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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
fd897522 GM |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
4 | @c Free Software Foundation, Inc. | |
3e01fd9d RS |
5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/files | |
7 | @node Files, Backups and Auto-Saving, Documentation, Top | |
8 | @comment node-name, next, previous, up | |
9 | @chapter Files | |
10 | ||
11 | In Emacs, you can find, create, view, save, and otherwise work with | |
12 | files and file directories. This chapter describes most of the | |
13 | file-related functions of Emacs Lisp, but a few others are described in | |
14 | @ref{Buffers}, and those related to backups and auto-saving are | |
15 | described in @ref{Backups and Auto-Saving}. | |
16 | ||
b22f3a19 RS |
17 | Many of the file functions take one or more arguments that are file |
18 | names. A file name is actually a string. Most of these functions | |
a9f0a989 | 19 | expand file name arguments by calling @code{expand-file-name}, so that |
b22f3a19 RS |
20 | @file{~} is handled correctly, as are relative file names (including |
21 | @samp{../}). These functions don't recognize environment variable | |
22 | substitutions such as @samp{$HOME}. @xref{File Name Expansion}. | |
23 | ||
2468d0c0 DL |
24 | When file I/O functions signal Lisp errors, they usually use the |
25 | condition @code{file-error} (@pxref{Handling Errors}). The error | |
26 | message is in most cases obtained from the operating system, according | |
27 | to locale @code{system-message-locale}, and decoded using coding system | |
28 | @code{locale-coding-system} (@pxref{Locales}). | |
29 | ||
3e01fd9d RS |
30 | @menu |
31 | * Visiting Files:: Reading files into Emacs buffers for editing. | |
32 | * Saving Buffers:: Writing changed buffers back into files. | |
33 | * Reading from Files:: Reading files into buffers without visiting. | |
34 | * Writing to Files:: Writing new files from parts of buffers. | |
35 | * File Locks:: Locking and unlocking files, to prevent | |
36 | simultaneous editing by two people. | |
37 | * Information about Files:: Testing existence, accessibility, size of files. | |
f9f59935 | 38 | * Changing Files:: Renaming files, changing protection, etc. |
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39 | * File Names:: Decomposing and expanding file names. |
40 | * Contents of Directories:: Getting a list of the files in a directory. | |
41 | * Create/Delete Dirs:: Creating and Deleting Directories. | |
42 | * Magic File Names:: Defining "magic" special handling | |
43 | for certain file names. | |
22697dac | 44 | * Format Conversion:: Conversion to and from various file formats. |
3e01fd9d RS |
45 | @end menu |
46 | ||
47 | @node Visiting Files | |
48 | @section Visiting Files | |
49 | @cindex finding files | |
50 | @cindex visiting files | |
51 | ||
52 | Visiting a file means reading a file into a buffer. Once this is | |
53 | done, we say that the buffer is @dfn{visiting} that file, and call the | |
54 | file ``the visited file'' of the buffer. | |
55 | ||
56 | A file and a buffer are two different things. A file is information | |
57 | recorded permanently in the computer (unless you delete it). A buffer, | |
58 | on the other hand, is information inside of Emacs that will vanish at | |
59 | the end of the editing session (or when you kill the buffer). Usually, | |
60 | a buffer contains information that you have copied from a file; then we | |
61 | say the buffer is visiting that file. The copy in the buffer is what | |
62 | you modify with editing commands. Such changes to the buffer do not | |
63 | change the file; therefore, to make the changes permanent, you must | |
64 | @dfn{save} the buffer, which means copying the altered buffer contents | |
65 | back into the file. | |
66 | ||
67 | In spite of the distinction between files and buffers, people often | |
68 | refer to a file when they mean a buffer and vice-versa. Indeed, we say, | |
b22f3a19 | 69 | ``I am editing a file,'' rather than, ``I am editing a buffer that I |
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70 | will soon save as a file of the same name.'' Humans do not usually need |
71 | to make the distinction explicit. When dealing with a computer program, | |
72 | however, it is good to keep the distinction in mind. | |
73 | ||
74 | @menu | |
75 | * Visiting Functions:: The usual interface functions for visiting. | |
76 | * Subroutines of Visiting:: Lower-level subroutines that they use. | |
77 | @end menu | |
78 | ||
79 | @node Visiting Functions | |
80 | @subsection Functions for Visiting Files | |
81 | ||
82 | This section describes the functions normally used to visit files. | |
83 | For historical reasons, these functions have names starting with | |
84 | @samp{find-} rather than @samp{visit-}. @xref{Buffer File Name}, for | |
85 | functions and variables that access the visited file name of a buffer or | |
86 | that find an existing buffer by its visited file name. | |
87 | ||
bfe721d1 KH |
88 | In a Lisp program, if you want to look at the contents of a file but |
89 | not alter it, the fastest way is to use @code{insert-file-contents} in a | |
90 | temporary buffer. Visiting the file is not necessary and takes longer. | |
91 | @xref{Reading from Files}. | |
92 | ||
b6954afd | 93 | @deffn Command find-file filename &optional wildcards |
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94 | This command selects a buffer visiting the file @var{filename}, |
95 | using an existing buffer if there is one, and otherwise creating a | |
96 | new buffer and reading the file into it. It also returns that buffer. | |
97 | ||
98 | The body of the @code{find-file} function is very simple and looks | |
99 | like this: | |
100 | ||
101 | @example | |
102 | (switch-to-buffer (find-file-noselect filename)) | |
103 | @end example | |
104 | ||
105 | @noindent | |
106 | (See @code{switch-to-buffer} in @ref{Displaying Buffers}.) | |
107 | ||
b6954afd RS |
108 | If @var{wildcards} is non-@code{nil}, which is always true in an |
109 | interactive call, then @code{find-file} expands wildcard characters in | |
110 | @var{filename} and visits all the matching files. | |
111 | ||
3e01fd9d RS |
112 | When @code{find-file} is called interactively, it prompts for |
113 | @var{filename} in the minibuffer. | |
114 | @end deffn | |
115 | ||
b6954afd | 116 | @defun find-file-noselect filename &optional nowarn rawfile wildcards |
3e01fd9d RS |
117 | This function is the guts of all the file-visiting functions. It finds |
118 | or creates a buffer visiting the file @var{filename}, and returns it. | |
119 | It uses an existing buffer if there is one, and otherwise creates a new | |
120 | buffer and reads the file into it. You may make the buffer current or | |
121 | display it in a window if you wish, but this function does not do so. | |
122 | ||
08f0f5e9 KH |
123 | If @var{wildcards} is non-@code{nil}, |
124 | then @code{find-file-noselect} expands wildcard | |
b6954afd RS |
125 | characters in @var{filename} and visits all the matching files. |
126 | ||
3e01fd9d RS |
127 | When @code{find-file-noselect} uses an existing buffer, it first |
128 | verifies that the file has not changed since it was last visited or | |
129 | saved in that buffer. If the file has changed, then this function asks | |
130 | the user whether to reread the changed file. If the user says | |
131 | @samp{yes}, any changes previously made in the buffer are lost. | |
132 | ||
f9f59935 | 133 | This function displays warning or advisory messages in various peculiar |
969fe9b5 RS |
134 | cases, unless the optional argument @var{nowarn} is non-@code{nil}. For |
135 | example, if it needs to create a buffer, and there is no file named | |
8241495d | 136 | @var{filename}, it displays the message @samp{(New file)} in the echo |
969fe9b5 | 137 | area, and leaves the buffer empty. |
f9f59935 RS |
138 | |
139 | The @code{find-file-noselect} function normally calls | |
140 | @code{after-find-file} after reading the file (@pxref{Subroutines of | |
141 | Visiting}). That function sets the buffer major mode, parses local | |
142 | variables, warns the user if there exists an auto-save file more recent | |
143 | than the file just visited, and finishes by running the functions in | |
144 | @code{find-file-hooks}. | |
145 | ||
146 | If the optional argument @var{rawfile} is non-@code{nil}, then | |
147 | @code{after-find-file} is not called, and the | |
148 | @code{find-file-not-found-hooks} are not run in case of failure. What's | |
149 | more, a non-@code{nil} @var{rawfile} value suppresses coding system | |
150 | conversion (@pxref{Coding Systems}) and format conversion (@pxref{Format | |
151 | Conversion}). | |
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152 | |
153 | The @code{find-file-noselect} function returns the buffer that is | |
154 | visiting the file @var{filename}. | |
155 | ||
156 | @example | |
157 | @group | |
158 | (find-file-noselect "/etc/fstab") | |
159 | @result{} #<buffer fstab> | |
160 | @end group | |
161 | @end example | |
162 | @end defun | |
163 | ||
b6954afd | 164 | @deffn Command find-file-other-window filename &optional wildcards |
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165 | This command selects a buffer visiting the file @var{filename}, but |
166 | does so in a window other than the selected window. It may use another | |
167 | existing window or split a window; see @ref{Displaying Buffers}. | |
168 | ||
169 | When this command is called interactively, it prompts for | |
170 | @var{filename}. | |
171 | @end deffn | |
172 | ||
b6954afd | 173 | @deffn Command find-file-read-only filename &optional wildcards |
3e01fd9d RS |
174 | This command selects a buffer visiting the file @var{filename}, like |
175 | @code{find-file}, but it marks the buffer as read-only. @xref{Read Only | |
176 | Buffers}, for related functions and variables. | |
177 | ||
178 | When this command is called interactively, it prompts for | |
179 | @var{filename}. | |
180 | @end deffn | |
181 | ||
182 | @deffn Command view-file filename | |
f1e2c45e RS |
183 | This command visits @var{filename} using View mode, returning to the |
184 | previous buffer when you exit View mode. View mode is a minor mode that | |
185 | provides commands to skim rapidly through the file, but does not let you | |
186 | modify the text. Entering View mode runs the normal hook | |
bfe721d1 | 187 | @code{view-mode-hook}. @xref{Hooks}. |
3e01fd9d RS |
188 | |
189 | When @code{view-file} is called interactively, it prompts for | |
190 | @var{filename}. | |
191 | @end deffn | |
192 | ||
b6954afd RS |
193 | @tindex find-file-wildcards |
194 | @defvar find-file-wildcards | |
195 | If this variable is non-@code{nil}, then the various @code{find-file} | |
196 | commands check for wildcard characters and visit all the files that | |
197 | match them. If this is @code{nil}, then wildcard characters are | |
198 | not treated specially. | |
199 | @end defvar | |
200 | ||
3e01fd9d RS |
201 | @defvar find-file-hooks |
202 | The value of this variable is a list of functions to be called after a | |
203 | file is visited. The file's local-variables specification (if any) will | |
204 | have been processed before the hooks are run. The buffer visiting the | |
205 | file is current when the hook functions are run. | |
206 | ||
207 | This variable works just like a normal hook, but we think that renaming | |
f1e2c45e | 208 | it would not be advisable. @xref{Hooks}. |
3e01fd9d RS |
209 | @end defvar |
210 | ||
211 | @defvar find-file-not-found-hooks | |
212 | The value of this variable is a list of functions to be called when | |
213 | @code{find-file} or @code{find-file-noselect} is passed a nonexistent | |
214 | file name. @code{find-file-noselect} calls these functions as soon as | |
215 | it detects a nonexistent file. It calls them in the order of the list, | |
216 | until one of them returns non-@code{nil}. @code{buffer-file-name} is | |
217 | already set up. | |
218 | ||
219 | This is not a normal hook because the values of the functions are | |
f9f59935 | 220 | used, and in many cases only some of the functions are called. |
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221 | @end defvar |
222 | ||
223 | @node Subroutines of Visiting | |
224 | @comment node-name, next, previous, up | |
225 | @subsection Subroutines of Visiting | |
226 | ||
a9f0a989 RS |
227 | The @code{find-file-noselect} function uses two important subroutines |
228 | which are sometimes useful in user Lisp code: @code{create-file-buffer} | |
229 | and @code{after-find-file}. This section explains how to use them. | |
3e01fd9d RS |
230 | |
231 | @defun create-file-buffer filename | |
232 | This function creates a suitably named buffer for visiting | |
233 | @var{filename}, and returns it. It uses @var{filename} (sans directory) | |
234 | as the name if that name is free; otherwise, it appends a string such as | |
235 | @samp{<2>} to get an unused name. See also @ref{Creating Buffers}. | |
236 | ||
237 | @strong{Please note:} @code{create-file-buffer} does @emph{not} | |
238 | associate the new buffer with a file and does not select the buffer. | |
bfe721d1 | 239 | It also does not use the default major mode. |
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240 | |
241 | @example | |
242 | @group | |
243 | (create-file-buffer "foo") | |
244 | @result{} #<buffer foo> | |
245 | @end group | |
246 | @group | |
247 | (create-file-buffer "foo") | |
248 | @result{} #<buffer foo<2>> | |
249 | @end group | |
250 | @group | |
251 | (create-file-buffer "foo") | |
252 | @result{} #<buffer foo<3>> | |
253 | @end group | |
254 | @end example | |
255 | ||
256 | This function is used by @code{find-file-noselect}. | |
257 | It uses @code{generate-new-buffer} (@pxref{Creating Buffers}). | |
258 | @end defun | |
259 | ||
2468d0c0 | 260 | @defun after-find-file &optional error warn noauto after-find-file-from-revert-buffer nomodes |
3e01fd9d RS |
261 | This function sets the buffer major mode, and parses local variables |
262 | (@pxref{Auto Major Mode}). It is called by @code{find-file-noselect} | |
263 | and by the default revert function (@pxref{Reverting}). | |
264 | ||
265 | @cindex new file message | |
266 | @cindex file open error | |
267 | If reading the file got an error because the file does not exist, but | |
268 | its directory does exist, the caller should pass a non-@code{nil} value | |
269 | for @var{error}. In that case, @code{after-find-file} issues a warning: | |
8241495d | 270 | @samp{(New file)}. For more serious errors, the caller should usually not |
3e01fd9d RS |
271 | call @code{after-find-file}. |
272 | ||
273 | If @var{warn} is non-@code{nil}, then this function issues a warning | |
274 | if an auto-save file exists and is more recent than the visited file. | |
275 | ||
2468d0c0 DL |
276 | If @var{noauto} is non-@code{nil}, that says not to enable or disable |
277 | Auto-Save mode. The mode remains enabled if it was enabled before. | |
278 | ||
279 | If @var{after-find-file-from-revert-buffer} is non-@code{nil}, that | |
280 | means this call was from @code{revert-buffer}. This has no direct | |
