p "/usr/spool/mqueue")
+@result{} nil
+@end group
+@end example
+@end defun
+@c Emacs 19 feature
+@defun 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.  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.
+@end defun
+@defun 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.
+@example
+@group
+(file-writable-p "~/foo")
+@result{} t
+@end group
+@group
+(file-writable-p "/foo")
+@result{} nil
+@end group
+@group
+(file-writable-p "~/no-such-dir/foo")
+@result{} nil
+@end group
+@end example
+@end defun
+@c Emacs 19 feature
+@defun 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 or the file name of a
+directory.
+Example: after the following,
+@example
+(file-accessible-directory-p "/foo")
+@result{} nil
+@end example
+@noindent
+we can deduce that any attempt to read a file in @file{/foo/} will
+give an error.
+@end defun
+@defun 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.
+@end defun
+@defun file-newer-than-file-p filename1 filename2
+@cindex file age
+@cindex 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{filename2} does not exist,
+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
+@file{no-file} doesn't exist at all.
+@example
+@group
+(file-newer-than-file-p "aug-19" "aug-20")
+@result{} nil
+@end group
+@group
+(file-newer-than-file-p "aug-20" "aug-19")
+@result{} t
+@end group
+@group
+(file-newer-than-file-p "aug-19" "no-file")
+@result{} t
+@end group
+@group
+(file-newer-than-file-p "no-file" "aug-19")
+@result{} nil
+@end group
+@end example
+You can use @code{file-attributes} to get a file's last modification
+time as a list of two numbers.  @xref{File Attributes}.
+@end defun
+@node Kinds of Files
+@subsection Distinguishing Kinds of Files
+This section describes how to distinguish various kinds of files, such
+as directories, symbolic links, and ordinary files.
+@defun file-symlink-p filename
+@cindex file symbolic links
+If the file @var{filename} is a symbolic link, the @code{file-symlink-p}
+function returns the file name to which it is linked.  This may be the
+name of a text file, a directory, or even another symbolic link, or it
+may be a nonexistent file name.
+If the file @var{filename} is not a symbolic link (or there is no such file),
+@code{file-symlink-p} returns @code{nil}.
+@example
+@group
+(file-symlink-p "foo")
+@result{} nil
+@end group
+@group
+(file-symlink-p "sym-link")
+@result{} "foo"
+@end group
+@group
+(file-symlink-p "sym-link2")
+@result{} "sym-link"
+@end group
+@group
+(file-symlink-p "/bin")
+@result{} "/pub/bin"
+@end group
+@end example
+@c !!! file-symlink-p: should show output of ls -l for comparison
+@end defun
+@defun file-directory-p filename
+This function returns @code{t} if @var{filename} is the name of an
+existing directory, @code{nil} otherwise.
+@example
+@group
+(file-directory-p "~rms")
+@result{} t
+@end group
+@group
+(file-directory-p "~rms/lewis/files.texi")
+@result{} nil
+@end group
+@group
+(file-directory-p "~rms/lewis/no-such-file")
+@result{} nil
+@end group
+@group
+(file-directory-p "$HOME")
+@result{} nil
+@end group
+@group
+(file-directory-p
+(substitute-in-file-name "$HOME"))
+@result{} t
+@end group
+@end example
+@end defun
+@defun file-regular-p filename
+This function returns @code{t} if the file @var{filename} exists and is
+a regular file (not a directory, symbolic link, named pipe, terminal, or
+other I/O device).
+@end defun
+@node Truenames
+@subsection Truenames
+@cindex truename (of file)
+@c Emacs 19 features
+The @dfn{truename} of a file is the name that you get by following
+symbolic links until none remain, then expanding to get rid of @samp{.}
+and @samp{..} as components.  Strictly speaking, a file need not 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.
+@defun file-truename filename &optional default
+The function @code{file-truename} returns the true name of the file
+@var{filename}.  This is the name that you get by following symbolic
+links until none remain.
+@c XEmacs allows relative filenames
+If the filename is relative, @var{default} is the directory to start
+with.  If @var{default} is @code{nil} or missing, the current buffer's
+value of @code{default-directory} is used.
+@end defun
+@xref{Buffer File Name}, for related information.
+@node File Attributes
+@subsection 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.
+@defun file-modes filename
+@cindex permission
+@cindex 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 @sc{suid} bit
+is set for both others and group, and that the sticky bit is set.
+@example
+@group
+(file-modes "~/junk/diffs")
+@result{} 492               ; @r{Decimal integer.}
+@end group
+@group
+(format "%o" 492)
+@result{} "754"             ; @r{Convert to octal.}
+@end group
+@group
+(set-file-modes "~/junk/diffs" 438)
+@result{} nil
+@end group
+@group
+(format "%o" 438)
+@result{} "666"             ; @r{Convert to octal.}
+@end group
+@group
+% ls -l diffs
+-rw-rw-rw-  1 lewis 0 3063 Oct 30 16:00 diffs
+@end group
+@end example
+@end defun
+@defun 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.
