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annotate man/lispref/backups.texi @ 5940:c608d4b0b75e cygwin64 tip
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| author | Henry Thompson <ht@markup.co.uk> |
|---|---|
| date | Thu, 16 Dec 2021 18:48:58 +0000 |
| parents | 9fae6227ede5 |
| children |
| rev | line source |
|---|---|
| 0 | 1 @c -*-texinfo-*- |
| 2 @c This is part of the XEmacs Lisp Reference Manual. | |
| 444 | 3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. |
| 0 | 4 @c See the file lispref.texi for copying conditions. |
| 5 @setfilename ../../info/backups.info | |
| 6 @node Backups and Auto-Saving, Buffers, Files, Top | |
| 7 @chapter Backups and Auto-Saving | |
| 8 | |
| 9 Backup files and auto-save files are two methods by which XEmacs tries | |
| 10 to protect the user from the consequences of crashes or of the user's | |
| 11 own errors. Auto-saving preserves the text from earlier in the current | |
| 12 editing session; backup files preserve file contents prior to the | |
| 13 current session. | |
| 14 | |
| 15 @menu | |
| 16 * Backup Files:: How backup files are made; how their names are chosen. | |
| 17 * Auto-Saving:: How auto-save files are made; how their names are chosen. | |
| 18 * Reverting:: @code{revert-buffer}, and how to customize what it does. | |
| 19 @end menu | |
| 20 | |
|
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21 @node Backup Files, Auto-Saving, Backups and Auto-Saving, Backups and Auto-Saving |
| 0 | 22 @section Backup Files |
| 23 @cindex backup file | |
| 24 | |
| 25 A @dfn{backup file} is a copy of the old contents of a file you are | |
| 26 editing. XEmacs makes a backup file the first time you save a buffer | |
| 27 into its visited file. Normally, this means that the backup file | |
| 28 contains the contents of the file as it was before the current editing | |
| 29 session. The contents of the backup file normally remain unchanged once | |
| 30 it exists. | |
| 31 | |
| 32 Backups are usually made by renaming the visited file to a new name. | |
| 33 Optionally, you can specify that backup files should be made by copying | |
| 34 the visited file. This choice makes a difference for files with | |
| 35 multiple names; it also can affect whether the edited file remains owned | |
| 36 by the original owner or becomes owned by the user editing it. | |
| 37 | |
| 38 By default, XEmacs makes a single backup file for each file edited. | |
| 39 You can alternatively request numbered backups; then each new backup | |
| 40 file gets a new name. You can delete old numbered backups when you | |
| 41 don't want them any more, or XEmacs can delete them automatically. | |
| 42 | |
| 43 @menu | |
| 44 * Making Backups:: How XEmacs makes backup files, and when. | |
| 45 * Rename or Copy:: Two alternatives: renaming the old file or copying it. | |
| 46 * Numbered Backups:: Keeping multiple backups for each source file. | |
| 47 * Backup Names:: How backup file names are computed; customization. | |
| 48 @end menu | |
| 49 | |
|
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50 @node Making Backups, Rename or Copy, Backup Files, Backup Files |
| 0 | 51 @subsection Making Backup Files |
| 52 | |
| 53 @defun backup-buffer | |
| 54 This function makes a backup of the file visited by the current | |
| 55 buffer, if appropriate. It is called by @code{save-buffer} before | |
| 56 saving the buffer the first time. | |
| 57 @end defun | |
| 58 | |
| 59 @defvar buffer-backed-up | |
| 60 This buffer-local variable indicates whether this buffer's file has | |
| 61 been backed up on account of this buffer. If it is non-@code{nil}, then | |
| 62 the backup file has been written. Otherwise, the file should be backed | |
| 63 up when it is next saved (if backups are enabled). This is a | |
| 64 permanent local; @code{kill-local-variables} does not alter it. | |
| 65 @end defvar | |
| 66 | |
| 67 @defopt make-backup-files | |
| 68 This variable determines whether or not to make backup files. If it | |
| 69 is non-@code{nil}, then XEmacs creates a backup of each file when it is | |
| 70 saved for the first time---provided that @code{backup-inhibited} | |
| 71 is @code{nil} (see below). | |
| 72 | |
| 73 The following example shows how to change the @code{make-backup-files} | |
| 74 variable only in the @file{RMAIL} buffer and not elsewhere. Setting it | |
| 75 @code{nil} stops XEmacs from making backups of the @file{RMAIL} file, | |
| 76 which may save disk space. (You would put this code in your | |
| 77 @file{.emacs} file.) | |
| 78 | |
| 79 @smallexample | |
| 80 @group | |
| 444 | 81 (add-hook 'rmail-mode-hook |
| 0 | 82 (function (lambda () |
| 444 | 83 (make-local-variable |
| 0 | 84 'make-backup-files) |
| 85 (setq make-backup-files nil)))) | |
| 86 @end group | |
| 87 @end smallexample | |
| 88 @end defopt | |
| 89 | |
| 90 @defvar backup-enable-predicate | |
| 91 This variable's value is a function to be called on certain occasions to | |
| 92 decide whether a file should have backup files. The function receives | |
| 93 one argument, a file name to consider. If the function returns | |
| 94 @code{nil}, backups are disabled for that file. Otherwise, the other | |