281 | effect, but some mode functions and hook functions check the value | |
282 | of this variable. | |
283 | ||
284 | If @var{nomodes} is non-@code{nil}, that means don't alter the buffer's | |
285 | major mode, don't process local variables specifications in the file, | |
286 | and don't run @code{find-file-hooks}. This feature is used by | |
287 | @code{revert-buffer} in some cases. | |
288 | ||
3e01fd9d | 289 | The last thing @code{after-find-file} does is call all the functions |
a9f0a989 | 290 | in the list @code{find-file-hooks}. |
3e01fd9d RS |
291 | @end defun |
292 | ||
293 | @node Saving Buffers | |
294 | @section Saving Buffers | |
295 | ||
296 | When you edit a file in Emacs, you are actually working on a buffer | |
297 | that is visiting that file---that is, the contents of the file are | |
298 | copied into the buffer and the copy is what you edit. Changes to the | |
299 | buffer do not change the file until you @dfn{save} the buffer, which | |
300 | means copying the contents of the buffer into the file. | |
301 | ||
302 | @deffn Command save-buffer &optional backup-option | |
303 | This function saves the contents of the current buffer in its visited | |
304 | file if the buffer has been modified since it was last visited or saved. | |
305 | Otherwise it does nothing. | |
306 | ||
307 | @code{save-buffer} is responsible for making backup files. Normally, | |
308 | @var{backup-option} is @code{nil}, and @code{save-buffer} makes a backup | |
b22f3a19 RS |
309 | file only if this is the first save since visiting the file. Other |
310 | values for @var{backup-option} request the making of backup files in | |
311 | other circumstances: | |
3e01fd9d RS |
312 | |
313 | @itemize @bullet | |
314 | @item | |
315 | With an argument of 4 or 64, reflecting 1 or 3 @kbd{C-u}'s, the | |
316 | @code{save-buffer} function marks this version of the file to be | |
317 | backed up when the buffer is next saved. | |
318 | ||
319 | @item | |
320 | With an argument of 16 or 64, reflecting 2 or 3 @kbd{C-u}'s, the | |
321 | @code{save-buffer} function unconditionally backs up the previous | |
322 | version of the file before saving it. | |
323 | @end itemize | |
324 | @end deffn | |
325 | ||
77ba49d8 | 326 | @deffn Command save-some-buffers &optional save-silently-p pred |
3e01fd9d RS |
327 | This command saves some modified file-visiting buffers. Normally it |
328 | asks the user about each buffer. But if @var{save-silently-p} is | |
329 | non-@code{nil}, it saves all the file-visiting buffers without querying | |
330 | the user. | |
331 | ||
77ba49d8 RS |
332 | The optional @var{pred} argument controls which buffers to ask about. |
333 | If it is @code{nil}, that means to ask only about file-visiting buffers. | |
334 | If it is @code{t}, that means also offer to save certain other non-file | |
335 | buffers---those that have a non-@code{nil} buffer-local value of | |
336 | @code{buffer-offer-save}. (A user who says @samp{yes} to saving a | |
337 | non-file buffer is asked to specify the file name to use.) The | |
338 | @code{save-buffers-kill-emacs} function passes the value @code{t} for | |
339 | @var{pred}. | |
340 | ||
341 | If @var{pred} is neither @code{t} nor @code{nil}, then it should be | |
342 | a function of no arguments. It will be called in each buffer to decide | |
343 | whether to offer to save that buffer. If it returns a non-@code{nil} | |
344 | value in a certain buffer, that means do offer to save that buffer. | |
3e01fd9d RS |
345 | @end deffn |
346 | ||
2468d0c0 | 347 | @deffn Command write-file filename &optional confirm |
3e01fd9d RS |
348 | This function writes the current buffer into file @var{filename}, makes |
349 | the buffer visit that file, and marks it not modified. Then it renames | |
350 | the buffer based on @var{filename}, appending a string like @samp{<2>} | |
351 | if necessary to make a unique buffer name. It does most of this work by | |
969fe9b5 RS |
352 | calling @code{set-visited-file-name} (@pxref{Buffer File Name}) and |
353 | @code{save-buffer}. | |
2468d0c0 DL |
354 | |
355 | If @var{confirm} is non-@code{nil}, that means to ask for confirmation | |
356 | before overwriting an existing file. | |
3e01fd9d RS |
357 | @end deffn |
358 | ||
2dd7b854 RS |
359 | Saving a buffer runs several hooks. It also performs format |
360 | conversion (@pxref{Format Conversion}), and may save text properties in | |
361 | ``annotations'' (@pxref{Saving Properties}). | |
362 | ||
3e01fd9d RS |
363 | @defvar write-file-hooks |
364 | The value of this variable is a list of functions to be called before | |
365 | writing out a buffer to its visited file. If one of them returns | |
366 | non-@code{nil}, the file is considered already written and the rest of | |
367 | the functions are not called, nor is the usual code for writing the file | |
368 | executed. | |
369 | ||
370 | If a function in @code{write-file-hooks} returns non-@code{nil}, it | |
371 | is responsible for making a backup file (if that is appropriate). | |
372 | To do so, execute the following code: | |
373 | ||
374 | @example | |
375 | (or buffer-backed-up (backup-buffer)) | |
376 | @end example | |
377 | ||
378 | You might wish to save the file modes value returned by | |
379 | @code{backup-buffer} and use that to set the mode bits of the file that | |
380 | you write. This is what @code{save-buffer} normally does. | |
381 | ||
a9f0a989 RS |
382 | The hook functions in @code{write-file-hooks} are also responsible for |
383 | encoding the data (if desired): they must choose a suitable coding | |
384 | system (@pxref{Lisp and Coding Systems}), perform the encoding | |
385 | (@pxref{Explicit Encoding}), and set @code{last-coding-system-used} to | |
f1e2c45e | 386 | the coding system that was used (@pxref{Encoding and I/O}). |
a9f0a989 | 387 | |
f9f59935 RS |
388 | Do not make this variable buffer-local. To set up buffer-specific hook |
389 | functions, use @code{write-contents-hooks} instead. | |
390 | ||
3e01fd9d RS |
391 | Even though this is not a normal hook, you can use @code{add-hook} and |
392 | @code{remove-hook} to manipulate the list. @xref{Hooks}. | |
393 | @end defvar | |
394 | ||
395 | @c Emacs 19 feature | |
396 | @defvar local-write-file-hooks | |
f9f59935 | 397 | This works just like @code{write-file-hooks}, but it is intended to be |
969fe9b5 RS |
398 | made buffer-local in particular buffers, and used for hooks that pertain |
399 | to the file name or the way the buffer contents were obtained. | |
3e01fd9d RS |
400 | |
401 | The variable is marked as a permanent local, so that changing the major | |
402 | mode does not alter a buffer-local value. This is convenient for | |
403 | packages that read ``file'' contents in special ways, and set up hooks | |
404 | to save the data in a corresponding way. | |
405 | @end defvar | |
406 | ||
407 | @c Emacs 19 feature | |
408 | @defvar write-contents-hooks | |
409 | This works just like @code{write-file-hooks}, but it is intended for | |
410 | hooks that pertain to the contents of the file, as opposed to hooks that | |
9d000842 | 411 | pertain to where the file came from. Such hooks are usually set up by |
633d651d RS |
412 | major modes, as buffer-local bindings for this variable. |
413 | ||
414 | This variable automatically becomes buffer-local whenever it is set; | |
415 | switching to a new major mode always resets this variable. When you use | |
416 | @code{add-hooks} to add an element to this hook, you should @emph{not} | |
417 | specify a non-@code{nil} @var{local} argument, since this variable is | |
969fe9b5 | 418 | used @emph{only} buffer-locally. |
3e01fd9d RS |
419 | @end defvar |
420 | ||
421 | @c Emacs 19 feature | |
422 | @defvar after-save-hook | |
423 | This normal hook runs after a buffer has been saved in its visited file. | |
f1e2c45e RS |
424 | One use of this hook is in Fast Lock mode; it uses this hook to save the |
425 | highlighting information in a cache file. | |
3e01fd9d RS |
426 | @end defvar |
427 | ||
428 | @defvar file-precious-flag | |
429 | If this variable is non-@code{nil}, then @code{save-buffer} protects | |
430 | against I/O errors while saving by writing the new file to a temporary | |
431 | name instead of the name it is supposed to have, and then renaming it to | |
432 | the intended name after it is clear there are no errors. This procedure | |
433 | prevents problems such as a lack of disk space from resulting in an | |
434 | invalid file. | |
435 | ||
63ff95ee MW |
436 | As a side effect, backups are necessarily made by copying. @xref{Rename |
437 | or Copy}. Yet, at the same time, saving a precious file always breaks | |
438 | all hard links between the file you save and other file names. | |
3e01fd9d | 439 | |
f1e2c45e | 440 | Some modes give this variable a non-@code{nil} buffer-local value |
969fe9b5 | 441 | in particular buffers. |
3e01fd9d RS |
442 | @end defvar |
443 | ||
444 | @defopt require-final-newline | |
445 | This variable determines whether files may be written out that do | |
446 | @emph{not} end with a newline. If the value of the variable is | |
447 | @code{t}, then @code{save-buffer} silently adds a newline at the end of | |
448 | the file whenever the buffer being saved does not already end in one. | |
449 | If the value of the variable is non-@code{nil}, but not @code{t}, then | |
450 | @code{save-buffer} asks the user whether to add a newline each time the | |
451 | case arises. | |
452 | ||
453 | If the value of the variable is @code{nil}, then @code{save-buffer} | |
454 | doesn't add newlines at all. @code{nil} is the default value, but a few | |
455 | major modes set it to @code{t} in particular buffers. | |
456 | @end defopt | |
457 | ||
969fe9b5 RS |
458 | See also the function @code{set-visited-file-name} (@pxref{Buffer File |
459 | Name}). | |
fbc1b72c | 460 | |
3e01fd9d RS |
461 | @node Reading from Files |
462 | @comment node-name, next, previous, up | |
463 | @section Reading from Files | |
464 | ||
465 | You can copy a file from the disk and insert it into a buffer | |
466 | using the @code{insert-file-contents} function. Don't use the user-level | |
467 | command @code{insert-file} in a Lisp program, as that sets the mark. | |
468 | ||
469 | @defun insert-file-contents filename &optional visit beg end replace | |
470 | This function inserts the contents of file @var{filename} into the | |
63ff95ee | 471 | current buffer after point. It returns a list of the absolute file name |
3e01fd9d RS |
472 | and the length of the data inserted. An error is signaled if |
473 | @var{filename} is not the name of a file that can be read. | |
474 | ||
bfe721d1 KH |
475 | The function @code{insert-file-contents} checks the file contents |
476 | against the defined file formats, and converts the file contents if | |
477 | appropriate. @xref{Format Conversion}. It also calls the functions in | |
478 | the list @code{after-insert-file-functions}; see @ref{Saving | |
8241495d RS |
479 | Properties}. Normally, one of the functions in the |
480 | @code{after-insert-file-functions} list determines the coding system | |
481 | (@pxref{Coding Systems}) used for decoding the file's contents. | |
3e01fd9d RS |
482 | |
483 | If @var{visit} is non-@code{nil}, this function additionally marks the | |
484 | buffer as unmodified and sets up various fields in the buffer so that it | |
485 | is visiting the file @var{filename}: these include the buffer's visited | |
486 | file name and its last save file modtime. This feature is used by | |
487 | @code{find-file-noselect} and you probably should not use it yourself. | |
488 | ||
489 | If @var{beg} and @var{end} are non-@code{nil}, they should be integers | |
490 | specifying the portion of the file to insert. In this case, @var{visit} | |
491 | must be @code{nil}. For example, | |
492 | ||
493 | @example | |
494 | (insert-file-contents filename nil 0 500) | |
495 | @end example | |
496 | ||
497 | @noindent | |
498 | inserts the first 500 characters of a file. | |
499 | ||
500 | If the argument @var{replace} is non-@code{nil}, it means to replace the | |
501 | contents of the buffer (actually, just the accessible portion) with the | |
502 | contents of the file. This is better than simply deleting the buffer | |
503 | contents and inserting the whole file, because (1) it preserves some | |
504 | marker positions and (2) it puts less data in the undo list. | |
f9f59935 | 505 | |
a9f0a989 RS |
506 | It is possible to read a special file (such as a FIFO or an I/O device) |
507 | with @code{insert-file-contents}, as long as @var{replace} and | |
508 | @var{visit} are @code{nil}. | |
f9f59935 RS |
509 | @end defun |
510 | ||
f9f59935 RS |
511 | @defun insert-file-contents-literally filename &optional visit beg end replace |
512 | This function works like @code{insert-file-contents} except that it does | |
513 | not do format decoding (@pxref{Format Conversion}), does not do | |
514 | character code conversion (@pxref{Coding Systems}), does not run | |
515 | @code{find-file-hooks}, does not perform automatic uncompression, and so | |
516 | on. | |
3e01fd9d RS |
517 | @end defun |
518 | ||
519 | If you want to pass a file name to another process so that another | |
520 | program can read the file, use the function @code{file-local-copy}; see | |
521 | @ref{Magic File Names}. | |
522 | ||
523 | @node Writing to Files | |
524 | @comment node-name, next, previous, up | |
525 | @section Writing to Files | |
526 | ||
527 | You can write the contents of a buffer, or part of a buffer, directly | |
528 | to a file on disk using the @code{append-to-file} and | |
529 | @code{write-region} functions. Don't use these functions to write to | |
530 | files that are being visited; that could cause confusion in the | |
531 | mechanisms for visiting. | |
532 | ||
533 | @deffn Command append-to-file start end filename | |
534 | This function appends the contents of the region delimited by | |
535 | @var{start} and @var{end} in the current buffer to the end of file | |
536 | @var{filename}. If that file does not exist, it is created. This | |
537 | function returns @code{nil}. | |
538 | ||
539 | An error is signaled if @var{filename} specifies a nonwritable file, | |
540 | or a nonexistent file in a directory where files cannot be created. | |
541 | @end deffn | |
542 | ||
2468d0c0 | 543 | @deffn Command write-region start end filename &optional append visit lockname mustbenew |
3e01fd9d RS |
544 | This function writes the region delimited by @var{start} and @var{end} |
545 | in the current buffer into the file specified by @var{filename}. | |
546 | ||
547 | @c Emacs 19 feature | |
548 | If @var{start} is a string, then @code{write-region} writes or appends | |
8241495d RS |
549 | that string, rather than text from the buffer. @var{end} is ignored in |
550 | this case. | |
3e01fd9d RS |
551 | |
552 | If @var{append} is non-@code{nil}, then the specified text is appended | |
82400f56 DL |
553 | to the existing file contents (if any). Starting in Emacs 21, if |
554 | @var{append} is an integer, then @code{write-region} seeks to that byte | |
555 | offset from the start of the file and writes the data from there. | |
3e01fd9d | 556 | |
8241495d | 557 | If @var{mustbenew} is non-@code{nil}, then @code{write-region} asks |
