2 @c This is part of the XEmacs Lisp Reference Manual.
3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
4 @c See the file lispref.texi for copying conditions.
5 @setfilename ../../info/files.info
6 @node Files, Backups and Auto-Saving, Documentation, Top
9 In XEmacs, you can find, create, view, save, and otherwise work with
10 files and file directories. This chapter describes most of the
11 file-related functions of XEmacs Lisp, but a few others are described in
12 @ref{Buffers}, and those related to backups and auto-saving are
13 described in @ref{Backups and Auto-Saving}.
15 Many of the file functions take one or more arguments that are file
16 names. A file name is actually a string. Most of these functions
17 expand file name arguments using @code{expand-file-name}, so that
18 @file{~} is handled correctly, as are relative file names (including
19 @samp{../}). These functions don't recognize environment variable
20 substitutions such as @samp{$HOME}. @xref{File Name Expansion}.
23 * Visiting Files:: Reading files into Emacs buffers for editing.
24 * Saving Buffers:: Writing changed buffers back into files.
25 * Reading from Files:: Reading files into buffers without visiting.
26 * Writing to Files:: Writing new files from parts of buffers.
27 * File Locks:: Locking and unlocking files, to prevent
28 simultaneous editing by two people.
29 * Information about Files:: Testing existence, accessibility, size of files.
30 * Changing File Attributes:: Renaming files, changing protection, etc.
31 * File Names:: Decomposing and expanding file names.
32 * Contents of Directories:: Getting a list of the files in a directory.
33 * Create/Delete Dirs:: Creating and Deleting Directories.
34 * Magic File Names:: Defining "magic" special handling
35 for certain file names.
36 * Partial Files:: Treating a section of a buffer as a file.
37 * Format Conversion:: Conversion to and from various file formats.
38 * Files and MS-DOS:: Distinguishing text and binary files on MS-DOS.
42 @section Visiting Files
44 @cindex visiting files
46 Visiting a file means reading a file into a buffer. Once this is
47 done, we say that the buffer is @dfn{visiting} that file, and call the
48 file ``the visited file'' of the buffer.
50 A file and a buffer are two different things. A file is information
51 recorded permanently in the computer (unless you delete it). A buffer,
52 on the other hand, is information inside of XEmacs that will vanish at
53 the end of the editing session (or when you kill the buffer). Usually,
54 a buffer contains information that you have copied from a file; then we
55 say the buffer is visiting that file. The copy in the buffer is what
56 you modify with editing commands. Such changes to the buffer do not
57 change the file; therefore, to make the changes permanent, you must
58 @dfn{save} the buffer, which means copying the altered buffer contents
61 In spite of the distinction between files and buffers, people often
62 refer to a file when they mean a buffer and vice-versa. Indeed, we say,
63 ``I am editing a file,'' rather than, ``I am editing a buffer that I
64 will soon save as a file of the same name.'' Humans do not usually need
65 to make the distinction explicit. When dealing with a computer program,
66 however, it is good to keep the distinction in mind.
69 * Visiting Functions:: The usual interface functions for visiting.
70 * Subroutines of Visiting:: Lower-level subroutines that they use.
73 @node Visiting Functions
74 @subsection Functions for Visiting Files
76 This section describes the functions normally used to visit files.
77 For historical reasons, these functions have names starting with
78 @samp{find-} rather than @samp{visit-}. @xref{Buffer File Name}, for
79 functions and variables that access the visited file name of a buffer or
80 that find an existing buffer by its visited file name.
82 In a Lisp program, if you want to look at the contents of a file but
83 not alter it, the fastest way is to use @code{insert-file-contents} in a
84 temporary buffer. Visiting the file is not necessary and takes longer.
85 @xref{Reading from Files}.
87 @deffn Command find-file filename
88 This command selects a buffer visiting the file @var{filename},
89 using an existing buffer if there is one, and otherwise creating a
90 new buffer and reading the file into it. It also returns that buffer.
92 The body of the @code{find-file} function is very simple and looks
96 (switch-to-buffer (find-file-noselect filename))
100 (See @code{switch-to-buffer} in @ref{Displaying Buffers}.)
102 When @code{find-file} is called interactively, it prompts for
103 @var{filename} in the minibuffer.
106 @defun find-file-noselect filename &optional nowarn
107 This function is the guts of all the file-visiting functions. It finds
108 or creates a buffer visiting the file @var{filename}, and returns it.
109 It uses an existing buffer if there is one, and otherwise creates a new
110 buffer and reads the file into it. You may make the buffer current or
111 display it in a window if you wish, but this function does not do so.
113 When @code{find-file-noselect} uses an existing buffer, it first
114 verifies that the file has not changed since it was last visited or
115 saved in that buffer. If the file has changed, then this function asks
116 the user whether to reread the changed file. If the user says
117 @samp{yes}, any changes previously made in the buffer are lost.
119 If @code{find-file-noselect} needs to create a buffer, and there is no
120 file named @var{filename}, it displays the message @samp{New file} in
121 the echo area, and leaves the buffer empty.
124 If @var{no-warn} is non-@code{nil}, various warnings that XEmacs normally
125 gives (e.g. if another buffer is already visiting @var{filename} but
126 @var{filename} has been removed from disk since that buffer was created)
129 The @code{find-file-noselect} function calls @code{after-find-file}
130 after reading the file (@pxref{Subroutines of Visiting}). That function
131 sets the buffer major mode, parses local variables, warns the user if
132 there exists an auto-save file more recent than the file just visited,
133 and finishes by running the functions in @code{find-file-hooks}.
135 The @code{find-file-noselect} function returns the buffer that is
136 visiting the file @var{filename}.
140 (find-file-noselect "/etc/fstab")
141 @result{} #<buffer fstab>
146 @deffn Command find-file-other-window filename
147 This command selects a buffer visiting the file @var{filename}, but
148 does so in a window other than the selected window. It may use another
149 existing window or split a window; see @ref{Displaying Buffers}.
151 When this command is called interactively, it prompts for
155 @deffn Command find-file-read-only filename
156 This command selects a buffer visiting the file @var{filename}, like
157 @code{find-file}, but it marks the buffer as read-only. @xref{Read Only
158 Buffers}, for related functions and variables.
160 When this command is called interactively, it prompts for
164 @deffn Command view-file filename
165 This command visits @var{filename} in View mode, and displays it in a
166 recursive edit, returning to the previous buffer when done. View mode
167 is a mode that allows you to skim rapidly through the file but does not
168 let you modify it. Entering View mode runs the normal hook
169 @code{view-mode-hook}. @xref{Hooks}.
171 When @code{view-file} is called interactively, it prompts for
175 @defvar find-file-hooks
176 The value of this variable is a list of functions to be called after a
177 file is visited. The file's local-variables specification (if any) will
178 have been processed before the hooks are run. The buffer visiting the
179 file is current when the hook functions are run.
181 This variable works just like a normal hook, but we think that renaming
182 it would not be advisable.
185 @defvar find-file-not-found-hooks
186 The value of this variable is a list of functions to be called when
187 @code{find-file} or @code{find-file-noselect} is passed a nonexistent
188 file name. @code{find-file-noselect} calls these functions as soon as
189 it detects a nonexistent file. It calls them in the order of the list,
190 until one of them returns non-@code{nil}. @code{buffer-file-name} is
193 This is not a normal hook because the values of the functions are
194 used and they may not all be called.
197 @node Subroutines of Visiting
198 @subsection Subroutines of Visiting
200 The @code{find-file-noselect} function uses the
201 @code{create-file-buffer} and @code{after-find-file} functions as
202 subroutines. Sometimes it is useful to call them directly.
204 @defun create-file-buffer filename
205 This function creates a suitably named buffer for visiting
206 @var{filename}, and returns it. It uses @var{filename} (sans directory)
207 as the name if that name is free; otherwise, it appends a string such as
208 @samp{<2>} to get an unused name. See also @ref{Creating Buffers}.
210 @strong{Please note:} @code{create-file-buffer} does @emph{not}
211 associate the new buffer with a file and does not select the buffer.
212 It also does not use the default major mode.
216 (create-file-buffer "foo")
217 @result{} #<buffer foo>
220 (create-file-buffer "foo")
221 @result{} #<buffer foo<2>>
224 (create-file-buffer "foo")
225 @result{} #<buffer foo<3>>
229 This function is used by @code{find-file-noselect}.
230 It uses @code{generate-new-buffer} (@pxref{Creating Buffers}).
233 @defun after-find-file &optional error warn noauto
234 This function sets the buffer major mode, and parses local variables
235 (@pxref{Auto Major Mode}). It is called by @code{find-file-noselect}
236 and by the default revert function (@pxref{Reverting}).
238 @cindex new file message
239 @cindex file open error
240 If reading the file got an error because the file does not exist, but
241 its directory does exist, the caller should pass a non-@code{nil} value
242 for @var{error}. In that case, @code{after-find-file} issues a warning:
243 @samp{(New File)}. For more serious errors, the caller should usually not
244 call @code{after-find-file}.
246 If @var{warn} is non-@code{nil}, then this function issues a warning
247 if an auto-save file exists and is more recent than the visited file.
250 If @var{noauto} is non-@code{nil}, then this function does not turn
251 on auto-save mode; otherwise, it does.