+@example
+@group
+% 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
+@end group
+@group
+(file-nlinks "foo")
+@result{} 2
+@end group
+@group
+(file-nlinks "doesnt-exist")
+@result{} nil
+@end group
+@end example
+@end defun
+@defun file-attributes filename
+This function returns a list of attributes of file @var{filename}.  If
+the specified file cannot be opened, it returns @code{nil}.
+The elements of the list, in order, are:
+@enumerate 0
+@item
+@code{t} for a directory, a string for a symbolic link (the name
+linked to), or @code{nil} for a text file.
+@c Wordy so as to prevent an overfull hbox.  --rjc 15mar92
+@item
+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 File Attributes}).
+@item
+The file's @sc{uid}.
+@item
+The file's @sc{gid}.
+@item
+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}.)
+@item
+The time of last modification as a list of two integers (as above).
+@item
+The time of last status change as a list of two integers (as above).
+@item
+The size of the file in bytes.
+@item
+The file's modes, as a string of ten letters or dashes,
+as in @samp{ls -l}.
+@item
+@code{t} if the file's @sc{gid} would change if file were
+deleted and recreated; @code{nil} otherwise.
+@item
+The file's inode number.
+@item
+The file system number of the file system that the file is in.  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.
+@end enumerate
+For example, here are the file attributes for @file{files.texi}:
+@example
+@group
+(file-attributes "files.texi")
+@result{}  (nil
+1
+2235
+75
+(8489 20284)
+(8489 20284)
+(8489 20285)
+14906
+"-rw-rw-rw-"
+nil
+129500
+-32252)
+@end group
+@end example
+@noindent
+and here is how the result is interpreted:
+@table @code
+@item nil
+is neither a directory nor a symbolic link.
+@item 1
+has only one name (the name @file{files.texi} in the current default
+directory).
+@item 2235
+is owned by the user with @sc{uid} 2235.
+@item 75
+is in the group with @sc{gid} 75.
+@item (8489 20284)
+was last accessed on Aug 19 00:09.  Unfortunately, you cannot convert
+this number into a time string in XEmacs.
+@item (8489 20284)
+was last modified on Aug 19 00:09.
+@item (8489 20285)
+last had its inode changed on Aug 19 00:09.
+@item 14906
+is 14906 characters long.
+@item "-rw-rw-rw-"
+has a mode of read and write access for the owner, group, and world.
+@item nil
+would retain the same @sc{gid} if it were recreated.
+@item 129500
+has an inode number of 129500.
+@item -32252
+is on file system number -32252.
+@end table
+@end defun
+@node Changing File Attributes
+@section Changing File Names and Attributes
+@cindex renaming files
+@cindex copying files
+@cindex deleting files
+@cindex linking files
+@cindex 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}:
+@itemize @bullet
+@item
+Signal a @code{file-already-exists} error if
+@var{ok-if-already-exists} is @code{nil}.
+@item
+Request confirmation if @var{ok-if-already-exists} is a number.
+@item
+Replace the old file without confirmation if @var{ok-if-already-exists}
+is any other value.
+@end itemize
+@deffn Command add-name-to-file oldname newname &optional ok-if-already-exists
+@cindex file with multiple names
+@cindex file hard link
+This function gives the file named @var{oldname} the additional name
+@var{newname}.  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,
+@file{foo} and @file{foo3}.
+@example
+@group
+% ls -l fo*
+-rw-rw-rw-  1 rms       29 Aug 18 20:32 foo
+-rw-rw-rw-  1 rms       24 Aug 18 20:31 foo3
+@end group
+@end example
+Then we evaluate the form @code{(add-name-to-file "~/lewis/foo"
+"~/lewis/foo2")}.  Again we list the files.  This shows two names,
+@file{foo} and @file{foo2}.
+@example
+@group
+(add-name-to-file "~/lewis/foo1" "~/lewis/foo2")
+@result{} nil
+@end group
+@group
+% ls -l fo*
+-rw-rw-rw-  2 rms       29 Aug 18 20:32 foo
+-rw-rw-rw-  2 rms       29 Aug 18 20:32 foo2
+-rw-rw-rw-  1 rms       24 Aug 18 20:31 foo3
+@end group
+@end example
+@c !!! Check whether this set of examples is consistent.  --rjc 15mar92
+Finally, we evaluate the following:
+@example
+(add-name-to-file "~/lewis/foo" "~/lewis/foo3" t)
+@end example
+@noindent
+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.
+@example
+@group
+(add-name-to-file "~/lewis/foo1" "~/lewis/foo3")
+@result{} nil
+@end group
+@group
+% ls -l fo*
+-rw-rw-rw-  3 rms       29 Aug 18 20:32 foo
+-rw-rw-rw-  3 rms       29 Aug 18 20:32 foo2
+-rw-rw-rw-  3 rms       29 Aug 18 20:32 foo3
+@end group
+@end example
+This function is meaningless on VMS, where multiple names for one file
+are not allowed.
+See also @code{file-nlinks} in @ref{File Attributes}.
+@end deffn
+@deffn 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.
+In an interactive call, this function prompts for @var{filename} and
+@var{newname} in the minibuffer; also, it requests confirmation if
+@var{newname} already exists.