a9f0a989 | 558 | for confirmation if @var{filename} names an existing file. |
8241495d RS |
559 | Starting in Emacs 21, if @var{mustbenew} is the symbol @code{excl}, |
560 | then @code{write-region} does not ask for confirmation, but instead | |
561 | it signals an error @code{file-already-exists} if the file already | |
562 | exists. | |
563 | ||
564 | The test for an existing file, when @var{mustbenew} is @code{excl}, uses | |
565 | a special system feature. At least for files on a local disk, there is | |
566 | no chance that some other program could create a file of the same name | |
567 | before Emacs does, without Emacs's noticing. | |
a9f0a989 | 568 | |
3e01fd9d RS |
569 | If @var{visit} is @code{t}, then Emacs establishes an association |
570 | between the buffer and the file: the buffer is then visiting that file. | |
571 | It also sets the last file modification time for the current buffer to | |
572 | @var{filename}'s modtime, and marks the buffer as not modified. This | |
573 | feature is used by @code{save-buffer}, but you probably should not use | |
574 | it yourself. | |
575 | ||
576 | @c Emacs 19 feature | |
577 | If @var{visit} is a string, it specifies the file name to visit. This | |
578 | way, you can write the data to one file (@var{filename}) while recording | |
579 | the buffer as visiting another file (@var{visit}). The argument | |
580 | @var{visit} is used in the echo area message and also for file locking; | |
581 | @var{visit} is stored in @code{buffer-file-name}. This feature is used | |
582 | to implement @code{file-precious-flag}; don't use it yourself unless you | |
583 | really know what you're doing. | |
584 | ||
2468d0c0 DL |
585 | The optional argument @var{lockname}, if non-@code{nil}, specifies the |
586 | file name to use for purposes of locking and unlocking, overriding | |
587 | @var{filename} and @var{visit} for that purpose. | |
588 | ||
bfe721d1 KH |
589 | The function @code{write-region} converts the data which it writes to |
590 | the appropriate file formats specified by @code{buffer-file-format}. | |
591 | @xref{Format Conversion}. It also calls the functions in the list | |
592 | @code{write-region-annotate-functions}; see @ref{Saving Properties}. | |
3e01fd9d | 593 | |
f1e2c45e | 594 | Normally, @code{write-region} displays the message @samp{Wrote |
3e01fd9d RS |
595 | @var{filename}} in the echo area. If @var{visit} is neither @code{t} |
596 | nor @code{nil} nor a string, then this message is inhibited. This | |
597 | feature is useful for programs that use files for internal purposes, | |
b22f3a19 | 598 | files that the user does not need to know about. |
3e01fd9d RS |
599 | @end deffn |
600 | ||
f9f59935 | 601 | @defmac with-temp-file file body... |
969fe9b5 RS |
602 | The @code{with-temp-file} macro evaluates the @var{body} forms with a |
603 | temporary buffer as the current buffer; then, at the end, it writes the | |
604 | buffer contents into file @var{file}. It kills the temporary buffer | |
605 | when finished, restoring the buffer that was current before the | |
606 | @code{with-temp-file} form. Then it returns the value of the last form | |
607 | in @var{body}. | |
f9f59935 RS |
608 | |
609 | The current buffer is restored even in case of an abnormal exit via | |
610 | @code{throw} or error (@pxref{Nonlocal Exits}). | |
611 | ||
612 | See also @code{with-temp-buffer} in @ref{Current Buffer}. | |
613 | @end defmac | |
614 | ||
3e01fd9d RS |
615 | @node File Locks |
616 | @section File Locks | |
617 | @cindex file locks | |
618 | ||
619 | When two users edit the same file at the same time, they are likely to | |
620 | interfere with each other. Emacs tries to prevent this situation from | |
621 | arising by recording a @dfn{file lock} when a file is being modified. | |
622 | Emacs can then detect the first attempt to modify a buffer visiting a | |
623 | file that is locked by another Emacs job, and ask the user what to do. | |
b6954afd RS |
624 | The file lock is really a file, a symbolic link with a special name, |
625 | stored in the same directory as the file you are editing. | |
3e01fd9d | 626 | |
b6954afd RS |
627 | When you access files using NFS, there may be a small probability that |
628 | you and another user will both lock the same file ``simultaneously''. | |
629 | If this happens, it is possible for the two users to make changes | |
630 | simultaneously, but Emacs will still warn the user who saves second. | |
631 | Also, the detection of modification of a buffer visiting a file changed | |
632 | on disk catches some cases of simultaneous editing; see | |
633 | @ref{Modification Time}. | |
3e01fd9d RS |
634 | |
635 | @defun file-locked-p filename | |
f1e2c45e RS |
636 | This function returns @code{nil} if the file @var{filename} is not |
637 | locked. It returns @code{t} if it is locked by this Emacs process, and | |
638 | it returns the name of the user who has locked it if it is locked by | |
639 | some other job. | |
3e01fd9d RS |
640 | |
641 | @example | |
642 | @group | |
643 | (file-locked-p "foo") | |
644 | @result{} nil | |
645 | @end group | |
646 | @end example | |
647 | @end defun | |
648 | ||
649 | @defun lock-buffer &optional filename | |
b6954afd | 650 | This function locks the file @var{filename}, if the current buffer is |
3e01fd9d RS |
651 | modified. The argument @var{filename} defaults to the current buffer's |
652 | visited file. Nothing is done if the current buffer is not visiting a | |
653 | file, or is not modified. | |
654 | @end defun | |
655 | ||
656 | @defun unlock-buffer | |
657 | This function unlocks the file being visited in the current buffer, | |
658 | if the buffer is modified. If the buffer is not modified, then | |
659 | the file should not be locked, so this function does nothing. It also | |
660 | does nothing if the current buffer is not visiting a file. | |
661 | @end defun | |
662 | ||
8241495d RS |
663 | File locking is not supported on some systems. On systems that do not |
664 | support it, the functions @code{lock-buffer}, @code{unlock-buffer} and | |
665 | @code{file-locked-p} do nothing and return @code{nil}. | |
666 | ||
3e01fd9d RS |
667 | @defun ask-user-about-lock file other-user |
668 | This function is called when the user tries to modify @var{file}, but it | |
f9f59935 RS |
669 | is locked by another user named @var{other-user}. The default |
670 | definition of this function asks the user to say what to do. The value | |
671 | this function returns determines what Emacs does next: | |
3e01fd9d RS |
672 | |
673 | @itemize @bullet | |
674 | @item | |
675 | A value of @code{t} says to grab the lock on the file. Then | |
676 | this user may edit the file and @var{other-user} loses the lock. | |
677 | ||
678 | @item | |
679 | A value of @code{nil} says to ignore the lock and let this | |
680 | user edit the file anyway. | |
681 | ||
682 | @item | |
683 | @kindex file-locked | |
684 | This function may instead signal a @code{file-locked} error, in which | |
685 | case the change that the user was about to make does not take place. | |
686 | ||
687 | The error message for this error looks like this: | |
688 | ||
689 | @example | |
690 | @error{} File is locked: @var{file} @var{other-user} | |
691 | @end example | |
692 | ||
693 | @noindent | |
694 | where @code{file} is the name of the file and @var{other-user} is the | |
695 | name of the user who has locked the file. | |
696 | @end itemize | |
697 | ||
f9f59935 RS |
698 | If you wish, you can replace the @code{ask-user-about-lock} function |
699 | with your own version that makes the decision in another way. The code | |
3e01fd9d RS |
700 | for its usual definition is in @file{userlock.el}. |
701 | @end defun | |
702 | ||
703 | @node Information about Files | |
704 | @section Information about Files | |
705 | ||
b22f3a19 RS |
706 | The functions described in this section all operate on strings that |
707 | designate file names. All the functions have names that begin with the | |
708 | word @samp{file}. These functions all return information about actual | |
709 | files or directories, so their arguments must all exist as actual files | |
710 | or directories unless otherwise noted. | |
3e01fd9d RS |
711 | |
712 | @menu | |
713 | * Testing Accessibility:: Is a given file readable? Writable? | |
714 | * Kinds of Files:: Is it a directory? A symbolic link? | |
715 | * Truenames:: Eliminating symbolic links from a file name. | |
716 | * File Attributes:: How large is it? Any other names? Etc. | |
717 | @end menu | |
718 | ||
719 | @node Testing Accessibility | |
720 | @comment node-name, next, previous, up | |
721 | @subsection Testing Accessibility | |
722 | @cindex accessibility of a file | |
723 | @cindex file accessibility | |
724 | ||
725 | These functions test for permission to access a file in specific ways. | |
726 | ||
727 | @defun file-exists-p filename | |
2468d0c0 DL |
728 | This function returns @code{t} if a file named @var{filename} appears to |
729 | exist. This does not mean you can necessarily read the file, only that | |
730 | you can find out its attributes. (On Unix and GNU/Linux, this is true | |
731 | if the file exists and you have execute permission on the containing | |
3e01fd9d RS |
732 | directories, regardless of the protection of the file itself.) |
733 | ||
734 | If the file does not exist, or if fascist access control policies | |
735 | prevent you from finding the attributes of the file, this function | |
736 | returns @code{nil}. | |
737 | @end defun | |
738 | ||
739 | @defun file-readable-p filename | |
740 | This function returns @code{t} if a file named @var{filename} exists | |
741 | and you can read it. It returns @code{nil} otherwise. | |
742 | ||
743 | @example | |
744 | @group | |
745 | (file-readable-p "files.texi") | |
746 | @result{} t | |
747 | @end group | |
748 | @group | |
749 | (file-exists-p "/usr/spool/mqueue") | |
750 | @result{} t | |
751 | @end group | |
752 | @group | |
753 | (file-readable-p "/usr/spool/mqueue") | |
754 | @result{} nil | |
755 | @end group | |
756 | @end example | |
757 | @end defun | |
758 | ||
759 | @c Emacs 19 feature | |
760 | @defun file-executable-p filename | |
761 | This function returns @code{t} if a file named @var{filename} exists and | |
2468d0c0 DL |
762 | you can execute it. It returns @code{nil} otherwise. On Unix and |
763 | GNU/Linux, if the file is a directory, execute permission means you can | |
764 | check the existence and attributes of files inside the directory, and | |
765 | open those files if their modes permit. | |
3e01fd9d RS |
766 | @end defun |
767 | ||
768 | @defun file-writable-p filename | |
b22f3a19 RS |
769 | This function returns @code{t} if the file @var{filename} can be written |
770 | or created by you, and @code{nil} otherwise. A file is writable if the | |
771 | file exists and you can write it. It is creatable if it does not exist, | |
772 | but the specified directory does exist and you can write in that | |
773 | directory. | |
3e01fd9d RS |
774 | |
775 | In the third example below, @file{foo} is not writable because the | |
776 | parent directory does not exist, even though the user could create such | |
777 | a directory. | |
778 | ||
779 | @example | |
780 | @group | |
781 | (file-writable-p "~/foo") | |
782 | @result{} t | |
783 | @end group | |
784 | @group | |
785 | (file-writable-p "/foo") | |
786 | @result{} nil | |
787 | @end group | |
788 | @group | |
789 | (file-writable-p "~/no-such-dir/foo") | |
790 | @result{} nil | |
791 | @end group | |
792 | @end example | |
793 | @end defun | |
794 | ||
795 | @c Emacs 19 feature | |
796 | @defun file-accessible-directory-p dirname | |
797 | This function returns @code{t} if you have permission to open existing | |
b22f3a19 RS |
798 | files in the directory whose name as a file is @var{dirname}; otherwise |
799 | (or if there is no such directory), it returns @code{nil}. The value | |
800 | of @var{dirname} may be either a directory name or the file name of a | |
f9f59935 | 801 | file which is a directory. |
3e01fd9d RS |
802 | |
803 | Example: after the following, | |
804 | ||
805 | @example | |
806 | (file-accessible-directory-p "/foo") | |
807 | @result{} nil | |
808 | @end example | |
809 | ||
810 | @noindent | |
811 | we can deduce that any attempt to read a file in @file{/foo/} will | |
812 | give an error. | |
813 | @end defun | |
814 | ||
f9f59935 RS |
815 | @defun access-file filename string |
816 | This function opens file @var{filename} for reading, then closes it and | |
817 | returns @code{nil}. However, if the open fails, it signals an error | |
818 | using @var{string} as the error message text. | |
819 | @end defun | |
820 | ||
22697dac KH |
821 | @defun file-ownership-preserved-p filename |
822 | This function returns @code{t} if deleting the file @var{filename} and | |
823 | then creating it anew would keep the file's owner unchanged. | |
824 | @end defun | |
825 | ||
3e01fd9d RS |
826 | @defun file-newer-than-file-p filename1 filename2 |
827 | @cindex file age | |
828 | @cindex file modification time | |
b22f3a19 | 829 | This function returns @code{t} if the file @var{filename1} is |
3e01fd9d RS |
830 | newer than file @var{filename2}. If @var{filename1} does not |
831 | exist, it returns @code{nil}. If @var{filename2} does not exist, | |
832 | it returns @code{t}. | |
833 | ||
b22f3a19 RS |
834 | In the following example, assume that the file @file{aug-19} was written |
835 | on the 19th, @file{aug-20} was written on the 20th, and the file | |
836 | @file{no-file} doesn't exist at all. | |
3e01fd9d RS |
837 | |
838 | @example | |
839 | @group | |
840 | (file-newer-than-file-p "aug-19" "aug-20") | |
841 | @result{} nil | |
842 | @end group | |
843 | @group | |
844 | (file-newer-than-file-p "aug-20" "aug-19") | |
845 | @result{} t | |
846 | @end group | |
847 | @group | |
848 | (file-newer-than-file-p "aug-19" "no-file") | |
849 | @result{} t | |
850 | @end group | |
851 | @group | |
852 | (file-newer-than-file-p "no-file" "aug-19") | |
853 | @result{} nil | |
854 | @end group | |
855 | @end example | |
856 | ||
857 | You can use @code{file-attributes} to get a file's last modification | |
858 | time as a list of two numbers. @xref{File Attributes}. | |
859 | @end defun | |
860 | ||
861 | @node Kinds of Files | |
862 | @comment node-name, next, previous, up | |
863 | @subsection Distinguishing Kinds of Files | |
864 | ||
bfe721d1 KH |
865 | This section describes how to distinguish various kinds of files, such |
866 | as directories, symbolic links, and ordinary files. | |
3e01fd9d RS |
867 | |
868 | @defun file-symlink-p filename | |
869 | @cindex file symbolic links | |
870 | If the file @var{filename} is a symbolic link, the @code{file-symlink-p} | |
871 | function returns the file name to which it is linked. This may be the | |
b22f3a19 RS |
872 | name of a text file, a directory, or even another symbolic link, or it |
873 | may be a nonexistent file name. | |
3e01fd9d RS |
874 | |
875 | If the file @var{filename} is not a symbolic link (or there is no such file), | |
876 | @code{file-symlink-p} returns @code{nil}. | |
877 | ||
878 | @example | |
879 | @group | |
880 | (file-symlink-p "foo") | |
881 | @result{} nil | |
882 | @end group | |
883 | @group | |