253 The last thing @code{after-find-file} does is call all the functions
254 in @code{find-file-hooks}.
258 @section Saving Buffers
260 When you edit a file in XEmacs, you are actually working on a buffer
261 that is visiting that file---that is, the contents of the file are
262 copied into the buffer and the copy is what you edit. Changes to the
263 buffer do not change the file until you @dfn{save} the buffer, which
264 means copying the contents of the buffer into the file.
266 @deffn Command save-buffer &optional backup-option
267 This function saves the contents of the current buffer in its visited
268 file if the buffer has been modified since it was last visited or saved.
269 Otherwise it does nothing.
271 @code{save-buffer} is responsible for making backup files. Normally,
272 @var{backup-option} is @code{nil}, and @code{save-buffer} makes a backup
273 file only if this is the first save since visiting the file. Other
274 values for @var{backup-option} request the making of backup files in
279 With an argument of 4 or 64, reflecting 1 or 3 @kbd{C-u}'s, the
280 @code{save-buffer} function marks this version of the file to be
281 backed up when the buffer is next saved.
284 With an argument of 16 or 64, reflecting 2 or 3 @kbd{C-u}'s, the
285 @code{save-buffer} function unconditionally backs up the previous
286 version of the file before saving it.
290 @deffn Command save-some-buffers &optional save-silently-p exiting
291 This command saves some modified file-visiting buffers. Normally it
292 asks the user about each buffer. But if @var{save-silently-p} is
293 non-@code{nil}, it saves all the file-visiting buffers without querying
296 The optional @var{exiting} argument, if non-@code{nil}, requests this
297 function to offer also to save certain other buffers that are not
298 visiting files. These are buffers that have a non-@code{nil} local
299 value of @code{buffer-offer-save}. (A user who says yes to saving one
300 of these is asked to specify a file name to use.) The
301 @code{save-buffers-kill-emacs} function passes a non-@code{nil} value
305 @defvar buffer-offer-save
306 When this variable is non-@code{nil} in a buffer, XEmacs offers to save
307 the buffer on exit even if the buffer is not visiting a file. The
308 variable is automatically local in all buffers. Normally, Mail mode
309 (used for editing outgoing mail) sets this to @code{t}.
312 @deffn Command write-file filename
313 This function writes the current buffer into file @var{filename}, makes
314 the buffer visit that file, and marks it not modified. Then it renames
315 the buffer based on @var{filename}, appending a string like @samp{<2>}
316 if necessary to make a unique buffer name. It does most of this work by
317 calling @code{set-visited-file-name} and @code{save-buffer}.
320 @defvar write-file-hooks
321 The value of this variable is a list of functions to be called before
322 writing out a buffer to its visited file. If one of them returns
323 non-@code{nil}, the file is considered already written and the rest of
324 the functions are not called, nor is the usual code for writing the file
327 If a function in @code{write-file-hooks} returns non-@code{nil}, it
328 is responsible for making a backup file (if that is appropriate).
329 To do so, execute the following code:
332 (or buffer-backed-up (backup-buffer))
335 You might wish to save the file modes value returned by
336 @code{backup-buffer} and use that to set the mode bits of the file that
337 you write. This is what @code{save-buffer} normally does.
339 Even though this is not a normal hook, you can use @code{add-hook} and
340 @code{remove-hook} to manipulate the list. @xref{Hooks}.
344 @defvar local-write-file-hooks
345 This works just like @code{write-file-hooks}, but it is intended
346 to be made local to particular buffers. It's not a good idea to make
347 @code{write-file-hooks} local to a buffer---use this variable instead.
349 The variable is marked as a permanent local, so that changing the major
350 mode does not alter a buffer-local value. This is convenient for
351 packages that read ``file'' contents in special ways, and set up hooks
352 to save the data in a corresponding way.
356 @defvar write-contents-hooks
357 This works just like @code{write-file-hooks}, but it is intended for
358 hooks that pertain to the contents of the file, as opposed to hooks that
359 pertain to where the file came from. Such hooks are usually set up by
360 major modes, as buffer-local bindings for this variable. Switching to a
361 new major mode always resets this variable.
365 @defvar after-save-hook
366 This normal hook runs after a buffer has been saved in its visited file.
369 @defvar file-precious-flag
370 If this variable is non-@code{nil}, then @code{save-buffer} protects
371 against I/O errors while saving by writing the new file to a temporary
372 name instead of the name it is supposed to have, and then renaming it to
373 the intended name after it is clear there are no errors. This procedure
374 prevents problems such as a lack of disk space from resulting in an
377 As a side effect, backups are necessarily made by copying. @xref{Rename
378 or Copy}. Yet, at the same time, saving a precious file always breaks
379 all hard links between the file you save and other file names.
381 Some modes set this variable non-@code{nil} locally in particular
385 @defopt require-final-newline
386 This variable determines whether files may be written out that do
387 @emph{not} end with a newline. If the value of the variable is
388 @code{t}, then @code{save-buffer} silently adds a newline at the end of
389 the file whenever the buffer being saved does not already end in one.
390 If the value of the variable is non-@code{nil}, but not @code{t}, then
391 @code{save-buffer} asks the user whether to add a newline each time the
394 If the value of the variable is @code{nil}, then @code{save-buffer}
395 doesn't add newlines at all. @code{nil} is the default value, but a few
396 major modes set it to @code{t} in particular buffers.
399 @node Reading from Files
400 @section Reading from Files
402 You can copy a file from the disk and insert it into a buffer
403 using the @code{insert-file-contents} function. Don't use the user-level
404 command @code{insert-file} in a Lisp program, as that sets the mark.
406 @defun insert-file-contents filename &optional visit beg end replace
407 This function inserts the contents of file @var{filename} into the
408 current buffer after point. It returns a list of the absolute file name
409 and the length of the data inserted. An error is signaled if
410 @var{filename} is not the name of a file that can be read.
412 The function @code{insert-file-contents} checks the file contents
413 against the defined file formats, and converts the file contents if
414 appropriate. @xref{Format Conversion}. It also calls the functions in
415 the list @code{after-insert-file-functions}; see @ref{Saving
418 If @var{visit} is non-@code{nil}, this function additionally marks the
419 buffer as unmodified and sets up various fields in the buffer so that it
420 is visiting the file @var{filename}: these include the buffer's visited
421 file name and its last save file modtime. This feature is used by
422 @code{find-file-noselect} and you probably should not use it yourself.
424 If @var{beg} and @var{end} are non-@code{nil}, they should be integers
425 specifying the portion of the file to insert. In this case, @var{visit}
426 must be @code{nil}. For example,
429 (insert-file-contents filename nil 0 500)
433 inserts the first 500 characters of a file.
435 If the argument @var{replace} is non-@code{nil}, it means to replace the
436 contents of the buffer (actually, just the accessible portion) with the
437 contents of the file. This is better than simply deleting the buffer
438 contents and inserting the whole file, because (1) it preserves some
439 marker positions and (2) it puts less data in the undo list.
442 If you want to pass a file name to another process so that another
443 program can read the file, use the function @code{file-local-copy}; see
444 @ref{Magic File Names}.
446 @node Writing to Files
447 @section Writing to Files
449 You can write the contents of a buffer, or part of a buffer, directly
450 to a file on disk using the @code{append-to-file} and
451 @code{write-region} functions. Don't use these functions to write to
452 files that are being visited; that could cause confusion in the
453 mechanisms for visiting.
455 @deffn Command append-to-file start end filename
456 This function appends the contents of the region delimited by
457 @var{start} and @var{end} in the current buffer to the end of file
458 @var{filename}. If that file does not exist, it is created. If that
459 file exists it is overwritten. This function returns @code{nil}.
461 An error is signaled if @var{filename} specifies a nonwritable file,
462 or a nonexistent file in a directory where files cannot be created.
465 @deffn Command write-region start end filename &optional append visit
466 This function writes the region delimited by @var{start} and @var{end}
467 in the current buffer into the file specified by @var{filename}.
470 If @var{start} is a string, then @code{write-region} writes or appends
471 that string, rather than text from the buffer.
473 If @var{append} is non-@code{nil}, then the specified text is appended
474 to the existing file contents (if any).
476 If @var{visit} is @code{t}, then XEmacs establishes an association
477 between the buffer and the file: the buffer is then visiting that file.
478 It also sets the last file modification time for the current buffer to
479 @var{filename}'s modtime, and marks the buffer as not modified. This
480 feature is used by @code{save-buffer}, but you probably should not use
484 If @var{visit} is a string, it specifies the file name to visit. This
485 way, you can write the data to one file (@var{filename}) while recording
486 the buffer as visiting another file (@var{visit}). The argument
487 @var{visit} is used in the echo area message and also for file locking;
488 @var{visit} is stored in @code{buffer-file-name}. This feature is used
489 to implement @code{file-precious-flag}; don't use it yourself unless you
490 really know what you're doing.
492 The function @code{write-region} converts the data which it writes to
493 the appropriate file formats specified by @code{buffer-file-format}.
494 @xref{Format Conversion}. It also calls the functions in the list
495 @code{write-region-annotate-functions}; see @ref{Saving Properties}.