+@end deffn
+@deffn Command copy-file oldname newname &optional ok-if-exists time
+This command copies the file @var{oldname} to @var{newname}.  An
+error is signaled if @var{oldname} does not exist.
+If @var{time} is non-@code{nil}, then this functions gives the new
+file the same last-modified time that the old one has.  (This works on
+only some operating systems.)
+In an interactive call, this function prompts for @var{filename} and
+@var{newname} in the minibuffer; also, it requests confirmation if
+@var{newname} already exists.
+@end deffn
+@deffn Command delete-file filename
+@pindex rm
+This command deletes the file @var{filename}, like the shell command
+@samp{rm @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, a file is deletable if
+its directory is writable.)
+See also @code{delete-directory} in @ref{Create/Delete Dirs}.
+@end deffn
+@deffn Command make-symbolic-link filename newname  &optional ok-if-exists
+@pindex ln
+@kindex file-already-exists
+This command makes a symbolic link to @var{filename}, named
+@var{newname}.  This is like the shell command @samp{ln -s
+@var{filename} @var{newname}}.
+In an interactive call, this function prompts for @var{filename} and
+@var{newname} in the minibuffer; also, it requests confirmation if
+@var{newname} already exists.
+@end deffn
+@defun define-logical-name varname string
+This function defines the logical name @var{name} to have the value
+@var{string}.  It is available only on VMS.
+@end defun
+@defun 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.
+@end defun
+@c Emacs 19 feature
+@defun set-default-file-modes mode
+This function sets the default file protection for new files created by
+XEmacs and its subprocesses.  Every file created with XEmacs initially has
+this protection.  On Unix, the default protection is the bitwise
+complement of the ``umask'' value.
+The argument @var{mode} must be an integer.  Only the low 9 bits of
+@var{mode} are used.
+Saving a modified version of an existing file does not count as creating
+the file; it does not change the file's mode, and does not use the
+default file protection.
+@end defun
+@defun default-file-modes
+This function returns the current default protection value.
+@end defun
+@cindex MS-DOS and file modes
+@cindex 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 @samp{.com},
+@samp{.bat} or @samp{.exe}.  This is reflected in the values returned
+by @code{file-modes} and @code{file-attributes}.
+@node File Names
+@section File Names
+@cindex file names
+Files are generally referred to by their names, in XEmacs as elsewhere.
+File names in XEmacs are represented as strings.  The functions that
+operate on a file all expect a file name argument.
+In addition to operating on files themselves, XEmacs Lisp programs
+often need to operate on the 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 VMS, all these functions understand both VMS file-name syntax and
+Unix syntax.  This is so that all the standard Lisp libraries can
+specify file names in Unix syntax and work properly on VMS without
+change.  On MS-DOS, these functions understand MS-DOS file-name syntax
+as well as Unix syntax.
+@menu
+* File Name Components::  The directory part of a file name, and the rest.
+* Directory Names::       A directory's name as a directory
+is different from its name as a file.
+* Relative File Names::   Some file names are relative to a current directory.
+* 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.
+@end menu
+@node File Name Components
+@subsection File Name Components
+@cindex directory part (of file name)
+@cindex nondirectory part (of file name)
+@cindex 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, XEmacs 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 Unix, the directory part is everything up to and including the last
+slash; 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 Unix, 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
+XEmacs omits the version number.  Version numbers are found mostly in
+directory lists.
+@defun file-name-directory filename
+This function returns the directory part of @var{filename} (or
+@code{nil} if @var{filename} does not include a directory part).  On
+Unix, the function returns a string ending in a slash.  On VMS, it
+returns a string ending in one of the three characters @samp{:},
+@samp{]}, or @samp{>}.
+@example
+@group
+(file-name-directory "lewis/foo")  ; @r{Unix example}
+@result{} "lewis/"
+@end group
+@group
+(file-name-directory "foo")        ; @r{Unix example}
+@result{} nil
+@end group
+@group
+(file-name-directory "[X]FOO.TMP") ; @r{VMS example}
+@result{} "[X]"
+@end group
+@end example
+@end defun
+@defun file-name-nondirectory filename
+This function returns the nondirectory part of @var{filename}.
+@example
+@group
+(file-name-nondirectory "lewis/foo")
+@result{} "foo"
+@end group
+@group
+(file-name-nondirectory "foo")
+@result{} "foo"
+@end group
+@group
+;; @r{The following example is accurate only on VMS.}
+(file-name-nondirectory "[X]FOO.TMP")
+@result{} "FOO.TMP"
+@end group
+@end example
+@end defun
+@defun file-name-sans-versions filename &optional keep-backup-version
+This function returns @var{filename} without any file version numbers,
+backup version numbers, or trailing tildes.
+@c XEmacs feature?
+If @var{keep-backup-version} is non-@code{nil}, we do not remove backup
+version numbers, only true file version numbers.
+@example
+@group
+(file-name-sans-versions "~rms/foo.~1~")
+@result{} "~rms/foo"
+@end group
+@group
+(file-name-sans-versions "~rms/foo~")
+@result{} "~rms/foo"
+@end group
+@group
+(file-name-sans-versions "~rms/foo")
+@result{} "~rms/foo"
+@end group
+@group
+;; @r{The following example applies to VMS only.}
+(file-name-sans-versions "foo;23")
+@result{} "foo"
+@end group
+@end example
+@end defun
+@defun file-name-sans-extension filename
+This function returns @var{filename} minus its ``extension,'' if any.
