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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
fd897522 | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
177c0ea7 | 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. |
3e01fd9d RS |
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 |
3e01fd9d RS |
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 |
3e01fd9d | 94 | This command selects a buffer visiting the file @var{filename}, |
177c0ea7 | 95 | using an existing buffer if there is one, and otherwise creating a |
3e01fd9d RS |
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 | |
f2aa473a | 144 | @code{find-file-hook}. |
f9f59935 RS |
145 | |
146 | If the optional argument @var{rawfile} is non-@code{nil}, then | |
147 | @code{after-find-file} is not called, and the | |
f2aa473a | 148 | @code{find-file-not-found-functions} are not run in case of failure. What's |
f9f59935 RS |
149 | more, a non-@code{nil} @var{rawfile} value suppresses coding system |
150 | conversion (@pxref{Coding Systems}) and format conversion (@pxref{Format | |
151 | Conversion}). | |
3e01fd9d | 152 | |
80e8b2c2 KH |
153 | The @code{find-file-noselect} function usually returns the buffer that |
154 | is visiting the file @var{filename}. But, if wildcards are actually | |
a540f6ed | 155 | used and expanded, it returns a list of buffers that are visiting the |
80e8b2c2 | 156 | various files. |
3e01fd9d RS |
157 | |
158 | @example | |
159 | @group | |
160 | (find-file-noselect "/etc/fstab") | |
161 | @result{} #<buffer fstab> | |
162 | @end group | |
163 | @end example | |
164 | @end defun | |
165 | ||
b6954afd | 166 | @deffn Command find-file-other-window filename &optional wildcards |
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167 | This command selects a buffer visiting the file @var{filename}, but |
168 | does so in a window other than the selected window. It may use another | |
169 | existing window or split a window; see @ref{Displaying Buffers}. | |
170 | ||
171 | When this command is called interactively, it prompts for | |
172 | @var{filename}. | |
173 | @end deffn | |
174 | ||
b6954afd | 175 | @deffn Command find-file-read-only filename &optional wildcards |
3e01fd9d RS |
176 | This command selects a buffer visiting the file @var{filename}, like |
177 | @code{find-file}, but it marks the buffer as read-only. @xref{Read Only | |
178 | Buffers}, for related functions and variables. | |
179 | ||
180 | When this command is called interactively, it prompts for | |
181 | @var{filename}. | |
182 | @end deffn | |
183 | ||
184 | @deffn Command view-file filename | |
f1e2c45e RS |
185 | This command visits @var{filename} using View mode, returning to the |
186 | previous buffer when you exit View mode. View mode is a minor mode that | |
187 | provides commands to skim rapidly through the file, but does not let you | |
188 | modify the text. Entering View mode runs the normal hook | |
bfe721d1 | 189 | @code{view-mode-hook}. @xref{Hooks}. |
3e01fd9d RS |
190 | |
191 | When @code{view-file} is called interactively, it prompts for | |
192 | @var{filename}. | |
193 | @end deffn | |
194 | ||
b6954afd RS |
195 | @tindex find-file-wildcards |
196 | @defvar find-file-wildcards | |
197 | If this variable is non-@code{nil}, then the various @code{find-file} | |
198 | commands check for wildcard characters and visit all the files that | |
199 | match them. If this is @code{nil}, then wildcard characters are | |
200 | not treated specially. | |
201 | @end defvar | |
202 | ||
f2aa473a | 203 | @defvar find-file-hook |
3e01fd9d RS |
204 | The value of this variable is a list of functions to be called after a |
205 | file is visited. The file's local-variables specification (if any) will | |
206 | have been processed before the hooks are run. The buffer visiting the | |
207 | file is current when the hook functions are run. | |
208 | ||
209 | This variable works just like a normal hook, but we think that renaming | |
f1e2c45e | 210 | it would not be advisable. @xref{Hooks}. |
3e01fd9d RS |
211 | @end defvar |
212 | ||
f2aa473a | 213 | @defvar find-file-not-found-functions |
3e01fd9d RS |
214 | The value of this variable is a list of functions to be called when |
215 | @code{find-file} or @code{find-file-noselect} is passed a nonexistent | |
216 | file name. @code{find-file-noselect} calls these functions as soon as | |
217 | it detects a nonexistent file. It calls them in the order of the list, | |
218 | until one of them returns non-@code{nil}. @code{buffer-file-name} is | |
219 | already set up. | |
220 | ||
221 | This is not a normal hook because the values of the functions are | |
f9f59935 | 222 | used, and in many cases only some of the functions are called. |
3e01fd9d RS |
223 | @end defvar |
224 | ||
225 | @node Subroutines of Visiting | |
226 | @comment node-name, next, previous, up | |
227 | @subsection Subroutines of Visiting | |
228 | ||
a9f0a989 RS |
229 | The @code{find-file-noselect} function uses two important subroutines |
230 | which are sometimes useful in user Lisp code: @code{create-file-buffer} | |
231 | and @code{after-find-file}. This section explains how to use them. | |
3e01fd9d RS |
232 | |
233 | @defun create-file-buffer filename | |
234 | This function creates a suitably named buffer for visiting | |
235 | @var{filename}, and returns it. It uses @var{filename} (sans directory) | |
236 | as the name if that name is free; otherwise, it appends a string such as | |
237 | @samp{<2>} to get an unused name. See also @ref{Creating Buffers}. | |
238 | ||
239 | @strong{Please note:} @code{create-file-buffer} does @emph{not} | |
240 | associate the new buffer with a file and does not select the buffer. | |
bfe721d1 | 241 | It also does not use the default major mode. |
3e01fd9d RS |
242 | |
243 | @example | |
244 | @group | |
245 | (create-file-buffer "foo") | |
246 | @result{} #<buffer foo> | |
247 | @end group | |
248 | @group | |
249 | (create-file-buffer "foo") | |
250 | @result{} #<buffer foo<2>> | |
251 | @end group | |
252 | @group | |
253 | (create-file-buffer "foo") | |
254 | @result{} #<buffer foo<3>> | |
255 | @end group | |
256 | @end example | |
257 | ||
258 | This function is used by @code{find-file-noselect}. | |
259 | It uses @code{generate-new-buffer} (@pxref{Creating Buffers}). | |
260 | @end defun | |
261 | ||
2468d0c0 | 262 | @defun after-find-file &optional error warn noauto after-find-file-from-revert-buffer nomodes |
3e01fd9d RS |
263 | This function sets the buffer major mode, and parses local variables |
264 | (@pxref{Auto Major Mode}). It is called by @code{find-file-noselect} | |
265 | and by the default revert function (@pxref{Reverting}). | |
266 | ||
267 | @cindex new file message | |
268 | @cindex file open error | |
269 | If reading the file got an error because the file does not exist, but | |
270 | its directory does exist, the caller should pass a non-@code{nil} value | |
271 | for @var{error}. In that case, @code{after-find-file} issues a warning: | |
8241495d | 272 | @samp{(New file)}. For more serious errors, the caller should usually not |
3e01fd9d RS |
273 | call @code{after-find-file}. |
274 | ||
275 | If @var{warn} is non-@code{nil}, then this function issues a warning | |
276 | if an auto-save file exists and is more recent than the visited file. | |
277 | ||
2468d0c0 DL |
278 | If @var{noauto} is non-@code{nil}, that says not to enable or disable |
279 | Auto-Save mode. The mode remains enabled if it was enabled before. | |
280 | ||
281 | If @var{after-find-file-from-revert-buffer} is non-@code{nil}, that | |
282 | means this call was from @code{revert-buffer}. This has no direct | |
283 | effect, but some mode functions and hook functions check the value | |
284 | of this variable. | |
285 | ||
286 | If @var{nomodes} is non-@code{nil}, that means don't alter the buffer's | |
287 | major mode, don't process local variables specifications in the file, | |
f2aa473a | 288 | and don't run @code{find-file-hook}. This feature is used by |
2468d0c0 DL |
289 | @code{revert-buffer} in some cases. |
290 | ||
3e01fd9d | 291 | The last thing @code{after-find-file} does is call all the functions |
f2aa473a | 292 | in the list @code{find-file-hook}. |
3e01fd9d RS |
293 | @end defun |
294 | ||
295 | @node Saving Buffers | |
296 | @section Saving Buffers | |
297 | ||
298 | When you edit a file in Emacs, you are actually working on a buffer | |
299 | that is visiting that file---that is, the contents of the file are | |
300 | copied into the buffer and the copy is what you edit. Changes to the | |
301 | buffer do not change the file until you @dfn{save} the buffer, which | |
302 | means copying the contents of the buffer into the file. | |
303 | ||
304 | @deffn Command save-buffer &optional backup-option | |
305 | This function saves the contents of the current buffer in its visited | |
306 | file if the buffer has been modified since it was last visited or saved. | |
307 | Otherwise it does nothing. | |
308 | ||
309 | @code{save-buffer} is responsible for making backup files. Normally, | |
310 | @var{backup-option} is @code{nil}, and @code{save-buffer} makes a backup | |
b22f3a19 RS |
311 | file only if this is the first save since visiting the file. Other |
312 | values for @var{backup-option} request the making of backup files in | |
313 | other circumstances: | |
3e01fd9d RS |
314 | |
315 | @itemize @bullet | |
316 | @item | |
317 | With an argument of 4 or 64, reflecting 1 or 3 @kbd{C-u}'s, the | |
318 | @code{save-buffer} function marks this version of the file to be | |
319 | backed up when the buffer is next saved. | |
320 | ||
321 | @item | |
322 | With an argument of 16 or 64, reflecting 2 or 3 @kbd{C-u}'s, the | |
323 | @code{save-buffer} function unconditionally backs up the previous | |
324 | version of the file before saving it. | |
325 | @end itemize | |
326 | @end deffn | |
327 | ||
77ba49d8 | 328 | @deffn Command save-some-buffers &optional save-silently-p pred |
3e01fd9d RS |
329 | This command saves some modified file-visiting buffers. Normally it |
330 | asks the user about each buffer. But if @var{save-silently-p} is | |
331 | non-@code{nil}, it saves all the file-visiting buffers without querying | |
332 | the user. | |
333 | ||
77ba49d8 RS |
334 | The optional @var{pred} argument controls which buffers to ask about. |
335 | If it is @code{nil}, that means to ask only about file-visiting buffers. | |
336 | If it is @code{t}, that means also offer to save certain other non-file | |
337 | buffers---those that have a non-@code{nil} buffer-local value of | |
338 | @code{buffer-offer-save}. (A user who says @samp{yes} to saving a | |
339 | non-file buffer is asked to specify the file name to use.) The | |
340 | @code{save-buffers-kill-emacs} function passes the value @code{t} for | |
341 | @var{pred}. | |
342 | ||
343 | If @var{pred} is neither @code{t} nor @code{nil}, then it should be | |
344 | a function of no arguments. It will be called in each buffer to decide | |
345 | whether to offer to save that buffer. If it returns a non-@code{nil} | |
346 | value in a certain buffer, that means do offer to save that buffer. | |
3e01fd9d RS |
347 | @end deffn |
348 | ||
2468d0c0 | 349 | @deffn Command write-file filename &optional confirm |
3e01fd9d RS |
350 | This function writes the current buffer into file @var{filename}, makes |
351 | the buffer visit that file, and marks it not modified. Then it renames | |
352 | the buffer based on @var{filename}, appending a string like @samp{<2>} | |
353 | if necessary to make a unique buffer name. It does most of this work by | |
969fe9b5 RS |
354 | calling @code{set-visited-file-name} (@pxref{Buffer File Name}) and |
355 | @code{save-buffer}. | |
2468d0c0 DL |
356 | |
357 | If @var{confirm} is non-@code{nil}, that means to ask for confirmation | |
358 | before overwriting an existing file. | |
3e01fd9d RS |
359 | @end deffn |
360 | ||
2dd7b854 RS |
361 | Saving a buffer runs several hooks. It also performs format |
362 | conversion (@pxref{Format Conversion}), and may save text properties in | |
363 | ``annotations'' (@pxref{Saving Properties}). | |
364 | ||
f2aa473a | 365 | @defvar write-file-functions |
3e01fd9d RS |
366 | The value of this variable is a list of functions to be called before |
367 | writing out a buffer to its visited file. If one of them returns | |
368 | non-@code{nil}, the file is considered already written and the rest of | |
369 | the functions are not called, nor is the usual code for writing the file | |
370 | executed. | |
371 | ||
f2aa473a | 372 | If a function in @code{write-file-functions} returns non-@code{nil}, it |
3e01fd9d RS |
373 | is responsible for making a backup file (if that is appropriate). |
374 | To do so, execute the following code: | |
375 | ||
376 | @example | |
377 | (or buffer-backed-up (backup-buffer)) | |
378 | @end example | |
379 | ||
380 | You might wish to save the file modes value returned by | |
381 | @code{backup-buffer} and use that to set the mode bits of the file that | |
382 | you write. This is what @code{save-buffer} normally does. | |
383 | ||
f2aa473a | 384 | The hook functions in @code{write-file-functions} are also responsible for |
a9f0a989 RS |
385 | encoding the data (if desired): they must choose a suitable coding |
386 | system (@pxref{Lisp and Coding Systems}), perform the encoding | |
387 | (@pxref{Explicit Encoding}), and set @code{last-coding-system-used} to | |
f1e2c45e | 388 | the coding system that was used (@pxref{Encoding and I/O}). |
a9f0a989 | 389 | |
f2aa473a SM |
390 | If you set this hook locally in a buffer, it is assumed to be |
391 | associated with the file or the way the contents of the buffer were | |
392 | obtained. Thus the variable is marked as a permanent local, so that | |
393 | changing the major mode does not alter a buffer-local value. On the | |
394 | other hand, calling @code{set-visited-file-name} will reset it. | |
395 | If this is not what you want, you might like to use | |
396 | @code{write-contents-functions} instead. | |
f9f59935 | 397 | |
3e01fd9d RS |
398 | Even though this is not a normal hook, you can use @code{add-hook} and |
399 | @code{remove-hook} to manipulate the list. @xref{Hooks}. | |
400 | @end defvar | |
401 | ||
402 | @c Emacs 19 feature | |
f2aa473a SM |
403 | @defvar write-contents-functions |
404 | This works just like @code{write-file-functions}, but it is intended for | |
3e01fd9d | 405 | hooks that pertain to the contents of the file, as opposed to hooks that |
9d000842 | 406 | pertain to where the file came from. Such hooks are usually set up by |
633d651d RS |
407 | major modes, as buffer-local bindings for this variable. |
408 | ||
409 | This variable automatically becomes buffer-local whenever it is set; | |
f2aa473a | 410 | switching to a new major mode always resets this variable. |
3e01fd9d RS |
411 | @end defvar |
412 | ||