497 Normally, @code{write-region} displays a message @samp{Wrote file
498 @var{filename}} in the echo area. If @var{visit} is neither @code{t}
499 nor @code{nil} nor a string, then this message is inhibited. This
500 feature is useful for programs that use files for internal purposes,
501 files that the user does not need to know about.
508 When two users edit the same file at the same time, they are likely to
509 interfere with each other. XEmacs tries to prevent this situation from
510 arising by recording a @dfn{file lock} when a file is being modified.
511 XEmacs can then detect the first attempt to modify a buffer visiting a
512 file that is locked by another XEmacs process, and ask the user what to do.
514 File locks do not work properly when multiple machines can share
515 file systems, such as with NFS. Perhaps a better file locking system
516 will be implemented in the future. When file locks do not work, it is
517 possible for two users to make changes simultaneously, but XEmacs can
518 still warn the user who saves second. Also, the detection of
519 modification of a buffer visiting a file changed on disk catches some
520 cases of simultaneous editing; see @ref{Modification Time}.
522 @c Not optional in FSF Emacs 19
523 @defun file-locked-p &optional filename
524 This function returns @code{nil} if the file @var{filename} is not
525 locked by this XEmacs process. It returns @code{t} if it is locked by
526 this XEmacs, and it returns the name of the user who has locked it if it
527 is locked by someone else.
531 (file-locked-p "foo")
537 @defun lock-buffer &optional filename
538 This function locks the file @var{filename}, if the current buffer is
539 modified. The argument @var{filename} defaults to the current buffer's
540 visited file. Nothing is done if the current buffer is not visiting a
541 file, or is not modified.
545 This function unlocks the file being visited in the current buffer,
546 if the buffer is modified. If the buffer is not modified, then
547 the file should not be locked, so this function does nothing. It also
548 does nothing if the current buffer is not visiting a file.
551 @defun ask-user-about-lock file other-user
552 This function is called when the user tries to modify @var{file}, but it
553 is locked by another user named @var{other-user}. The value it returns
554 determines what happens next:
558 A value of @code{t} says to grab the lock on the file. Then
559 this user may edit the file and @var{other-user} loses the lock.
562 A value of @code{nil} says to ignore the lock and let this
563 user edit the file anyway.
567 This function may instead signal a @code{file-locked} error, in which
568 case the change that the user was about to make does not take place.
570 The error message for this error looks like this:
573 @error{} File is locked: @var{file} @var{other-user}
577 where @code{file} is the name of the file and @var{other-user} is the
578 name of the user who has locked the file.
581 The default definition of this function asks the user to choose what
582 to do. If you wish, you can replace the @code{ask-user-about-lock}
583 function with your own version that decides in another way. The code
584 for its usual definition is in @file{userlock.el}.
587 @node Information about Files
588 @section Information about Files
590 The functions described in this section all operate on strings that
591 designate file names. All the functions have names that begin with the
592 word @samp{file}. These functions all return information about actual
593 files or directories, so their arguments must all exist as actual files
594 or directories unless otherwise noted.
597 * Testing Accessibility:: Is a given file readable? Writable?
598 * Kinds of Files:: Is it a directory? A symbolic link?
599 * Truenames:: Eliminating symbolic links from a file name.
600 * File Attributes:: How large is it? Any other names? Etc.
603 @node Testing Accessibility
604 @subsection Testing Accessibility
605 @cindex accessibility of a file
606 @cindex file accessibility
608 These functions test for permission to access a file in specific ways.
610 @defun file-exists-p filename
611 This function returns @code{t} if a file named @var{filename} appears
612 to exist. This does not mean you can necessarily read the file, only
613 that you can find out its attributes. (On Unix, this is true if the
614 file exists and you have execute permission on the containing
615 directories, regardless of the protection of the file itself.)
617 If the file does not exist, or if fascist access control policies
618 prevent you from finding the attributes of the file, this function
622 @defun file-readable-p filename
623 This function returns @code{t} if a file named @var{filename} exists
624 and you can read it. It returns @code{nil} otherwise.
628 (file-readable-p "files.texi")
632 (file-exists-p "/usr/spool/mqueue")
636 (file-readable-p "/usr/spool/mqueue")
643 @defun file-executable-p filename
644 This function returns @code{t} if a file named @var{filename} exists and
645 you can execute it. It returns @code{nil} otherwise. If the file is a
646 directory, execute permission means you can check the existence and
647 attributes of files inside the directory, and open those files if their
651 @defun file-writable-p filename
652 This function returns @code{t} if the file @var{filename} can be written
653 or created by you, and @code{nil} otherwise. A file is writable if the
654 file exists and you can write it. It is creatable if it does not exist,
655 but the specified directory does exist and you can write in that
658 In the third example below, @file{foo} is not writable because the
659 parent directory does not exist, even though the user could create such
664 (file-writable-p "~/foo")
668 (file-writable-p "/foo")
672 (file-writable-p "~/no-such-dir/foo")
679 @defun file-accessible-directory-p dirname
680 This function returns @code{t} if you have permission to open existing
681 files in the directory whose name as a file is @var{dirname}; otherwise
682 (or if there is no such directory), it returns @code{nil}. The value
683 of @var{dirname} may be either a directory name or the file name of a
686 Example: after the following,
689 (file-accessible-directory-p "/foo")
694 we can deduce that any attempt to read a file in @file{/foo/} will
698 @defun file-ownership-preserved-p filename
699 This function returns @code{t} if deleting the file @var{filename} and
700 then creating it anew would keep the file's owner unchanged.
703 @defun file-newer-than-file-p filename1 filename2
705 @cindex file modification time
706 This function returns @code{t} if the file @var{filename1} is
707 newer than file @var{filename2}. If @var{filename1} does not
708 exist, it returns @code{nil}. If @var{filename2} does not exist,
711 In the following example, assume that the file @file{aug-19} was written
712 on the 19th, @file{aug-20} was written on the 20th, and the file
713 @file{no-file} doesn't exist at all.
717 (file-newer-than-file-p "aug-19" "aug-20")
721 (file-newer-than-file-p "aug-20" "aug-19")
725 (file-newer-than-file-p "aug-19" "no-file")
729 (file-newer-than-file-p "no-file" "aug-19")
734 You can use @code{file-attributes} to get a file's last modification
735 time as a list of two numbers. @xref{File Attributes}.
739 @subsection Distinguishing Kinds of Files
741 This section describes how to distinguish various kinds of files, such
742 as directories, symbolic links, and ordinary files.
744 @defun file-symlink-p filename
745 @cindex file symbolic links
746 If the file @var{filename} is a symbolic link, the @code{file-symlink-p}
747 function returns the file name to which it is linked. This may be the
748 name of a text file, a directory, or even another symbolic link, or it
749 may be a nonexistent file name.
751 If the file @var{filename} is not a symbolic link (or there is no such file),
752 @code{file-symlink-p} returns @code{nil}.
756 (file-symlink-p "foo")
760 (file-symlink-p "sym-link")
764 (file-symlink-p "sym-link2")
768 (file-symlink-p "/bin")
773 @c !!! file-symlink-p: should show output of ls -l for comparison
776 @defun file-directory-p filename
777 This function returns @code{t} if @var{filename} is the name of an
778 existing directory, @code{nil} otherwise.
782 (file-directory-p "~rms")
786 (file-directory-p "~rms/lewis/files.texi")
790 (file-directory-p "~rms/lewis/no-such-file")
794 (file-directory-p "$HOME")
799 (substitute-in-file-name "$HOME"))
805 @defun file-regular-p filename
806 This function returns @code{t} if the file @var{filename} exists and is
807 a regular file (not a directory, symbolic link, named pipe, terminal, or
812 @subsection Truenames
813 @cindex truename (of file)
816 The @dfn{truename} of a file is the name that you get by following
817 symbolic links until none remain, then expanding to get rid of @samp{.}
818 and @samp{..} as components. Strictly speaking, a file need not have a
819 unique truename; the number of distinct truenames a file has is equal to
820 the number of hard links to the file. However, truenames are useful
821 because they eliminate symbolic links as a cause of name variation.
823 @defun file-truename filename &optional default
824 The function @code{file-truename} returns the true name of the file
825 @var{filename}. This is the name that you get by following symbolic
826 links until none remain.
828 @c XEmacs allows relative filenames
829 If the filename is relative, @var{default} is the directory to start
830 with. If @var{default} is @code{nil} or missing, the current buffer's
831 value of @code{default-directory} is used.
834 @xref{Buffer File Name}, for related information.
836 @node File Attributes
837 @subsection Other Information about Files
839 This section describes the functions for getting detailed information
840 about a file, other than its contents. This information includes the
841 mode bits that control access permission, the owner and group numbers,
842 the number of names, the inode number, the size, and the times of access
845 @defun file-modes filename
847 @cindex file attributes
848 This function returns the mode bits of @var{filename}, as an integer.
849 The mode bits are also called the file permissions, and they specify
850 access control in the usual Unix fashion. If the low-order bit is 1,
851 then the file is executable by all users, if the second-lowest-order bit
852 is 1, then the file is writable by all users, etc.
854 The highest value returnable is 4095 (7777 octal), meaning that
855 everyone has read, write, and execute permission, that the @sc{suid} bit
856 is set for both others and group, and that the sticky bit is set.