884 | (file-symlink-p "sym-link") | |
885 | @result{} "foo" | |
886 | @end group | |
887 | @group | |
888 | (file-symlink-p "sym-link2") | |
889 | @result{} "sym-link" | |
890 | @end group | |
891 | @group | |
892 | (file-symlink-p "/bin") | |
893 | @result{} "/pub/bin" | |
894 | @end group | |
895 | @end example | |
896 | ||
897 | @c !!! file-symlink-p: should show output of ls -l for comparison | |
898 | @end defun | |
899 | ||
900 | @defun file-directory-p filename | |
901 | This function returns @code{t} if @var{filename} is the name of an | |
902 | existing directory, @code{nil} otherwise. | |
903 | ||
904 | @example | |
905 | @group | |
906 | (file-directory-p "~rms") | |
907 | @result{} t | |
908 | @end group | |
909 | @group | |
910 | (file-directory-p "~rms/lewis/files.texi") | |
911 | @result{} nil | |
912 | @end group | |
913 | @group | |
914 | (file-directory-p "~rms/lewis/no-such-file") | |
915 | @result{} nil | |
916 | @end group | |
917 | @group | |
918 | (file-directory-p "$HOME") | |
919 | @result{} nil | |
920 | @end group | |
921 | @group | |
922 | (file-directory-p | |
923 | (substitute-in-file-name "$HOME")) | |
924 | @result{} t | |
925 | @end group | |
926 | @end example | |
927 | @end defun | |
928 | ||
22697dac KH |
929 | @defun file-regular-p filename |
930 | This function returns @code{t} if the file @var{filename} exists and is | |
b6954afd | 931 | a regular file (not a directory, named pipe, terminal, or |
22697dac KH |
932 | other I/O device). |
933 | @end defun | |
934 | ||
3e01fd9d RS |
935 | @node Truenames |
936 | @subsection Truenames | |
937 | @cindex truename (of file) | |
938 | ||
939 | @c Emacs 19 features | |
940 | The @dfn{truename} of a file is the name that you get by following | |
2468d0c0 DL |
941 | symbolic links at all levels until none remain, then simplifying away |
942 | @samp{.}@: and @samp{..}@: appearing as name components. This results | |
943 | in a sort of canonical name for the file. A file does not always have a | |
944 | unique truename; the number of distinct truenames a file has is equal to | |
945 | the number of hard links to the file. However, truenames are useful | |
946 | because they eliminate symbolic links as a cause of name variation. | |
3e01fd9d RS |
947 | |
948 | @defun file-truename filename | |
2468d0c0 DL |
949 | The function @code{file-truename} returns the truename of the file |
950 | @var{filename}. The argument must be an absolute file name. | |
3e01fd9d RS |
951 | @end defun |
952 | ||
2468d0c0 DL |
953 | @defun file-chase-links filename |
954 | This function follows symbolic links, starting with @var{filename}, | |
955 | until it finds a file name which is not the name of a symbolic link. | |
956 | Then it returns that file name. | |
957 | @end defun | |
958 | ||
959 | To illustrate the difference between @code{file-chase-links} and | |
960 | @code{file-truename}, suppose that @file{/usr/foo} is a symbolic link to | |
961 | the directory @file{/home/foo}, and @file{/home/foo/hello} is an | |
962 | ordinary file (or at least, not a symbolic link) or nonexistent. Then | |
963 | we would have: | |
964 | ||
965 | @example | |
966 | (file-chase-links "/usr/foo/hello") | |
967 | ;; @r{This does not follow the links in the parent directories.} | |
968 | @result{} "/usr/foo/hello" | |
969 | (file-truename "/usr/foo/hello") | |
970 | ;; @r{Assuming that @file{/home} is not a symbolic link.} | |
971 | @result{} "/home/foo/hello" | |
972 | @end example | |
973 | ||
3e01fd9d RS |
974 | @xref{Buffer File Name}, for related information. |
975 | ||
976 | @node File Attributes | |
977 | @comment node-name, next, previous, up | |
978 | @subsection Other Information about Files | |
979 | ||
980 | This section describes the functions for getting detailed information | |
981 | about a file, other than its contents. This information includes the | |
982 | mode bits that control access permission, the owner and group numbers, | |
983 | the number of names, the inode number, the size, and the times of access | |
984 | and modification. | |
985 | ||
986 | @defun file-modes filename | |
987 | @cindex permission | |
988 | @cindex file attributes | |
989 | This function returns the mode bits of @var{filename}, as an integer. | |
990 | The mode bits are also called the file permissions, and they specify | |
991 | access control in the usual Unix fashion. If the low-order bit is 1, | |
b22f3a19 | 992 | then the file is executable by all users, if the second-lowest-order bit |
3e01fd9d RS |
993 | is 1, then the file is writable by all users, etc. |
994 | ||
995 | The highest value returnable is 4095 (7777 octal), meaning that | |
996 | everyone has read, write, and execute permission, that the @sc{suid} bit | |
997 | is set for both others and group, and that the sticky bit is set. | |
998 | ||
999 | @example | |
1000 | @group | |
1001 | (file-modes "~/junk/diffs") | |
1002 | @result{} 492 ; @r{Decimal integer.} | |
1003 | @end group | |
1004 | @group | |
1005 | (format "%o" 492) | |
1006 | @result{} "754" ; @r{Convert to octal.} | |
1007 | @end group | |
1008 | ||
1009 | @group | |
1010 | (set-file-modes "~/junk/diffs" 438) | |
1011 | @result{} nil | |
1012 | @end group | |
1013 | ||
1014 | @group | |
1015 | (format "%o" 438) | |
1016 | @result{} "666" ; @r{Convert to octal.} | |
1017 | @end group | |
1018 | ||
1019 | @group | |
1020 | % ls -l diffs | |
1021 | -rw-rw-rw- 1 lewis 0 3063 Oct 30 16:00 diffs | |
1022 | @end group | |
1023 | @end example | |
1024 | @end defun | |
1025 | ||
1026 | @defun file-nlinks filename | |
1027 | This functions returns the number of names (i.e., hard links) that | |
1028 | file @var{filename} has. If the file does not exist, then this function | |
1029 | returns @code{nil}. Note that symbolic links have no effect on this | |
1030 | function, because they are not considered to be names of the files they | |
1031 | link to. | |
1032 | ||
1033 | @example | |
1034 | @group | |
1035 | % ls -l foo* | |
1036 | -rw-rw-rw- 2 rms 4 Aug 19 01:27 foo | |
1037 | -rw-rw-rw- 2 rms 4 Aug 19 01:27 foo1 | |
1038 | @end group | |
1039 | ||
1040 | @group | |
1041 | (file-nlinks "foo") | |
1042 | @result{} 2 | |
1043 | @end group | |
1044 | @group | |
1045 | (file-nlinks "doesnt-exist") | |
1046 | @result{} nil | |
1047 | @end group | |
1048 | @end example | |
1049 | @end defun | |
1050 | ||
1051 | @defun file-attributes filename | |
1052 | This function returns a list of attributes of file @var{filename}. If | |
1053 | the specified file cannot be opened, it returns @code{nil}. | |
1054 | ||
1055 | The elements of the list, in order, are: | |
1056 | ||
1057 | @enumerate 0 | |
1058 | @item | |
1059 | @code{t} for a directory, a string for a symbolic link (the name | |
1060 | linked to), or @code{nil} for a text file. | |
1061 | ||
1062 | @c Wordy so as to prevent an overfull hbox. --rjc 15mar92 | |
1063 | @item | |
1064 | The number of names the file has. Alternate names, also known as hard | |
1065 | links, can be created by using the @code{add-name-to-file} function | |
f9f59935 | 1066 | (@pxref{Changing Files}). |
3e01fd9d RS |
1067 | |
1068 | @item | |
1069 | The file's @sc{uid}. | |
1070 | ||
1071 | @item | |
1072 | The file's @sc{gid}. | |
1073 | ||
1074 | @item | |
1075 | The time of last access, as a list of two integers. | |
1076 | The first integer has the high-order 16 bits of time, | |
1077 | the second has the low 16 bits. (This is similar to the | |
1078 | value of @code{current-time}; see @ref{Time of Day}.) | |
1079 | ||
1080 | @item | |
1081 | The time of last modification as a list of two integers (as above). | |
1082 | ||
1083 | @item | |
1084 | The time of last status change as a list of two integers (as above). | |
1085 | ||
1086 | @item | |
b6954afd RS |
1087 | The size of the file in bytes. If the size is too large to fit in a |
1088 | Lisp integer, this is a floating point number. | |
3e01fd9d RS |
1089 | |
1090 | @item | |
b22f3a19 | 1091 | The file's modes, as a string of ten letters or dashes, |
3e01fd9d RS |
1092 | as in @samp{ls -l}. |
1093 | ||
1094 | @item | |
1095 | @code{t} if the file's @sc{gid} would change if file were | |
1096 | deleted and recreated; @code{nil} otherwise. | |
1097 | ||
1098 | @item | |
2a7d4505 RS |
1099 | The file's inode number. If possible, this is an integer. If the inode |
1100 | number is too large to be represented as an integer in Emacs Lisp, then | |
1101 | the value has the form @code{(@var{high} . @var{low})}, where @var{low} | |
1102 | holds the low 16 bits. | |
3e01fd9d RS |
1103 | |
1104 | @item | |
1105 | The file system number of the file system that the file is in. This | |
b22f3a19 RS |
1106 | element and the file's inode number together give enough information to |
1107 | distinguish any two files on the system---no two files can have the same | |
1108 | values for both of these numbers. | |
3e01fd9d RS |
1109 | @end enumerate |
1110 | ||
1111 | For example, here are the file attributes for @file{files.texi}: | |
1112 | ||
1113 | @example | |
1114 | @group | |
1115 | (file-attributes "files.texi") | |
969fe9b5 | 1116 | @result{} (nil 1 2235 75 |
3e01fd9d RS |
1117 | (8489 20284) |
1118 | (8489 20284) | |
1119 | (8489 20285) | |
969fe9b5 RS |
1120 | 14906 "-rw-rw-rw-" |
1121 | nil 129500 -32252) | |
3e01fd9d RS |
1122 | @end group |
1123 | @end example | |
1124 | ||
1125 | @noindent | |
1126 | and here is how the result is interpreted: | |
1127 | ||
1128 | @table @code | |
1129 | @item nil | |
1130 | is neither a directory nor a symbolic link. | |
1131 | ||
1132 | @item 1 | |
1133 | has only one name (the name @file{files.texi} in the current default | |
1134 | directory). | |
1135 | ||
1136 | @item 2235 | |
1137 | is owned by the user with @sc{uid} 2235. | |
1138 | ||
1139 | @item 75 | |
1140 | is in the group with @sc{gid} 75. | |
1141 | ||
1142 | @item (8489 20284) | |
6784ada3 | 1143 | was last accessed on Aug 19 00:09. |
3e01fd9d RS |
1144 | |
1145 | @item (8489 20284) | |
1146 | was last modified on Aug 19 00:09. | |
1147 | ||
1148 | @item (8489 20285) | |
1149 | last had its inode changed on Aug 19 00:09. | |
1150 | ||
1151 | @item 14906 | |
8241495d RS |
1152 | is 14906 bytes long. (It may not contain 14906 characters, though, |
1153 | if some of the bytes belong to multibyte sequences.) | |
3e01fd9d RS |
1154 | |
1155 | @item "-rw-rw-rw-" | |
1156 | has a mode of read and write access for the owner, group, and world. | |
1157 | ||
1158 | @item nil | |
1159 | would retain the same @sc{gid} if it were recreated. | |
1160 | ||
1161 | @item 129500 | |
1162 | has an inode number of 129500. | |
1163 | @item -32252 | |
1164 | is on file system number -32252. | |
1165 | @end table | |
1166 | @end defun | |
1167 | ||
f9f59935 | 1168 | @node Changing Files |
3e01fd9d RS |
1169 | @section Changing File Names and Attributes |
1170 | @cindex renaming files | |
1171 | @cindex copying files | |
1172 | @cindex deleting files | |
1173 | @cindex linking files | |
1174 | @cindex setting modes of files | |
1175 | ||
1176 | The functions in this section rename, copy, delete, link, and set the | |
1177 | modes of files. | |
1178 | ||
1179 | In the functions that have an argument @var{newname}, if a file by the | |
1180 | name of @var{newname} already exists, the actions taken depend on the | |
1181 | value of the argument @var{ok-if-already-exists}: | |
1182 | ||
1183 | @itemize @bullet | |
1184 | @item | |
1185 | Signal a @code{file-already-exists} error if | |
1186 | @var{ok-if-already-exists} is @code{nil}. | |
1187 | ||
1188 | @item | |
1189 | Request confirmation if @var{ok-if-already-exists} is a number. | |
1190 | ||
1191 | @item | |
1192 | Replace the old file without confirmation if @var{ok-if-already-exists} | |
1193 | is any other value. | |
1194 | @end itemize | |
1195 | ||
1196 | @defun add-name-to-file oldname newname &optional ok-if-already-exists | |
1197 | @cindex file with multiple names | |
1198 | @cindex file hard link | |
1199 | This function gives the file named @var{oldname} the additional name | |
1200 | @var{newname}. This means that @var{newname} becomes a new ``hard | |
1201 | link'' to @var{oldname}. | |
1202 | ||
1203 | In the first part of the following example, we list two files, | |
1204 | @file{foo} and @file{foo3}. | |
1205 | ||
1206 | @example | |
1207 | @group | |
a9f0a989 RS |
1208 | % ls -li fo* |
1209 | 81908 -rw-rw-rw- 1 rms 29 Aug 18 20:32 foo | |
1210 | 84302 -rw-rw-rw- 1 rms 24 Aug 18 20:31 foo3 | |
3e01fd9d RS |
1211 | @end group |
1212 | @end example | |
1213 | ||
9e2b495b RS |
1214 | Now we create a hard link, by calling @code{add-name-to-file}, then list |
1215 | the files again. This shows two names for one file, @file{foo} and | |
1216 | @file{foo2}. | |
3e01fd9d RS |
1217 | |
1218 | @example | |
1219 | @group | |
a9f0a989 | 1220 | (add-name-to-file "foo" "foo2") |
3e01fd9d RS |
1221 | @result{} nil |
1222 | @end group | |
1223 | ||
1224 | @group | |
a9f0a989 RS |
1225 | % ls -li fo* |
1226 | 81908 -rw-rw-rw- 2 rms 29 Aug 18 20:32 foo | |
1227 | 81908 -rw-rw-rw- 2 rms 29 Aug 18 20:32 foo2 | |
1228 | 84302 -rw-rw-rw- 1 rms 24 Aug 18 20:31 foo3 | |
3e01fd9d RS |
1229 | @end group |
1230 | @end example | |
1231 | ||
a9f0a989 | 1232 | Finally, we evaluate the following: |
3e01fd9d RS |
1233 | |
1234 | @example | |
a9f0a989 | 1235 | (add-name-to-file "foo" "foo3" t) |
3e01fd9d RS |
1236 | @end example |
1237 | ||
1238 | @noindent | |
1239 | and list the files again. Now there are three names | |
1240 | for one file: @file{foo}, @file{foo2}, and @file{foo3}. The old | |
1241 | contents of @file{foo3} are lost. | |
1242 | ||
1243 | @example | |
1244 | @group | |
a9f0a989 | 1245 | (add-name-to-file "foo1" "foo3") |
3e01fd9d RS |
1246 | @result{} nil |
1247 | @end group | |
1248 | ||
1249 | @group | |
a9f0a989 RS |
1250 | % ls -li fo* |
1251 | 81908 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo | |
1252 | 81908 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo2 | |
1253 | 81908 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo3 | |
3e01fd9d RS |
1254 | @end group |
1255 | @end example | |
1256 | ||
a9f0a989 | 1257 | This function is meaningless on operating systems where multiple names |
8241495d RS |
1258 | for one file are not allowed. Some systems implement multiple names |
1259 | by copying the file instead. | |
3e01fd9d | 1260 | |
a9f0a989 | 1261 | See also @code{file-nlinks} in @ref{File Attributes}. |
3e01fd9d RS |
1262 | @end defun |
1263 | ||
1264 | @deffn Command rename-file filename newname &optional ok-if-already-exists | |
1265 | This command renames the file @var{filename} as @var{newname}. | |
1266 | ||
1267 | If @var{filename} has additional names aside from @var{filename}, it | |
1268 | continues to have those names. In fact, adding the name @var{newname} | |
1269 | with @code{add-name-to-file} and then deleting @var{filename} has the | |
1270 | same effect as renaming, aside from momentary intermediate states. | |
1271 | ||
1272 | In an interactive call, this function prompts for @var{filename} and | |
1273 | @var{newname} in the minibuffer; also, it requests confirmation if | |
1274 | @var{newname} already exists. | |
1275 | @end deffn | |
1276 | ||
1277 | @deffn Command copy-file oldname newname &optional ok-if-exists time | |