413 | @c Emacs 19 feature | |
414 | @defvar after-save-hook | |
415 | This normal hook runs after a buffer has been saved in its visited file. | |
f1e2c45e RS |
416 | One use of this hook is in Fast Lock mode; it uses this hook to save the |
417 | highlighting information in a cache file. | |
3e01fd9d RS |
418 | @end defvar |
419 | ||
420 | @defvar file-precious-flag | |
421 | If this variable is non-@code{nil}, then @code{save-buffer} protects | |
422 | against I/O errors while saving by writing the new file to a temporary | |
423 | name instead of the name it is supposed to have, and then renaming it to | |
424 | the intended name after it is clear there are no errors. This procedure | |
425 | prevents problems such as a lack of disk space from resulting in an | |
426 | invalid file. | |
427 | ||
63ff95ee MW |
428 | As a side effect, backups are necessarily made by copying. @xref{Rename |
429 | or Copy}. Yet, at the same time, saving a precious file always breaks | |
430 | all hard links between the file you save and other file names. | |
3e01fd9d | 431 | |
f1e2c45e | 432 | Some modes give this variable a non-@code{nil} buffer-local value |
969fe9b5 | 433 | in particular buffers. |
3e01fd9d RS |
434 | @end defvar |
435 | ||
436 | @defopt require-final-newline | |
437 | This variable determines whether files may be written out that do | |
438 | @emph{not} end with a newline. If the value of the variable is | |
439 | @code{t}, then @code{save-buffer} silently adds a newline at the end of | |
440 | the file whenever the buffer being saved does not already end in one. | |
441 | If the value of the variable is non-@code{nil}, but not @code{t}, then | |
442 | @code{save-buffer} asks the user whether to add a newline each time the | |
443 | case arises. | |
444 | ||
445 | If the value of the variable is @code{nil}, then @code{save-buffer} | |
446 | doesn't add newlines at all. @code{nil} is the default value, but a few | |
447 | major modes set it to @code{t} in particular buffers. | |
448 | @end defopt | |
449 | ||
969fe9b5 RS |
450 | See also the function @code{set-visited-file-name} (@pxref{Buffer File |
451 | Name}). | |
fbc1b72c | 452 | |
3e01fd9d RS |
453 | @node Reading from Files |
454 | @comment node-name, next, previous, up | |
455 | @section Reading from Files | |
456 | ||
457 | You can copy a file from the disk and insert it into a buffer | |
458 | using the @code{insert-file-contents} function. Don't use the user-level | |
459 | command @code{insert-file} in a Lisp program, as that sets the mark. | |
460 | ||
461 | @defun insert-file-contents filename &optional visit beg end replace | |
462 | This function inserts the contents of file @var{filename} into the | |
63ff95ee | 463 | current buffer after point. It returns a list of the absolute file name |
3e01fd9d RS |
464 | and the length of the data inserted. An error is signaled if |
465 | @var{filename} is not the name of a file that can be read. | |
466 | ||
bfe721d1 KH |
467 | The function @code{insert-file-contents} checks the file contents |
468 | against the defined file formats, and converts the file contents if | |
469 | appropriate. @xref{Format Conversion}. It also calls the functions in | |
470 | the list @code{after-insert-file-functions}; see @ref{Saving | |
8241495d RS |
471 | Properties}. Normally, one of the functions in the |
472 | @code{after-insert-file-functions} list determines the coding system | |
473 | (@pxref{Coding Systems}) used for decoding the file's contents. | |
3e01fd9d RS |
474 | |
475 | If @var{visit} is non-@code{nil}, this function additionally marks the | |
476 | buffer as unmodified and sets up various fields in the buffer so that it | |
477 | is visiting the file @var{filename}: these include the buffer's visited | |
478 | file name and its last save file modtime. This feature is used by | |
479 | @code{find-file-noselect} and you probably should not use it yourself. | |
480 | ||
481 | If @var{beg} and @var{end} are non-@code{nil}, they should be integers | |
482 | specifying the portion of the file to insert. In this case, @var{visit} | |
483 | must be @code{nil}. For example, | |
484 | ||
485 | @example | |
486 | (insert-file-contents filename nil 0 500) | |
487 | @end example | |
488 | ||
489 | @noindent | |
490 | inserts the first 500 characters of a file. | |
491 | ||
492 | If the argument @var{replace} is non-@code{nil}, it means to replace the | |
493 | contents of the buffer (actually, just the accessible portion) with the | |
494 | contents of the file. This is better than simply deleting the buffer | |
495 | contents and inserting the whole file, because (1) it preserves some | |
496 | marker positions and (2) it puts less data in the undo list. | |
f9f59935 | 497 | |
a9f0a989 RS |
498 | It is possible to read a special file (such as a FIFO or an I/O device) |
499 | with @code{insert-file-contents}, as long as @var{replace} and | |
500 | @var{visit} are @code{nil}. | |
f9f59935 RS |
501 | @end defun |
502 | ||
f9f59935 RS |
503 | @defun insert-file-contents-literally filename &optional visit beg end replace |
504 | This function works like @code{insert-file-contents} except that it does | |
505 | not do format decoding (@pxref{Format Conversion}), does not do | |
506 | character code conversion (@pxref{Coding Systems}), does not run | |
f2aa473a | 507 | @code{find-file-hook}, does not perform automatic uncompression, and so |
f9f59935 | 508 | on. |
3e01fd9d RS |
509 | @end defun |
510 | ||
511 | If you want to pass a file name to another process so that another | |
512 | program can read the file, use the function @code{file-local-copy}; see | |
513 | @ref{Magic File Names}. | |
514 | ||
515 | @node Writing to Files | |
516 | @comment node-name, next, previous, up | |
517 | @section Writing to Files | |
518 | ||
519 | You can write the contents of a buffer, or part of a buffer, directly | |
520 | to a file on disk using the @code{append-to-file} and | |
521 | @code{write-region} functions. Don't use these functions to write to | |
522 | files that are being visited; that could cause confusion in the | |
523 | mechanisms for visiting. | |
524 | ||
525 | @deffn Command append-to-file start end filename | |
526 | This function appends the contents of the region delimited by | |
527 | @var{start} and @var{end} in the current buffer to the end of file | |
528 | @var{filename}. If that file does not exist, it is created. This | |
529 | function returns @code{nil}. | |
530 | ||
531 | An error is signaled if @var{filename} specifies a nonwritable file, | |
532 | or a nonexistent file in a directory where files cannot be created. | |
533 | @end deffn | |
534 | ||
2468d0c0 | 535 | @deffn Command write-region start end filename &optional append visit lockname mustbenew |
3e01fd9d RS |
536 | This function writes the region delimited by @var{start} and @var{end} |
537 | in the current buffer into the file specified by @var{filename}. | |
538 | ||
539 | @c Emacs 19 feature | |
540 | If @var{start} is a string, then @code{write-region} writes or appends | |
8241495d RS |
541 | that string, rather than text from the buffer. @var{end} is ignored in |
542 | this case. | |
3e01fd9d RS |
543 | |
544 | If @var{append} is non-@code{nil}, then the specified text is appended | |
82400f56 DL |
545 | to the existing file contents (if any). Starting in Emacs 21, if |
546 | @var{append} is an integer, then @code{write-region} seeks to that byte | |
547 | offset from the start of the file and writes the data from there. | |
3e01fd9d | 548 | |
8241495d | 549 | If @var{mustbenew} is non-@code{nil}, then @code{write-region} asks |
a9f0a989 | 550 | for confirmation if @var{filename} names an existing file. |
177c0ea7 | 551 | Starting in Emacs 21, if @var{mustbenew} is the symbol @code{excl}, |
8241495d RS |
552 | then @code{write-region} does not ask for confirmation, but instead |
553 | it signals an error @code{file-already-exists} if the file already | |
554 | exists. | |
555 | ||
556 | The test for an existing file, when @var{mustbenew} is @code{excl}, uses | |
557 | a special system feature. At least for files on a local disk, there is | |
558 | no chance that some other program could create a file of the same name | |
559 | before Emacs does, without Emacs's noticing. | |
a9f0a989 | 560 | |
3e01fd9d RS |
561 | If @var{visit} is @code{t}, then Emacs establishes an association |
562 | between the buffer and the file: the buffer is then visiting that file. | |
563 | It also sets the last file modification time for the current buffer to | |
564 | @var{filename}'s modtime, and marks the buffer as not modified. This | |
565 | feature is used by @code{save-buffer}, but you probably should not use | |
566 | it yourself. | |
567 | ||
568 | @c Emacs 19 feature | |
569 | If @var{visit} is a string, it specifies the file name to visit. This | |
570 | way, you can write the data to one file (@var{filename}) while recording | |
571 | the buffer as visiting another file (@var{visit}). The argument | |
572 | @var{visit} is used in the echo area message and also for file locking; | |
573 | @var{visit} is stored in @code{buffer-file-name}. This feature is used | |
574 | to implement @code{file-precious-flag}; don't use it yourself unless you | |
575 | really know what you're doing. | |
576 | ||
2468d0c0 DL |
577 | The optional argument @var{lockname}, if non-@code{nil}, specifies the |
578 | file name to use for purposes of locking and unlocking, overriding | |
579 | @var{filename} and @var{visit} for that purpose. | |
580 | ||
bfe721d1 KH |
581 | The function @code{write-region} converts the data which it writes to |
582 | the appropriate file formats specified by @code{buffer-file-format}. | |
583 | @xref{Format Conversion}. It also calls the functions in the list | |
584 | @code{write-region-annotate-functions}; see @ref{Saving Properties}. | |
3e01fd9d | 585 | |
f1e2c45e | 586 | Normally, @code{write-region} displays the message @samp{Wrote |
3e01fd9d RS |
587 | @var{filename}} in the echo area. If @var{visit} is neither @code{t} |
588 | nor @code{nil} nor a string, then this message is inhibited. This | |
589 | feature is useful for programs that use files for internal purposes, | |
b22f3a19 | 590 | files that the user does not need to know about. |
3e01fd9d RS |
591 | @end deffn |
592 | ||
f9f59935 | 593 | @defmac with-temp-file file body... |
969fe9b5 RS |
594 | The @code{with-temp-file} macro evaluates the @var{body} forms with a |
595 | temporary buffer as the current buffer; then, at the end, it writes the | |
596 | buffer contents into file @var{file}. It kills the temporary buffer | |
597 | when finished, restoring the buffer that was current before the | |
598 | @code{with-temp-file} form. Then it returns the value of the last form | |
599 | in @var{body}. | |
f9f59935 RS |
600 | |
601 | The current buffer is restored even in case of an abnormal exit via | |
602 | @code{throw} or error (@pxref{Nonlocal Exits}). | |
603 | ||
604 | See also @code{with-temp-buffer} in @ref{Current Buffer}. | |
605 | @end defmac | |
606 | ||
3e01fd9d RS |
607 | @node File Locks |
608 | @section File Locks | |
609 | @cindex file locks | |
610 | ||
611 | When two users edit the same file at the same time, they are likely to | |
612 | interfere with each other. Emacs tries to prevent this situation from | |
613 | arising by recording a @dfn{file lock} when a file is being modified. | |
614 | Emacs can then detect the first attempt to modify a buffer visiting a | |
615 | file that is locked by another Emacs job, and ask the user what to do. | |
b6954afd RS |
616 | The file lock is really a file, a symbolic link with a special name, |
617 | stored in the same directory as the file you are editing. | |
3e01fd9d | 618 | |
b6954afd RS |
619 | When you access files using NFS, there may be a small probability that |
620 | you and another user will both lock the same file ``simultaneously''. | |
621 | If this happens, it is possible for the two users to make changes | |
622 | simultaneously, but Emacs will still warn the user who saves second. | |
623 | Also, the detection of modification of a buffer visiting a file changed | |
624 | on disk catches some cases of simultaneous editing; see | |
625 | @ref{Modification Time}. | |
3e01fd9d RS |
626 | |
627 | @defun file-locked-p filename | |
f1e2c45e RS |
628 | This function returns @code{nil} if the file @var{filename} is not |
629 | locked. It returns @code{t} if it is locked by this Emacs process, and | |
630 | it returns the name of the user who has locked it if it is locked by | |
631 | some other job. | |
3e01fd9d RS |
632 | |
633 | @example | |
634 | @group | |
635 | (file-locked-p "foo") | |
636 | @result{} nil | |
637 | @end group | |
638 | @end example | |
639 | @end defun | |
640 | ||
641 | @defun lock-buffer &optional filename | |
b6954afd | 642 | This function locks the file @var{filename}, if the current buffer is |
3e01fd9d RS |
643 | modified. The argument @var{filename} defaults to the current buffer's |
644 | visited file. Nothing is done if the current buffer is not visiting a | |
645 | file, or is not modified. | |
646 | @end defun | |
647 | ||
648 | @defun unlock-buffer | |
649 | This function unlocks the file being visited in the current buffer, | |
650 | if the buffer is modified. If the buffer is not modified, then | |
651 | the file should not be locked, so this function does nothing. It also | |
652 | does nothing if the current buffer is not visiting a file. | |
653 | @end defun | |
654 | ||
8241495d RS |
655 | File locking is not supported on some systems. On systems that do not |
656 | support it, the functions @code{lock-buffer}, @code{unlock-buffer} and | |
657 | @code{file-locked-p} do nothing and return @code{nil}. | |
658 | ||
3e01fd9d RS |
659 | @defun ask-user-about-lock file other-user |
660 | This function is called when the user tries to modify @var{file}, but it | |
f9f59935 RS |
661 | is locked by another user named @var{other-user}. The default |
662 | definition of this function asks the user to say what to do. The value | |
663 | this function returns determines what Emacs does next: | |
3e01fd9d RS |
664 | |
665 | @itemize @bullet | |
666 | @item | |
667 | A value of @code{t} says to grab the lock on the file. Then | |
668 | this user may edit the file and @var{other-user} loses the lock. | |
669 | ||
670 | @item | |
671 | A value of @code{nil} says to ignore the lock and let this | |
672 | user edit the file anyway. | |
673 | ||
674 | @item | |
675 | @kindex file-locked | |
676 | This function may instead signal a @code{file-locked} error, in which | |
677 | case the change that the user was about to make does not take place. | |
678 | ||
679 | The error message for this error looks like this: | |
680 | ||
681 | @example | |
682 | @error{} File is locked: @var{file} @var{other-user} | |
683 | @end example | |
684 | ||