860 (file-modes "~/junk/diffs")
861 @result{} 492 ; @r{Decimal integer.}
865 @result{} "754" ; @r{Convert to octal.}
869 (set-file-modes "~/junk/diffs" 438)
875 @result{} "666" ; @r{Convert to octal.}
880 -rw-rw-rw- 1 lewis 0 3063 Oct 30 16:00 diffs
885 @defun file-nlinks filename
886 This functions returns the number of names (i.e., hard links) that
887 file @var{filename} has. If the file does not exist, then this function
888 returns @code{nil}. Note that symbolic links have no effect on this
889 function, because they are not considered to be names of the files they
895 -rw-rw-rw- 2 rms 4 Aug 19 01:27 foo
896 -rw-rw-rw- 2 rms 4 Aug 19 01:27 foo1
904 (file-nlinks "doesnt-exist")
910 @defun file-attributes filename
911 This function returns a list of attributes of file @var{filename}. If
912 the specified file cannot be opened, it returns @code{nil}.
914 The elements of the list, in order, are:
918 @code{t} for a directory, a string for a symbolic link (the name
919 linked to), or @code{nil} for a text file.
921 @c Wordy so as to prevent an overfull hbox. --rjc 15mar92
923 The number of names the file has. Alternate names, also known as hard
924 links, can be created by using the @code{add-name-to-file} function
925 (@pxref{Changing File Attributes}).
934 The time of last access, as a list of two integers.
935 The first integer has the high-order 16 bits of time,
936 the second has the low 16 bits. (This is similar to the
937 value of @code{current-time}; see @ref{Time of Day}.)
940 The time of last modification as a list of two integers (as above).
943 The time of last status change as a list of two integers (as above).
946 The size of the file in bytes.
949 The file's modes, as a string of ten letters or dashes,
953 @code{t} if the file's @sc{gid} would change if file were
954 deleted and recreated; @code{nil} otherwise.
957 The file's inode number.
960 The file system number of the file system that the file is in. This
961 element and the file's inode number together give enough information to
962 distinguish any two files on the system---no two files can have the same
963 values for both of these numbers.
966 For example, here are the file attributes for @file{files.texi}:
970 (file-attributes "files.texi")
987 and here is how the result is interpreted:
991 is neither a directory nor a symbolic link.
994 has only one name (the name @file{files.texi} in the current default
998 is owned by the user with @sc{uid} 2235.
1001 is in the group with @sc{gid} 75.
1004 was last accessed on Aug 19 00:09. Use @code{format-time-string} to
1005 ! convert this number into a time string. @xref{Time Conversion}.
1008 was last modified on Aug 19 00:09.
1011 last had its inode changed on Aug 19 00:09.
1014 is 14906 characters long.
1017 has a mode of read and write access for the owner, group, and world.
1020 would retain the same @sc{gid} if it were recreated.
1023 has an inode number of 129500.
1025 is on file system number -32252.
1029 @node Changing File Attributes
1030 @section Changing File Names and Attributes
1031 @cindex renaming files
1032 @cindex copying files
1033 @cindex deleting files
1034 @cindex linking files
1035 @cindex setting modes of files
1037 The functions in this section rename, copy, delete, link, and set the
1040 In the functions that have an argument @var{newname}, if a file by the
1041 name of @var{newname} already exists, the actions taken depend on the
1042 value of the argument @var{ok-if-already-exists}:
1046 Signal a @code{file-already-exists} error if
1047 @var{ok-if-already-exists} is @code{nil}.
1050 Request confirmation if @var{ok-if-already-exists} is a number.
1053 Replace the old file without confirmation if @var{ok-if-already-exists}
1057 @deffn Command add-name-to-file oldname newname &optional ok-if-already-exists
1058 @cindex file with multiple names
1059 @cindex file hard link
1060 This function gives the file named @var{oldname} the additional name
1061 @var{newname}. This means that @var{newname} becomes a new ``hard
1062 link'' to @var{oldname}.
1064 In the first part of the following example, we list two files,
1065 @file{foo} and @file{foo3}.
1070 -rw-rw-rw- 1 rms 29 Aug 18 20:32 foo
1071 -rw-rw-rw- 1 rms 24 Aug 18 20:31 foo3
1075 Then we evaluate the form @code{(add-name-to-file "~/lewis/foo"
1076 "~/lewis/foo2")}. Again we list the files. This shows two names,
1077 @file{foo} and @file{foo2}.
1081 (add-name-to-file "~/lewis/foo1" "~/lewis/foo2")
1087 -rw-rw-rw- 2 rms 29 Aug 18 20:32 foo
1088 -rw-rw-rw- 2 rms 29 Aug 18 20:32 foo2
1089 -rw-rw-rw- 1 rms 24 Aug 18 20:31 foo3
1093 @c !!! Check whether this set of examples is consistent. --rjc 15mar92
1094 Finally, we evaluate the following:
1097 (add-name-to-file "~/lewis/foo" "~/lewis/foo3" t)
1101 and list the files again. Now there are three names
1102 for one file: @file{foo}, @file{foo2}, and @file{foo3}. The old
1103 contents of @file{foo3} are lost.
1107 (add-name-to-file "~/lewis/foo1" "~/lewis/foo3")
1113 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo
1114 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo2
1115 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo3
1119 This function is meaningless on VMS, where multiple names for one file
1122 See also @code{file-nlinks} in @ref{File Attributes}.
1125 @deffn Command rename-file filename newname &optional ok-if-already-exists
1126 This command renames the file @var{filename} as @var{newname}.
1128 If @var{filename} has additional names aside from @var{filename}, it
1129 continues to have those names. In fact, adding the name @var{newname}
1130 with @code{add-name-to-file} and then deleting @var{filename} has the
1131 same effect as renaming, aside from momentary intermediate states.
1133 In an interactive call, this function prompts for @var{filename} and
1134 @var{newname} in the minibuffer; also, it requests confirmation if
1135 @var{newname} already exists.
1138 @deffn Command copy-file oldname newname &optional ok-if-exists time
1139 This command copies the file @var{oldname} to @var{newname}. An
1140 error is signaled if @var{oldname} does not exist.
1142 If @var{time} is non-@code{nil}, then this functions gives the new
1143 file the same last-modified time that the old one has. (This works on
1144 only some operating systems.)
1146 In an interactive call, this function prompts for @var{filename} and
1147 @var{newname} in the minibuffer; also, it requests confirmation if
1148 @var{newname} already exists.
1151 @deffn Command delete-file filename
1153 This command deletes the file @var{filename}, like the shell command
1154 @samp{rm @var{filename}}. If the file has multiple names, it continues
1155 to exist under the other names.
1157 A suitable kind of @code{file-error} error is signaled if the file
1158 does not exist, or is not deletable. (On Unix, a file is deletable if
1159 its directory is writable.)
1161 See also @code{delete-directory} in @ref{Create/Delete Dirs}.
1164 @deffn Command make-symbolic-link filename newname &optional ok-if-exists
1166 @kindex file-already-exists
1167 This command makes a symbolic link to @var{filename}, named
1168 @var{newname}. This is like the shell command @samp{ln -s
1169 @var{filename} @var{newname}}.
1171 In an interactive call, this function prompts for @var{filename} and
1172 @var{newname} in the minibuffer; also, it requests confirmation if
1173 @var{newname} already exists.
1176 @defun define-logical-name varname string
1177 This function defines the logical name @var{name} to have the value
1178 @var{string}. It is available only on VMS.
1181 @defun set-file-modes filename mode
1182 This function sets mode bits of @var{filename} to @var{mode} (which must
1183 be an integer). Only the low 12 bits of @var{mode} are used.
1187 @defun set-default-file-modes mode
1188 This function sets the default file protection for new files created by
1189 XEmacs and its subprocesses. Every file created with XEmacs initially has
1190 this protection. On Unix, the default protection is the bitwise
1191 complement of the ``umask'' value.
1193 The argument @var{mode} must be an integer. Only the low 9 bits of
1194 @var{mode} are used.
1196 Saving a modified version of an existing file does not count as creating
1197 the file; it does not change the file's mode, and does not use the
1198 default file protection.
1201 @defun default-file-modes
1202 This function returns the current default protection value.
1205 @cindex MS-DOS and file modes
1206 @cindex file modes and MS-DOS
1207 On MS-DOS, there is no such thing as an ``executable'' file mode bit.
1208 So Emacs considers a file executable if its name ends in @samp{.com},
1209 @samp{.bat} or @samp{.exe}. This is reflected in the values returned
1210 by @code{file-modes} and @code{file-attributes}.
1216 Files are generally referred to by their names, in XEmacs as elsewhere.
1217 File names in XEmacs are represented as strings. The functions that
1218 operate on a file all expect a file name argument.
1220 In addition to operating on files themselves, XEmacs Lisp programs
1221 often need to operate on the names; i.e., to take them apart and to use
1222 part of a name to construct related file names. This section describes
1223 how to manipulate file names.
1225 The functions in this section do not actually access files, so they
1226 can operate on file names that do not refer to an existing file or
1229 On VMS, all these functions understand both VMS file-name syntax and
1230 Unix syntax. This is so that all the standard Lisp libraries can
1231 specify file names in Unix syntax and work properly on VMS without
1232 change. On MS-DOS, these functions understand MS-DOS file-name syntax
1233 as well as Unix syntax.