+The extension, in a file name, is the part that starts with the last
+@samp{.} in the last name component.  For example,
+@example
+(file-name-sans-extension "foo.lose.c")
+@result{} "foo.lose"
+(file-name-sans-extension "big.hack/foo")
+@result{} "big.hack/foo"
+@end example
+@end defun
+@node Directory Names
+@subsection Directory Names
+@cindex directory name
+@cindex file name of directory
+A @dfn{directory name} is the name of a directory.  A directory is a
+kind of file, and 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 Unix, this is simple: a
+directory name ends in a slash, whereas the directory's name as a file
+lacks that slash.  On VMS, the relationship is more complicated.
+The difference between a directory name and its name as a file is
+subtle but crucial.  When an XEmacs variable or function argument is
+described as being a directory name, a file name of a directory is not
+acceptable.
+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{~}, and @samp{..}.
+@defun 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.  In
+Unix, this means appending a slash to the string.  On VMS, the function
+converts a string of the form @file{[X]Y.DIR.1} to the form
+@file{[X.Y]}.
+@example
+@group
+(file-name-as-directory "~rms/lewis")
+@result{} "~rms/lewis/"
+@end group
+@end example
+@end defun
+@defun 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
+Unix, this means removing a final slash from the string.  On VMS, the
+function converts a string of the form @file{[X.Y]} to
+@file{[X]Y.DIR.1}.
+@example
+@group
+(directory-file-name "~lewis/")
+@result{} "~lewis"
+@end group
+@end example
+@end defun
+@cindex 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, XEmacs shows users the
+abbreviation instead.
+If you wish to convert a directory name to its abbreviation, use this
+function:
+@defun abbreviate-file-name dirname &optional hack-homedir
+This function applies abbreviations from @code{directory-abbrev-alist}
+to its argument, and substitutes @samp{~} for the user's home
+directory.
+@c XEmacs feature?
+If @var{hack-homedir} is non-@code{nil}, then this also substitutes
+@samp{~} for the user's home directory.
+@end defun
+@defvar directory-abbrev-alist
+The variable @code{directory-abbrev-alist} contains an alist of
+abbreviations to use for file directories.  Each element has the form
+@code{(@var{from} . @var{to})}, and says to replace @var{from} with
+@var{to} when it appears in a directory name.  The @var{from} string is
+actually a regular expression; it should always start with @samp{^}.
+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.
+@example
+(("^/home/fsf" . "/fsf")
+("^/home/gp" . "/gp")
+("^/home/gd" . "/gd"))
+@end example
+@end defvar
+@c  To convert a directory name to its abbreviation, use this
+@c function:
+@c
+@c @defun abbreviate-file-name dirname
+@c This function applies abbreviations from @code{directory-abbrev-alist}
+@c to its argument, and substitutes @samp{~} for the user's home
+@c directory.
+@c @end defun
+@node Relative File Names
+@subsection Absolute and Relative File Names
+@cindex absolute file name
+@cindex 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, an absolute file name starts with a slash or a
+tilde (@samp{~}), and a relative one does not.  The rules on VMS are
+complicated.
+@defun 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.
+@example
+@group
+(file-name-absolute-p "~rms/foo")
+@result{} t
+@end group
+@group
+(file-name-absolute-p "rms/foo")
+@result{} nil
+@end group
+@group
+(file-name-absolute-p "/user/rms/foo")
+@result{} t
+@end group
+@end example
+@end defun
+@node File Name Expansion
+@subsection Functions that Expand Filenames
+@cindex 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 @file{@var{name}/../}.
+@defun expand-file-name filename &optional directory
+This function converts @var{filename} to an absolute file name.  If
+@var{directory} is supplied, it is the directory to start with if
+@var{filename} is relative.  (The value of @var{directory} should itself
+be an absolute directory name; it may start with @samp{~}.)
+Otherwise, the current buffer's value of @code{default-directory} is
+used.  For example:
+@example
+@group
+(expand-file-name "foo")
+@result{} "/xcssun/users/rms/lewis/foo"
+@end group
+@group
+(expand-file-name "../foo")
+@result{} "/xcssun/users/rms/foo"
+@end group
+@group
+(expand-file-name "foo" "/usr/spool/")
+@result{} "/usr/spool/foo"
+@end group
+@group
+(expand-file-name "$HOME/foo")
+@result{} "/xcssun/users/rms/lewis/$HOME/foo"
+@end group
+@end example
+Filenames containing @samp{.} or @samp{..} are simplified to their
+canonical form:
+@example
+@group
+(expand-file-name "bar/../foo")
+@result{} "/xcssun/users/rms/lewis/foo"
+@end group
+@end example
+@samp{~/} is expanded into the user's home directory.  A @samp{/} or
+@samp{~} following a @samp{/} is taken to be the start of an absolute
+file name that overrides what precedes it, so everything before that
+@samp{/} or @samp{~} is deleted.  For example:
+@example
+@group
+(expand-file-name
+"/a1/gnu//usr/local/lib/emacs/etc/MACHINES")
+@result{} "/usr/local/lib/emacs/etc/MACHINES"
+@end group
+@group
+(expand-file-name "/a1/gnu/~/foo")
+@result{} "/xcssun/users/rms/foo"
+@end group
+@end example
+@noindent
+In both cases, @file{/a1/gnu/} is discarded because an absolute file
+name follows it.