685 | @noindent | |
686 | where @code{file} is the name of the file and @var{other-user} is the | |
687 | name of the user who has locked the file. | |
688 | @end itemize | |
689 | ||
f9f59935 RS |
690 | If you wish, you can replace the @code{ask-user-about-lock} function |
691 | with your own version that makes the decision in another way. The code | |
3e01fd9d RS |
692 | for its usual definition is in @file{userlock.el}. |
693 | @end defun | |
694 | ||
695 | @node Information about Files | |
696 | @section Information about Files | |
697 | ||
b22f3a19 RS |
698 | The functions described in this section all operate on strings that |
699 | designate file names. All the functions have names that begin with the | |
700 | word @samp{file}. These functions all return information about actual | |
701 | files or directories, so their arguments must all exist as actual files | |
702 | or directories unless otherwise noted. | |
3e01fd9d RS |
703 | |
704 | @menu | |
705 | * Testing Accessibility:: Is a given file readable? Writable? | |
706 | * Kinds of Files:: Is it a directory? A symbolic link? | |
707 | * Truenames:: Eliminating symbolic links from a file name. | |
708 | * File Attributes:: How large is it? Any other names? Etc. | |
709 | @end menu | |
710 | ||
711 | @node Testing Accessibility | |
712 | @comment node-name, next, previous, up | |
713 | @subsection Testing Accessibility | |
714 | @cindex accessibility of a file | |
715 | @cindex file accessibility | |
716 | ||
717 | These functions test for permission to access a file in specific ways. | |
718 | ||
719 | @defun file-exists-p filename | |
2468d0c0 DL |
720 | This function returns @code{t} if a file named @var{filename} appears to |
721 | exist. This does not mean you can necessarily read the file, only that | |
722 | you can find out its attributes. (On Unix and GNU/Linux, this is true | |
723 | if the file exists and you have execute permission on the containing | |
3e01fd9d RS |
724 | directories, regardless of the protection of the file itself.) |
725 | ||
726 | If the file does not exist, or if fascist access control policies | |
727 | prevent you from finding the attributes of the file, this function | |
728 | returns @code{nil}. | |
729 | @end defun | |
730 | ||
731 | @defun file-readable-p filename | |
732 | This function returns @code{t} if a file named @var{filename} exists | |
733 | and you can read it. It returns @code{nil} otherwise. | |
734 | ||
735 | @example | |
736 | @group | |
737 | (file-readable-p "files.texi") | |
738 | @result{} t | |
739 | @end group | |
740 | @group | |
741 | (file-exists-p "/usr/spool/mqueue") | |
742 | @result{} t | |
743 | @end group | |
744 | @group | |
745 | (file-readable-p "/usr/spool/mqueue") | |
746 | @result{} nil | |
747 | @end group | |
748 | @end example | |
749 | @end defun | |
750 | ||
751 | @c Emacs 19 feature | |
752 | @defun file-executable-p filename | |
753 | This function returns @code{t} if a file named @var{filename} exists and | |
2468d0c0 DL |
754 | you can execute it. It returns @code{nil} otherwise. On Unix and |
755 | GNU/Linux, if the file is a directory, execute permission means you can | |
756 | check the existence and attributes of files inside the directory, and | |
757 | open those files if their modes permit. | |
3e01fd9d RS |
758 | @end defun |
759 | ||
760 | @defun file-writable-p filename | |
b22f3a19 RS |
761 | This function returns @code{t} if the file @var{filename} can be written |
762 | or created by you, and @code{nil} otherwise. A file is writable if the | |
763 | file exists and you can write it. It is creatable if it does not exist, | |
764 | but the specified directory does exist and you can write in that | |
765 | directory. | |
3e01fd9d RS |
766 | |
767 | In the third example below, @file{foo} is not writable because the | |
768 | parent directory does not exist, even though the user could create such | |
769 | a directory. | |
770 | ||
771 | @example | |
772 | @group | |
773 | (file-writable-p "~/foo") | |
774 | @result{} t | |
775 | @end group | |
776 | @group | |
777 | (file-writable-p "/foo") | |
778 | @result{} nil | |
779 | @end group | |
780 | @group | |
781 | (file-writable-p "~/no-such-dir/foo") | |
782 | @result{} nil | |
783 | @end group | |
784 | @end example | |
785 | @end defun | |
786 | ||
787 | @c Emacs 19 feature | |
788 | @defun file-accessible-directory-p dirname | |
789 | This function returns @code{t} if you have permission to open existing | |
b22f3a19 RS |
790 | files in the directory whose name as a file is @var{dirname}; otherwise |
791 | (or if there is no such directory), it returns @code{nil}. The value | |
792 | of @var{dirname} may be either a directory name or the file name of a | |
f9f59935 | 793 | file which is a directory. |
3e01fd9d RS |
794 | |
795 | Example: after the following, | |
796 | ||
797 | @example | |
798 | (file-accessible-directory-p "/foo") | |
799 | @result{} nil | |
800 | @end example | |
801 | ||
802 | @noindent | |
803 | we can deduce that any attempt to read a file in @file{/foo/} will | |
804 | give an error. | |
805 | @end defun | |
806 | ||
f9f59935 RS |
807 | @defun access-file filename string |
808 | This function opens file @var{filename} for reading, then closes it and | |
809 | returns @code{nil}. However, if the open fails, it signals an error | |
810 | using @var{string} as the error message text. | |
811 | @end defun | |
812 | ||
22697dac KH |
813 | @defun file-ownership-preserved-p filename |
814 | This function returns @code{t} if deleting the file @var{filename} and | |
815 | then creating it anew would keep the file's owner unchanged. | |
816 | @end defun | |
817 | ||
3e01fd9d RS |
818 | @defun file-newer-than-file-p filename1 filename2 |
819 | @cindex file age | |
820 | @cindex file modification time | |
b22f3a19 | 821 | This function returns @code{t} if the file @var{filename1} is |
3e01fd9d RS |
822 | newer than file @var{filename2}. If @var{filename1} does not |
823 | exist, it returns @code{nil}. If @var{filename2} does not exist, | |
824 | it returns @code{t}. | |
825 | ||
b22f3a19 RS |
826 | In the following example, assume that the file @file{aug-19} was written |
827 | on the 19th, @file{aug-20} was written on the 20th, and the file | |
828 | @file{no-file} doesn't exist at all. | |
3e01fd9d RS |
829 | |
830 | @example | |
831 | @group | |
832 | (file-newer-than-file-p "aug-19" "aug-20") | |
833 | @result{} nil | |
834 | @end group | |
835 | @group | |
836 | (file-newer-than-file-p "aug-20" "aug-19") | |
837 | @result{} t | |
838 | @end group | |
839 | @group | |
840 | (file-newer-than-file-p "aug-19" "no-file") | |
841 | @result{} t | |
842 | @end group | |
843 | @group | |
844 | (file-newer-than-file-p "no-file" "aug-19") | |
845 | @result{} nil | |
846 | @end group | |
847 | @end example | |
848 | ||
849 | You can use @code{file-attributes} to get a file's last modification | |
850 | time as a list of two numbers. @xref{File Attributes}. | |
851 | @end defun | |
852 | ||
853 | @node Kinds of Files | |
854 | @comment node-name, next, previous, up | |
855 | @subsection Distinguishing Kinds of Files | |
856 | ||
bfe721d1 KH |
857 | This section describes how to distinguish various kinds of files, such |
858 | as directories, symbolic links, and ordinary files. | |
3e01fd9d RS |
859 | |
860 | @defun file-symlink-p filename | |
861 | @cindex file symbolic links | |
862 | If the file @var{filename} is a symbolic link, the @code{file-symlink-p} | |
863 | function returns the file name to which it is linked. This may be the | |
b22f3a19 RS |
864 | name of a text file, a directory, or even another symbolic link, or it |
865 | may be a nonexistent file name. | |
3e01fd9d RS |
866 | |
867 | If the file @var{filename} is not a symbolic link (or there is no such file), | |
177c0ea7 | 868 | @code{file-symlink-p} returns @code{nil}. |
3e01fd9d RS |
869 | |
870 | @example | |
871 | @group | |
872 | (file-symlink-p "foo") | |
873 | @result{} nil | |
874 | @end group | |
875 | @group | |
876 | (file-symlink-p "sym-link") | |
877 | @result{} "foo" | |
878 | @end group | |
879 | @group | |
880 | (file-symlink-p "sym-link2") | |
881 | @result{} "sym-link" | |
882 | @end group | |
883 | @group | |
884 | (file-symlink-p "/bin") | |
885 | @result{} "/pub/bin" | |
886 | @end group | |
887 | @end example | |
888 | ||
889 | @c !!! file-symlink-p: should show output of ls -l for comparison | |
890 | @end defun | |
891 | ||
892 | @defun file-directory-p filename | |
893 | This function returns @code{t} if @var{filename} is the name of an | |
894 | existing directory, @code{nil} otherwise. | |
895 | ||
896 | @example | |
897 | @group | |
898 | (file-directory-p "~rms") | |
899 | @result{} t | |
900 | @end group | |
901 | @group | |
902 | (file-directory-p "~rms/lewis/files.texi") | |
903 | @result{} nil | |
904 | @end group | |
905 | @group | |
906 | (file-directory-p "~rms/lewis/no-such-file") | |
907 | @result{} nil | |
908 | @end group | |
909 | @group | |
910 | (file-directory-p "$HOME") | |
911 | @result{} nil | |
912 | @end group | |
913 | @group | |
914 | (file-directory-p | |
915 | (substitute-in-file-name "$HOME")) | |
916 | @result{} t | |
917 | @end group | |
918 | @end example | |
919 | @end defun | |
920 | ||
22697dac KH |
921 | @defun file-regular-p filename |
922 | This function returns @code{t} if the file @var{filename} exists and is | |
b6954afd | 923 | a regular file (not a directory, named pipe, terminal, or |
22697dac KH |
924 | other I/O device). |
925 | @end defun | |
926 | ||
3e01fd9d RS |
927 | @node Truenames |
928 | @subsection Truenames | |
929 | @cindex truename (of file) | |
930 | ||
931 | @c Emacs 19 features | |
932 | The @dfn{truename} of a file is the name that you get by following | |
2468d0c0 DL |
933 | symbolic links at all levels until none remain, then simplifying away |
934 | @samp{.}@: and @samp{..}@: appearing as name components. This results | |
935 | in a sort of canonical name for the file. A file does not always have a | |
936 | unique truename; the number of distinct truenames a file has is equal to | |
937 | the number of hard links to the file. However, truenames are useful | |
938 | because they eliminate symbolic links as a cause of name variation. | |
3e01fd9d RS |
939 | |
940 | @defun file-truename filename | |
2468d0c0 DL |
941 | The function @code{file-truename} returns the truename of the file |
942 | @var{filename}. The argument must be an absolute file name. | |
3e01fd9d RS |
943 | @end defun |
944 | ||
2468d0c0 DL |
945 | @defun file-chase-links filename |
946 | This function follows symbolic links, starting with @var{filename}, | |
947 | until it finds a file name which is not the name of a symbolic link. | |
948 | Then it returns that file name. | |
949 | @end defun | |
950 | ||
951 | To illustrate the difference between @code{file-chase-links} and | |
952 | @code{file-truename}, suppose that @file{/usr/foo} is a symbolic link to | |
953 | the directory @file{/home/foo}, and @file{/home/foo/hello} is an | |
954 | ordinary file (or at least, not a symbolic link) or nonexistent. Then | |
955 | we would have: | |
956 | ||
957 | @example | |
958 | (file-chase-links "/usr/foo/hello") | |
959 | ;; @r{This does not follow the links in the parent directories.} | |
960 | @result{} "/usr/foo/hello" | |
961 | (file-truename "/usr/foo/hello") | |
962 | ;; @r{Assuming that @file{/home} is not a symbolic link.} | |
963 | @result{} "/home/foo/hello" | |
964 | @end example | |
965 | ||
3e01fd9d RS |
966 | @xref{Buffer File Name}, for related information. |
967 | ||
968 | @node File Attributes | |
969 | @comment node-name, next, previous, up | |
970 | @subsection Other Information about Files | |
971 | ||
972 | This section describes the functions for getting detailed information | |
973 | about a file, other than its contents. This information includes the | |
974 | mode bits that control access permission, the owner and group numbers, | |
975 | the number of names, the inode number, the size, and the times of access | |
976 | and modification. | |
977 | ||
978 | @defun file-modes filename | |
979 | @cindex permission | |
980 | @cindex file attributes | |
981 | This function returns the mode bits of @var{filename}, as an integer. | |
982 | The mode bits are also called the file permissions, and they specify | |
983 | access control in the usual Unix fashion. If the low-order bit is 1, | |
b22f3a19 | 984 | then the file is executable by all users, if the second-lowest-order bit |
3e01fd9d RS |
985 | is 1, then the file is writable by all users, etc. |
986 | ||
987 | The highest value returnable is 4095 (7777 octal), meaning that | |
988 | everyone has read, write, and execute permission, that the @sc{suid} bit | |
989 | is set for both others and group, and that the sticky bit is set. | |
990 | ||
991 | @example | |
992 | @group | |
993 | (file-modes "~/junk/diffs") | |
994 | @result{} 492 ; @r{Decimal integer.} | |
995 | @end group | |
996 | @group | |
997 | (format "%o" 492) | |
998 | @result{} "754" ; @r{Convert to octal.} | |
999 | @end group | |
1000 | ||
1001 | @group | |
1002 | (set-file-modes "~/junk/diffs" 438) | |
1003 | @result{} nil | |
1004 | @end group | |
1005 | ||
1006 | @group | |
1007 | (format "%o" 438) | |
1008 | @result{} "666" ; @r{Convert to octal.} | |
1009 | @end group | |
1010 | ||
1011 | @group | |
1012 | % ls -l diffs | |
1013 | -rw-rw-rw- 1 lewis 0 3063 Oct 30 16:00 diffs | |
1014 | @end group | |
1015 | @end example | |
1016 | @end defun | |
1017 | ||
1018 | @defun file-nlinks filename | |
1019 | This functions returns the number of names (i.e., hard links) that | |
1020 | file @var{filename} has. If the file does not exist, then this function | |
1021 | returns @code{nil}. Note that symbolic links have no effect on this | |
1022 | function, because they are not considered to be names of the files they | |
1023 | link to. | |
1024 | ||
1025 | @example | |
1026 | @group | |
1027 | % ls -l foo* | |
1028 | -rw-rw-rw- 2 rms 4 Aug 19 01:27 foo | |
1029 | -rw-rw-rw- 2 rms 4 Aug 19 01:27 foo1 | |
1030 | @end group | |
1031 | ||
1032 | @group | |
1033 | (file-nlinks "foo") | |
1034 | @result{} 2 | |
1035 | @end group | |
1036 | @group | |
1037 | (file-nlinks "doesnt-exist") | |
1038 | @result{} nil | |
1039 | @end group | |
1040 | @end example | |
1041 | @end defun | |
1042 | ||
1043 | @defun file-attributes filename | |
1044 | This function returns a list of attributes of file @var{filename}. If | |
1045 | the specified file cannot be opened, it returns @code{nil}. | |
1046 | ||
1047 | The elements of the list, in order, are: | |
1048 | ||
1049 | @enumerate 0 | |
1050 | @item | |
1051 | @code{t} for a directory, a string for a symbolic link (the name | |
1052 | linked to), or @code{nil} for a text file. | |
1053 | ||
1054 | @c Wordy so as to prevent an overfull hbox. --rjc 15mar92 | |
1055 | @item | |