1236 * File Name Components:: The directory part of a file name, and the rest.
1237 * Directory Names:: A directory's name as a directory
1238 is different from its name as a file.
1239 * Relative File Names:: Some file names are relative to a current directory.
1240 * File Name Expansion:: Converting relative file names to absolute ones.
1241 * Unique File Names:: Generating names for temporary files.
1242 * File Name Completion:: Finding the completions for a given file name.
1243 * User Name Completion:: Finding the completions for a given user name.
1246 @node File Name Components
1247 @subsection File Name Components
1248 @cindex directory part (of file name)
1249 @cindex nondirectory part (of file name)
1250 @cindex version number (in file name)
1252 The operating system groups files into directories. To specify a
1253 file, you must specify the directory and the file's name within that
1254 directory. Therefore, XEmacs considers a file name as having two main
1255 parts: the @dfn{directory name} part, and the @dfn{nondirectory} part
1256 (or @dfn{file name within the directory}). Either part may be empty.
1257 Concatenating these two parts reproduces the original file name.
1259 On Unix, the directory part is everything up to and including the last
1260 slash; the nondirectory part is the rest. The rules in VMS syntax are
1263 For some purposes, the nondirectory part is further subdivided into
1264 the name proper and the @dfn{version number}. On Unix, only backup
1265 files have version numbers in their names; on VMS, every file has a
1266 version number, but most of the time the file name actually used in
1267 XEmacs omits the version number. Version numbers are found mostly in
1270 @defun file-name-directory filename
1271 This function returns the directory part of @var{filename} (or
1272 @code{nil} if @var{filename} does not include a directory part). On
1273 Unix, the function returns a string ending in a slash. On VMS, it
1274 returns a string ending in one of the three characters @samp{:},
1275 @samp{]}, or @samp{>}.
1279 (file-name-directory "lewis/foo") ; @r{Unix example}
1283 (file-name-directory "foo") ; @r{Unix example}
1287 (file-name-directory "[X]FOO.TMP") ; @r{VMS example}
1293 @defun file-name-nondirectory filename
1294 This function returns the nondirectory part of @var{filename}.
1298 (file-name-nondirectory "lewis/foo")
1302 (file-name-nondirectory "foo")
1306 ;; @r{The following example is accurate only on VMS.}
1307 (file-name-nondirectory "[X]FOO.TMP")
1313 @defun file-name-sans-versions filename &optional keep-backup-version
1314 This function returns @var{filename} without any file version numbers,
1315 backup version numbers, or trailing tildes.
1318 If @var{keep-backup-version} is non-@code{nil}, we do not remove backup
1319 version numbers, only true file version numbers.
1323 (file-name-sans-versions "~rms/foo.~1~")
1324 @result{} "~rms/foo"
1327 (file-name-sans-versions "~rms/foo~")
1328 @result{} "~rms/foo"
1331 (file-name-sans-versions "~rms/foo")
1332 @result{} "~rms/foo"
1335 ;; @r{The following example applies to VMS only.}
1336 (file-name-sans-versions "foo;23")
1342 @defun file-name-sans-extension filename
1343 This function returns @var{filename} minus its ``extension,'' if any.
1344 The extension, in a file name, is the part that starts with the last
1345 @samp{.} in the last name component. For example,
1348 (file-name-sans-extension "foo.lose.c")
1349 @result{} "foo.lose"
1350 (file-name-sans-extension "big.hack/foo")
1351 @result{} "big.hack/foo"
1355 @node Directory Names
1356 @subsection Directory Names
1357 @cindex directory name
1358 @cindex file name of directory
1360 A @dfn{directory name} is the name of a directory. A directory is a
1361 kind of file, and it has a file name, which is related to the directory
1362 name but not identical to it. (This is not quite the same as the usual
1363 Unix terminology.) These two different names for the same entity are
1364 related by a syntactic transformation. On Unix, this is simple: a
1365 directory name ends in a slash, whereas the directory's name as a file
1366 lacks that slash. On VMS, the relationship is more complicated.
1368 The difference between a directory name and its name as a file is
1369 subtle but crucial. When an XEmacs variable or function argument is
1370 described as being a directory name, a file name of a directory is not
1373 The following two functions convert between directory names and file
1374 names. They do nothing special with environment variable substitutions
1375 such as @samp{$HOME}, and the constructs @samp{~}, and @samp{..}.
1377 @defun file-name-as-directory filename
1378 This function returns a string representing @var{filename} in a form
1379 that the operating system will interpret as the name of a directory. In
1380 Unix, this means appending a slash to the string. On VMS, the function
1381 converts a string of the form @file{[X]Y.DIR.1} to the form
1386 (file-name-as-directory "~rms/lewis")
1387 @result{} "~rms/lewis/"
1392 @defun directory-file-name dirname
1393 This function returns a string representing @var{dirname} in a form
1394 that the operating system will interpret as the name of a file. On
1395 Unix, this means removing a final slash from the string. On VMS, the
1396 function converts a string of the form @file{[X.Y]} to
1401 (directory-file-name "~lewis/")
1407 @cindex directory name abbreviation
1408 Directory name abbreviations are useful for directories that are
1409 normally accessed through symbolic links. Sometimes the users recognize
1410 primarily the link's name as ``the name'' of the directory, and find it
1411 annoying to see the directory's ``real'' name. If you define the link
1412 name as an abbreviation for the ``real'' name, XEmacs shows users the
1413 abbreviation instead.
1415 If you wish to convert a directory name to its abbreviation, use this
1418 @defun abbreviate-file-name dirname &optional hack-homedir
1419 This function applies abbreviations from @code{directory-abbrev-alist}
1420 to its argument, and substitutes @samp{~} for the user's home
1424 If @var{hack-homedir} is non-@code{nil}, then this also substitutes
1425 @samp{~} for the user's home directory.
1429 @defvar directory-abbrev-alist
1430 The variable @code{directory-abbrev-alist} contains an alist of
1431 abbreviations to use for file directories. Each element has the form
1432 @code{(@var{from} . @var{to})}, and says to replace @var{from} with
1433 @var{to} when it appears in a directory name. The @var{from} string is
1434 actually a regular expression; it should always start with @samp{^}.
1435 The function @code{abbreviate-file-name} performs these substitutions.
1437 You can set this variable in @file{site-init.el} to describe the
1438 abbreviations appropriate for your site.
1440 Here's an example, from a system on which file system @file{/home/fsf}
1441 and so on are normally accessed through symbolic links named @file{/fsf}
1445 (("^/home/fsf" . "/fsf")
1446 ("^/home/gp" . "/gp")
1447 ("^/home/gd" . "/gd"))
1451 @c To convert a directory name to its abbreviation, use this
1454 @c @defun abbreviate-file-name dirname
1455 @c This function applies abbreviations from @code{directory-abbrev-alist}
1456 @c to its argument, and substitutes @samp{~} for the user's home
1460 @node Relative File Names
1461 @subsection Absolute and Relative File Names
1462 @cindex absolute file name
1463 @cindex relative file name
1465 All the directories in the file system form a tree starting at the
1466 root directory. A file name can specify all the directory names
1467 starting from the root of the tree; then it is called an @dfn{absolute}
1468 file name. Or it can specify the position of the file in the tree
1469 relative to a default directory; then it is called a @dfn{relative}
1470 file name. On Unix, an absolute file name starts with a slash or a
1471 tilde (@samp{~}), and a relative one does not. The rules on VMS are
1474 @defun file-name-absolute-p filename
1475 This function returns @code{t} if file @var{filename} is an absolute
1476 file name, @code{nil} otherwise. On VMS, this function understands both
1477 Unix syntax and VMS syntax.
1481 (file-name-absolute-p "~rms/foo")
1485 (file-name-absolute-p "rms/foo")
1489 (file-name-absolute-p "/user/rms/foo")
1495 @node File Name Expansion
1496 @subsection Functions that Expand Filenames
1497 @cindex expansion of file names
1499 @dfn{Expansion} of a file name means converting a relative file name
1500 to an absolute one. Since this is done relative to a default directory,
1501 you must specify the default directory name as well as the file name to
1502 be expanded. Expansion also simplifies file names by eliminating
1503 redundancies such as @file{./} and @file{@var{name}/../}.
1505 @defun expand-file-name filename &optional directory
1506 This function converts @var{filename} to an absolute file name. If
1507 @var{directory} is supplied, it is the directory to start with if
1508 @var{filename} is relative. (The value of @var{directory} should itself
1509 be an absolute directory name; it may start with @samp{~}.)
1510 Otherwise, the current buffer's value of @code{default-directory} is
1515 (expand-file-name "foo")
1516 @result{} "/xcssun/users/rms/lewis/foo"
1519 (expand-file-name "../foo")
1520 @result{} "/xcssun/users/rms/foo"
1523 (expand-file-name "foo" "/usr/spool/")
1524 @result{} "/usr/spool/foo"
1527 (expand-file-name "$HOME/foo")
1528 @result{} "/xcssun/users/rms/lewis/$HOME/foo"
1532 Filenames containing @samp{.} or @samp{..} are simplified to their
1537 (expand-file-name "bar/../foo")
1538 @result{} "/xcssun/users/rms/lewis/foo"
1542 @samp{~/} at the beginning is expanded into the user's home directory.