1278 | This command copies the file @var{oldname} to @var{newname}. An | |
1279 | error is signaled if @var{oldname} does not exist. | |
1280 | ||
a9f0a989 | 1281 | If @var{time} is non-@code{nil}, then this function gives the new file |
f9f59935 RS |
1282 | the same last-modified time that the old one has. (This works on only |
1283 | some operating systems.) If setting the time gets an error, | |
1284 | @code{copy-file} signals a @code{file-date-error} error. | |
3e01fd9d RS |
1285 | |
1286 | In an interactive call, this function prompts for @var{filename} and | |
1287 | @var{newname} in the minibuffer; also, it requests confirmation if | |
1288 | @var{newname} already exists. | |
1289 | @end deffn | |
1290 | ||
1291 | @deffn Command delete-file filename | |
1292 | @pindex rm | |
1293 | This command deletes the file @var{filename}, like the shell command | |
1294 | @samp{rm @var{filename}}. If the file has multiple names, it continues | |
1295 | to exist under the other names. | |
1296 | ||
2468d0c0 DL |
1297 | A suitable kind of @code{file-error} error is signaled if the file does |
1298 | not exist, or is not deletable. (On Unix and GNU/Linux, a file is | |
1299 | deletable if its directory is writable.) | |
3e01fd9d RS |
1300 | |
1301 | See also @code{delete-directory} in @ref{Create/Delete Dirs}. | |
1302 | @end deffn | |
1303 | ||
1304 | @deffn Command make-symbolic-link filename newname &optional ok-if-exists | |
1305 | @pindex ln | |
1306 | @kindex file-already-exists | |
1307 | This command makes a symbolic link to @var{filename}, named | |
1308 | @var{newname}. This is like the shell command @samp{ln -s | |
1309 | @var{filename} @var{newname}}. | |
1310 | ||
b22f3a19 RS |
1311 | In an interactive call, this function prompts for @var{filename} and |
1312 | @var{newname} in the minibuffer; also, it requests confirmation if | |
1313 | @var{newname} already exists. | |
8241495d RS |
1314 | |
1315 | This function is not available on systems that don't support symbolic | |
1316 | links. | |
3e01fd9d RS |
1317 | @end deffn |
1318 | ||
1319 | @defun define-logical-name varname string | |
1320 | This function defines the logical name @var{name} to have the value | |
1321 | @var{string}. It is available only on VMS. | |
1322 | @end defun | |
1323 | ||
1324 | @defun set-file-modes filename mode | |
1325 | This function sets mode bits of @var{filename} to @var{mode} (which must | |
b22f3a19 | 1326 | be an integer). Only the low 12 bits of @var{mode} are used. |
3e01fd9d RS |
1327 | @end defun |
1328 | ||
1329 | @c Emacs 19 feature | |
1330 | @defun set-default-file-modes mode | |
1331 | This function sets the default file protection for new files created by | |
1332 | Emacs and its subprocesses. Every file created with Emacs initially has | |
f74bbbbf RS |
1333 | this protection, or a subset of it (@code{write-region} will not give a |
1334 | file execute permission even if the default file protection allows | |
1335 | execute permission). On Unix and GNU/Linux, the default protection is | |
1336 | the bitwise complement of the ``umask'' value. | |
3e01fd9d | 1337 | |
f9f59935 | 1338 | The argument @var{mode} must be an integer. On most systems, only the |
f74bbbbf RS |
1339 | low 9 bits of @var{mode} are meaningful. You can use the Lisp construct |
1340 | for octal character codes to enter @var{mode}; for example, | |
1341 | ||
1342 | @example | |
1343 | (set-default-file-modes ?\644) | |
1344 | @end example | |
3e01fd9d RS |
1345 | |
1346 | Saving a modified version of an existing file does not count as creating | |
f74bbbbf RS |
1347 | the file; it preserves the existing file's mode, whatever that is. So |
1348 | the default file protection has no effect. | |
3e01fd9d RS |
1349 | @end defun |
1350 | ||
1351 | @defun default-file-modes | |
1352 | This function returns the current default protection value. | |
1353 | @end defun | |
1354 | ||
841e483d RS |
1355 | @cindex MS-DOS and file modes |
1356 | @cindex file modes and MS-DOS | |
1357 | On MS-DOS, there is no such thing as an ``executable'' file mode bit. | |
8241495d RS |
1358 | So Emacs considers a file executable if its name ends in one of the |
1359 | standard executable extensions, such as @file{.com}, @file{.bat}, | |
1360 | @file{.exe}, and some others. Files that begin with the Unix-standard | |
1361 | @samp{#!} signature, such as shell and Perl scripts, are also considered | |
1362 | as executable files. This is reflected in the values returned by | |
1363 | @code{file-modes} and @code{file-attributes}. Directories are also | |
1364 | reported with executable bit set, for compatibility with Unix. | |
841e483d | 1365 | |
3e01fd9d RS |
1366 | @node File Names |
1367 | @section File Names | |
1368 | @cindex file names | |
1369 | ||
1370 | Files are generally referred to by their names, in Emacs as elsewhere. | |
1371 | File names in Emacs are represented as strings. The functions that | |
1372 | operate on a file all expect a file name argument. | |
1373 | ||
1374 | In addition to operating on files themselves, Emacs Lisp programs | |
f9f59935 | 1375 | often need to operate on file names; i.e., to take them apart and to use |
3e01fd9d RS |
1376 | part of a name to construct related file names. This section describes |
1377 | how to manipulate file names. | |
1378 | ||
1379 | The functions in this section do not actually access files, so they | |
1380 | can operate on file names that do not refer to an existing file or | |
1381 | directory. | |
1382 | ||
5557b83b RS |
1383 | On MS-DOS and MS-Windows, these functions (like the function that |
1384 | actually operate on files) accept MS-DOS or MS-Windows file-name syntax, | |
1385 | where backslashes separate the components, as well as Unix syntax; but | |
1386 | they always return Unix syntax. On VMS, these functions (and the ones | |
1387 | that operate on files) understand both VMS file-name syntax and Unix | |
1388 | syntax. This enables Lisp programs to specify file names in Unix syntax | |
1389 | and work properly on all systems without change. | |
3e01fd9d RS |
1390 | |
1391 | @menu | |
1392 | * File Name Components:: The directory part of a file name, and the rest. | |
1393 | * Directory Names:: A directory's name as a directory | |
1394 | is different from its name as a file. | |
1395 | * Relative File Names:: Some file names are relative to a current directory. | |
1396 | * File Name Expansion:: Converting relative file names to absolute ones. | |
1397 | * Unique File Names:: Generating names for temporary files. | |
1398 | * File Name Completion:: Finding the completions for a given file name. | |
fbc1b72c RS |
1399 | * Standard File Names:: If your package uses a fixed file name, |
1400 | how to handle various operating systems simply. | |
3e01fd9d RS |
1401 | @end menu |
1402 | ||
1403 | @node File Name Components | |
1404 | @subsection File Name Components | |
1405 | @cindex directory part (of file name) | |
1406 | @cindex nondirectory part (of file name) | |
1407 | @cindex version number (in file name) | |
1408 | ||
1409 | The operating system groups files into directories. To specify a | |
b22f3a19 RS |
1410 | file, you must specify the directory and the file's name within that |
1411 | directory. Therefore, Emacs considers a file name as having two main | |
1412 | parts: the @dfn{directory name} part, and the @dfn{nondirectory} part | |
1413 | (or @dfn{file name within the directory}). Either part may be empty. | |
1414 | Concatenating these two parts reproduces the original file name. | |
3e01fd9d | 1415 | |
8241495d | 1416 | On most systems, the directory part is everything up to and including |
5557b83b RS |
1417 | the last slash (backslash is also allowed in input on MS-DOS or |
1418 | MS-Windows); the nondirectory part is the rest. The rules in VMS syntax | |
1419 | are complicated. | |
3e01fd9d RS |
1420 | |
1421 | For some purposes, the nondirectory part is further subdivided into | |
8241495d RS |
1422 | the name proper and the @dfn{version number}. On most systems, only |
1423 | backup files have version numbers in their names. On VMS, every file | |
1424 | has a version number, but most of the time the file name actually used | |
1425 | in Emacs omits the version number, so that version numbers in Emacs are | |
f9f59935 | 1426 | found mostly in directory lists. |
3e01fd9d RS |
1427 | |
1428 | @defun file-name-directory filename | |
f9f59935 | 1429 | This function returns the directory part of @var{filename} (or |
3e01fd9d | 1430 | @code{nil} if @var{filename} does not include a directory part). On |
8241495d RS |
1431 | most systems, the function returns a string ending in a slash. On VMS, |
1432 | it returns a string ending in one of the three characters @samp{:}, | |
3e01fd9d RS |
1433 | @samp{]}, or @samp{>}. |
1434 | ||
1435 | @example | |
1436 | @group | |
1437 | (file-name-directory "lewis/foo") ; @r{Unix example} | |
1438 | @result{} "lewis/" | |
1439 | @end group | |
1440 | @group | |
1441 | (file-name-directory "foo") ; @r{Unix example} | |
1442 | @result{} nil | |
1443 | @end group | |
1444 | @group | |
1445 | (file-name-directory "[X]FOO.TMP") ; @r{VMS example} | |
1446 | @result{} "[X]" | |
1447 | @end group | |
1448 | @end example | |
1449 | @end defun | |
1450 | ||
1451 | @defun file-name-nondirectory filename | |
f9f59935 | 1452 | This function returns the nondirectory part of @var{filename}. |
3e01fd9d RS |
1453 | |
1454 | @example | |
1455 | @group | |
1456 | (file-name-nondirectory "lewis/foo") | |
1457 | @result{} "foo" | |
1458 | @end group | |
1459 | @group | |
1460 | (file-name-nondirectory "foo") | |
1461 | @result{} "foo" | |
1462 | @end group | |
1463 | @group | |
1464 | ;; @r{The following example is accurate only on VMS.} | |
1465 | (file-name-nondirectory "[X]FOO.TMP") | |
1466 | @result{} "FOO.TMP" | |
1467 | @end group | |
1468 | @end example | |
1469 | @end defun | |
1470 | ||
2468d0c0 | 1471 | @defun file-name-sans-versions filename &optional keep-backup-version |
f9f59935 | 1472 | This function returns @var{filename} with any file version numbers, |
2468d0c0 DL |
1473 | backup version numbers, or trailing tildes discarded. |
1474 | ||
1475 | If @var{keep-backup-version} is non-@code{nil}, then true file version | |
1476 | numbers understood as such by the file system are discarded from the | |
1477 | return value, but backup version numbers are kept. | |
3e01fd9d RS |
1478 | |
1479 | @example | |
1480 | @group | |
1481 | (file-name-sans-versions "~rms/foo.~1~") | |
1482 | @result{} "~rms/foo" | |
1483 | @end group | |
1484 | @group | |
1485 | (file-name-sans-versions "~rms/foo~") | |
1486 | @result{} "~rms/foo" | |
1487 | @end group | |
1488 | @group | |
1489 | (file-name-sans-versions "~rms/foo") | |
1490 | @result{} "~rms/foo" | |
1491 | @end group | |
1492 | @group | |
1493 | ;; @r{The following example applies to VMS only.} | |
1494 | (file-name-sans-versions "foo;23") | |
1495 | @result{} "foo" | |
1496 | @end group | |
1497 | @end example | |
1498 | @end defun | |
1499 | ||
22697dac | 1500 | @defun file-name-sans-extension filename |
bfe721d1 KH |
1501 | This function returns @var{filename} minus its ``extension,'' if any. |
1502 | The extension, in a file name, is the part that starts with the last | |
1503 | @samp{.} in the last name component. For example, | |
1504 | ||
1505 | @example | |
1506 | (file-name-sans-extension "foo.lose.c") | |
1507 | @result{} "foo.lose" | |
1508 | (file-name-sans-extension "big.hack/foo") | |
1509 | @result{} "big.hack/foo" | |
1510 | @end example | |
22697dac KH |
1511 | @end defun |
1512 | ||
5557b83b RS |
1513 | @ignore |
1514 | Andrew Innes says that this | |
1515 | ||
1516 | @c @defvar directory-sep-char | |
1517 | @c @tindex directory-sep-char | |
1518 | This variable holds the character that Emacs normally uses to separate | |
1519 | file name components. The default value is @code{?/}, but on MS-Windows | |
1520 | you can set it to @code{?\\}; then the functions that transform file names | |
1521 | use backslashes in their output. | |
1522 | ||
1523 | File names using backslashes work as input to Lisp primitives even on | |
1524 | MS-DOS and MS-Windows, even if @code{directory-sep-char} has its default | |
1525 | value of @code{?/}. | |
f855fad2 | 1526 | @end defvar |
5557b83b | 1527 | @end ignore |
f855fad2 | 1528 | |
3e01fd9d RS |
1529 | @node Directory Names |
1530 | @comment node-name, next, previous, up | |
1531 | @subsection Directory Names | |
1532 | @cindex directory name | |
1533 | @cindex file name of directory | |
1534 | ||
1535 | A @dfn{directory name} is the name of a directory. A directory is a | |
1536 | kind of file, and it has a file name, which is related to the directory | |
1537 | name but not identical to it. (This is not quite the same as the usual | |
1538 | Unix terminology.) These two different names for the same entity are | |
5557b83b RS |
1539 | related by a syntactic transformation. On most systems, this is simple: |
1540 | a directory name ends in a slash (or backslash), whereas the directory's | |
1541 | name as a file lacks that slash. On VMS, the relationship is more | |
1542 | complicated. | |
3e01fd9d RS |
1543 | |
1544 | The difference between a directory name and its name as a file is | |
1545 | subtle but crucial. When an Emacs variable or function argument is | |
1546 | described as being a directory name, a file name of a directory is not | |
1547 | acceptable. | |
1548 | ||
b22f3a19 RS |
1549 | The following two functions convert between directory names and file |
1550 | names. They do nothing special with environment variable substitutions | |
1551 | such as @samp{$HOME}, and the constructs @samp{~}, and @samp{..}. | |
3e01fd9d RS |
1552 | |
1553 | @defun file-name-as-directory filename | |
1554 | This function returns a string representing @var{filename} in a form | |
8241495d RS |
1555 | that the operating system will interpret as the name of a directory. On |
1556 | most systems, this means appending a slash to the string (if it does not | |
1557 | already end in one). On VMS, the function converts a string of the form | |
f9f59935 | 1558 | @file{[X]Y.DIR.1} to the form @file{[X.Y]}. |
3e01fd9d RS |
1559 | |
1560 | @example | |
1561 | @group | |
1562 | (file-name-as-directory "~rms/lewis") | |
1563 | @result{} "~rms/lewis/" | |
1564 | @end group | |
1565 | @end example | |
1566 | @end defun | |
1567 | ||
1568 | @defun directory-file-name dirname | |
f9f59935 | 1569 | This function returns a string representing @var{dirname} in a form that |
8241495d | 1570 | the operating system will interpret as the name of a file. On most |
5557b83b RS |
1571 | systems, this means removing the final slash (or backslash) from the |
1572 | string. On VMS, the function converts a string of the form @file{[X.Y]} | |
1573 | to @file{[X]Y.DIR.1}. | |
3e01fd9d RS |
1574 | |
1575 | @example | |
1576 | @group | |
1577 | (directory-file-name "~lewis/") | |
1578 | @result{} "~lewis" | |
1579 | @end group | |
1580 | @end example | |
1581 | @end defun | |
1582 | ||
1583 | @cindex directory name abbreviation | |
1584 | Directory name abbreviations are useful for directories that are | |
1585 | normally accessed through symbolic links. Sometimes the users recognize | |