1056 | The number of names the file has. Alternate names, also known as hard | |
1057 | links, can be created by using the @code{add-name-to-file} function | |
f9f59935 | 1058 | (@pxref{Changing Files}). |
3e01fd9d RS |
1059 | |
1060 | @item | |
1061 | The file's @sc{uid}. | |
1062 | ||
1063 | @item | |
1064 | The file's @sc{gid}. | |
1065 | ||
1066 | @item | |
1067 | The time of last access, as a list of two integers. | |
1068 | The first integer has the high-order 16 bits of time, | |
1069 | the second has the low 16 bits. (This is similar to the | |
1070 | value of @code{current-time}; see @ref{Time of Day}.) | |
1071 | ||
1072 | @item | |
1073 | The time of last modification as a list of two integers (as above). | |
1074 | ||
1075 | @item | |
1076 | The time of last status change as a list of two integers (as above). | |
1077 | ||
1078 | @item | |
b6954afd RS |
1079 | The size of the file in bytes. If the size is too large to fit in a |
1080 | Lisp integer, this is a floating point number. | |
3e01fd9d RS |
1081 | |
1082 | @item | |
b22f3a19 | 1083 | The file's modes, as a string of ten letters or dashes, |
3e01fd9d RS |
1084 | as in @samp{ls -l}. |
1085 | ||
1086 | @item | |
1087 | @code{t} if the file's @sc{gid} would change if file were | |
1088 | deleted and recreated; @code{nil} otherwise. | |
1089 | ||
1090 | @item | |
2a7d4505 RS |
1091 | The file's inode number. If possible, this is an integer. If the inode |
1092 | number is too large to be represented as an integer in Emacs Lisp, then | |
1093 | the value has the form @code{(@var{high} . @var{low})}, where @var{low} | |
1094 | holds the low 16 bits. | |
3e01fd9d RS |
1095 | |
1096 | @item | |
773e81c7 EZ |
1097 | The file system number of the file system that the file is in. |
1098 | Depending on the magnitude of the value, this can be either an integer | |
1099 | or a cons cell, in the same manner as the inode number. This element | |
1100 | and the file's inode number together give enough information to | |
b22f3a19 RS |
1101 | distinguish any two files on the system---no two files can have the same |
1102 | values for both of these numbers. | |
3e01fd9d RS |
1103 | @end enumerate |
1104 | ||
1105 | For example, here are the file attributes for @file{files.texi}: | |
1106 | ||
1107 | @example | |
1108 | @group | |
1109 | (file-attributes "files.texi") | |
177c0ea7 JB |
1110 | @result{} (nil 1 2235 75 |
1111 | (8489 20284) | |
1112 | (8489 20284) | |
3e01fd9d | 1113 | (8489 20285) |
177c0ea7 | 1114 | 14906 "-rw-rw-rw-" |
969fe9b5 | 1115 | nil 129500 -32252) |
3e01fd9d RS |
1116 | @end group |
1117 | @end example | |
1118 | ||
1119 | @noindent | |
1120 | and here is how the result is interpreted: | |
1121 | ||
1122 | @table @code | |
1123 | @item nil | |
1124 | is neither a directory nor a symbolic link. | |
1125 | ||
1126 | @item 1 | |
1127 | has only one name (the name @file{files.texi} in the current default | |
1128 | directory). | |
1129 | ||
1130 | @item 2235 | |
1131 | is owned by the user with @sc{uid} 2235. | |
1132 | ||
1133 | @item 75 | |
1134 | is in the group with @sc{gid} 75. | |
1135 | ||
1136 | @item (8489 20284) | |
6784ada3 | 1137 | was last accessed on Aug 19 00:09. |
3e01fd9d RS |
1138 | |
1139 | @item (8489 20284) | |
1140 | was last modified on Aug 19 00:09. | |
1141 | ||
1142 | @item (8489 20285) | |
1143 | last had its inode changed on Aug 19 00:09. | |
1144 | ||
1145 | @item 14906 | |
8241495d RS |
1146 | is 14906 bytes long. (It may not contain 14906 characters, though, |
1147 | if some of the bytes belong to multibyte sequences.) | |
3e01fd9d RS |
1148 | |
1149 | @item "-rw-rw-rw-" | |
1150 | has a mode of read and write access for the owner, group, and world. | |
1151 | ||
1152 | @item nil | |
1153 | would retain the same @sc{gid} if it were recreated. | |
1154 | ||
1155 | @item 129500 | |
1156 | has an inode number of 129500. | |
1157 | @item -32252 | |
1158 | is on file system number -32252. | |
1159 | @end table | |
1160 | @end defun | |
1161 | ||
f9f59935 | 1162 | @node Changing Files |
3e01fd9d RS |
1163 | @section Changing File Names and Attributes |
1164 | @cindex renaming files | |
1165 | @cindex copying files | |
1166 | @cindex deleting files | |
1167 | @cindex linking files | |
1168 | @cindex setting modes of files | |
1169 | ||
1170 | The functions in this section rename, copy, delete, link, and set the | |
1171 | modes of files. | |
1172 | ||
1173 | In the functions that have an argument @var{newname}, if a file by the | |
1174 | name of @var{newname} already exists, the actions taken depend on the | |
1175 | value of the argument @var{ok-if-already-exists}: | |
1176 | ||
1177 | @itemize @bullet | |
1178 | @item | |
1179 | Signal a @code{file-already-exists} error if | |
1180 | @var{ok-if-already-exists} is @code{nil}. | |
1181 | ||
1182 | @item | |
1183 | Request confirmation if @var{ok-if-already-exists} is a number. | |
1184 | ||
1185 | @item | |
1186 | Replace the old file without confirmation if @var{ok-if-already-exists} | |
1187 | is any other value. | |
1188 | @end itemize | |
1189 | ||
1190 | @defun add-name-to-file oldname newname &optional ok-if-already-exists | |
1191 | @cindex file with multiple names | |
1192 | @cindex file hard link | |
1193 | This function gives the file named @var{oldname} the additional name | |
1194 | @var{newname}. This means that @var{newname} becomes a new ``hard | |
1195 | link'' to @var{oldname}. | |
1196 | ||
1197 | In the first part of the following example, we list two files, | |
1198 | @file{foo} and @file{foo3}. | |
1199 | ||
1200 | @example | |
1201 | @group | |
a9f0a989 RS |
1202 | % ls -li fo* |
1203 | 81908 -rw-rw-rw- 1 rms 29 Aug 18 20:32 foo | |
1204 | 84302 -rw-rw-rw- 1 rms 24 Aug 18 20:31 foo3 | |
3e01fd9d RS |
1205 | @end group |
1206 | @end example | |
1207 | ||
9e2b495b RS |
1208 | Now we create a hard link, by calling @code{add-name-to-file}, then list |
1209 | the files again. This shows two names for one file, @file{foo} and | |
1210 | @file{foo2}. | |
3e01fd9d RS |
1211 | |
1212 | @example | |
1213 | @group | |
a9f0a989 | 1214 | (add-name-to-file "foo" "foo2") |
3e01fd9d RS |
1215 | @result{} nil |
1216 | @end group | |
1217 | ||
1218 | @group | |
a9f0a989 RS |
1219 | % ls -li fo* |
1220 | 81908 -rw-rw-rw- 2 rms 29 Aug 18 20:32 foo | |
1221 | 81908 -rw-rw-rw- 2 rms 29 Aug 18 20:32 foo2 | |
1222 | 84302 -rw-rw-rw- 1 rms 24 Aug 18 20:31 foo3 | |
3e01fd9d RS |
1223 | @end group |
1224 | @end example | |
1225 | ||
a9f0a989 | 1226 | Finally, we evaluate the following: |
3e01fd9d RS |
1227 | |
1228 | @example | |
a9f0a989 | 1229 | (add-name-to-file "foo" "foo3" t) |
3e01fd9d RS |
1230 | @end example |
1231 | ||
1232 | @noindent | |
1233 | and list the files again. Now there are three names | |
1234 | for one file: @file{foo}, @file{foo2}, and @file{foo3}. The old | |
1235 | contents of @file{foo3} are lost. | |
1236 | ||
1237 | @example | |
1238 | @group | |
a9f0a989 | 1239 | (add-name-to-file "foo1" "foo3") |
3e01fd9d RS |
1240 | @result{} nil |
1241 | @end group | |
1242 | ||
1243 | @group | |
a9f0a989 RS |
1244 | % ls -li fo* |
1245 | 81908 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo | |
1246 | 81908 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo2 | |
1247 | 81908 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo3 | |
3e01fd9d RS |
1248 | @end group |
1249 | @end example | |
1250 | ||
a9f0a989 | 1251 | This function is meaningless on operating systems where multiple names |
8241495d RS |
1252 | for one file are not allowed. Some systems implement multiple names |
1253 | by copying the file instead. | |
3e01fd9d | 1254 | |
a9f0a989 | 1255 | See also @code{file-nlinks} in @ref{File Attributes}. |
3e01fd9d RS |
1256 | @end defun |
1257 | ||
1258 | @deffn Command rename-file filename newname &optional ok-if-already-exists | |
1259 | This command renames the file @var{filename} as @var{newname}. | |
1260 | ||
1261 | If @var{filename} has additional names aside from @var{filename}, it | |
1262 | continues to have those names. In fact, adding the name @var{newname} | |
1263 | with @code{add-name-to-file} and then deleting @var{filename} has the | |
1264 | same effect as renaming, aside from momentary intermediate states. | |
1265 | ||
1266 | In an interactive call, this function prompts for @var{filename} and | |
1267 | @var{newname} in the minibuffer; also, it requests confirmation if | |
1268 | @var{newname} already exists. | |
1269 | @end deffn | |
1270 | ||
1271 | @deffn Command copy-file oldname newname &optional ok-if-exists time | |
1272 | This command copies the file @var{oldname} to @var{newname}. An | |
1273 | error is signaled if @var{oldname} does not exist. | |
1274 | ||
a9f0a989 | 1275 | If @var{time} is non-@code{nil}, then this function gives the new file |
f9f59935 RS |
1276 | the same last-modified time that the old one has. (This works on only |
1277 | some operating systems.) If setting the time gets an error, | |
1278 | @code{copy-file} signals a @code{file-date-error} error. | |
3e01fd9d RS |
1279 | |
1280 | In an interactive call, this function prompts for @var{filename} and | |
1281 | @var{newname} in the minibuffer; also, it requests confirmation if | |
1282 | @var{newname} already exists. | |
1283 | @end deffn | |
1284 | ||
1285 | @deffn Command delete-file filename | |
1286 | @pindex rm | |
1287 | This command deletes the file @var{filename}, like the shell command | |
1288 | @samp{rm @var{filename}}. If the file has multiple names, it continues | |
1289 | to exist under the other names. | |
1290 | ||
2468d0c0 DL |
1291 | A suitable kind of @code{file-error} error is signaled if the file does |
1292 | not exist, or is not deletable. (On Unix and GNU/Linux, a file is | |
1293 | deletable if its directory is writable.) | |
3e01fd9d RS |
1294 | |
1295 | See also @code{delete-directory} in @ref{Create/Delete Dirs}. | |
1296 | @end deffn | |
1297 | ||
1298 | @deffn Command make-symbolic-link filename newname &optional ok-if-exists | |
1299 | @pindex ln | |
1300 | @kindex file-already-exists | |
1301 | This command makes a symbolic link to @var{filename}, named | |
1302 | @var{newname}. This is like the shell command @samp{ln -s | |
1303 | @var{filename} @var{newname}}. | |
1304 | ||
b22f3a19 RS |
1305 | In an interactive call, this function prompts for @var{filename} and |
1306 | @var{newname} in the minibuffer; also, it requests confirmation if | |
1307 | @var{newname} already exists. | |
8241495d RS |
1308 | |
1309 | This function is not available on systems that don't support symbolic | |
1310 | links. | |
3e01fd9d RS |
1311 | @end deffn |
1312 | ||
1313 | @defun define-logical-name varname string | |
1314 | This function defines the logical name @var{name} to have the value | |
1315 | @var{string}. It is available only on VMS. | |
1316 | @end defun | |
1317 | ||
1318 | @defun set-file-modes filename mode | |
1319 | This function sets mode bits of @var{filename} to @var{mode} (which must | |
b22f3a19 | 1320 | be an integer). Only the low 12 bits of @var{mode} are used. |
3e01fd9d RS |
1321 | @end defun |
1322 | ||
1323 | @c Emacs 19 feature | |
1324 | @defun set-default-file-modes mode | |
7231e819 | 1325 | @cindex umask |
3e01fd9d RS |
1326 | This function sets the default file protection for new files created by |
1327 | Emacs and its subprocesses. Every file created with Emacs initially has | |
f74bbbbf RS |
1328 | this protection, or a subset of it (@code{write-region} will not give a |
1329 | file execute permission even if the default file protection allows | |
1330 | execute permission). On Unix and GNU/Linux, the default protection is | |
1331 | the bitwise complement of the ``umask'' value. | |
3e01fd9d | 1332 | |
f9f59935 | 1333 | The argument @var{mode} must be an integer. On most systems, only the |
f74bbbbf RS |
1334 | low 9 bits of @var{mode} are meaningful. You can use the Lisp construct |
1335 | for octal character codes to enter @var{mode}; for example, | |
1336 | ||
1337 | @example | |
1338 | (set-default-file-modes ?\644) | |
1339 | @end example | |
3e01fd9d RS |
1340 | |
1341 | Saving a modified version of an existing file does not count as creating | |
f74bbbbf RS |
1342 | the file; it preserves the existing file's mode, whatever that is. So |
1343 | the default file protection has no effect. | |
3e01fd9d RS |
1344 | @end defun |
1345 | ||
1346 | @defun default-file-modes | |
1347 | This function returns the current default protection value. | |
1348 | @end defun | |
1349 | ||
841e483d RS |
1350 | @cindex MS-DOS and file modes |
1351 | @cindex file modes and MS-DOS | |
1352 | On MS-DOS, there is no such thing as an ``executable'' file mode bit. | |
8241495d RS |
1353 | So Emacs considers a file executable if its name ends in one of the |
1354 | standard executable extensions, such as @file{.com}, @file{.bat}, | |
1355 | @file{.exe}, and some others. Files that begin with the Unix-standard | |
1356 | @samp{#!} signature, such as shell and Perl scripts, are also considered | |
1357 | as executable files. This is reflected in the values returned by | |
1358 | @code{file-modes} and @code{file-attributes}. Directories are also | |
1359 | reported with executable bit set, for compatibility with Unix. | |
841e483d | 1360 | |
3e01fd9d RS |
1361 | @node File Names |
1362 | @section File Names | |
1363 | @cindex file names | |
1364 | ||
1365 | Files are generally referred to by their names, in Emacs as elsewhere. | |
1366 | File names in Emacs are represented as strings. The functions that | |
1367 | operate on a file all expect a file name argument. | |
1368 | ||
1369 | In addition to operating on files themselves, Emacs Lisp programs | |
f9f59935 | 1370 | often need to operate on file names; i.e., to take them apart and to use |
3e01fd9d RS |
1371 | part of a name to construct related file names. This section describes |
1372 | how to manipulate file names. | |
1373 | ||
1374 | The functions in this section do not actually access files, so they | |
1375 | can operate on file names that do not refer to an existing file or | |
1376 | directory. | |
1377 | ||
5557b83b RS |
1378 | On MS-DOS and MS-Windows, these functions (like the function that |
1379 | actually operate on files) accept MS-DOS or MS-Windows file-name syntax, | |
1380 | where backslashes separate the components, as well as Unix syntax; but | |
1381 | they always return Unix syntax. On VMS, these functions (and the ones | |
1382 | that operate on files) understand both VMS file-name syntax and Unix | |
1383 | syntax. This enables Lisp programs to specify file names in Unix syntax | |
1384 | and work properly on all systems without change. | |
3e01fd9d RS |
1385 | |
1386 | @menu | |
1387 | * File Name Components:: The directory part of a file name, and the rest. | |
85df4f66 | 1388 | * Relative File Names:: Some file names are relative to a current directory. |
3e01fd9d RS |