+Note that @code{expand-file-name} does @emph{not} expand environment
+variables; only @code{substitute-in-file-name} does that.
+@end defun
+@c Emacs 19 feature
+@defun file-relative-name filename &optional directory
+This function does the inverse of expansion---it tries to return a
+relative name that is equivalent to @var{filename} when interpreted
+relative to @var{directory}.  (If such a relative name would be longer
+than the absolute name, it returns the absolute name instead.)
+@c XEmacs feature?
+If @var{directory} is @code{nil} or omitted, the value of
+@code{default-directory} is used.
+@example
+(file-relative-name "/foo/bar" "/foo/")
+@result{} "bar")
+(file-relative-name "/foo/bar" "/hack/")
+@result{} "/foo/bar")
+@end example
+@end defun
+@defvar 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 local in every buffer.
+@code{expand-file-name} uses the default directory when its second
+argument is @code{nil}.
+On Unix systems, the value is always a string ending with a slash.
+@example
+@group
+default-directory
+@result{} "/user/lewis/manual/"
+@end group
+@end example
+@end defvar
+@defun substitute-in-file-name filename
+This function replaces environment variable references in
+@var{filename} with the environment variable values.  Following standard
+Unix shell syntax, @samp{$} is the prefix to substitute an environment
+variable value.
+The environment variable name is the series of alphanumeric characters
+(including underscores) that follow the @samp{$}.  If the character following
+the @samp{$} is a @samp{@{}, then the variable name is everything up to the
+matching @samp{@}}.
+@c Wordy to avoid overfull hbox.  --rjc 15mar92
+Here we assume that the environment variable @code{HOME}, which holds
+the user's home directory name, has value @samp{/xcssun/users/rms}.
+@example
+@group
+(substitute-in-file-name "$HOME/foo")
+@result{} "/xcssun/users/rms/foo"
+@end group
+@end example
+@c If a @samp{~} or a @samp{/} appears following a @samp{/}, after
+@c substitution, everything before the following @samp{/} is discarded:
+After substitution, a @samp{/} or @samp{~} following a @samp{/} is taken
+to be the start of an absolute file name that overrides what precedes
+it, so everything before that @samp{/} or @samp{~} is deleted.  For
+example:
+@example
+@group
+(substitute-in-file-name "bar/~/foo")
+@result{} "~/foo"
+@end group
+@group
+(substitute-in-file-name "/usr/local/$HOME/foo")
+@result{} "/xcssun/users/rms/foo"
+@end group
+@end example
+On VMS, @samp{$} substitution is not done, so this function does nothing
+on VMS except discard superfluous initial components as shown above.
+@end defun
+@node Unique File Names
+@subsection Generating Unique File Names
+Some programs need to write temporary files.  Here is the usual way to
+construct a name for such a file:
+@example
+(make-temp-name (concat "/tmp/" @var{name-of-application}))
+@end example
+@noindent
+Here we use the directory @file{/tmp/} because that is the standard
+place on Unix for temporary files.  The job of @code{make-temp-name} is
+to prevent two different users or two different processes from trying to
+use the same name.
+@defun make-temp-name string
+This function generates a string that can be used as a unique name.  The
+name starts with @var{string}, and ends with a number that is different
+in each XEmacs process.
+@example
+@group
+(make-temp-name "/tmp/foo")
+@result{} "/tmp/foo021304"
+@end group
+@end example
+To prevent conflicts among different libraries running in the same
+XEmacs, each Lisp program that uses @code{make-temp-name} should have its
+own @var{string}.  The number added to the end of the name distinguishes
+between the same application running in different XEmacs processes.
+@end defun
+@node File Name Completion
+@subsection File Name Completion
+@cindex file name completion subroutines
+@cindex completion, file name
+This section describes low-level subroutines for completing a file
+name.  For other completion functions, see @ref{Completion}.
+@defun 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
+@var{directory}.  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.  The current buffer's default directory is
+prepended to @var{directory}, if @var{directory} is not absolute.
+In the following example, suppose that the current default directory,
+@file{~rms/lewis}, has five files whose names begin with @samp{f}:
+@file{foo}, @file{file~}, @file{file.c}, @file{file.c.~1~}, and
+@file{file.c.~2~}.@refill
+@example
+@group
+(file-name-all-completions "f" "")
+@result{} ("foo" "file~" "file.c.~2~"
+"file.c.~1~" "file.c")
+@end group
+@group
+(file-name-all-completions "fo" "")
+@result{} ("foo")
+@end group
+@end example
+@end defun
+@defun file-name-completion filename directory
+This function completes the file name @var{filename} in directory
+@var{directory}.  It returns the longest prefix common to all file names
+in directory @var{directory} that start with @var{filename}.