1586 | primarily the link's name as ``the name'' of the directory, and find it | |
1587 | annoying to see the directory's ``real'' name. If you define the link | |
1588 | name as an abbreviation for the ``real'' name, Emacs shows users the | |
1589 | abbreviation instead. | |
1590 | ||
1591 | @defvar directory-abbrev-alist | |
1592 | The variable @code{directory-abbrev-alist} contains an alist of | |
1593 | abbreviations to use for file directories. Each element has the form | |
1594 | @code{(@var{from} . @var{to})}, and says to replace @var{from} with | |
1595 | @var{to} when it appears in a directory name. The @var{from} string is | |
1596 | actually a regular expression; it should always start with @samp{^}. | |
1597 | The function @code{abbreviate-file-name} performs these substitutions. | |
1598 | ||
1599 | You can set this variable in @file{site-init.el} to describe the | |
1600 | abbreviations appropriate for your site. | |
1601 | ||
1602 | Here's an example, from a system on which file system @file{/home/fsf} | |
1603 | and so on are normally accessed through symbolic links named @file{/fsf} | |
1604 | and so on. | |
1605 | ||
1606 | @example | |
1607 | (("^/home/fsf" . "/fsf") | |
1608 | ("^/home/gp" . "/gp") | |
1609 | ("^/home/gd" . "/gd")) | |
1610 | @end example | |
1611 | @end defvar | |
1612 | ||
1613 | To convert a directory name to its abbreviation, use this | |
1614 | function: | |
1615 | ||
1616 | @defun abbreviate-file-name dirname | |
1617 | This function applies abbreviations from @code{directory-abbrev-alist} | |
1618 | to its argument, and substitutes @samp{~} for the user's home | |
1619 | directory. | |
1620 | @end defun | |
1621 | ||
1622 | @node Relative File Names | |
1623 | @subsection Absolute and Relative File Names | |
1624 | @cindex absolute file name | |
1625 | @cindex relative file name | |
1626 | ||
1627 | All the directories in the file system form a tree starting at the | |
1628 | root directory. A file name can specify all the directory names | |
1629 | starting from the root of the tree; then it is called an @dfn{absolute} | |
1630 | file name. Or it can specify the position of the file in the tree | |
2468d0c0 DL |
1631 | relative to a default directory; then it is called a @dfn{relative} file |
1632 | name. On Unix and GNU/Linux, an absolute file name starts with a slash | |
1633 | or a tilde (@samp{~}), and a relative one does not. On MS-DOS and | |
8241495d RS |
1634 | MS-Windows, an absolute file name starts with a slash or a backslash, or |
1635 | with a drive specification @samp{@var{x}:/}, where @var{x} is the | |
2468d0c0 | 1636 | @dfn{drive letter}. The rules on VMS are complicated. |
3e01fd9d RS |
1637 | |
1638 | @defun file-name-absolute-p filename | |
1639 | This function returns @code{t} if file @var{filename} is an absolute | |
1640 | file name, @code{nil} otherwise. On VMS, this function understands both | |
1641 | Unix syntax and VMS syntax. | |
1642 | ||
1643 | @example | |
1644 | @group | |
1645 | (file-name-absolute-p "~rms/foo") | |
1646 | @result{} t | |
1647 | @end group | |
1648 | @group | |
1649 | (file-name-absolute-p "rms/foo") | |
1650 | @result{} nil | |
1651 | @end group | |
1652 | @group | |
1653 | (file-name-absolute-p "/user/rms/foo") | |
1654 | @result{} t | |
1655 | @end group | |
1656 | @end example | |
1657 | @end defun | |
1658 | ||
1659 | @node File Name Expansion | |
1660 | @subsection Functions that Expand Filenames | |
1661 | @cindex expansion of file names | |
1662 | ||
1663 | @dfn{Expansion} of a file name means converting a relative file name | |
1664 | to an absolute one. Since this is done relative to a default directory, | |
1665 | you must specify the default directory name as well as the file name to | |
1666 | be expanded. Expansion also simplifies file names by eliminating | |
1667 | redundancies such as @file{./} and @file{@var{name}/../}. | |
1668 | ||
1669 | @defun expand-file-name filename &optional directory | |
1670 | This function converts @var{filename} to an absolute file name. If | |
f9f59935 RS |
1671 | @var{directory} is supplied, it is the default directory to start with |
1672 | if @var{filename} is relative. (The value of @var{directory} should | |
1673 | itself be an absolute directory name; it may start with @samp{~}.) | |
3e01fd9d RS |
1674 | Otherwise, the current buffer's value of @code{default-directory} is |
1675 | used. For example: | |
1676 | ||
1677 | @example | |
1678 | @group | |
1679 | (expand-file-name "foo") | |
1680 | @result{} "/xcssun/users/rms/lewis/foo" | |
1681 | @end group | |
1682 | @group | |
1683 | (expand-file-name "../foo") | |
1684 | @result{} "/xcssun/users/rms/foo" | |
1685 | @end group | |
1686 | @group | |
1687 | (expand-file-name "foo" "/usr/spool/") | |
1688 | @result{} "/usr/spool/foo" | |
1689 | @end group | |
1690 | @group | |
1691 | (expand-file-name "$HOME/foo") | |
1692 | @result{} "/xcssun/users/rms/lewis/$HOME/foo" | |
1693 | @end group | |
1694 | @end example | |
1695 | ||
1696 | Filenames containing @samp{.} or @samp{..} are simplified to their | |
1697 | canonical form: | |
1698 | ||
1699 | @example | |
1700 | @group | |
1701 | (expand-file-name "bar/../foo") | |
1702 | @result{} "/xcssun/users/rms/lewis/foo" | |
1703 | @end group | |
1704 | @end example | |
1705 | ||
3e01fd9d RS |
1706 | Note that @code{expand-file-name} does @emph{not} expand environment |
1707 | variables; only @code{substitute-in-file-name} does that. | |
1708 | @end defun | |
1709 | ||
1710 | @c Emacs 19 feature | |
2468d0c0 | 1711 | @defun file-relative-name filename &optional directory |
3e01fd9d | 1712 | This function does the inverse of expansion---it tries to return a |
b22f3a19 | 1713 | relative name that is equivalent to @var{filename} when interpreted |
2468d0c0 DL |
1714 | relative to @var{directory}. If @var{directory} is omitted or |
1715 | @code{nil}, it defaults to the current buffer's default directory. | |
89c77172 RS |
1716 | |
1717 | On some operating systems, an absolute file name begins with a device | |
1718 | name. On such systems, @var{filename} has no relative equivalent based | |
1719 | on @var{directory} if they start with two different device names. In | |
1720 | this case, @code{file-relative-name} returns @var{filename} in absolute | |
1721 | form. | |
3e01fd9d RS |
1722 | |
1723 | @example | |
1724 | (file-relative-name "/foo/bar" "/foo/") | |
a9f0a989 | 1725 | @result{} "bar" |
3e01fd9d | 1726 | (file-relative-name "/foo/bar" "/hack/") |
39a5713c | 1727 | @result{} "../foo/bar" |
3e01fd9d RS |
1728 | @end example |
1729 | @end defun | |
1730 | ||
1731 | @defvar default-directory | |
1732 | The value of this buffer-local variable is the default directory for the | |
1733 | current buffer. It should be an absolute directory name; it may start | |
969fe9b5 | 1734 | with @samp{~}. This variable is buffer-local in every buffer. |
3e01fd9d RS |
1735 | |
1736 | @code{expand-file-name} uses the default directory when its second | |
1737 | argument is @code{nil}. | |
1738 | ||
8241495d | 1739 | Aside from VMS, the value is always a string ending with a slash. |
3e01fd9d RS |
1740 | |
1741 | @example | |
1742 | @group | |
1743 | default-directory | |
1744 | @result{} "/user/lewis/manual/" | |
1745 | @end group | |
1746 | @end example | |
1747 | @end defvar | |
1748 | ||
1749 | @defun substitute-in-file-name filename | |
1750 | This function replaces environment variables references in | |
1751 | @var{filename} with the environment variable values. Following standard | |
1752 | Unix shell syntax, @samp{$} is the prefix to substitute an environment | |
1753 | variable value. | |
1754 | ||
1755 | The environment variable name is the series of alphanumeric characters | |
1756 | (including underscores) that follow the @samp{$}. If the character following | |
1757 | the @samp{$} is a @samp{@{}, then the variable name is everything up to the | |
1758 | matching @samp{@}}. | |
1759 | ||
1760 | @c Wordy to avoid overfull hbox. --rjc 15mar92 | |
1761 | Here we assume that the environment variable @code{HOME}, which holds | |
1762 | the user's home directory name, has value @samp{/xcssun/users/rms}. | |
1763 | ||
1764 | @example | |
1765 | @group | |
1766 | (substitute-in-file-name "$HOME/foo") | |
1767 | @result{} "/xcssun/users/rms/foo" | |
1768 | @end group | |
1769 | @end example | |
1770 | ||
969fe9b5 RS |
1771 | After substitution, if a @samp{~} or a @samp{/} appears following a |
1772 | @samp{/}, everything before the following @samp{/} is discarded: | |
3e01fd9d RS |
1773 | |
1774 | @example | |
1775 | @group | |
1776 | (substitute-in-file-name "bar/~/foo") | |
1777 | @result{} "~/foo" | |
1778 | @end group | |
1779 | @group | |
1780 | (substitute-in-file-name "/usr/local/$HOME/foo") | |
1781 | @result{} "/xcssun/users/rms/foo" | |
f9f59935 | 1782 | ;; @r{@file{/usr/local/} has been discarded.} |
3e01fd9d RS |
1783 | @end group |
1784 | @end example | |
1785 | ||
1786 | On VMS, @samp{$} substitution is not done, so this function does nothing | |
1787 | on VMS except discard superfluous initial components as shown above. | |
1788 | @end defun | |
1789 | ||
1790 | @node Unique File Names | |
1791 | @subsection Generating Unique File Names | |
1792 | ||
1793 | Some programs need to write temporary files. Here is the usual way to | |
8241495d | 1794 | construct a name for such a file, starting in Emacs 21: |
3e01fd9d RS |
1795 | |
1796 | @example | |
8241495d | 1797 | (make-temp-file @var{name-of-application}) |
3e01fd9d RS |
1798 | @end example |
1799 | ||
1800 | @noindent | |
8241495d RS |
1801 | The job of @code{make-temp-file} is to prevent two different users or |
1802 | two different jobs from trying to use the exact same file name. | |
3e01fd9d | 1803 | |
8241495d RS |
1804 | @defun make-temp-file prefix &optional dir-flag |
1805 | @tindex make-temp-file | |
1806 | This function creates a temporary file and returns its name. | |
1807 | The name starts with @var{prefix}; it also contains a number that is | |
1808 | different in each Emacs job. If @var{prefix} is a relative file name, | |
1809 | it is expanded against @code{temporary-file-directory}. | |
3e01fd9d RS |
1810 | |
1811 | @example | |
1812 | @group | |
8241495d | 1813 | (make-temp-file "foo") |
a9f0a989 | 1814 | @result{} "/tmp/foo232J6v" |
3e01fd9d RS |
1815 | @end group |
1816 | @end example | |
1817 | ||
8241495d RS |
1818 | When @code{make-temp-file} returns, the file has been created and is |
1819 | empty. At that point, you should write the intended contents into the | |
1820 | file. | |
1821 | ||
1822 | If @var{dir-flag} is non-@code{nil}, @code{make-temp-file} creates | |
1823 | an empty directory instead of an empty file. | |
1824 | ||
3e01fd9d | 1825 | To prevent conflicts among different libraries running in the same |
8241495d RS |
1826 | Emacs, each Lisp program that uses @code{make-temp-file} should have its |
1827 | own @var{prefix}. The number added to the end of @var{prefix} | |
a9f0a989 RS |
1828 | distinguishes between the same application running in different Emacs |
1829 | jobs. Additional added characters permit a large number of distinct | |
1830 | names even in one Emacs job. | |
8241495d RS |
1831 | @end defun |
1832 | ||
1833 | The default directory for temporary files is controlled by the | |
1834 | variable @code{temporary-file-directory}. This variable gives the user | |
1835 | a uniform way to specify the directory for all temporary files. Some | |
1836 | programs use @code{small-temporary-file-directory} instead, if that is | |
1837 | non-@code{nil}. To use it, you should expand the prefix against | |
1838 | the proper directory before calling @code{make-temp-file}. | |
1839 | ||
1840 | In older Emacs versions where @code{make-temp-file} does not exist, | |
1841 | you should use @code{make-temp-name} instead: | |
1842 | ||
1843 | @example | |
1844 | (make-temp-name | |
1845 | (expand-file-name @var{name-of-application} | |
1846 | temporary-file-directory)) | |
1847 | @end example | |
1848 | ||
1849 | @defun make-temp-name string | |
1850 | This function generates a string that can be used as a unique file name. | |
1851 | The name starts with @var{string}, and contains a number that is | |
1852 | different in each Emacs job. It is like @code{make-temp-file} except | |
1853 | that it just constructs a name, and does not create a file. On MS-DOS, | |
1854 | the @var{string} prefix can be truncated to fit into the 8+3 file-name | |
1855 | limits. | |
3e01fd9d RS |
1856 | @end defun |
1857 | ||
a9f0a989 | 1858 | @defvar temporary-file-directory |
8241495d RS |
1859 | @cindex @code{TMPDIR} environment variable |
1860 | @cindex @code{TMP} environment variable | |
1861 | @cindex @code{TEMP} environment variable | |
a9f0a989 RS |
1862 | This variable specifies the directory name for creating temporary files. |
1863 | Its value should be a directory name (@pxref{Directory Names}), but it | |
f1e2c45e RS |
1864 | is good for Lisp programs to cope if the value is a directory's file |
1865 | name instead. Using the value as the second argument to | |
1866 | @code{expand-file-name} is a good way to achieve that. | |
a9f0a989 RS |
1867 | |
1868 | The default value is determined in a reasonable way for your operating | |
8241495d RS |
1869 | system; it is based on the @code{TMPDIR}, @code{TMP} and @code{TEMP} |
1870 | environment variables, with a fall-back to a system-dependent name if | |
1871 | none of these variables is defined. | |
a9f0a989 RS |
1872 | |
1873 | Even if you do not use @code{make-temp-name} to choose the temporary | |
1874 | file's name, you should still use this variable to decide which | |
8241495d RS |
1875 | directory to put the file in. However, if you expect the file to be |
1876 | small, you should use @code{small-temporary-file-directory} first if | |
1877 | that is non-@code{nil}. | |
1878 | @end defvar | |
1879 | ||
1880 | @tindex small-temporary-file-directory | |
1881 | @defvar small-temporary-file-directory | |
1882 | This variable (new in Emacs 21) specifies the directory name for | |
1883 | creating certain temporary files, which are likely to be small. | |
1884 | ||
1885 | If you want to write a temporary file which is likely to be small, you | |
1886 | should compute the directory like this: | |
1887 | ||
1888 | @example | |
1889 | (make-temp-file | |
1890 | (expand-file-name @var{prefix} | |
1891 | (or small-temporary-file-directory | |
1892 | temporary-file-directory))) | |
1893 | @end example | |
a9f0a989 RS |
1894 | @end defvar |
1895 | ||
3e01fd9d RS |
1896 | @node File Name Completion |
1897 | @subsection File Name Completion | |
1898 | @cindex file name completion subroutines | |
1899 | @cindex completion, file name | |
1900 | ||
1901 | This section describes low-level subroutines for completing a file | |
1902 | name. For other completion functions, see @ref{Completion}. | |
1903 | ||
1904 | @defun file-name-all-completions partial-filename directory | |
1905 | This function returns a list of all possible completions for a file | |
1906 | whose name starts with @var{partial-filename} in directory | |
1907 | @var{directory}. The order of the completions is the order of the files | |
1908 | in the directory, which is unpredictable and conveys no useful | |