1389 | * Directory Names:: A directory's name as a directory |
1390 | is different from its name as a file. | |
3e01fd9d RS |
1391 | * File Name Expansion:: Converting relative file names to absolute ones. |
1392 | * Unique File Names:: Generating names for temporary files. | |
1393 | * File Name Completion:: Finding the completions for a given file name. | |
fbc1b72c RS |
1394 | * Standard File Names:: If your package uses a fixed file name, |
1395 | how to handle various operating systems simply. | |
3e01fd9d RS |
1396 | @end menu |
1397 | ||
1398 | @node File Name Components | |
1399 | @subsection File Name Components | |
1400 | @cindex directory part (of file name) | |
1401 | @cindex nondirectory part (of file name) | |
1402 | @cindex version number (in file name) | |
1403 | ||
1404 | The operating system groups files into directories. To specify a | |
b22f3a19 RS |
1405 | file, you must specify the directory and the file's name within that |
1406 | directory. Therefore, Emacs considers a file name as having two main | |
1407 | parts: the @dfn{directory name} part, and the @dfn{nondirectory} part | |
1408 | (or @dfn{file name within the directory}). Either part may be empty. | |
1409 | Concatenating these two parts reproduces the original file name. | |
3e01fd9d | 1410 | |
8241495d | 1411 | On most systems, the directory part is everything up to and including |
5557b83b RS |
1412 | the last slash (backslash is also allowed in input on MS-DOS or |
1413 | MS-Windows); the nondirectory part is the rest. The rules in VMS syntax | |
1414 | are complicated. | |
3e01fd9d RS |
1415 | |
1416 | For some purposes, the nondirectory part is further subdivided into | |
8241495d RS |
1417 | the name proper and the @dfn{version number}. On most systems, only |
1418 | backup files have version numbers in their names. On VMS, every file | |
1419 | has a version number, but most of the time the file name actually used | |
1420 | in Emacs omits the version number, so that version numbers in Emacs are | |
f9f59935 | 1421 | found mostly in directory lists. |
3e01fd9d RS |
1422 | |
1423 | @defun file-name-directory filename | |
85df4f66 RS |
1424 | This function returns the directory part of @var{filename}, as a |
1425 | directory name (@pxref{Directory Names}), or @code{nil} if | |
1426 | @var{filename} does not include a directory part. | |
1427 | ||
1428 | On GNU and Unix systems, a string returned by this function always | |
1429 | ends in a slash. On MSDOS it can also end in a colon. On VMS, it | |
1430 | returns a string ending in one of the three characters @samp{:}, | |
3e01fd9d RS |
1431 | @samp{]}, or @samp{>}. |
1432 | ||
1433 | @example | |
1434 | @group | |
1435 | (file-name-directory "lewis/foo") ; @r{Unix example} | |
1436 | @result{} "lewis/" | |
1437 | @end group | |
1438 | @group | |
1439 | (file-name-directory "foo") ; @r{Unix example} | |
1440 | @result{} nil | |
1441 | @end group | |
1442 | @group | |
1443 | (file-name-directory "[X]FOO.TMP") ; @r{VMS example} | |
1444 | @result{} "[X]" | |
1445 | @end group | |
1446 | @end example | |
1447 | @end defun | |
1448 | ||
1449 | @defun file-name-nondirectory filename | |
f9f59935 | 1450 | This function returns the nondirectory part of @var{filename}. |
3e01fd9d RS |
1451 | |
1452 | @example | |
1453 | @group | |
1454 | (file-name-nondirectory "lewis/foo") | |
1455 | @result{} "foo" | |
1456 | @end group | |
1457 | @group | |
1458 | (file-name-nondirectory "foo") | |
1459 | @result{} "foo" | |
1460 | @end group | |
1461 | @group | |
85df4f66 RS |
1462 | (file-name-nondirectory "lewis/") |
1463 | @result{} "" | |
1464 | @end group | |
1465 | @group | |
3e01fd9d RS |
1466 | ;; @r{The following example is accurate only on VMS.} |
1467 | (file-name-nondirectory "[X]FOO.TMP") | |
1468 | @result{} "FOO.TMP" | |
1469 | @end group | |
1470 | @end example | |
1471 | @end defun | |
1472 | ||
85df4f66 RS |
1473 | @defun file-name-extension filename &optional period |
1474 | This function returns @var{filename}'s final ``extension,'' if any, | |
1475 | after applying @code{file-name-sans-versions} to remove any | |
1476 | version/backup part. It returns @code{nil} for extensionless file | |
1477 | names such as @file{foo}. If @var{period} is non-nil, then the | |
1478 | returned value includes the period that delimits the extension, and if | |
1479 | @var{filename} has no extension, the value is @code{""}. If the last | |
1480 | component of a file name begins with a @samp{.}, that @samp{.} doesn't | |
1481 | count as the beginning of an extension, so, for example, | |
1482 | @file{.emacs}'s ``extension'' is @code{nil}, not @samp{.emacs}. | |
1483 | @end defun | |
1484 | ||
2468d0c0 | 1485 | @defun file-name-sans-versions filename &optional keep-backup-version |
f9f59935 | 1486 | This function returns @var{filename} with any file version numbers, |
2468d0c0 DL |
1487 | backup version numbers, or trailing tildes discarded. |
1488 | ||
1489 | If @var{keep-backup-version} is non-@code{nil}, then true file version | |
1490 | numbers understood as such by the file system are discarded from the | |
1491 | return value, but backup version numbers are kept. | |
3e01fd9d RS |
1492 | |
1493 | @example | |
1494 | @group | |
1495 | (file-name-sans-versions "~rms/foo.~1~") | |
1496 | @result{} "~rms/foo" | |
1497 | @end group | |
1498 | @group | |
1499 | (file-name-sans-versions "~rms/foo~") | |
1500 | @result{} "~rms/foo" | |
1501 | @end group | |
1502 | @group | |
1503 | (file-name-sans-versions "~rms/foo") | |
1504 | @result{} "~rms/foo" | |
1505 | @end group | |
1506 | @group | |
1507 | ;; @r{The following example applies to VMS only.} | |
1508 | (file-name-sans-versions "foo;23") | |
1509 | @result{} "foo" | |
1510 | @end group | |
1511 | @end example | |
1512 | @end defun | |
1513 | ||
22697dac | 1514 | @defun file-name-sans-extension filename |
bfe721d1 KH |
1515 | This function returns @var{filename} minus its ``extension,'' if any. |
1516 | The extension, in a file name, is the part that starts with the last | |
98d7eccb EZ |
1517 | @samp{.} in the last name component, except if that @samp{.} is the |
1518 | first character of the file name's last component. For example, | |
bfe721d1 KH |
1519 | |
1520 | @example | |
1521 | (file-name-sans-extension "foo.lose.c") | |
1522 | @result{} "foo.lose" | |
1523 | (file-name-sans-extension "big.hack/foo") | |
1524 | @result{} "big.hack/foo" | |
98d7eccb | 1525 | (file-name-sans-extension "/my/home/.emacs") |
df140a68 | 1526 | @result{} "/my/home/.emacs" |
98d7eccb EZ |
1527 | (file-name-sans-extension "/my/home/.emacs.el") |
1528 | @result{} "/my/home/.emacs" | |
bfe721d1 | 1529 | @end example |
22697dac KH |
1530 | @end defun |
1531 | ||
5557b83b | 1532 | @ignore |
177c0ea7 | 1533 | Andrew Innes says that this |
5557b83b RS |
1534 | |
1535 | @c @defvar directory-sep-char | |
1536 | @c @tindex directory-sep-char | |
1537 | This variable holds the character that Emacs normally uses to separate | |
1538 | file name components. The default value is @code{?/}, but on MS-Windows | |
1539 | you can set it to @code{?\\}; then the functions that transform file names | |
1540 | use backslashes in their output. | |
1541 | ||
1542 | File names using backslashes work as input to Lisp primitives even on | |
1543 | MS-DOS and MS-Windows, even if @code{directory-sep-char} has its default | |
1544 | value of @code{?/}. | |
f855fad2 | 1545 | @end defvar |
5557b83b | 1546 | @end ignore |
f855fad2 | 1547 | |
85df4f66 RS |
1548 | @node Relative File Names |
1549 | @subsection Absolute and Relative File Names | |
1550 | @cindex absolute file name | |
1551 | @cindex relative file name | |
1552 | ||
1553 | All the directories in the file system form a tree starting at the | |
1554 | root directory. A file name can specify all the directory names | |
1555 | starting from the root of the tree; then it is called an @dfn{absolute} | |
1556 | file name. Or it can specify the position of the file in the tree | |
1557 | relative to a default directory; then it is called a @dfn{relative} file | |
1558 | name. On Unix and GNU/Linux, an absolute file name starts with a slash | |
1559 | or a tilde (@samp{~}), and a relative one does not. On MS-DOS and | |
1560 | MS-Windows, an absolute file name starts with a slash or a backslash, or | |
1561 | with a drive specification @samp{@var{x}:/}, where @var{x} is the | |
1562 | @dfn{drive letter}. The rules on VMS are complicated. | |
1563 | ||
1564 | @defun file-name-absolute-p filename | |
1565 | This function returns @code{t} if file @var{filename} is an absolute | |
1566 | file name, @code{nil} otherwise. On VMS, this function understands both | |
1567 | Unix syntax and VMS syntax. | |
1568 | ||
1569 | @example | |
1570 | @group | |
1571 | (file-name-absolute-p "~rms/foo") | |
1572 | @result{} t | |
1573 | @end group | |
1574 | @group | |
1575 | (file-name-absolute-p "rms/foo") | |
1576 | @result{} nil | |
1577 | @end group | |
1578 | @group | |
1579 | (file-name-absolute-p "/user/rms/foo") | |
1580 | @result{} t | |
1581 | @end group | |
1582 | @end example | |
1beefde7 DL |
1583 | @end defun |
1584 | ||
3e01fd9d RS |
1585 | @node Directory Names |
1586 | @comment node-name, next, previous, up | |
1587 | @subsection Directory Names | |
1588 | @cindex directory name | |
1589 | @cindex file name of directory | |
1590 | ||
85df4f66 RS |
1591 | A @dfn{directory name} is the name of a directory. A directory is |
1592 | actually a kind of file, so it has a file name, which is related to | |
1593 | the directory name but not identical to it. (This is not quite the | |
1594 | same as the usual Unix terminology.) These two different names for | |
1595 | the same entity are related by a syntactic transformation. On GNU and | |
1596 | Unix systems, this is simple: a directory name ends in a slash (or | |
1597 | backslash), whereas the directory's name as a file lacks that slash. | |
1598 | On MSDOS and VMS, the relationship is more complicated. | |
3e01fd9d RS |
1599 | |
1600 | The difference between a directory name and its name as a file is | |
1601 | subtle but crucial. When an Emacs variable or function argument is | |
1602 | described as being a directory name, a file name of a directory is not | |
85df4f66 RS |
1603 | acceptable. When @code{file-name-directory} returns a string, that is |
1604 | always a directory name. | |
3e01fd9d | 1605 | |
b22f3a19 RS |
1606 | The following two functions convert between directory names and file |
1607 | names. They do nothing special with environment variable substitutions | |
1608 | such as @samp{$HOME}, and the constructs @samp{~}, and @samp{..}. | |
3e01fd9d RS |
1609 | |
1610 | @defun file-name-as-directory filename | |
1611 | This function returns a string representing @var{filename} in a form | |
8241495d RS |
1612 | that the operating system will interpret as the name of a directory. On |
1613 | most systems, this means appending a slash to the string (if it does not | |
1614 | already end in one). On VMS, the function converts a string of the form | |
f9f59935 | 1615 | @file{[X]Y.DIR.1} to the form @file{[X.Y]}. |
3e01fd9d RS |
1616 | |
1617 | @example | |
1618 | @group | |
1619 | (file-name-as-directory "~rms/lewis") | |
1620 | @result{} "~rms/lewis/" | |
1621 | @end group | |
1622 | @end example | |
1623 | @end defun | |
1624 | ||
1625 | @defun directory-file-name dirname | |
f9f59935 | 1626 | This function returns a string representing @var{dirname} in a form that |
8241495d | 1627 | the operating system will interpret as the name of a file. On most |
5557b83b RS |
1628 | systems, this means removing the final slash (or backslash) from the |
1629 | string. On VMS, the function converts a string of the form @file{[X.Y]} | |
1630 | to @file{[X]Y.DIR.1}. | |
3e01fd9d RS |
1631 | |
1632 | @example | |
1633 | @group | |
1634 | (directory-file-name "~lewis/") | |
1635 | @result{} "~lewis" | |
1636 | @end group | |
1637 | @end example | |
1638 | @end defun | |
1639 | ||
85df4f66 RS |
1640 | Given a directory name, you can combine it with a relative file name |
1641 | using @code{concat}: | |
1642 | ||
1643 | @example | |
1644 | (concat @var{dirname} @var{relfile}) | |
1645 | @end example | |
1646 | ||
1647 | @noindent | |
1648 | Be sure to verify that the file name is relative before doing that. | |
1649 | If you use an absolute file name, the results could be syntactically | |
1650 | invalid or refer to the wrong file. | |
1651 | ||
1652 | If you want to use a directory file name in making such a | |
1653 | combination, you must first convert it to a directory name using | |
1654 | @code{file-name-as-directory}: | |
1655 | ||
1656 | @example | |
1657 | (concat (file-name-as-directory @var{dirfile}) @var{relfile}) | |
1658 | @end example | |
1659 | ||
1660 | @noindent | |
1661 | Don't try concatenating a slash by hand, as in | |
1662 | ||
1663 | @example | |
1664 | ;;; @r{Wrong!} | |
1665 | (concat @var{dirfile} "/" @var{relfile}) | |
1666 | @end example | |
1667 | ||
1668 | @noindent | |
1669 | because this is not portable. Always use | |
1670 | @code{file-name-as-directory}. | |
1671 | ||
3e01fd9d RS |
1672 | @cindex directory name abbreviation |
1673 | Directory name abbreviations are useful for directories that are | |
1674 | normally accessed through symbolic links. Sometimes the users recognize | |
1675 | primarily the link's name as ``the name'' of the directory, and find it | |
1676 | annoying to see the directory's ``real'' name. If you define the link | |
1677 | name as an abbreviation for the ``real'' name, Emacs shows users the | |
1678 | abbreviation instead. | |
1679 | ||
1680 | @defvar directory-abbrev-alist | |
1681 | The variable @code{directory-abbrev-alist} contains an alist of | |
1682 | abbreviations to use for file directories. Each element has the form | |
1683 | @code{(@var{from} . @var{to})}, and says to replace @var{from} with | |
1684 | @var{to} when it appears in a directory name. The @var{from} string is | |
1685 | actually a regular expression; it should always start with @samp{^}. | |
1686 | The function @code{abbreviate-file-name} performs these substitutions. | |
1687 | ||
1688 | You can set this variable in @file{site-init.el} to describe the | |
1689 | abbreviations appropriate for your site. | |
1690 | ||
1691 | Here's an example, from a system on which file system @file{/home/fsf} | |
1692 | and so on are normally accessed through symbolic links named @file{/fsf} | |
1693 | and so on. | |
1694 | ||
1695 | @example | |
1696 | (("^/home/fsf" . "/fsf") | |
1697 | ("^/home/gp" . "/gp") | |
1698 | ("^/home/gd" . "/gd")) | |
1699 | @end example | |
1700 | @end defvar | |
1701 | ||
1702 | To convert a directory name to its abbreviation, use this | |
1703 | function: | |
1704 | ||
85df4f66 | 1705 | @defun abbreviate-file-name filename |
3e01fd9d RS |
1706 | This function applies abbreviations from @code{directory-abbrev-alist} |