+If only one match exists and @var{filename} matches it exactly, the
+function returns @code{t}.  The function returns @code{nil} if directory
+@var{directory} 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},
+@file{file~}, @file{file.c}, @file{file.c.~1~}, and
+@file{file.c.~2~}.@refill
+@example
+@group
+(file-name-completion "fi" "")
+@result{} "file"
+@end group
+@group
+(file-name-completion "file.c.~1" "")
+@result{} "file.c.~1~"
+@end group
+@group
+(file-name-completion "file.c.~1~" "")
+@result{} t
+@end group
+@group
+(file-name-completion "file.c.~3" "")
+@result{} nil
+@end group
+@end example
+@end defun
+@defopt completion-ignored-extensions
+@code{file-name-completion} 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 or when a buffer showing all
+possible completions is displayed.@refill
+A typical value might look like this:
+@example
+@group
+completion-ignored-extensions
+@result{} (".o" ".elc" "~" ".dvi")
+@end group
+@end example
+@end defopt
+@node Contents of Directories
+@section Contents of Directories
+@cindex directory-oriented functions
+@cindex 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.
+XEmacs 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 value of switches passed to the @code{ls} command.
+@defun directory-files directory &optional full-name match-regexp nosort files-only
+This function returns a list of the names of the files in the directory
+@var{directory}.  By default, the list is in alphabetical order.
+If @var{full-name} is non-@code{nil}, the function returns the files'
+absolute file names.  Otherwise, it returns just the names relative to
+the specified directory.
+If @var{match-regexp} is non-@code{nil}, this function returns only
+those file names that contain that regular expression---the other file
+names are discarded from the list.
+@c Emacs 19 feature
+If @var{nosort} is non-@code{nil}, @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.
+@c XEmacs feature
+If @var{files-only} is the symbol @code{t}, then only the ``files'' in
+the directory will be returned; subdirectories will be excluded.  If
+@var{files-only} is not @code{nil} and not @code{t}, then only the
+subdirectories will be returned.  Otherwise, if @var{files-only} is
+@code{nil} (the default) then both files and subdirectories will be
+returned.
+@example
+@group
+(directory-files "~lewis")
+@result{} ("#foo#" "#foo.el#" "." ".."
+"dired-mods.el" "files.texi"
+"files.texi.~1~")
+@end group
+@end example
+An error is signaled if @var{directory} is not the name of a directory
+that can be read.
+@end defun
+@ignore  @c Not in XEmacs
+@defun file-name-all-versions file dirname
+This function returns a list of all versions of the file named
+@var{file} in directory @var{dirname}.
+@end defun
+@end ignore
+@defun 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
+@var{switches}.  It leaves point after the inserted text.
+The argument @var{file} may be either a directory name or a file
+specification including wildcard characters.  If @var{wildcard} is
+non-@code{nil}, that means treat @var{file} as a file specification with
+wildcards.
+If @var{full-directory-p} is non-@code{nil}, that means @var{file} is a
+directory and switches do not contain @samp{-d}, so that the listing
+should show the full contents of the directory.  (The @samp{-d} option
+to @code{ls} says to describe a directory itself rather than its
+contents.)
+This function works by running a directory listing program whose name is
+in the variable @code{insert-directory-program}.  If @var{wildcard} is
+non-@code{nil}, it also runs the shell specified by
+@code{shell-file-name}, to expand the wildcards.
+@end defun
+@defvar insert-directory-program
+This variable's value is the program to run to generate a directory listing
+for the function @code{insert-directory}.
+@end defvar
+@node Create/Delete Dirs
+@section Creating and Deleting Directories
+@c Emacs 19 features
+Most XEmacs 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.
+@deffn Command make-directory dirname &optional parents
+This function creates a directory named @var{dirname}.  Interactively,
+the default choice of directory to create is the current default
+directory for file names.  That is useful when you have visited a file
+in a nonexistent directory.
+@c XEmacs feature
+Non-interactively, optional argument @var{parents} says whether to
+create parent directories if they don't exist. (Interactively, this
+always happens.)
+@end deffn
+@deffn Command delete-directory dirname
+This function deletes the directory named @var{dirname}.  The function
+@code{delete-file} does not work for files that are directories; you
+must use @code{delete-directory} in that case.