1543 A @samp{/} or @samp{~} following a @samp{/}.
1545 Note that @code{expand-file-name} does @emph{not} expand environment
1546 variables; only @code{substitute-in-file-name} does that.
1550 @defun file-relative-name filename &optional directory
1551 This function does the inverse of expansion---it tries to return a
1552 relative name that is equivalent to @var{filename} when interpreted
1553 relative to @var{directory}.
1556 If @var{directory} is @code{nil} or omitted, the value of
1557 @code{default-directory} is used.
1560 (file-relative-name "/foo/bar" "/foo/")
1562 (file-relative-name "/foo/bar" "/hack/")
1563 @result{} "../foo/bar")
1567 @defvar default-directory
1568 The value of this buffer-local variable is the default directory for the
1569 current buffer. It should be an absolute directory name; it may start
1570 with @samp{~}. This variable is local in every buffer.
1572 @code{expand-file-name} uses the default directory when its second
1573 argument is @code{nil}.
1575 On Unix systems, the value is always a string ending with a slash.
1580 @result{} "/user/lewis/manual/"
1585 @defun substitute-in-file-name filename
1586 This function replaces environment variable references in
1587 @var{filename} with the environment variable values. Following standard
1588 Unix shell syntax, @samp{$} is the prefix to substitute an environment
1591 The environment variable name is the series of alphanumeric characters
1592 (including underscores) that follow the @samp{$}. If the character following
1593 the @samp{$} is a @samp{@{}, then the variable name is everything up to the
1596 @c Wordy to avoid overfull hbox. --rjc 15mar92
1597 Here we assume that the environment variable @code{HOME}, which holds
1598 the user's home directory name, has value @samp{/xcssun/users/rms}.
1602 (substitute-in-file-name "$HOME/foo")
1603 @result{} "/xcssun/users/rms/foo"
1607 @c If a @samp{~} or a @samp{/} appears following a @samp{/}, after
1608 @c substitution, everything before the following @samp{/} is discarded:
1610 After substitution, a @samp{/} or @samp{~} following a @samp{/} is taken
1611 to be the start of an absolute file name that overrides what precedes
1612 it, so everything before that @samp{/} or @samp{~} is deleted. For
1617 (substitute-in-file-name "bar/~/foo")
1621 (substitute-in-file-name "/usr/local/$HOME/foo")
1622 @result{} "/xcssun/users/rms/foo"
1626 On VMS, @samp{$} substitution is not done, so this function does nothing
1627 on VMS except discard superfluous initial components as shown above.
1630 @node Unique File Names
1631 @subsection Generating Unique File Names
1633 Some programs need to write temporary files. Here is the usual way to
1634 construct a name for such a file:
1637 (make-temp-name (expand-file-name @var{name-of-application} (temp-directory)))
1641 Here we use @code{(temp-directory)} to specify a directory for temporary
1642 files---under Unix, it will normally evaluate to @file{"/tmp/"}. The
1643 job of @code{make-temp-name} is to prevent two different users or two
1644 different processes from trying to use the same name.
1646 @defun temp-directory
1647 This function returns the name of the directory to use for temporary
1648 files. Under Unix, this will be the value of @code{TMPDIR}, defaulting
1649 to @file{/tmp}. On Windows, this will be obtained from the @code{TEMP}
1650 or @code{TMP} environment variables, defaulting to @file{/}.
1652 Note that the @code{temp-directory} function does not exist under FSF
1656 @defun make-temp-name prefix
1657 This function generates a temporary file name starting with
1658 @var{prefix}. The Emacs process number forms part of the result, so
1659 there is no danger of generating a name being used by another process.
1663 (make-temp-name "/tmp/foo")
1664 @result{} "/tmp/fooGaAQjC"
1668 In addition, this function makes an attempt to choose a name that does
1669 not specify an existing file. To make this work, @var{prefix} should be
1670 an absolute file name.
1672 To avoid confusion, each Lisp application should preferably use a unique
1673 @var{prefix} to @code{make-temp-name}.
1676 @node File Name Completion
1677 @subsection File Name Completion
1678 @cindex file name completion subroutines
1679 @cindex completion, file name
1681 This section describes low-level subroutines for completing a file
1682 name. For other completion functions, see @ref{Completion}.
1684 @defun file-name-all-completions partial-filename directory
1685 This function returns a list of all possible completions for a file
1686 whose name starts with @var{partial-filename} in directory
1687 @var{directory}. The order of the completions is the order of the files
1688 in the directory, which is unpredictable and conveys no useful
1691 The argument @var{partial-filename} must be a file name containing no
1692 directory part and no slash. The current buffer's default directory is
1693 prepended to @var{directory}, if @var{directory} is not absolute.
1695 In the following example, suppose that the current default directory,
1696 @file{~rms/lewis}, has five files whose names begin with @samp{f}:
1697 @file{foo}, @file{file~}, @file{file.c}, @file{file.c.~1~}, and
1698 @file{file.c.~2~}.@refill
1702 (file-name-all-completions "f" "")
1703 @result{} ("foo" "file~" "file.c.~2~"
1704 "file.c.~1~" "file.c")
1708 (file-name-all-completions "fo" "")
1714 @defun file-name-completion filename directory
1715 This function completes the file name @var{filename} in directory
1716 @var{directory}. It returns the longest prefix common to all file names
1717 in directory @var{directory} that start with @var{filename}.
1719 If only one match exists and @var{filename} matches it exactly, the
1720 function returns @code{t}. The function returns @code{nil} if directory
1721 @var{directory} contains no name starting with @var{filename}.
1723 In the following example, suppose that the current default directory
1724 has five files whose names begin with @samp{f}: @file{foo},
1725 @file{file~}, @file{file.c}, @file{file.c.~1~}, and
1726 @file{file.c.~2~}.@refill
1730 (file-name-completion "fi" "")
1735 (file-name-completion "file.c.~1" "")
1736 @result{} "file.c.~1~"
1740 (file-name-completion "file.c.~1~" "")
1745 (file-name-completion "file.c.~3" "")
1751 @defopt completion-ignored-extensions
1752 @code{file-name-completion} usually ignores file names that end in any
1753 string in this list. It does not ignore them when all the possible
1754 completions end in one of these suffixes or when a buffer showing all
1755 possible completions is displayed.@refill
1757 A typical value might look like this:
1761 completion-ignored-extensions
1762 @result{} (".o" ".elc" "~" ".dvi")
1767 @node User Name Completion
1768 @subsection User Name Completion
1769 @cindex user name completion subroutines
1770 @cindex completion, user name
1772 This section describes low-level subroutines for completing a user
1773 name. For other completion functions, see @ref{Completion}.
1775 @defun user-name-all-completions partial-username
1776 This function returns a list of all possible completions for a user
1777 whose name starts with @var{partial-username}. The order of the
1778 completions is unpredictable and conveys no useful information.
1780 The argument @var{partial-username} must be a partial user name
1781 containing no tilde character and no slash.
1784 @defun user-name-completion username
1785 This function completes the user name @var{username}. It returns the
1786 longest prefix common to all user names that start with @var{username}.
1788 If only one match exists and @var{username} matches it exactly, the
1789 function returns @code{t}. The function returns @code{nil} if no user
1790 name starting with @var{username} exists.
1793 @defun user-name-completion-1 username
1794 This function completes the user name @var{username}, like
1795 @code{user-name-completion}, differing only in the return value.
1796 This function returns the cons of the completion returned by
1797 @code{user-name-completion}, and a boolean indicating whether that
1798 completion was unique.
1802 @node Contents of Directories
1803 @section Contents of Directories
1804 @cindex directory-oriented functions
1805 @cindex file names in directory
1807 A directory is a kind of file that contains other files entered under
1808 various names. Directories are a feature of the file system.
1810 XEmacs can list the names of the files in a directory as a Lisp list,
1811 or display the names in a buffer using the @code{ls} shell command. In
1812 the latter case, it can optionally display information about each file,
1813 depending on the value of switches passed to the @code{ls} command.
1815 @defun directory-files directory &optional full-name match-regexp nosort files-only
1816 This function returns a list of the names of the files in the directory
1817 @var{directory}. By default, the list is in alphabetical order.
1819 If @var{full-name} is non-@code{nil}, the function returns the files'
1820 absolute file names. Otherwise, it returns just the names relative to
1821 the specified directory.
1823 If @var{match-regexp} is non-@code{nil}, this function returns only
1824 those file names that contain that regular expression---the other file
1825 names are discarded from the list.
1828 If @var{nosort} is non-@code{nil}, @code{directory-files} does not sort
1829 the list, so you get the file names in no particular order. Use this if
1830 you want the utmost possible speed and don't care what order the files
1831 are processed in. If the order of processing is visible to the user,
1832 then the user will probably be happier if you do sort the names.
1835 If @var{files-only} is the symbol @code{t}, then only the ``files'' in
1836 the directory will be returned; subdirectories will be excluded. If
1837 @var{files-only} is not @code{nil} and not @code{t}, then only the
1838 subdirectories will be returned. Otherwise, if @var{files-only} is
1839 @code{nil} (the default) then both files and subdirectories will be
1844 (directory-files "~lewis")
1845 @result{} ("#foo#" "#foo.el#" "." ".."