1707 | to its argument, and substitutes @samp{~} for the user's home | |
85df4f66 RS |
1708 | directory. You can use it for directory names and for file names, |
1709 | because it recognizes abbreviations even as part of the name. | |
3e01fd9d RS |
1710 | @end defun |
1711 | ||
1712 | @node File Name Expansion | |
1713 | @subsection Functions that Expand Filenames | |
1714 | @cindex expansion of file names | |
1715 | ||
1716 | @dfn{Expansion} of a file name means converting a relative file name | |
1717 | to an absolute one. Since this is done relative to a default directory, | |
1718 | you must specify the default directory name as well as the file name to | |
1719 | be expanded. Expansion also simplifies file names by eliminating | |
1720 | redundancies such as @file{./} and @file{@var{name}/../}. | |
1721 | ||
1722 | @defun expand-file-name filename &optional directory | |
1723 | This function converts @var{filename} to an absolute file name. If | |
f9f59935 RS |
1724 | @var{directory} is supplied, it is the default directory to start with |
1725 | if @var{filename} is relative. (The value of @var{directory} should | |
1726 | itself be an absolute directory name; it may start with @samp{~}.) | |
3e01fd9d RS |
1727 | Otherwise, the current buffer's value of @code{default-directory} is |
1728 | used. For example: | |
1729 | ||
1730 | @example | |
1731 | @group | |
1732 | (expand-file-name "foo") | |
1733 | @result{} "/xcssun/users/rms/lewis/foo" | |
1734 | @end group | |
1735 | @group | |
1736 | (expand-file-name "../foo") | |
1737 | @result{} "/xcssun/users/rms/foo" | |
1738 | @end group | |
1739 | @group | |
1740 | (expand-file-name "foo" "/usr/spool/") | |
1741 | @result{} "/usr/spool/foo" | |
1742 | @end group | |
1743 | @group | |
1744 | (expand-file-name "$HOME/foo") | |
1745 | @result{} "/xcssun/users/rms/lewis/$HOME/foo" | |
1746 | @end group | |
1747 | @end example | |
1748 | ||
1749 | Filenames containing @samp{.} or @samp{..} are simplified to their | |
1750 | canonical form: | |
1751 | ||
1752 | @example | |
1753 | @group | |
1754 | (expand-file-name "bar/../foo") | |
1755 | @result{} "/xcssun/users/rms/lewis/foo" | |
1756 | @end group | |
1757 | @end example | |
1758 | ||
3e01fd9d RS |
1759 | Note that @code{expand-file-name} does @emph{not} expand environment |
1760 | variables; only @code{substitute-in-file-name} does that. | |
1761 | @end defun | |
1762 | ||
1763 | @c Emacs 19 feature | |
2468d0c0 | 1764 | @defun file-relative-name filename &optional directory |
3e01fd9d | 1765 | This function does the inverse of expansion---it tries to return a |
b22f3a19 | 1766 | relative name that is equivalent to @var{filename} when interpreted |
2468d0c0 DL |
1767 | relative to @var{directory}. If @var{directory} is omitted or |
1768 | @code{nil}, it defaults to the current buffer's default directory. | |
89c77172 RS |
1769 | |
1770 | On some operating systems, an absolute file name begins with a device | |
1771 | name. On such systems, @var{filename} has no relative equivalent based | |
1772 | on @var{directory} if they start with two different device names. In | |
1773 | this case, @code{file-relative-name} returns @var{filename} in absolute | |
1774 | form. | |
3e01fd9d RS |
1775 | |
1776 | @example | |
1777 | (file-relative-name "/foo/bar" "/foo/") | |
a9f0a989 | 1778 | @result{} "bar" |
3e01fd9d | 1779 | (file-relative-name "/foo/bar" "/hack/") |
39a5713c | 1780 | @result{} "../foo/bar" |
3e01fd9d RS |
1781 | @end example |
1782 | @end defun | |
1783 | ||
1784 | @defvar default-directory | |
1785 | The value of this buffer-local variable is the default directory for the | |
1786 | current buffer. It should be an absolute directory name; it may start | |
969fe9b5 | 1787 | with @samp{~}. This variable is buffer-local in every buffer. |
3e01fd9d RS |
1788 | |
1789 | @code{expand-file-name} uses the default directory when its second | |
1790 | argument is @code{nil}. | |
1791 | ||
8241495d | 1792 | Aside from VMS, the value is always a string ending with a slash. |
3e01fd9d RS |
1793 | |
1794 | @example | |
1795 | @group | |
1796 | default-directory | |
1797 | @result{} "/user/lewis/manual/" | |
1798 | @end group | |
1799 | @end example | |
1800 | @end defvar | |
1801 | ||
1802 | @defun substitute-in-file-name filename | |
1803 | This function replaces environment variables references in | |
1804 | @var{filename} with the environment variable values. Following standard | |
1805 | Unix shell syntax, @samp{$} is the prefix to substitute an environment | |
1806 | variable value. | |
1807 | ||
1808 | The environment variable name is the series of alphanumeric characters | |
1809 | (including underscores) that follow the @samp{$}. If the character following | |
1810 | the @samp{$} is a @samp{@{}, then the variable name is everything up to the | |
1811 | matching @samp{@}}. | |
1812 | ||
1813 | @c Wordy to avoid overfull hbox. --rjc 15mar92 | |
1814 | Here we assume that the environment variable @code{HOME}, which holds | |
1815 | the user's home directory name, has value @samp{/xcssun/users/rms}. | |
1816 | ||
1817 | @example | |
1818 | @group | |
1819 | (substitute-in-file-name "$HOME/foo") | |
1820 | @result{} "/xcssun/users/rms/foo" | |
1821 | @end group | |
1822 | @end example | |
1823 | ||
969fe9b5 RS |
1824 | After substitution, if a @samp{~} or a @samp{/} appears following a |
1825 | @samp{/}, everything before the following @samp{/} is discarded: | |
3e01fd9d RS |
1826 | |
1827 | @example | |
1828 | @group | |
1829 | (substitute-in-file-name "bar/~/foo") | |
1830 | @result{} "~/foo" | |
1831 | @end group | |
1832 | @group | |
1833 | (substitute-in-file-name "/usr/local/$HOME/foo") | |
1834 | @result{} "/xcssun/users/rms/foo" | |
f9f59935 | 1835 | ;; @r{@file{/usr/local/} has been discarded.} |
3e01fd9d RS |
1836 | @end group |
1837 | @end example | |
1838 | ||
1839 | On VMS, @samp{$} substitution is not done, so this function does nothing | |
1840 | on VMS except discard superfluous initial components as shown above. | |
1841 | @end defun | |
1842 | ||
1843 | @node Unique File Names | |
1844 | @subsection Generating Unique File Names | |
1845 | ||
1846 | Some programs need to write temporary files. Here is the usual way to | |
8241495d | 1847 | construct a name for such a file, starting in Emacs 21: |
3e01fd9d RS |
1848 | |
1849 | @example | |
8241495d | 1850 | (make-temp-file @var{name-of-application}) |
3e01fd9d RS |
1851 | @end example |
1852 | ||
1853 | @noindent | |
8241495d RS |
1854 | The job of @code{make-temp-file} is to prevent two different users or |
1855 | two different jobs from trying to use the exact same file name. | |
3e01fd9d | 1856 | |
8241495d RS |
1857 | @defun make-temp-file prefix &optional dir-flag |
1858 | @tindex make-temp-file | |
1859 | This function creates a temporary file and returns its name. | |
1860 | The name starts with @var{prefix}; it also contains a number that is | |
1861 | different in each Emacs job. If @var{prefix} is a relative file name, | |
1862 | it is expanded against @code{temporary-file-directory}. | |
3e01fd9d RS |
1863 | |
1864 | @example | |
1865 | @group | |
8241495d | 1866 | (make-temp-file "foo") |
a9f0a989 | 1867 | @result{} "/tmp/foo232J6v" |
3e01fd9d RS |
1868 | @end group |
1869 | @end example | |
1870 | ||
8241495d RS |
1871 | When @code{make-temp-file} returns, the file has been created and is |
1872 | empty. At that point, you should write the intended contents into the | |
1873 | file. | |
1874 | ||
1875 | If @var{dir-flag} is non-@code{nil}, @code{make-temp-file} creates | |
1876 | an empty directory instead of an empty file. | |
1877 | ||
3e01fd9d | 1878 | To prevent conflicts among different libraries running in the same |
8241495d RS |
1879 | Emacs, each Lisp program that uses @code{make-temp-file} should have its |
1880 | own @var{prefix}. The number added to the end of @var{prefix} | |
a9f0a989 RS |
1881 | distinguishes between the same application running in different Emacs |
1882 | jobs. Additional added characters permit a large number of distinct | |
1883 | names even in one Emacs job. | |
8241495d RS |
1884 | @end defun |
1885 | ||
1886 | The default directory for temporary files is controlled by the | |
1887 | variable @code{temporary-file-directory}. This variable gives the user | |
1888 | a uniform way to specify the directory for all temporary files. Some | |
1889 | programs use @code{small-temporary-file-directory} instead, if that is | |
1890 | non-@code{nil}. To use it, you should expand the prefix against | |
1891 | the proper directory before calling @code{make-temp-file}. | |
1892 | ||
1893 | In older Emacs versions where @code{make-temp-file} does not exist, | |
1894 | you should use @code{make-temp-name} instead: | |
1895 | ||
1896 | @example | |
1897 | (make-temp-name | |
1898 | (expand-file-name @var{name-of-application} | |
1899 | temporary-file-directory)) | |
1900 | @end example | |
1901 | ||
1902 | @defun make-temp-name string | |
1903 | This function generates a string that can be used as a unique file name. | |
1904 | The name starts with @var{string}, and contains a number that is | |
1905 | different in each Emacs job. It is like @code{make-temp-file} except | |
1906 | that it just constructs a name, and does not create a file. On MS-DOS, | |
1907 | the @var{string} prefix can be truncated to fit into the 8+3 file-name | |
1908 | limits. | |
3e01fd9d RS |
1909 | @end defun |
1910 | ||
a9f0a989 | 1911 | @defvar temporary-file-directory |
8241495d RS |
1912 | @cindex @code{TMPDIR} environment variable |
1913 | @cindex @code{TMP} environment variable | |
1914 | @cindex @code{TEMP} environment variable | |
a9f0a989 RS |
1915 | This variable specifies the directory name for creating temporary files. |
1916 | Its value should be a directory name (@pxref{Directory Names}), but it | |
f1e2c45e RS |
1917 | is good for Lisp programs to cope if the value is a directory's file |
1918 | name instead. Using the value as the second argument to | |
1919 | @code{expand-file-name} is a good way to achieve that. | |
a9f0a989 RS |
1920 | |
1921 | The default value is determined in a reasonable way for your operating | |
8241495d RS |
1922 | system; it is based on the @code{TMPDIR}, @code{TMP} and @code{TEMP} |
1923 | environment variables, with a fall-back to a system-dependent name if | |
1924 | none of these variables is defined. | |
a9f0a989 RS |
1925 | |
1926 | Even if you do not use @code{make-temp-name} to choose the temporary | |
1927 | file's name, you should still use this variable to decide which | |
8241495d RS |
1928 | directory to put the file in. However, if you expect the file to be |
1929 | small, you should use @code{small-temporary-file-directory} first if | |
1930 | that is non-@code{nil}. | |
1931 | @end defvar | |
1932 | ||
1933 | @tindex small-temporary-file-directory | |
1934 | @defvar small-temporary-file-directory | |
1935 | This variable (new in Emacs 21) specifies the directory name for | |
1936 | creating certain temporary files, which are likely to be small. | |
1937 | ||
1938 | If you want to write a temporary file which is likely to be small, you | |
1939 | should compute the directory like this: | |
1940 | ||
1941 | @example | |
1942 | (make-temp-file | |
1943 | (expand-file-name @var{prefix} | |
1944 | (or small-temporary-file-directory | |
1945 | temporary-file-directory))) | |
1946 | @end example | |
a9f0a989 RS |
1947 | @end defvar |
1948 | ||
3e01fd9d RS |
1949 | @node File Name Completion |
1950 | @subsection File Name Completion | |
1951 | @cindex file name completion subroutines | |
1952 | @cindex completion, file name | |
1953 | ||
1954 | This section describes low-level subroutines for completing a file | |
1955 | name. For other completion functions, see @ref{Completion}. | |
1956 | ||
1957 | @defun file-name-all-completions partial-filename directory | |
1958 | This function returns a list of all possible completions for a file | |
1959 | whose name starts with @var{partial-filename} in directory | |
1960 | @var{directory}. The order of the completions is the order of the files | |
1961 | in the directory, which is unpredictable and conveys no useful | |
1962 | information. | |
1963 | ||
1964 | The argument @var{partial-filename} must be a file name containing no | |
5557b83b RS |
1965 | directory part and no slash (or backslash on some systems). The current |
1966 | buffer's default directory is prepended to @var{directory}, if | |
1967 | @var{directory} is not absolute. | |
3e01fd9d | 1968 | |
9e2b495b RS |
1969 | In the following example, suppose that @file{~rms/lewis} is the current |
1970 | default directory, and has five files whose names begin with @samp{f}: | |
3e01fd9d RS |
1971 | @file{foo}, @file{file~}, @file{file.c}, @file{file.c.~1~}, and |
1972 | @file{file.c.~2~}.@refill | |
1973 | ||
1974 | @example | |
1975 | @group | |
1976 | (file-name-all-completions "f" "") | |
177c0ea7 | 1977 | @result{} ("foo" "file~" "file.c.~2~" |
3e01fd9d RS |
1978 | "file.c.~1~" "file.c") |
1979 | @end group | |
1980 | ||
1981 | @group | |
177c0ea7 | 1982 | (file-name-all-completions "fo" "") |
3e01fd9d RS |
1983 | @result{} ("foo") |
1984 | @end group | |
1985 | @end example | |
1986 | @end defun | |
1987 | ||
1988 | @defun file-name-completion filename directory | |
1989 | This function completes the file name @var{filename} in directory | |
1990 | @var{directory}. It returns the longest prefix common to all file names | |
1991 | in directory @var{directory} that start with @var{filename}. | |
1992 | ||
1993 | If only one match exists and @var{filename} matches it exactly, the | |
1994 | function returns @code{t}. The function returns @code{nil} if directory | |
1995 | @var{directory} contains no name starting with @var{filename}. | |
1996 | ||
1997 | In the following example, suppose that the current default directory | |
1998 | has five files whose names begin with @samp{f}: @file{foo}, | |
1999 | @file{file~}, @file{file.c}, @file{file.c.~1~}, and | |
2000 | @file{file.c.~2~}.@refill | |
2001 | ||
2002 | @example | |
2003 | @group | |
2004 | (file-name-completion "fi" "") | |
2005 | @result{} "file" | |
2006 | @end group | |
2007 | ||
2008 | @group | |
2009 | (file-name-completion "file.c.~1" "") | |
2010 | @result{} "file.c.~1~" | |
2011 | @end group | |
2012 | ||
2013 | @group | |
2014 | (file-name-completion "file.c.~1~" "") | |
2015 | @result{} t | |
2016 | @end group | |
2017 | ||
2018 | @group | |
2019 | (file-name-completion "file.c.~3" "") | |
2020 | @result{} nil | |
2021 | @end group | |
2022 | @end example | |
2023 | @end defun | |
2024 | ||
2025 | @defopt completion-ignored-extensions | |
2026 | @code{file-name-completion} usually ignores file names that end in any | |
2027 | string in this list. It does not ignore them when all the possible | |