+@end deffn
+@node Magic File Names
+@section Making Certain File Names ``Magic''
+@cindex magic file names
+@c Emacs 19 feature
+You can implement special handling for certain file names.  This is
+called making those names @dfn{magic}.  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
+XEmacs 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:
+@example
+(@var{regexp} . @var{handler})
+@end example
+@noindent
+All the XEmacs 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;
+the remaining arguments are the arguments that were passed to that
+operation.  (The first of these arguments is typically the file name
+itself.)  For example, if you do this:
+@example
+(file-exists-p @var{filename})
+@end example
+@noindent
+and @var{filename} has handler @var{handler}, then @var{handler} is
+called like this:
+@example
+(funcall @var{handler} 'file-exists-p @var{filename})
+@end example
+Here are the operations that a magic file name handler gets to handle:
+@noindent
+@code{add-name-to-file}, @code{copy-file}, @code{delete-directory},
+@code{delete-file},@*
+@code{diff-latest-backup-file},
+@code{directory-file-name},
+@code{directory-files},
+@code{dired-compress-file}, @code{dired-uncache},
+@code{expand-file-name},@*
+@code{file-accessible-directory-p},
+@code{file-attributes}, @code{file-directory-p},
+@code{file-executable-p}, @code{file-exists-p}, @code{file-local-copy},
+@code{file-modes}, @code{file-name-all-completions},
+@code{file-name-as-directory}, @code{file-name-completion},
+@code{file-name-directory}, @code{file-name-nondirectory},
+@code{file-name-sans-versions}, @code{file-newer-than-file-p},
+@code{file-readable-p}, @code{file-regular-p}, @code{file-symlink-p},
+@code{file-truename}, @code{file-writable-p},
+@code{get-file-buffer},
+@code{insert-directory},
+@code{insert-file-contents}, @code{load}, @code{make-directory},
+@code{make-symbolic-link}, @code{rename-file}, @code{set-file-modes},
+@code{set-visited-file-modtime}, @code{unhandled-file-name-directory},
+@code{verify-visited-file-modtime}, @code{write-region}.
+Handlers for @code{insert-file-contents} typically need to clear the
+buffer's modified flag, with @code{(set-buffer-modified-p nil)}, if the
+@var{visit} argument is non-@code{nil}.  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:
+@smallexample
+(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)))))
+@end 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
+@code{inhibit-file-name-handlers} and
+@code{inhibit-file-name-operation}.  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.
+@defvar inhibit-file-name-handlers
+This variable holds a list of handlers whose use is presently inhibited
+for a certain operation.
+@end defvar
+@defvar inhibit-file-name-operation
+The operation for which certain handlers are presently inhibited.
+@end defvar
+@defun 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.  The operation is needed
+for comparison with @code{inhibit-file-name-operation}.
+@end defun
+@defun file-local-copy filename
+This function copies file @var{filename} to an ordinary non-magic file,
+if it isn't one already.
+If @var{filename} specifies a ``magic'' file name, which programs
+outside Emacs cannot directly read or write, this copies the contents to
+an ordinary file and returns that file's name.
+If @var{filename} is an ordinary file name, not magic, then this function
+does nothing and returns @code{nil}.
+@end defun
+@defun 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.
+Otherwise, it asks the handler what to do.
+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.
+@end defun
+@node Partial Files
+@section Partial Files
+@cindex partial files
+@menu
+* Intro to Partial Files::
+* Creating a Partial File::
+* Detached Partial Files::
+@end menu
+@node Intro to Partial Files
+@subsection Intro to Partial Files
+A @dfn{partial file} is a section of a buffer (called the @dfn{master
+buffer}) that is placed in its own buffer and treated as its own file.
+Changes made to the partial file are not reflected in the master buffer
+until the partial file is ``saved'' using the standard buffer save
+commands.  Partial files can be ``reverted'' (from the master buffer)
+just like normal files.  When a file part is active on a master buffer,
+that section of the master buffer is marked as read-only.  Two file
+parts on the same master buffer are not allowed to overlap.  Partial
+file buffers are indicated by the words @samp{File Part} in the
+modeline.
+The master buffer knows about all the partial files that are active on
+it, and thus killing or reverting the master buffer will be handled
+properly.  When the master buffer is saved, if there are any unsaved
+partial files active on it then the user will be given the opportunity
+to first save these files.
+When a partial file buffer is first modified, the master buffer is
+automatically marked as modified so that saving the master buffer will
+work correctly.
+@node Creating a Partial File
+@subsection Creating a Partial File
+@defun make-file-part &optional start end name buffer
+Make a file part on buffer @var{buffer} out of the region.  Call it
+@var{name}.  This command creates a new buffer containing the contents
+of the region and marks the buffer as referring to the specified buffer,
+called the @dfn{master buffer}.  When the file-part buffer is saved, its
+changes are integrated back into the master buffer.  When the master
+buffer is deleted, all file parts are deleted with it.
+When called from a function, expects four arguments, @var{start},
+@var{end}, @var{name}, and @var{buffer}, all of which are optional and
+default to the beginning of @var{buffer}, the end of @var{buffer}, a
+name generated from @var{buffer} name, and the current buffer,
+respectively.
+@end defun
+@node Detached Partial Files
+@subsection Detached Partial Files
+Every partial file has an extent in the master buffer associated with it
+(called the @dfn{master extent}), marking where in the master buffer the
+partial file begins and ends.  If the text in master buffer that is
+contained by the extent is deleted, then the extent becomes
+``detached'', meaning that it no longer refers to a specific region of
+the master buffer.  This can happen either when the text is deleted
+directly or when the master buffer is reverted.  Neither of these should
+happen in normal usage because the master buffer should generally not be
+edited directly.
+Before doing any operation that references a partial file's master
+extent, XEmacs checks to make sure that the extent is not detached.  If
+this is the case, XEmacs warns the user of this and the master extent is
+deleted out of the master buffer, disconnecting the file part.  The file
+part's filename is cleared and thus must be explicitly specified if the
+detached file part is to be saved.