1846 "dired-mods.el" "files.texi"
1851 An error is signaled if @var{directory} is not the name of a directory
1855 @ignore @c Not in XEmacs
1856 @defun file-name-all-versions file dirname
1857 This function returns a list of all versions of the file named
1858 @var{file} in directory @var{dirname}.
1862 @defun insert-directory file switches &optional wildcard full-directory-p
1863 This function inserts (in the current buffer) a directory listing for
1864 directory @var{file}, formatted with @code{ls} according to
1865 @var{switches}. It leaves point after the inserted text.
1867 The argument @var{file} may be either a directory name or a file
1868 specification including wildcard characters. If @var{wildcard} is
1869 non-@code{nil}, that means treat @var{file} as a file specification with
1872 If @var{full-directory-p} is non-@code{nil}, that means @var{file} is a
1873 directory and switches do not contain @samp{-d}, so that the listing
1874 should show the full contents of the directory. (The @samp{-d} option
1875 to @code{ls} says to describe a directory itself rather than its
1878 This function works by running a directory listing program whose name is
1879 in the variable @code{insert-directory-program}. If @var{wildcard} is
1880 non-@code{nil}, it also runs the shell specified by
1881 @code{shell-file-name}, to expand the wildcards.
1884 @defvar insert-directory-program
1885 This variable's value is the program to run to generate a directory listing
1886 for the function @code{insert-directory}.
1889 @node Create/Delete Dirs
1890 @section Creating and Deleting Directories
1891 @c Emacs 19 features
1893 Most XEmacs Lisp file-manipulation functions get errors when used on
1894 files that are directories. For example, you cannot delete a directory
1895 with @code{delete-file}. These special functions exist to create and
1898 @deffn Command make-directory dirname &optional parents
1899 This function creates a directory named @var{dirname}. Interactively,
1900 the default choice of directory to create is the current default
1901 directory for file names. That is useful when you have visited a file
1902 in a nonexistent directory.
1905 Non-interactively, optional argument @var{parents} says whether to
1906 create parent directories if they don't exist. (Interactively, this
1910 @deffn Command delete-directory dirname
1911 This function deletes the directory named @var{dirname}. The function
1912 @code{delete-file} does not work for files that are directories; you
1913 must use @code{delete-directory} in that case.
1916 @node Magic File Names
1917 @section Making Certain File Names ``Magic''
1918 @cindex magic file names
1921 You can implement special handling for certain file names. This is
1922 called making those names @dfn{magic}. You must supply a regular
1923 expression to define the class of names (all those that match the
1924 regular expression), plus a handler that implements all the primitive
1925 XEmacs file operations for file names that do match.
1927 The variable @code{file-name-handler-alist} holds a list of handlers,
1928 together with regular expressions that determine when to apply each
1929 handler. Each element has this form:
1932 (@var{regexp} . @var{handler})
1936 All the XEmacs primitives for file access and file name transformation
1937 check the given file name against @code{file-name-handler-alist}. If
1938 the file name matches @var{regexp}, the primitives handle that file by
1939 calling @var{handler}.
1941 The first argument given to @var{handler} is the name of the primitive;
1942 the remaining arguments are the arguments that were passed to that
1943 operation. (The first of these arguments is typically the file name
1944 itself.) For example, if you do this:
1947 (file-exists-p @var{filename})
1951 and @var{filename} has handler @var{handler}, then @var{handler} is
1955 (funcall @var{handler} 'file-exists-p @var{filename})
1958 Here are the operations that a magic file name handler gets to handle:
1961 @code{add-name-to-file}, @code{copy-file}, @code{delete-directory},
1962 @code{delete-file},@*
1963 @code{diff-latest-backup-file},
1964 @code{directory-file-name},
1965 @code{directory-files},
1966 @code{dired-compress-file}, @code{dired-uncache},
1967 @code{expand-file-name},@*
1968 @code{file-accessible-directory-p},
1969 @code{file-attributes}, @code{file-directory-p},
1970 @code{file-executable-p}, @code{file-exists-p}, @code{file-local-copy},
1971 @code{file-modes}, @code{file-name-all-completions},
1972 @code{file-name-as-directory}, @code{file-name-completion},
1973 @code{file-name-directory}, @code{file-name-nondirectory},
1974 @code{file-name-sans-versions}, @code{file-newer-than-file-p},
1975 @code{file-readable-p}, @code{file-regular-p}, @code{file-symlink-p},
1976 @code{file-truename}, @code{file-writable-p},
1977 @code{get-file-buffer},
1978 @code{insert-directory},
1979 @code{insert-file-contents}, @code{load}, @code{make-directory},
1980 @code{make-symbolic-link}, @code{rename-file}, @code{set-file-modes},
1981 @code{set-visited-file-modtime}, @code{unhandled-file-name-directory},
1982 @code{verify-visited-file-modtime}, @code{write-region}.
1984 Handlers for @code{insert-file-contents} typically need to clear the
1985 buffer's modified flag, with @code{(set-buffer-modified-p nil)}, if the
1986 @var{visit} argument is non-@code{nil}. This also has the effect of
1987 unlocking the buffer if it is locked.
1989 The handler function must handle all of the above operations, and
1990 possibly others to be added in the future. It need not implement all
1991 these operations itself---when it has nothing special to do for a
1992 certain operation, it can reinvoke the primitive, to handle the
1993 operation ``in the usual way''. It should always reinvoke the primitive
1994 for an operation it does not recognize. Here's one way to do this:
1997 (defun my-file-handler (operation &rest args)
1998 ;; @r{First check for the specific operations}
1999 ;; @r{that we have special handling for.}
2000 (cond ((eq operation 'insert-file-contents) @dots{})
2001 ((eq operation 'write-region) @dots{})
2003 ;; @r{Handle any operation we don't know about.}
2004 (t (let ((inhibit-file-name-handlers
2005 (cons 'my-file-handler
2006 (and (eq inhibit-file-name-operation operation)
2007 inhibit-file-name-handlers)))
2008 (inhibit-file-name-operation operation))
2009 (apply operation args)))))
2012 When a handler function decides to call the ordinary Emacs primitive for
2013 the operation at hand, it needs to prevent the primitive from calling
2014 the same handler once again, thus leading to an infinite recursion. The
2015 example above shows how to do this, with the variables
2016 @code{inhibit-file-name-handlers} and
2017 @code{inhibit-file-name-operation}. Be careful to use them exactly as
2018 shown above; the details are crucial for proper behavior in the case of
2019 multiple handlers, and for operations that have two file names that may
2022 @defvar inhibit-file-name-handlers
2023 This variable holds a list of handlers whose use is presently inhibited
2024 for a certain operation.
2027 @defvar inhibit-file-name-operation
2028 The operation for which certain handlers are presently inhibited.
2031 @defun find-file-name-handler file operation
2032 This function returns the handler function for file name @var{file}, or
2033 @code{nil} if there is none. The argument @var{operation} should be the
2034 operation to be performed on the file---the value you will pass to the
2035 handler as its first argument when you call it. The operation is needed
2036 for comparison with @code{inhibit-file-name-operation}.
2039 @defun file-local-copy filename
2040 This function copies file @var{filename} to an ordinary non-magic file,
2041 if it isn't one already.
2043 If @var{filename} specifies a ``magic'' file name, which programs
2044 outside Emacs cannot directly read or write, this copies the contents to
2045 an ordinary file and returns that file's name.
2047 If @var{filename} is an ordinary file name, not magic, then this function
2048 does nothing and returns @code{nil}.
2051 @defun unhandled-file-name-directory filename
2052 This function returns the name of a directory that is not magic.
2053 It uses the directory part of @var{filename} if that is not magic.
2054 Otherwise, it asks the handler what to do.
2056 This is useful for running a subprocess; every subprocess must have a
2057 non-magic directory to serve as its current directory, and this function
2058 is a good way to come up with one.
2062 @section Partial Files
2063 @cindex partial files
2066 * Intro to Partial Files::
2067 * Creating a Partial File::
2068 * Detached Partial Files::
2071 @node Intro to Partial Files
2072 @subsection Intro to Partial Files
2074 A @dfn{partial file} is a section of a buffer (called the @dfn{master
2075 buffer}) that is placed in its own buffer and treated as its own file.
2076 Changes made to the partial file are not reflected in the master buffer
2077 until the partial file is ``saved'' using the standard buffer save
2078 commands. Partial files can be ``reverted'' (from the master buffer)
2079 just like normal files. When a file part is active on a master buffer,
2080 that section of the master buffer is marked as read-only. Two file
2081 parts on the same master buffer are not allowed to overlap. Partial
2082 file buffers are indicated by the words @samp{File Part} in the
2085 The master buffer knows about all the partial files that are active on
2086 it, and thus killing or reverting the master buffer will be handled
2087 properly. When the master buffer is saved, if there are any unsaved
2088 partial files active on it then the user will be given the opportunity
2089 to first save these files.
2091 When a partial file buffer is first modified, the master buffer is
2092 automatically marked as modified so that saving the master buffer will
2095 @node Creating a Partial File
2096 @subsection Creating a Partial File
2098 @defun make-file-part &optional start end name buffer
2099 Make a file part on buffer @var{buffer} out of the region. Call it
2100 @var{name}. This command creates a new buffer containing the contents
2101 of the region and marks the buffer as referring to the specified buffer,
2102 called the @dfn{master buffer}. When the file-part buffer is saved, its
2103 changes are integrated back into the master buffer. When the master
2104 buffer is deleted, all file parts are deleted with it.