2028 | completions end in one of these suffixes or when a buffer showing all | |
2029 | possible completions is displayed.@refill | |
2030 | ||
2031 | A typical value might look like this: | |
2032 | ||
2033 | @example | |
2034 | @group | |
2035 | completion-ignored-extensions | |
2036 | @result{} (".o" ".elc" "~" ".dvi") | |
2037 | @end group | |
2038 | @end example | |
8333f721 EZ |
2039 | |
2040 | If an element of @code{completion-ignored-extensions} ends in a slash | |
2041 | @samp{/}, it signals a directory. The elements which do @emph{not} end | |
2042 | in a slash will never match a directory; thus, the above value will not | |
2043 | filter out a directory named @file{foo.elc}. | |
3e01fd9d RS |
2044 | @end defopt |
2045 | ||
fbc1b72c RS |
2046 | @node Standard File Names |
2047 | @subsection Standard File Names | |
2048 | ||
2049 | Most of the file names used in Lisp programs are entered by the user. | |
2050 | But occasionally a Lisp program needs to specify a standard file name | |
2051 | for a particular use---typically, to hold customization information | |
2052 | about each user. For example, abbrev definitions are stored (by | |
2053 | default) in the file @file{~/.abbrev_defs}; the @code{completion} | |
2054 | package stores completions in the file @file{~/.completions}. These are | |
2055 | two of the many standard file names used by parts of Emacs for certain | |
2056 | purposes. | |
2057 | ||
2058 | Various operating systems have their own conventions for valid file | |
2059 | names and for which file names to use for user profile data. A Lisp | |
2060 | program which reads a file using a standard file name ought to use, on | |
2061 | each type of system, a file name suitable for that system. The function | |
2062 | @code{convert-standard-filename} makes this easy to do. | |
2063 | ||
2064 | @defun convert-standard-filename filename | |
2065 | This function alters the file name @var{filename} to fit the conventions | |
2066 | of the operating system in use, and returns the result as a new string. | |
2067 | @end defun | |
2068 | ||
2069 | The recommended way to specify a standard file name in a Lisp program | |
2070 | is to choose a name which fits the conventions of GNU and Unix systems, | |
2071 | usually with a nondirectory part that starts with a period, and pass it | |
2072 | to @code{convert-standard-filename} instead of using it directly. Here | |
2073 | is an example from the @code{completion} package: | |
2074 | ||
2075 | @example | |
2076 | (defvar save-completions-file-name | |
2077 | (convert-standard-filename "~/.completions") | |
2078 | "*The file name to save completions to.") | |
2079 | @end example | |
2080 | ||
2081 | On GNU and Unix systems, and on some other systems as well, | |
2082 | @code{convert-standard-filename} returns its argument unchanged. On | |
a9f0a989 | 2083 | some other systems, it alters the name to fit the system's conventions. |
fbc1b72c RS |
2084 | |
2085 | For example, on MS-DOS the alterations made by this function include | |
2086 | converting a leading @samp{.} to @samp{_}, converting a @samp{_} in the | |
2087 | middle of the name to @samp{.} if there is no other @samp{.}, inserting | |
2088 | a @samp{.} after eight characters if there is none, and truncating to | |
2089 | three characters after the @samp{.}. (It makes other changes as well.) | |
2090 | Thus, @file{.abbrev_defs} becomes @file{_abbrev.def}, and | |
2091 | @file{.completions} becomes @file{_complet.ion}. | |
2092 | ||
3e01fd9d RS |
2093 | @node Contents of Directories |
2094 | @section Contents of Directories | |
2095 | @cindex directory-oriented functions | |
2096 | @cindex file names in directory | |
2097 | ||
2098 | A directory is a kind of file that contains other files entered under | |
2099 | various names. Directories are a feature of the file system. | |
2100 | ||
2101 | Emacs can list the names of the files in a directory as a Lisp list, | |
2102 | or display the names in a buffer using the @code{ls} shell command. In | |
2103 | the latter case, it can optionally display information about each file, | |
2104 | depending on the options passed to the @code{ls} command. | |
2105 | ||
2106 | @defun directory-files directory &optional full-name match-regexp nosort | |
2107 | This function returns a list of the names of the files in the directory | |
2108 | @var{directory}. By default, the list is in alphabetical order. | |
2109 | ||
2110 | If @var{full-name} is non-@code{nil}, the function returns the files' | |
2111 | absolute file names. Otherwise, it returns the names relative to | |
2112 | the specified directory. | |
2113 | ||
2114 | If @var{match-regexp} is non-@code{nil}, this function returns only | |
2115 | those file names that contain a match for that regular expression---the | |
2116 | other file names are excluded from the list. | |
2117 | ||
2118 | @c Emacs 19 feature | |
2119 | If @var{nosort} is non-@code{nil}, @code{directory-files} does not sort | |
2120 | the list, so you get the file names in no particular order. Use this if | |
2121 | you want the utmost possible speed and don't care what order the files | |
2122 | are processed in. If the order of processing is visible to the user, | |
2123 | then the user will probably be happier if you do sort the names. | |
2124 | ||
2125 | @example | |
2126 | @group | |
2127 | (directory-files "~lewis") | |
2128 | @result{} ("#foo#" "#foo.el#" "." ".." | |
177c0ea7 | 2129 | "dired-mods.el" "files.texi" |
3e01fd9d RS |
2130 | "files.texi.~1~") |
2131 | @end group | |
2132 | @end example | |
2133 | ||
2134 | An error is signaled if @var{directory} is not the name of a directory | |
2135 | that can be read. | |
2136 | @end defun | |
2137 | ||
2138 | @defun file-name-all-versions file dirname | |
2139 | This function returns a list of all versions of the file named | |
2140 | @var{file} in directory @var{dirname}. | |
2141 | @end defun | |
2142 | ||
b6954afd RS |
2143 | @tindex file-expand-wildcards |
2144 | @defun file-expand-wildcards pattern &optional full | |
2145 | This function expands the wildcard pattern @var{pattern}, returning | |
08f0f5e9 | 2146 | a list of file names that match it. |
b6954afd | 2147 | |
08f0f5e9 | 2148 | If @var{pattern} is written as an absolute file name, |
b6954afd RS |
2149 | the values are absolute also. |
2150 | ||
2151 | If @var{pattern} is written as a relative file name, it is interpreted | |
2152 | relative to the current default directory. The file names returned are | |
2153 | normally also relative to the current default directory. However, if | |
2154 | @var{full} is non-@code{nil}, they are absolute. | |
2155 | @end defun | |
2156 | ||
3e01fd9d | 2157 | @defun insert-directory file switches &optional wildcard full-directory-p |
b22f3a19 RS |
2158 | This function inserts (in the current buffer) a directory listing for |
2159 | directory @var{file}, formatted with @code{ls} according to | |
2160 | @var{switches}. It leaves point after the inserted text. | |
3e01fd9d | 2161 | |
b22f3a19 | 2162 | The argument @var{file} may be either a directory name or a file |
3e01fd9d RS |
2163 | specification including wildcard characters. If @var{wildcard} is |
2164 | non-@code{nil}, that means treat @var{file} as a file specification with | |
2165 | wildcards. | |
2166 | ||
a9f0a989 RS |
2167 | If @var{full-directory-p} is non-@code{nil}, that means the directory |
2168 | listing is expected to show the full contents of a directory. You | |
2169 | should specify @code{t} when @var{file} is a directory and switches do | |
2170 | not contain @samp{-d}. (The @samp{-d} option to @code{ls} says to | |
2171 | describe a directory itself as a file, rather than showing its | |
2172 | contents.) | |
3e01fd9d | 2173 | |
8241495d RS |
2174 | On most systems, this function works by running a directory listing |
2175 | program whose name is in the variable @code{insert-directory-program}. | |
2176 | If @var{wildcard} is non-@code{nil}, it also runs the shell specified by | |
3e01fd9d | 2177 | @code{shell-file-name}, to expand the wildcards. |
8241495d RS |
2178 | |
2179 | MS-DOS and MS-Windows systems usually lack the standard Unix program | |
2180 | @code{ls}, so this function emulates the standard Unix program @code{ls} | |
2181 | with Lisp code. | |
3e01fd9d RS |
2182 | @end defun |
2183 | ||
2184 | @defvar insert-directory-program | |
2185 | This variable's value is the program to run to generate a directory listing | |
8241495d RS |
2186 | for the function @code{insert-directory}. It is ignored on systems |
2187 | which generate the listing with Lisp code. | |
3e01fd9d RS |
2188 | @end defvar |
2189 | ||
2190 | @node Create/Delete Dirs | |
2191 | @section Creating and Deleting Directories | |
2192 | @c Emacs 19 features | |
2193 | ||
b22f3a19 RS |
2194 | Most Emacs Lisp file-manipulation functions get errors when used on |
2195 | files that are directories. For example, you cannot delete a directory | |
2196 | with @code{delete-file}. These special functions exist to create and | |
2197 | delete directories. | |
2198 | ||
2468d0c0 | 2199 | @defun make-directory dirname &optional parents |
3e01fd9d | 2200 | This function creates a directory named @var{dirname}. |
2468d0c0 DL |
2201 | If @var{parents} is non-@code{nil}, that means to create |
2202 | the parent directories first, if they don't already exist. | |
3e01fd9d RS |
2203 | @end defun |
2204 | ||
2205 | @defun delete-directory dirname | |
2206 | This function deletes the directory named @var{dirname}. The function | |
2207 | @code{delete-file} does not work for files that are directories; you | |
bfe721d1 KH |
2208 | must use @code{delete-directory} for them. If the directory contains |
2209 | any files, @code{delete-directory} signals an error. | |
3e01fd9d RS |
2210 | @end defun |
2211 | ||
2212 | @node Magic File Names | |
2213 | @section Making Certain File Names ``Magic'' | |
2214 | @cindex magic file names | |
2215 | ||
2216 | @c Emacs 19 feature | |
f9f59935 RS |
2217 | You can implement special handling for certain file names. This is |
2218 | called making those names @dfn{magic}. The principal use for this | |
2219 | feature is in implementing remote file names (@pxref{Remote Files,, | |
2220 | Remote Files, emacs, The GNU Emacs Manual}). | |
2221 | ||
2222 | To define a kind of magic file name, you must supply a regular | |
b22f3a19 | 2223 | expression to define the class of names (all those that match the |
3e01fd9d RS |
2224 | regular expression), plus a handler that implements all the primitive |
2225 | Emacs file operations for file names that do match. | |
2226 | ||
f9f59935 | 2227 | The variable @code{file-name-handler-alist} holds a list of handlers, |
3e01fd9d RS |
2228 | together with regular expressions that determine when to apply each |
2229 | handler. Each element has this form: | |
2230 | ||
2231 | @example | |
2232 | (@var{regexp} . @var{handler}) | |
2233 | @end example | |
2234 | ||
2235 | @noindent | |
2236 | All the Emacs primitives for file access and file name transformation | |
2237 | check the given file name against @code{file-name-handler-alist}. If | |
2238 | the file name matches @var{regexp}, the primitives handle that file by | |
2239 | calling @var{handler}. | |
2240 | ||
2241 | The first argument given to @var{handler} is the name of the primitive; | |
2242 | the remaining arguments are the arguments that were passed to that | |
0fe6819f | 2243 | primitive. (The first of these arguments is most often the file name |
3e01fd9d RS |
2244 | itself.) For example, if you do this: |
2245 | ||
2246 | @example | |
2247 | (file-exists-p @var{filename}) | |
2248 | @end example | |
2249 | ||
2250 | @noindent | |
2251 | and @var{filename} has handler @var{handler}, then @var{handler} is | |
2252 | called like this: | |
2253 | ||
2254 | @example | |
2255 | (funcall @var{handler} 'file-exists-p @var{filename}) | |
2256 | @end example | |
2257 | ||
0fe6819f RS |
2258 | When a function takes two or more arguments that must be file names, |
2259 | it checks each of those names for a handler. For example, if you do | |
2260 | this: | |
2261 | ||
2262 | @example | |
2263 | (expand-file-name @var{filename} @var{dirname}) | |
2264 | @end example | |
2265 | ||
2266 | @noindent | |
2267 | then it checks for a handler for @var{filename} and then for a handler | |
2268 | for @var{dirname}. In either case, the @var{handler} is called like | |
2269 | this: | |
2270 | ||
2271 | @example | |
2272 | (funcall @var{handler} 'expand-file-name @var{filename} @var{dirname}) | |
2273 | @end example | |
2274 | ||
2275 | @noindent | |
2276 | The @var{handler} then needs to figure out whether to handle | |
2277 | @var{filename} or @var{dirname}. | |
2278 | ||
b22f3a19 | 2279 | Here are the operations that a magic file name handler gets to handle: |
3e01fd9d | 2280 | |
37680279 | 2281 | @ifnottex |
3e01fd9d | 2282 | @noindent |
df140a68 KG |
2283 | @code{access-file}, @code{add-name-to-file}, |
2284 | @code{byte-compiler-base-file-name},@* | |
2285 | @code{copy-file}, @code{delete-directory}, | |
969fe9b5 | 2286 | @code{delete-file}, |
63ff95ee | 2287 | @code{diff-latest-backup-file}, |
3e01fd9d | 2288 | @code{directory-file-name}, |
969fe9b5 | 2289 | @code{directory-files}, |
df140a68 | 2290 | @code{directory-files-and-attributes}, |
9e2b495b | 2291 | @code{dired-call-process}, |
df140a68 | 2292 | @code{dired-compress-file}, @code{dired-uncache},@* |
969fe9b5 | 2293 | @code{expand-file-name}, |
df140a68 | 2294 | @code{file-accessible-directory-p}, |
969fe9b5 RS |
2295 | @code{file-attributes}, |
2296 | @code{file-directory-p}, | |
df140a68 | 2297 | @code{file-executable-p}, @code{file-exists-p}, |
969fe9b5 | 2298 | @code{file-local-copy}, |
df140a68 | 2299 | @code{file-modes}, @code{file-name-all-completions}, |
969fe9b5 RS |
2300 | @code{file-name-as-directory}, |
2301 | @code{file-name-completion}, | |
9e2b495b RS |
2302 | @code{file-name-directory}, |
2303 | @code{file-name-nondirectory}, | |
3e01fd9d | 2304 | @code{file-name-sans-versions}, @code{file-newer-than-file-p}, |
fbc1b72c | 2305 | @code{file-ownership-preserved-p}, |
5949c48a | 2306 | @code{file-readable-p}, @code{file-regular-p}, @code{file-symlink-p}, |
63ff95ee | 2307 | @code{file-truename}, @code{file-writable-p}, |
fbc1b72c | 2308 | @code{find-backup-file-name}, |
df140a68 KG |
2309 | @code{find-file-noselect},@* |
2310 | @code{get-file-buffer}, | |
969fe9b5 | 2311 | @code{insert-directory}, |
df140a68 | 2312 | @code{insert-file-contents},@* |
fbc1b72c | 2313 | @code{load}, @code{make-directory}, |
df140a68 KG |
2314 | @code{make-directory-internal}, |
2315 | @code{make-symbolic-link},@* | |
2316 | @code{rename-file}, @code{set-file-modes}, | |
2317 | @code{set-visited-file-modtime}, @code{shell-command}, | |
2318 | @code{substitute-in-file-name},@* | |
969fe9b5 | 2319 | @code{unhandled-file-name-directory}, |
9e2b495b | 2320 | @code{vc-registered}, |
