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