+@node Format Conversion
+@section File Format Conversion
+@cindex file format conversion
+@cindex encoding file formats
+@cindex decoding file formats
+The variable @code{format-alist} defines a list of @dfn{file formats},
+which describe textual representations used in files for the data (text,
+text-properties, and possibly other information) in an Emacs buffer.
+Emacs performs format conversion if appropriate when reading and writing
+files.
+@defvar format-alist
+This list contains one format definition for each defined file format.
+@end defvar
+@cindex format definition
+Each format definition is a list of this form:
+@example
+(@var{name} @var{doc-string} @var{regexp} @var{from-fn} @var{to-fn} @var{modify} @var{mode-fn})
+@end example
+Here is what the elements in a format definition mean:
+@table @var
+@item name
+The name of this format.
+@item doc-string
+A documentation string for the format.
+@item regexp
+A regular expression which is used to recognize files represented in
+this format.
+@item from-fn
+A function to call to decode data in this format (to convert file data into
+the usual Emacs data representation).
+The @var{from-fn} is called with two args, @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.
+@item to-fn
+A function to call to encode data in this format (to convert
+the usual Emacs data representation into this format).
+The @var{to-fn} is called with two args, @var{begin} and @var{end},
+which specify the part of the buffer it should convert.  There are
+two ways it can do the conversion:
+@itemize @bullet
+@item
+By editing the buffer in place.  In this case, @var{to-fn} should
+return the end-position of the range of text, as modified.
+@item
+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
+@var{string} 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.
+@end itemize
+@item modify
+A flag, @code{t} if the encoding function modifies the buffer, and
+@code{nil} if it works by returning a list of annotations.
+@item mode
+A mode function to call after visiting a file converted from this
+format.
+@end 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
+@code{insert-file-contents}); 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}.
+@defvar 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 local in all
+buffers.
+@end 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.
+@defun format-write-file file format
+This command writes the current buffer contents into the file @var{file}
+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.
+@end defun
+@defun 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
+@code{nil}, no conversion takes place.  Interactively, typing just
+@key{RET} for @var{format} specifies @code{nil}.
+@end defun
+@defun 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
+non-@code{nil}, they specify which part of the file to read, as in
+@code{insert-file-contents} (@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
+@code{nil}, no conversion takes place.  Interactively, typing just
+@key{RET} for @var{format} specifies @code{nil}.
+@end defun
+@defun 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
+@code{nil}, no conversion takes place.  Interactively, typing just
+@key{RET} for @var{format} specifies @code{nil}.
+@end defun
+@defun 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
+non-@code{nil}, they specify which part of the file to read,
+as in @code{insert-file-contents} (@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
+@code{nil}, no conversion takes place.  Interactively, typing just
+@key{RET} for @var{format} specifies @code{nil}.
+@end defun
+@defvar 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
+@code{buffer-file-format}; but it is used instead of
+@code{buffer-file-format} for writing auto-save files.  This variable
+is always local in all buffers.
+@end defvar
+@node Files and MS-DOS
+@section Files and MS-DOS
+@cindex MS-DOS file types
+@cindex file types on MS-DOS
+@cindex text files and binary files
+@cindex binary files and text files
+Emacs on MS-DOS makes a distinction between text files and binary
+files.  This is necessary because ordinary text files on MS-DOS use a
+two character sequence between lines: carriage-return and linefeed
+(@sc{crlf}).  Emacs expects just a newline character (a linefeed) between
+lines.  When Emacs reads or writes a text file on MS-DOS, it needs to
+convert the line separators.  This means it needs to know which files
+are text files and which are binary.  It makes this decision when
+visiting a file, and records the decision in the variable
+@code{buffer-file-type} for use when the file is saved.
+@xref{MS-DOS Subprocesses}, for a related feature for subprocesses.
+@defvar buffer-file-type
+This variable, automatically local in each buffer, records the file type
+of the buffer's visited file.  The value is @code{nil} for text,
+@code{t} for binary.
+@end defvar
+@defun find-buffer-file-type filename
+This function determines whether file @var{filename} is a text file
+or a binary file.  It returns @code{nil} for text, @code{t} for binary.
+@end defun
+@defopt file-name-buffer-file-type-alist
+This variable holds an alist for distinguishing text files from binary
+files.  Each element has the form (@var{regexp} . @var{type}), where
+@var{regexp} is matched against the file name, and @var{type} may be is
+@code{nil} for text, @code{t} for binary, or a function to call to
+compute which.  If it is a function, then it is called with a single
+argument (the file name) and should return @code{t} or @code{nil}.
+@end defopt
+@defopt default-buffer-file-type
+This variable specifies the default file type for files whose names
+don't indicate anything in particular.  Its value should be @code{nil}
+for text, or @code{t} for binary.
+@end defopt
+@deffn Command find-file-text filename
+Like @code{find-file}, but treat the file as text regardless of its name.
+@end deffn
+@deffn Command find-file-binary filename
+Like @code{find-file}, but treat the file as binary regardless of its
+name.
+@end deffn

Mercurial > hg > xemacs-beta

comparison man/lispref/files.texi @ 0:376386a54a3c r19-14