969fe9b5 RS |
2321 | @code{verify-visited-file-modtime},@* |
2322 | @code{write-region}. | |
37680279 | 2323 | @end ifnottex |
f1e2c45e RS |
2324 | @iftex |
2325 | @noindent | |
8241495d | 2326 | @flushleft |
df140a68 KG |
2327 | @code{access-file}, @code{add-name-to-file}, |
2328 | @code{byte-com@discretionary{}{}{}piler-base-file-name}, | |
2329 | @code{copy-file}, @code{delete-directory}, | |
f1e2c45e RS |
2330 | @code{delete-file}, |
2331 | @code{diff-latest-backup-file}, | |
2332 | @code{directory-file-name}, | |
2333 | @code{directory-files}, | |
df140a68 | 2334 | @code{directory-files-and-at@discretionary{}{}{}tributes}, |
f1e2c45e RS |
2335 | @code{dired-call-process}, |
2336 | @code{dired-compress-file}, @code{dired-uncache}, | |
2337 | @code{expand-file-name}, | |
2338 | @code{file-accessible-direc@discretionary{}{}{}tory-p}, | |
2339 | @code{file-attributes}, | |
2340 | @code{file-direct@discretionary{}{}{}ory-p}, | |
2341 | @code{file-executable-p}, @code{file-exists-p}, | |
2342 | @code{file-local-copy}, | |
2343 | @code{file-modes}, @code{file-name-all-completions}, | |
2344 | @code{file-name-as-directory}, | |
2345 | @code{file-name-completion}, | |
2346 | @code{file-name-directory}, | |
2347 | @code{file-name-nondirec@discretionary{}{}{}tory}, | |
2348 | @code{file-name-sans-versions}, @code{file-newer-than-file-p}, | |
2349 | @code{file-ownership-pre@discretionary{}{}{}served-p}, | |
2350 | @code{file-readable-p}, @code{file-regular-p}, @code{file-symlink-p}, | |
2351 | @code{file-truename}, @code{file-writable-p}, | |
2352 | @code{find-backup-file-name}, | |
df140a68 | 2353 | @code{find-file-noselect}, |
f1e2c45e RS |
2354 | @code{get-file-buffer}, |
2355 | @code{insert-directory}, | |
2356 | @code{insert-file-contents}, | |
2357 | @code{load}, @code{make-direc@discretionary{}{}{}tory}, | |
df140a68 KG |
2358 | @code{make-direc@discretionary{}{}{}tory-internal}, |
2359 | @code{make-symbolic-link}, | |
2360 | @code{rename-file}, @code{set-file-modes}, | |
f1e2c45e | 2361 | @code{set-visited-file-modtime}, @code{shell-command}, |
df140a68 | 2362 | @code{substitute-in-file-name}, |
f1e2c45e RS |
2363 | @code{unhandled-file-name-directory}, |
2364 | @code{vc-regis@discretionary{}{}{}tered}, | |
2365 | @code{verify-visited-file-modtime}, | |
2366 | @code{write-region}. | |
8241495d | 2367 | @end flushleft |
f1e2c45e | 2368 | @end iftex |
3e01fd9d | 2369 | |
6ca88231 RS |
2370 | Handlers for @code{insert-file-contents} typically need to clear the |
2371 | buffer's modified flag, with @code{(set-buffer-modified-p nil)}, if the | |
2372 | @var{visit} argument is non-@code{nil}. This also has the effect of | |
2373 | unlocking the buffer if it is locked. | |
2374 | ||
3e01fd9d | 2375 | The handler function must handle all of the above operations, and |
b22f3a19 RS |
2376 | possibly others to be added in the future. It need not implement all |
2377 | these operations itself---when it has nothing special to do for a | |
2378 | certain operation, it can reinvoke the primitive, to handle the | |
2379 | operation ``in the usual way''. It should always reinvoke the primitive | |
2380 | for an operation it does not recognize. Here's one way to do this: | |
3e01fd9d | 2381 | |
841e483d | 2382 | @smallexample |
3e01fd9d RS |
2383 | (defun my-file-handler (operation &rest args) |
2384 | ;; @r{First check for the specific operations} | |
2385 | ;; @r{that we have special handling for.} | |
2386 | (cond ((eq operation 'insert-file-contents) @dots{}) | |
2387 | ((eq operation 'write-region) @dots{}) | |
2388 | @dots{} | |
2389 | ;; @r{Handle any operation we don't know about.} | |
841e483d | 2390 | (t (let ((inhibit-file-name-handlers |
177c0ea7 | 2391 | (cons 'my-file-handler |
f9f59935 RS |
2392 | (and (eq inhibit-file-name-operation operation) |
2393 | inhibit-file-name-handlers))) | |
2394 | (inhibit-file-name-operation operation)) | |
3e01fd9d | 2395 | (apply operation args))))) |
841e483d RS |
2396 | @end smallexample |
2397 | ||
2398 | When a handler function decides to call the ordinary Emacs primitive for | |
2399 | the operation at hand, it needs to prevent the primitive from calling | |
2400 | the same handler once again, thus leading to an infinite recursion. The | |
2401 | example above shows how to do this, with the variables | |
2402 | @code{inhibit-file-name-handlers} and | |
2403 | @code{inhibit-file-name-operation}. Be careful to use them exactly as | |
2404 | shown above; the details are crucial for proper behavior in the case of | |
2405 | multiple handlers, and for operations that have two file names that may | |
2406 | each have handlers. | |
2407 | ||
2408 | @defvar inhibit-file-name-handlers | |
2409 | This variable holds a list of handlers whose use is presently inhibited | |
2410 | for a certain operation. | |
2411 | @end defvar | |
3e01fd9d | 2412 | |
841e483d RS |
2413 | @defvar inhibit-file-name-operation |
2414 | The operation for which certain handlers are presently inhibited. | |
2415 | @end defvar | |
2416 | ||
2417 | @defun find-file-name-handler file operation | |
3e01fd9d | 2418 | This function returns the handler function for file name @var{file}, or |
841e483d RS |
2419 | @code{nil} if there is none. The argument @var{operation} should be the |
2420 | operation to be performed on the file---the value you will pass to the | |
2421 | handler as its first argument when you call it. The operation is needed | |
2422 | for comparison with @code{inhibit-file-name-operation}. | |
3e01fd9d RS |
2423 | @end defun |
2424 | ||
2425 | @defun file-local-copy filename | |
b22f3a19 RS |
2426 | This function copies file @var{filename} to an ordinary non-magic file, |
2427 | if it isn't one already. | |
2428 | ||
f1e2c45e | 2429 | If @var{filename} specifies a magic file name, which programs |
b22f3a19 RS |
2430 | outside Emacs cannot directly read or write, this copies the contents to |
2431 | an ordinary file and returns that file's name. | |
3e01fd9d RS |
2432 | |
2433 | If @var{filename} is an ordinary file name, not magic, then this function | |
2434 | does nothing and returns @code{nil}. | |
2435 | @end defun | |
2436 | ||
2437 | @defun unhandled-file-name-directory filename | |
f9f59935 RS |
2438 | This function returns the name of a directory that is not magic. It |
2439 | uses the directory part of @var{filename} if that is not magic. For a | |
2440 | magic file name, it invokes the file name handler, which therefore | |
2441 | decides what value to return. | |
3e01fd9d RS |
2442 | |
2443 | This is useful for running a subprocess; every subprocess must have a | |
2444 | non-magic directory to serve as its current directory, and this function | |
2445 | is a good way to come up with one. | |
2446 | @end defun | |
841e483d | 2447 | |
22697dac KH |
2448 | @node Format Conversion |
2449 | @section File Format Conversion | |
2450 | ||
2451 | @cindex file format conversion | |
2452 | @cindex encoding file formats | |
2453 | @cindex decoding file formats | |
2454 | The variable @code{format-alist} defines a list of @dfn{file formats}, | |
bfe721d1 | 2455 | which describe textual representations used in files for the data (text, |
22697dac | 2456 | text-properties, and possibly other information) in an Emacs buffer. |
bfe721d1 KH |
2457 | Emacs performs format conversion if appropriate when reading and writing |
2458 | files. | |
22697dac KH |
2459 | |
2460 | @defvar format-alist | |
2461 | This list contains one format definition for each defined file format. | |
2462 | @end defvar | |
2463 | ||
2464 | @cindex format definition | |
2465 | Each format definition is a list of this form: | |
2466 | ||
2467 | @example | |
2468 | (@var{name} @var{doc-string} @var{regexp} @var{from-fn} @var{to-fn} @var{modify} @var{mode-fn}) | |
2469 | @end example | |
2470 | ||
2471 | Here is what the elements in a format definition mean: | |
2472 | ||
2473 | @table @var | |
2474 | @item name | |
2475 | The name of this format. | |
2476 | ||
2477 | @item doc-string | |
2478 | A documentation string for the format. | |
2479 | ||
2480 | @item regexp | |
2481 | A regular expression which is used to recognize files represented in | |
2482 | this format. | |
2483 | ||
2484 | @item from-fn | |
969fe9b5 | 2485 | A shell command or function to decode data in this format (to convert |
f9f59935 | 2486 | file data into the usual Emacs data representation). |
22697dac | 2487 | |
969fe9b5 RS |
2488 | A shell command is represented as a string; Emacs runs the command as a |
2489 | filter to perform the conversion. | |
2490 | ||
2491 | If @var{from-fn} is a function, it is called with two arguments, @var{begin} | |
f9f59935 RS |
2492 | and @var{end}, which specify the part of the buffer it should convert. |
2493 | It should convert the text by editing it in place. Since this can | |
2494 | change the length of the text, @var{from-fn} should return the modified | |
2495 | end position. | |
22697dac | 2496 | |
bfe721d1 | 2497 | One responsibility of @var{from-fn} is to make sure that the beginning |
22697dac KH |
2498 | of the file no longer matches @var{regexp}. Otherwise it is likely to |
2499 | get called again. | |
2500 | ||
2501 | @item to-fn | |
969fe9b5 RS |
2502 | A shell command or function to encode data in this format---that is, to |
2503 | convert the usual Emacs data representation into this format. | |
22697dac | 2504 | |
f9f59935 RS |
2505 | If @var{to-fn} is a string, it is a shell command; Emacs runs the |
2506 | command as a filter to perform the conversion. | |
2507 | ||
969fe9b5 | 2508 | If @var{to-fn} is a function, it is called with two arguments, @var{begin} |
f9f59935 RS |
2509 | and @var{end}, which specify the part of the buffer it should convert. |
2510 | There are two ways it can do the conversion: | |
22697dac KH |
2511 | |
2512 | @itemize @bullet | |
2513 | @item | |
2514 | By editing the buffer in place. In this case, @var{to-fn} should | |
2515 | return the end-position of the range of text, as modified. | |
2516 | ||
2517 | @item | |
2518 | By returning a list of annotations. This is a list of elements of the | |
2519 | form @code{(@var{position} . @var{string})}, where @var{position} is an | |
2520 | integer specifying the relative position in the text to be written, and | |
2521 | @var{string} is the annotation to add there. The list must be sorted in | |
2522 | order of position when @var{to-fn} returns it. | |
2523 | ||
2524 | When @code{write-region} actually writes the text from the buffer to the | |
2525 | file, it intermixes the specified annotations at the corresponding | |
2526 | positions. All this takes place without modifying the buffer. | |
2527 | @end itemize | |
2528 | ||
2529 | @item modify | |
2530 | A flag, @code{t} if the encoding function modifies the buffer, and | |
2531 | @code{nil} if it works by returning a list of annotations. | |
2532 | ||
8f3efb4e RS |
2533 | @item mode-fn |
2534 | A minor-mode function to call after visiting a file converted from this | |
2535 | format. The function is called with one argument, the integer 1; | |
2536 | that tells a minor-mode function to enable the mode. | |
22697dac KH |
2537 | @end table |
2538 | ||
2539 | The function @code{insert-file-contents} automatically recognizes file | |
2540 | formats when it reads the specified file. It checks the text of the | |
2541 | beginning of the file against the regular expressions of the format | |
2542 | definitions, and if it finds a match, it calls the decoding function for | |
2543 | that format. Then it checks all the known formats over again. | |
2544 | It keeps checking them until none of them is applicable. | |
2545 | ||
2546 | Visiting a file, with @code{find-file-noselect} or the commands that use | |
2547 | it, performs conversion likewise (because it calls | |
bfe721d1 KH |
2548 | @code{insert-file-contents}); it also calls the mode function for each |
2549 | format that it decodes. It stores a list of the format names in the | |
2550 | buffer-local variable @code{buffer-file-format}. | |
22697dac KH |
2551 | |
2552 | @defvar buffer-file-format | |
bfe721d1 KH |
2553 | This variable states the format of the visited file. More precisely, |
2554 | this is a list of the file format names that were decoded in the course | |
969fe9b5 | 2555 | of visiting the current buffer's file. It is always buffer-local in all |
22697dac KH |
2556 | buffers. |
2557 | @end defvar | |
2558 | ||
2559 | When @code{write-region} writes data into a file, it first calls the | |
bfe721d1 KH |
2560 | encoding functions for the formats listed in @code{buffer-file-format}, |
2561 | in the order of appearance in the list. | |
22697dac | 2562 | |
f9f59935 | 2563 | @deffn Command format-write-file file format |
22697dac KH |
2564 | This command writes the current buffer contents into the file @var{file} |
2565 | in format @var{format}, and makes that format the default for future | |
bfe721d1 KH |
2566 | saves of the buffer. The argument @var{format} is a list of format |
2567 | names. | |
f9f59935 | 2568 | @end deffn |
22697dac | 2569 | |
f9f59935 | 2570 | @deffn Command format-find-file file format |
63ff95ee MW |
2571 | This command finds the file @var{file}, converting it according to |
2572 | format @var{format}. It also makes @var{format} the default if the | |
2573 | buffer is saved later. | |
2574 | ||
2575 | The argument @var{format} is a list of format names. If @var{format} is | |
2576 | @code{nil}, no conversion takes place. Interactively, typing just | |
2577 | @key{RET} for @var{format} specifies @code{nil}. | |
f9f59935 | 2578 | @end deffn |
63ff95ee | 2579 | |
969fe9b5 | 2580 | @deffn Command format-insert-file file format &optional beg end |
63ff95ee MW |
2581 | This command inserts the contents of file @var{file}, converting it |
2582 | according to format @var{format}. If @var{beg} and @var{end} are | |
2583 | non-@code{nil}, they specify which part of the file to read, as in | |
2584 | @code{insert-file-contents} (@pxref{Reading from Files}). | |
2585 | ||
2586 | The return value is like what @code{insert-file-contents} returns: a | |
2587 | list of the absolute file name and the length of the data inserted | |
2588 | (after conversion). | |
2589 | ||
2590 | The argument @var{format} is a list of format names. If @var{format} is | |
2591 | @code{nil}, no conversion takes place. Interactively, typing just | |
2592 | @key{RET} for @var{format} specifies @code{nil}. | |
f9f59935 | 2593 | @end deffn |
63ff95ee | 2594 | |
22697dac KH |
2595 | @defvar auto-save-file-format |
2596 | This variable specifies the format to use for auto-saving. Its value is | |
2597 | a list of format names, just like the value of | |
a9f0a989 RS |
2598 | @code{buffer-file-format}; however, it is used instead of |
2599 | @code{buffer-file-format} for writing auto-save files. This variable is | |
2600 | always buffer-local in all buffers. | |
841e483d | 2601 | @end defvar |