1909 | information. | |
1910 | ||
1911 | The argument @var{partial-filename} must be a file name containing no | |
5557b83b RS |
1912 | directory part and no slash (or backslash on some systems). The current |
1913 | buffer's default directory is prepended to @var{directory}, if | |
1914 | @var{directory} is not absolute. | |
3e01fd9d | 1915 | |
9e2b495b RS |
1916 | In the following example, suppose that @file{~rms/lewis} is the current |
1917 | default directory, and has five files whose names begin with @samp{f}: | |
3e01fd9d RS |
1918 | @file{foo}, @file{file~}, @file{file.c}, @file{file.c.~1~}, and |
1919 | @file{file.c.~2~}.@refill | |
1920 | ||
1921 | @example | |
1922 | @group | |
1923 | (file-name-all-completions "f" "") | |
1924 | @result{} ("foo" "file~" "file.c.~2~" | |
1925 | "file.c.~1~" "file.c") | |
1926 | @end group | |
1927 | ||
1928 | @group | |
1929 | (file-name-all-completions "fo" "") | |
1930 | @result{} ("foo") | |
1931 | @end group | |
1932 | @end example | |
1933 | @end defun | |
1934 | ||
1935 | @defun file-name-completion filename directory | |
1936 | This function completes the file name @var{filename} in directory | |
1937 | @var{directory}. It returns the longest prefix common to all file names | |
1938 | in directory @var{directory} that start with @var{filename}. | |
1939 | ||
1940 | If only one match exists and @var{filename} matches it exactly, the | |
1941 | function returns @code{t}. The function returns @code{nil} if directory | |
1942 | @var{directory} contains no name starting with @var{filename}. | |
1943 | ||
1944 | In the following example, suppose that the current default directory | |
1945 | has five files whose names begin with @samp{f}: @file{foo}, | |
1946 | @file{file~}, @file{file.c}, @file{file.c.~1~}, and | |
1947 | @file{file.c.~2~}.@refill | |
1948 | ||
1949 | @example | |
1950 | @group | |
1951 | (file-name-completion "fi" "") | |
1952 | @result{} "file" | |
1953 | @end group | |
1954 | ||
1955 | @group | |
1956 | (file-name-completion "file.c.~1" "") | |
1957 | @result{} "file.c.~1~" | |
1958 | @end group | |
1959 | ||
1960 | @group | |
1961 | (file-name-completion "file.c.~1~" "") | |
1962 | @result{} t | |
1963 | @end group | |
1964 | ||
1965 | @group | |
1966 | (file-name-completion "file.c.~3" "") | |
1967 | @result{} nil | |
1968 | @end group | |
1969 | @end example | |
1970 | @end defun | |
1971 | ||
1972 | @defopt completion-ignored-extensions | |
1973 | @code{file-name-completion} usually ignores file names that end in any | |
1974 | string in this list. It does not ignore them when all the possible | |
1975 | completions end in one of these suffixes or when a buffer showing all | |
1976 | possible completions is displayed.@refill | |
1977 | ||
1978 | A typical value might look like this: | |
1979 | ||
1980 | @example | |
1981 | @group | |
1982 | completion-ignored-extensions | |
1983 | @result{} (".o" ".elc" "~" ".dvi") | |
1984 | @end group | |
1985 | @end example | |
1986 | @end defopt | |
1987 | ||
fbc1b72c RS |
1988 | @node Standard File Names |
1989 | @subsection Standard File Names | |
1990 | ||
1991 | Most of the file names used in Lisp programs are entered by the user. | |
1992 | But occasionally a Lisp program needs to specify a standard file name | |
1993 | for a particular use---typically, to hold customization information | |
1994 | about each user. For example, abbrev definitions are stored (by | |
1995 | default) in the file @file{~/.abbrev_defs}; the @code{completion} | |
1996 | package stores completions in the file @file{~/.completions}. These are | |
1997 | two of the many standard file names used by parts of Emacs for certain | |
1998 | purposes. | |
1999 | ||
2000 | Various operating systems have their own conventions for valid file | |
2001 | names and for which file names to use for user profile data. A Lisp | |
2002 | program which reads a file using a standard file name ought to use, on | |
2003 | each type of system, a file name suitable for that system. The function | |
2004 | @code{convert-standard-filename} makes this easy to do. | |
2005 | ||
2006 | @defun convert-standard-filename filename | |
2007 | This function alters the file name @var{filename} to fit the conventions | |
2008 | of the operating system in use, and returns the result as a new string. | |
2009 | @end defun | |
2010 | ||
2011 | The recommended way to specify a standard file name in a Lisp program | |
2012 | is to choose a name which fits the conventions of GNU and Unix systems, | |
2013 | usually with a nondirectory part that starts with a period, and pass it | |
2014 | to @code{convert-standard-filename} instead of using it directly. Here | |
2015 | is an example from the @code{completion} package: | |
2016 | ||
2017 | @example | |
2018 | (defvar save-completions-file-name | |
2019 | (convert-standard-filename "~/.completions") | |
2020 | "*The file name to save completions to.") | |
2021 | @end example | |
2022 | ||
2023 | On GNU and Unix systems, and on some other systems as well, | |
2024 | @code{convert-standard-filename} returns its argument unchanged. On | |
a9f0a989 | 2025 | some other systems, it alters the name to fit the system's conventions. |
fbc1b72c RS |
2026 | |
2027 | For example, on MS-DOS the alterations made by this function include | |
2028 | converting a leading @samp{.} to @samp{_}, converting a @samp{_} in the | |
2029 | middle of the name to @samp{.} if there is no other @samp{.}, inserting | |
2030 | a @samp{.} after eight characters if there is none, and truncating to | |
2031 | three characters after the @samp{.}. (It makes other changes as well.) | |
2032 | Thus, @file{.abbrev_defs} becomes @file{_abbrev.def}, and | |
2033 | @file{.completions} becomes @file{_complet.ion}. | |
2034 | ||
3e01fd9d RS |
2035 | @node Contents of Directories |
2036 | @section Contents of Directories | |
2037 | @cindex directory-oriented functions | |
2038 | @cindex file names in directory | |
2039 | ||
2040 | A directory is a kind of file that contains other files entered under | |
2041 | various names. Directories are a feature of the file system. | |
2042 | ||
2043 | Emacs can list the names of the files in a directory as a Lisp list, | |
2044 | or display the names in a buffer using the @code{ls} shell command. In | |
2045 | the latter case, it can optionally display information about each file, | |
2046 | depending on the options passed to the @code{ls} command. | |
2047 | ||
2048 | @defun directory-files directory &optional full-name match-regexp nosort | |
2049 | This function returns a list of the names of the files in the directory | |
2050 | @var{directory}. By default, the list is in alphabetical order. | |
2051 | ||
2052 | If @var{full-name} is non-@code{nil}, the function returns the files' | |
2053 | absolute file names. Otherwise, it returns the names relative to | |
2054 | the specified directory. | |
2055 | ||
2056 | If @var{match-regexp} is non-@code{nil}, this function returns only | |
2057 | those file names that contain a match for that regular expression---the | |
2058 | other file names are excluded from the list. | |
2059 | ||
2060 | @c Emacs 19 feature | |
2061 | If @var{nosort} is non-@code{nil}, @code{directory-files} does not sort | |
2062 | the list, so you get the file names in no particular order. Use this if | |
2063 | you want the utmost possible speed and don't care what order the files | |
2064 | are processed in. If the order of processing is visible to the user, | |
2065 | then the user will probably be happier if you do sort the names. | |
2066 | ||
2067 | @example | |
2068 | @group | |
2069 | (directory-files "~lewis") | |
2070 | @result{} ("#foo#" "#foo.el#" "." ".." | |
2071 | "dired-mods.el" "files.texi" | |
2072 | "files.texi.~1~") | |
2073 | @end group | |
2074 | @end example | |
2075 | ||
2076 | An error is signaled if @var{directory} is not the name of a directory | |
2077 | that can be read. | |
2078 | @end defun | |
2079 | ||
2080 | @defun file-name-all-versions file dirname | |
2081 | This function returns a list of all versions of the file named | |
2082 | @var{file} in directory @var{dirname}. | |
2083 | @end defun | |
2084 | ||
b6954afd RS |
2085 | @tindex file-expand-wildcards |
2086 | @defun file-expand-wildcards pattern &optional full | |
2087 | This function expands the wildcard pattern @var{pattern}, returning | |
08f0f5e9 | 2088 | a list of file names that match it. |
b6954afd | 2089 | |
08f0f5e9 | 2090 | If @var{pattern} is written as an absolute file name, |
b6954afd RS |
2091 | the values are absolute also. |
2092 | ||
2093 | If @var{pattern} is written as a relative file name, it is interpreted | |
2094 | relative to the current default directory. The file names returned are | |
2095 | normally also relative to the current default directory. However, if | |
2096 | @var{full} is non-@code{nil}, they are absolute. | |
2097 | @end defun | |
2098 | ||
3e01fd9d | 2099 | @defun insert-directory file switches &optional wildcard full-directory-p |
b22f3a19 RS |
2100 | This function inserts (in the current buffer) a directory listing for |
2101 | directory @var{file}, formatted with @code{ls} according to | |
2102 | @var{switches}. It leaves point after the inserted text. | |
3e01fd9d | 2103 | |
b22f3a19 | 2104 | The argument @var{file} may be either a directory name or a file |
3e01fd9d RS |
2105 | specification including wildcard characters. If @var{wildcard} is |
2106 | non-@code{nil}, that means treat @var{file} as a file specification with | |
2107 | wildcards. | |
2108 | ||
a9f0a989 RS |
2109 | If @var{full-directory-p} is non-@code{nil}, that means the directory |
2110 | listing is expected to show the full contents of a directory. You | |
2111 | should specify @code{t} when @var{file} is a directory and switches do | |
2112 | not contain @samp{-d}. (The @samp{-d} option to @code{ls} says to | |
2113 | describe a directory itself as a file, rather than showing its | |
2114 | contents.) | |
3e01fd9d | 2115 | |
8241495d RS |
2116 | On most systems, this function works by running a directory listing |
2117 | program whose name is in the variable @code{insert-directory-program}. | |
2118 | If @var{wildcard} is non-@code{nil}, it also runs the shell specified by | |
3e01fd9d | 2119 | @code{shell-file-name}, to expand the wildcards. |
8241495d RS |
2120 | |
2121 | MS-DOS and MS-Windows systems usually lack the standard Unix program | |
2122 | @code{ls}, so this function emulates the standard Unix program @code{ls} | |
2123 | with Lisp code. | |
3e01fd9d RS |
2124 | @end defun |
2125 | ||
2126 | @defvar insert-directory-program | |
2127 | This variable's value is the program to run to generate a directory listing | |
8241495d RS |
2128 | for the function @code{insert-directory}. It is ignored on systems |
2129 | which generate the listing with Lisp code. | |
3e01fd9d RS |
2130 | @end defvar |
2131 | ||
2132 | @node Create/Delete Dirs | |
2133 | @section Creating and Deleting Directories | |
2134 | @c Emacs 19 features | |
2135 | ||
b22f3a19 RS |
2136 | Most Emacs Lisp file-manipulation functions get errors when used on |
2137 | files that are directories. For example, you cannot delete a directory | |
2138 | with @code{delete-file}. These special functions exist to create and | |
2139 | delete directories. | |
2140 | ||
2468d0c0 | 2141 | @defun make-directory dirname &optional parents |
3e01fd9d | 2142 | This function creates a directory named @var{dirname}. |
2468d0c0 DL |
2143 | If @var{parents} is non-@code{nil}, that means to create |
2144 | the parent directories first, if they don't already exist. | |
3e01fd9d RS |
2145 | @end defun |
2146 | ||
2147 | @defun delete-directory dirname | |
2148 | This function deletes the directory named @var{dirname}. The function | |
2149 | @code{delete-file} does not work for files that are directories; you | |
bfe721d1 KH |
2150 | must use @code{delete-directory} for them. If the directory contains |
2151 | any files, @code{delete-directory} signals an error. | |
3e01fd9d RS |
2152 | @end defun |
2153 | ||
2154 | @node Magic File Names | |
2155 | @section Making Certain File Names ``Magic'' | |
2156 | @cindex magic file names | |
2157 | ||
2158 | @c Emacs 19 feature | |
f9f59935 RS |
2159 | You can implement special handling for certain file names. This is |
2160 | called making those names @dfn{magic}. The principal use for this | |
2161 | feature is in implementing remote file names (@pxref{Remote Files,, | |
2162 | Remote Files, emacs, The GNU Emacs Manual}). | |
2163 | ||
2164 | To define a kind of magic file name, you must supply a regular | |
b22f3a19 | 2165 | expression to define the class of names (all those that match the |
3e01fd9d RS |
2166 | regular expression), plus a handler that implements all the primitive |
2167 | Emacs file operations for file names that do match. | |
2168 | ||
f9f59935 | 2169 | The variable @code{file-name-handler-alist} holds a list of handlers, |
3e01fd9d RS |
2170 | together with regular expressions that determine when to apply each |
2171 | handler. Each element has this form: | |
2172 | ||
2173 | @example | |
2174 | (@var{regexp} . @var{handler}) | |
2175 | @end example | |
2176 | ||
2177 | @noindent | |
2178 | All the Emacs primitives for file access and file name transformation | |
2179 | check the given file name against @code{file-name-handler-alist}. If | |
2180 | the file name matches @var{regexp}, the primitives handle that file by | |
2181 | calling @var{handler}. | |
2182 | ||
2183 | The first argument given to @var{handler} is the name of the primitive; | |
2184 | the remaining arguments are the arguments that were passed to that | |
2185 | operation. (The first of these arguments is typically the file name | |
2186 | itself.) For example, if you do this: | |
2187 | ||
2188 | @example | |
2189 | (file-exists-p @var{filename}) | |
2190 | @end example | |
2191 | ||
2192 | @noindent | |
2193 | and @var{filename} has handler @var{handler}, then @var{handler} is | |
2194 | called like this: | |
2195 | ||
2196 | @example | |
2197 | (funcall @var{handler} 'file-exists-p @var{filename}) | |
2198 | @end example | |
2199 | ||
b22f3a19 | 2200 | Here are the operations that a magic file name handler gets to handle: |
3e01fd9d | 2201 | |
37680279 | 2202 | @ifnottex |
3e01fd9d RS |
2203 | @noindent |
2204 | @code{add-name-to-file}, @code{copy-file}, @code{delete-directory}, | |
969fe9b5 | 2205 | @code{delete-file}, |
63ff95ee | 2206 | @code{diff-latest-backup-file}, |
3e01fd9d | 2207 | @code{directory-file-name}, |
969fe9b5 | 2208 | @code{directory-files}, |
9e2b495b | 2209 | @code{dired-call-process}, |
3e01fd9d | 2210 | @code{dired-compress-file}, @code{dired-uncache}, |
969fe9b5 RS |
2211 | @code{expand-file-name}, |
2212 | @code{file-accessible-directory-p},@* | |
2213 | @code{file-attributes}, | |
2214 | @code{file-directory-p}, | |
2215 | @code{file-executable-p}, @code{file-exists-p},@* | |
2216 | @code{file-local-copy}, | |
2217 | @code{file-modes}, @code{file-name-all-completions},@* | |
2218 | @code{file-name-as-directory}, | |
2219 | @code{file-name-completion}, | |
9e2b495b RS |
2220 | @code{file-name-directory}, |
2221 | @code{file-name-nondirectory}, | |