2106 When called from a function, expects four arguments, @var{start},
2107 @var{end}, @var{name}, and @var{buffer}, all of which are optional and
2108 default to the beginning of @var{buffer}, the end of @var{buffer}, a
2109 name generated from @var{buffer} name, and the current buffer,
2113 @node Detached Partial Files
2114 @subsection Detached Partial Files
2116 Every partial file has an extent in the master buffer associated with it
2117 (called the @dfn{master extent}), marking where in the master buffer the
2118 partial file begins and ends. If the text in master buffer that is
2119 contained by the extent is deleted, then the extent becomes
2120 ``detached'', meaning that it no longer refers to a specific region of
2121 the master buffer. This can happen either when the text is deleted
2122 directly or when the master buffer is reverted. Neither of these should
2123 happen in normal usage because the master buffer should generally not be
2126 Before doing any operation that references a partial file's master
2127 extent, XEmacs checks to make sure that the extent is not detached. If
2128 this is the case, XEmacs warns the user of this and the master extent is
2129 deleted out of the master buffer, disconnecting the file part. The file
2130 part's filename is cleared and thus must be explicitly specified if the
2131 detached file part is to be saved.
2133 @node Format Conversion
2134 @section File Format Conversion
2136 @cindex file format conversion
2137 @cindex encoding file formats
2138 @cindex decoding file formats
2139 The variable @code{format-alist} defines a list of @dfn{file formats},
2140 which describe textual representations used in files for the data (text,
2141 text-properties, and possibly other information) in an Emacs buffer.
2142 Emacs performs format conversion if appropriate when reading and writing
2145 @defvar format-alist
2146 This list contains one format definition for each defined file format.
2149 @cindex format definition
2150 Each format definition is a list of this form:
2153 (@var{name} @var{doc-string} @var{regexp} @var{from-fn} @var{to-fn} @var{modify} @var{mode-fn})
2156 Here is what the elements in a format definition mean:
2160 The name of this format.
2163 A documentation string for the format.
2166 A regular expression which is used to recognize files represented in
2170 A function to call to decode data in this format (to convert file data into
2171 the usual Emacs data representation).
2173 The @var{from-fn} is called with two args, @var{begin} and @var{end},
2174 which specify the part of the buffer it should convert. It should convert
2175 the text by editing it in place. Since this can change the length of the
2176 text, @var{from-fn} should return the modified end position.
2178 One responsibility of @var{from-fn} is to make sure that the beginning
2179 of the file no longer matches @var{regexp}. Otherwise it is likely to
2183 A function to call to encode data in this format (to convert
2184 the usual Emacs data representation into this format).
2186 The @var{to-fn} is called with two args, @var{begin} and @var{end},
2187 which specify the part of the buffer it should convert. There are
2188 two ways it can do the conversion:
2192 By editing the buffer in place. In this case, @var{to-fn} should
2193 return the end-position of the range of text, as modified.
2196 By returning a list of annotations. This is a list of elements of the
2197 form @code{(@var{position} . @var{string})}, where @var{position} is an
2198 integer specifying the relative position in the text to be written, and
2199 @var{string} is the annotation to add there. The list must be sorted in
2200 order of position when @var{to-fn} returns it.
2202 When @code{write-region} actually writes the text from the buffer to the
2203 file, it intermixes the specified annotations at the corresponding
2204 positions. All this takes place without modifying the buffer.
2208 A flag, @code{t} if the encoding function modifies the buffer, and
2209 @code{nil} if it works by returning a list of annotations.
2212 A mode function to call after visiting a file converted from this
2216 The function @code{insert-file-contents} automatically recognizes file
2217 formats when it reads the specified file. It checks the text of the
2218 beginning of the file against the regular expressions of the format
2219 definitions, and if it finds a match, it calls the decoding function for
2220 that format. Then it checks all the known formats over again.
2221 It keeps checking them until none of them is applicable.
2223 Visiting a file, with @code{find-file-noselect} or the commands that use
2224 it, performs conversion likewise (because it calls
2225 @code{insert-file-contents}); it also calls the mode function for each
2226 format that it decodes. It stores a list of the format names in the
2227 buffer-local variable @code{buffer-file-format}.
2229 @defvar buffer-file-format
2230 This variable states the format of the visited file. More precisely,
2231 this is a list of the file format names that were decoded in the course
2232 of visiting the current buffer's file. It is always local in all
2236 When @code{write-region} writes data into a file, it first calls the
2237 encoding functions for the formats listed in @code{buffer-file-format},
2238 in the order of appearance in the list.
2240 @defun format-write-file file format
2241 This command writes the current buffer contents into the file @var{file}
2242 in format @var{format}, and makes that format the default for future
2243 saves of the buffer. The argument @var{format} is a list of format
2247 @defun format-find-file file format
2248 This command finds the file @var{file}, converting it according to
2249 format @var{format}. It also makes @var{format} the default if the
2250 buffer is saved later.
2252 The argument @var{format} is a list of format names. If @var{format} is
2253 @code{nil}, no conversion takes place. Interactively, typing just
2254 @key{RET} for @var{format} specifies @code{nil}.
2257 @defun format-insert-file file format &optional beg end
2258 This command inserts the contents of file @var{file}, converting it
2259 according to format @var{format}. If @var{beg} and @var{end} are
2260 non-@code{nil}, they specify which part of the file to read, as in
2261 @code{insert-file-contents} (@pxref{Reading from Files}).
2263 The return value is like what @code{insert-file-contents} returns: a
2264 list of the absolute file name and the length of the data inserted
2267 The argument @var{format} is a list of format names. If @var{format} is
2268 @code{nil}, no conversion takes place. Interactively, typing just
2269 @key{RET} for @var{format} specifies @code{nil}.
2272 @defun format-find-file file format
2273 This command finds the file @var{file}, converting it according to
2274 format @var{format}. It also makes @var{format} the default if the
2275 buffer is saved later.
2277 The argument @var{format} is a list of format names. If @var{format} is
2278 @code{nil}, no conversion takes place. Interactively, typing just
2279 @key{RET} for @var{format} specifies @code{nil}.
2282 @defun format-insert-file file format &optional beg end
2283 This command inserts the contents of file @var{file}, converting it
2284 according to format @var{format}. If @var{beg} and @var{end} are
2285 non-@code{nil}, they specify which part of the file to read,
2286 as in @code{insert-file-contents} (@pxref{Reading from Files}).
2288 The return value is like what @code{insert-file-contents} returns: a
2289 list of the absolute file name and the length of the data inserted
2292 The argument @var{format} is a list of format names. If @var{format} is
2293 @code{nil}, no conversion takes place. Interactively, typing just
2294 @key{RET} for @var{format} specifies @code{nil}.
2297 @defvar auto-save-file-format
2298 This variable specifies the format to use for auto-saving. Its value is
2299 a list of format names, just like the value of
2300 @code{buffer-file-format}; but it is used instead of
2301 @code{buffer-file-format} for writing auto-save files. This variable
2302 is always local in all buffers.
2305 @node Files and MS-DOS
2306 @section Files and MS-DOS
2307 @cindex MS-DOS file types
2308 @cindex file types on MS-DOS
2309 @cindex text files and binary files
2310 @cindex binary files and text files
2312 Emacs on MS-DOS makes a distinction between text files and binary
2313 files. This is necessary because ordinary text files on MS-DOS use a
2314 two character sequence between lines: carriage-return and linefeed
2315 (@sc{crlf}). Emacs expects just a newline character (a linefeed) between
2316 lines. When Emacs reads or writes a text file on MS-DOS, it needs to
2317 convert the line separators. This means it needs to know which files
2318 are text files and which are binary. It makes this decision when
2319 visiting a file, and records the decision in the variable
2320 @code{buffer-file-type} for use when the file is saved.
2322 @xref{MS-DOS Subprocesses}, for a related feature for subprocesses.
2324 @defvar buffer-file-type
2325 This variable, automatically local in each buffer, records the file type
2326 of the buffer's visited file. The value is @code{nil} for text,
2327 @code{t} for binary.
2330 @defun find-buffer-file-type filename
2331 This function determines whether file @var{filename} is a text file
2332 or a binary file. It returns @code{nil} for text, @code{t} for binary.
2335 @defopt file-name-buffer-file-type-alist
2336 This variable holds an alist for distinguishing text files from binary
2337 files. Each element has the form (@var{regexp} . @var{type}), where
2338 @var{regexp} is matched against the file name, and @var{type} may be is
2339 @code{nil} for text, @code{t} for binary, or a function to call to
2340 compute which. If it is a function, then it is called with a single
2341 argument (the file name) and should return @code{t} or @code{nil}.
2344 @defopt default-buffer-file-type
2345 This variable specifies the default file type for files whose names
2346 don't indicate anything in particular. Its value should be @code{nil}
2347 for text, or @code{t} for binary.
2350 @deffn Command find-file-text filename
2351 Like @code{find-file}, but treat the file as text regardless of its name.
2354 @deffn Command find-file-binary filename
2355 Like @code{find-file}, but treat the file as binary regardless of its