3e01fd9d | 2222 | @code{file-name-sans-versions}, @code{file-newer-than-file-p}, |
fbc1b72c | 2223 | @code{file-ownership-preserved-p}, |
5949c48a | 2224 | @code{file-readable-p}, @code{file-regular-p}, @code{file-symlink-p}, |
63ff95ee | 2225 | @code{file-truename}, @code{file-writable-p}, |
fbc1b72c | 2226 | @code{find-backup-file-name}, |
969fe9b5 RS |
2227 | @code{get-file-buffer},@* |
2228 | @code{insert-directory}, | |
9e2b495b | 2229 | @code{insert-file-contents}, |
fbc1b72c | 2230 | @code{load}, @code{make-directory}, |
3e01fd9d | 2231 | @code{make-symbolic-link}, @code{rename-file}, @code{set-file-modes}, |
f1e2c45e | 2232 | @code{set-visited-file-modtime}, @code{shell-command},@* |
969fe9b5 | 2233 | @code{unhandled-file-name-directory}, |
9e2b495b | 2234 | @code{vc-registered}, |
969fe9b5 RS |
2235 | @code{verify-visited-file-modtime},@* |
2236 | @code{write-region}. | |
37680279 | 2237 | @end ifnottex |
f1e2c45e RS |
2238 | @iftex |
2239 | @noindent | |
8241495d | 2240 | @flushleft |
f1e2c45e RS |
2241 | @code{add-name-to-file}, @code{copy-file}, @code{delete-directory}, |
2242 | @code{delete-file}, | |
2243 | @code{diff-latest-backup-file}, | |
2244 | @code{directory-file-name}, | |
2245 | @code{directory-files}, | |
2246 | @code{dired-call-process}, | |
2247 | @code{dired-compress-file}, @code{dired-uncache}, | |
2248 | @code{expand-file-name}, | |
2249 | @code{file-accessible-direc@discretionary{}{}{}tory-p}, | |
2250 | @code{file-attributes}, | |
2251 | @code{file-direct@discretionary{}{}{}ory-p}, | |
2252 | @code{file-executable-p}, @code{file-exists-p}, | |
2253 | @code{file-local-copy}, | |
2254 | @code{file-modes}, @code{file-name-all-completions}, | |
2255 | @code{file-name-as-directory}, | |
2256 | @code{file-name-completion}, | |
2257 | @code{file-name-directory}, | |
2258 | @code{file-name-nondirec@discretionary{}{}{}tory}, | |
2259 | @code{file-name-sans-versions}, @code{file-newer-than-file-p}, | |
2260 | @code{file-ownership-pre@discretionary{}{}{}served-p}, | |
2261 | @code{file-readable-p}, @code{file-regular-p}, @code{file-symlink-p}, | |
2262 | @code{file-truename}, @code{file-writable-p}, | |
2263 | @code{find-backup-file-name}, | |
2264 | @code{get-file-buffer}, | |
2265 | @code{insert-directory}, | |
2266 | @code{insert-file-contents}, | |
2267 | @code{load}, @code{make-direc@discretionary{}{}{}tory}, | |
2268 | @code{make-symbolic-link}, @code{rename-file}, @code{set-file-modes}, | |
2269 | @code{set-visited-file-modtime}, @code{shell-command}, | |
2270 | @code{unhandled-file-name-directory}, | |
2271 | @code{vc-regis@discretionary{}{}{}tered}, | |
2272 | @code{verify-visited-file-modtime}, | |
2273 | @code{write-region}. | |
8241495d | 2274 | @end flushleft |
f1e2c45e | 2275 | @end iftex |
3e01fd9d | 2276 | |
6ca88231 RS |
2277 | Handlers for @code{insert-file-contents} typically need to clear the |
2278 | buffer's modified flag, with @code{(set-buffer-modified-p nil)}, if the | |
2279 | @var{visit} argument is non-@code{nil}. This also has the effect of | |
2280 | unlocking the buffer if it is locked. | |
2281 | ||
3e01fd9d | 2282 | The handler function must handle all of the above operations, and |
b22f3a19 RS |
2283 | possibly others to be added in the future. It need not implement all |
2284 | these operations itself---when it has nothing special to do for a | |
2285 | certain operation, it can reinvoke the primitive, to handle the | |
2286 | operation ``in the usual way''. It should always reinvoke the primitive | |
2287 | for an operation it does not recognize. Here's one way to do this: | |
3e01fd9d | 2288 | |
841e483d | 2289 | @smallexample |
3e01fd9d RS |
2290 | (defun my-file-handler (operation &rest args) |
2291 | ;; @r{First check for the specific operations} | |
2292 | ;; @r{that we have special handling for.} | |
2293 | (cond ((eq operation 'insert-file-contents) @dots{}) | |
2294 | ((eq operation 'write-region) @dots{}) | |
2295 | @dots{} | |
2296 | ;; @r{Handle any operation we don't know about.} | |
841e483d | 2297 | (t (let ((inhibit-file-name-handlers |
f9f59935 RS |
2298 | (cons 'my-file-handler |
2299 | (and (eq inhibit-file-name-operation operation) | |
2300 | inhibit-file-name-handlers))) | |
2301 | (inhibit-file-name-operation operation)) | |
3e01fd9d | 2302 | (apply operation args))))) |
841e483d RS |
2303 | @end smallexample |
2304 | ||
2305 | When a handler function decides to call the ordinary Emacs primitive for | |
2306 | the operation at hand, it needs to prevent the primitive from calling | |
2307 | the same handler once again, thus leading to an infinite recursion. The | |
2308 | example above shows how to do this, with the variables | |
2309 | @code{inhibit-file-name-handlers} and | |
2310 | @code{inhibit-file-name-operation}. Be careful to use them exactly as | |
2311 | shown above; the details are crucial for proper behavior in the case of | |
2312 | multiple handlers, and for operations that have two file names that may | |
2313 | each have handlers. | |
2314 | ||
2315 | @defvar inhibit-file-name-handlers | |
2316 | This variable holds a list of handlers whose use is presently inhibited | |
2317 | for a certain operation. | |
2318 | @end defvar | |
3e01fd9d | 2319 | |
841e483d RS |
2320 | @defvar inhibit-file-name-operation |
2321 | The operation for which certain handlers are presently inhibited. | |
2322 | @end defvar | |
2323 | ||
2324 | @defun find-file-name-handler file operation | |
3e01fd9d | 2325 | This function returns the handler function for file name @var{file}, or |
841e483d RS |
2326 | @code{nil} if there is none. The argument @var{operation} should be the |
2327 | operation to be performed on the file---the value you will pass to the | |
2328 | handler as its first argument when you call it. The operation is needed | |
2329 | for comparison with @code{inhibit-file-name-operation}. | |
3e01fd9d RS |
2330 | @end defun |
2331 | ||
2332 | @defun file-local-copy filename | |
b22f3a19 RS |
2333 | This function copies file @var{filename} to an ordinary non-magic file, |
2334 | if it isn't one already. | |
2335 | ||
f1e2c45e | 2336 | If @var{filename} specifies a magic file name, which programs |
b22f3a19 RS |
2337 | outside Emacs cannot directly read or write, this copies the contents to |
2338 | an ordinary file and returns that file's name. | |
3e01fd9d RS |
2339 | |
2340 | If @var{filename} is an ordinary file name, not magic, then this function | |
2341 | does nothing and returns @code{nil}. | |
2342 | @end defun | |
2343 | ||
2344 | @defun unhandled-file-name-directory filename | |
f9f59935 RS |
2345 | This function returns the name of a directory that is not magic. It |
2346 | uses the directory part of @var{filename} if that is not magic. For a | |
2347 | magic file name, it invokes the file name handler, which therefore | |
2348 | decides what value to return. | |
3e01fd9d RS |
2349 | |
2350 | This is useful for running a subprocess; every subprocess must have a | |
2351 | non-magic directory to serve as its current directory, and this function | |
2352 | is a good way to come up with one. | |
2353 | @end defun | |
841e483d | 2354 | |
22697dac KH |
2355 | @node Format Conversion |
2356 | @section File Format Conversion | |
2357 | ||
2358 | @cindex file format conversion | |
2359 | @cindex encoding file formats | |
2360 | @cindex decoding file formats | |
2361 | The variable @code{format-alist} defines a list of @dfn{file formats}, | |
bfe721d1 | 2362 | which describe textual representations used in files for the data (text, |
22697dac | 2363 | text-properties, and possibly other information) in an Emacs buffer. |
bfe721d1 KH |
2364 | Emacs performs format conversion if appropriate when reading and writing |
2365 | files. | |
22697dac KH |
2366 | |
2367 | @defvar format-alist | |
2368 | This list contains one format definition for each defined file format. | |
2369 | @end defvar | |
2370 | ||
2371 | @cindex format definition | |
2372 | Each format definition is a list of this form: | |
2373 | ||
2374 | @example | |
2375 | (@var{name} @var{doc-string} @var{regexp} @var{from-fn} @var{to-fn} @var{modify} @var{mode-fn}) | |
2376 | @end example | |
2377 | ||
2378 | Here is what the elements in a format definition mean: | |
2379 | ||
2380 | @table @var | |
2381 | @item name | |
2382 | The name of this format. | |
2383 | ||
2384 | @item doc-string | |
2385 | A documentation string for the format. | |
2386 | ||
2387 | @item regexp | |
2388 | A regular expression which is used to recognize files represented in | |
2389 | this format. | |
2390 | ||
2391 | @item from-fn | |
969fe9b5 | 2392 | A shell command or function to decode data in this format (to convert |
f9f59935 | 2393 | file data into the usual Emacs data representation). |
22697dac | 2394 | |
969fe9b5 RS |
2395 | A shell command is represented as a string; Emacs runs the command as a |
2396 | filter to perform the conversion. | |
2397 | ||
2398 | If @var{from-fn} is a function, it is called with two arguments, @var{begin} | |
f9f59935 RS |
2399 | and @var{end}, which specify the part of the buffer it should convert. |
2400 | It should convert the text by editing it in place. Since this can | |
2401 | change the length of the text, @var{from-fn} should return the modified | |
2402 | end position. | |
22697dac | 2403 | |
bfe721d1 | 2404 | One responsibility of @var{from-fn} is to make sure that the beginning |
22697dac KH |
2405 | of the file no longer matches @var{regexp}. Otherwise it is likely to |
2406 | get called again. | |
2407 | ||
2408 | @item to-fn | |
969fe9b5 RS |
2409 | A shell command or function to encode data in this format---that is, to |
2410 | convert the usual Emacs data representation into this format. | |
22697dac | 2411 | |
f9f59935 RS |
2412 | If @var{to-fn} is a string, it is a shell command; Emacs runs the |
2413 | command as a filter to perform the conversion. | |
2414 | ||
969fe9b5 | 2415 | If @var{to-fn} is a function, it is called with two arguments, @var{begin} |
f9f59935 RS |
2416 | and @var{end}, which specify the part of the buffer it should convert. |
2417 | There are two ways it can do the conversion: | |
22697dac KH |
2418 | |
2419 | @itemize @bullet | |
2420 | @item | |
2421 | By editing the buffer in place. In this case, @var{to-fn} should | |
2422 | return the end-position of the range of text, as modified. | |
2423 | ||
2424 | @item | |
2425 | By returning a list of annotations. This is a list of elements of the | |
2426 | form @code{(@var{position} . @var{string})}, where @var{position} is an | |
2427 | integer specifying the relative position in the text to be written, and | |
2428 | @var{string} is the annotation to add there. The list must be sorted in | |
2429 | order of position when @var{to-fn} returns it. | |
2430 | ||
2431 | When @code{write-region} actually writes the text from the buffer to the | |
2432 | file, it intermixes the specified annotations at the corresponding | |
2433 | positions. All this takes place without modifying the buffer. | |
2434 | @end itemize | |
2435 | ||
2436 | @item modify | |
2437 | A flag, @code{t} if the encoding function modifies the buffer, and | |
2438 | @code{nil} if it works by returning a list of annotations. | |
2439 | ||
8f3efb4e RS |
2440 | @item mode-fn |
2441 | A minor-mode function to call after visiting a file converted from this | |
2442 | format. The function is called with one argument, the integer 1; | |
2443 | that tells a minor-mode function to enable the mode. | |
22697dac KH |
2444 | @end table |
2445 | ||
2446 | The function @code{insert-file-contents} automatically recognizes file | |
2447 | formats when it reads the specified file. It checks the text of the | |
2448 | beginning of the file against the regular expressions of the format | |
2449 | definitions, and if it finds a match, it calls the decoding function for | |
2450 | that format. Then it checks all the known formats over again. | |
2451 | It keeps checking them until none of them is applicable. | |
2452 | ||
2453 | Visiting a file, with @code{find-file-noselect} or the commands that use | |
2454 | it, performs conversion likewise (because it calls | |
bfe721d1 KH |
2455 | @code{insert-file-contents}); it also calls the mode function for each |
2456 | format that it decodes. It stores a list of the format names in the | |
2457 | buffer-local variable @code{buffer-file-format}. | |
22697dac KH |
2458 | |
2459 | @defvar buffer-file-format | |
bfe721d1 KH |
2460 | This variable states the format of the visited file. More precisely, |
2461 | this is a list of the file format names that were decoded in the course | |
969fe9b5 | 2462 | of visiting the current buffer's file. It is always buffer-local in all |
22697dac KH |
2463 | buffers. |
2464 | @end defvar | |
2465 | ||
2466 | When @code{write-region} writes data into a file, it first calls the | |
bfe721d1 KH |
2467 | encoding functions for the formats listed in @code{buffer-file-format}, |
2468 | in the order of appearance in the list. | |
22697dac | 2469 | |
f9f59935 | 2470 | @deffn Command format-write-file file format |
22697dac KH |
2471 | This command writes the current buffer contents into the file @var{file} |
2472 | in format @var{format}, and makes that format the default for future | |
bfe721d1 KH |
2473 | saves of the buffer. The argument @var{format} is a list of format |
2474 | names. | |
f9f59935 | 2475 | @end deffn |
22697dac | 2476 | |
f9f59935 | 2477 | @deffn Command format-find-file file format |
63ff95ee MW |
2478 | This command finds the file @var{file}, converting it according to |
2479 | format @var{format}. It also makes @var{format} the default if the | |
2480 | buffer is saved later. | |
2481 | ||
2482 | The argument @var{format} is a list of format names. If @var{format} is | |
2483 | @code{nil}, no conversion takes place. Interactively, typing just | |
2484 | @key{RET} for @var{format} specifies @code{nil}. | |
f9f59935 | 2485 | @end deffn |
63ff95ee | 2486 | |
969fe9b5 | 2487 | @deffn Command format-insert-file file format &optional beg end |
63ff95ee MW |
2488 | This command inserts the contents of file @var{file}, converting it |
2489 | according to format @var{format}. If @var{beg} and @var{end} are | |
2490 | non-@code{nil}, they specify which part of the file to read, as in | |
2491 | @code{insert-file-contents} (@pxref{Reading from Files}). | |
2492 | ||
2493 | The return value is like what @code{insert-file-contents} returns: a | |
2494 | list of the absolute file name and the length of the data inserted | |
2495 | (after conversion). | |
2496 | ||
2497 | The argument @var{format} is a list of format names. If @var{format} is | |
2498 | @code{nil}, no conversion takes place. Interactively, typing just | |
2499 | @key{RET} for @var{format} specifies @code{nil}. | |
f9f59935 | 2500 | @end deffn |
63ff95ee | 2501 | |
22697dac KH |
2502 | @defvar auto-save-file-format |
2503 | This variable specifies the format to use for auto-saving. Its value is | |
2504 | a list of format names, just like the value of | |
a9f0a989 RS |
2505 | @code{buffer-file-format}; however, it is used instead of |
2506 | @code{buffer-file-format} for writing auto-save files. This variable is | |
2507 | always buffer-local in all buffers. | |
841e483d | 2508 | @end defvar |