| 95 variables in this section say whether and how to make backups. | |
| 96 | |
| 97 The default value is this: | |
| 98 | |
| 99 @example | |
| 100 (lambda (name) | |
| 101 (or (< (length name) 5) | |
| 102 (not (string-equal "/tmp/" | |
| 103 (substring name 0 5))))) | |
| 104 @end example | |
| 105 @end defvar | |
| 106 | |
| 107 @defvar backup-inhibited | |
| 108 If this variable is non-@code{nil}, backups are inhibited. It records | |
| 109 the result of testing @code{backup-enable-predicate} on the visited file | |
| 110 name. It can also coherently be used by other mechanisms that inhibit | |
| 111 backups based on which file is visited. For example, VC sets this | |
| 112 variable non-@code{nil} to prevent making backups for files managed | |
| 113 with a version control system. | |
| 114 | |
| 115 This is a permanent local, so that changing the major mode does not lose | |
| 116 its value. Major modes should not set this variable---they should set | |
| 117 @code{make-backup-files} instead. | |
| 118 @end defvar | |
| 119 | |
|
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120 @node Rename or Copy, Numbered Backups, Making Backups, Backup Files |
| 0 | 121 @subsection Backup by Renaming or by Copying? |
| 122 @cindex backup files, how to make them | |
| 123 | |
| 444 | 124 There are two ways that XEmacs can make a backup file: |
| 0 | 125 |
| 126 @itemize @bullet | |
| 127 @item | |
| 128 XEmacs can rename the original file so that it becomes a backup file, and | |
| 129 then write the buffer being saved into a new file. After this | |
| 130 procedure, any other names (i.e., hard links) of the original file now | |
| 131 refer to the backup file. The new file is owned by the user doing the | |
| 132 editing, and its group is the default for new files written by the user | |
| 133 in that directory. | |
| 134 | |
| 135 @item | |
| 136 XEmacs can copy the original file into a backup file, and then overwrite | |
| 137 the original file with new contents. After this procedure, any other | |
| 138 names (i.e., hard links) of the original file still refer to the current | |
| 139 version of the file. The file's owner and group will be unchanged. | |
| 140 @end itemize | |
| 141 | |
| 142 The first method, renaming, is the default. | |
| 143 | |
| 144 The variable @code{backup-by-copying}, if non-@code{nil}, says to use | |
| 145 the second method, which is to copy the original file and overwrite it | |
| 146 with the new buffer contents. The variable @code{file-precious-flag}, | |
| 147 if non-@code{nil}, also has this effect (as a sideline of its main | |
| 148 significance). @xref{Saving Buffers}. | |
| 149 | |
| 150 @defvar backup-by-copying | |
| 151 If this variable is non-@code{nil}, XEmacs always makes backup files by | |
| 152 copying. | |
| 153 @end defvar | |
| 154 | |
| 155 The following two variables, when non-@code{nil}, cause the second | |
| 156 method to be used in certain special cases. They have no effect on the | |
| 157 treatment of files that don't fall into the special cases. | |
| 158 | |
| 159 @defvar backup-by-copying-when-linked | |
| 160 If this variable is non-@code{nil}, XEmacs makes backups by copying for | |
| 161 files with multiple names (hard links). | |
| 162 | |
| 163 This variable is significant only if @code{backup-by-copying} is | |
| 164 @code{nil}, since copying is always used when that variable is | |
| 165 non-@code{nil}. | |
| 166 @end defvar | |
| 167 | |
| 168 @defvar backup-by-copying-when-mismatch | |
| 169 If this variable is non-@code{nil}, XEmacs makes backups by copying in cases | |
| 170 where renaming would change either the owner or the group of the file. | |
| 171 | |
| 172 The value has no effect when renaming would not alter the owner or | |
| 173 group of the file; that is, for files which are owned by the user and | |
| 174 whose group matches the default for a new file created there by the | |
| 175 user. | |
| 176 | |
| 177 This variable is significant only if @code{backup-by-copying} is | |
| 178 @code{nil}, since copying is always used when that variable is | |
| 179 non-@code{nil}. | |
| 180 @end defvar | |
| 181 | |
|
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182 @node Numbered Backups, Backup Names, Rename or Copy, Backup Files |
| 0 | 183 @subsection Making and Deleting Numbered Backup Files |
| 184 | |
| 185 If a file's name is @file{foo}, the names of its numbered backup | |
| 186 versions are @file{foo.~@var{v}~}, for various integers @var{v}, like | |
| 187 this: @file{foo.~1~}, @file{foo.~2~}, @file{foo.~3~}, @dots{}, | |
| 188 @file{foo.~259~}, and so on. | |
| 189 | |
| 190 @defopt version-control | |
| 191 This variable controls whether to make a single non-numbered backup | |
| 192 file or multiple numbered backups. | |
| 193 | |
| 194 @table @asis | |
| 195 @item @code{nil} | |
| 196 Make numbered backups if the visited file already has numbered backups; | |
| 197 otherwise, do not. | |
| 198 | |
| 199 @item @code{never} | |
| 200 Do not make numbered backups. | |
| 201 | |
| 202 @item @var{anything else} | |
| 203 Make numbered backups. | |
| 204 @end table | |
| 205 @end defopt | |
| 206 | |
| 207 The use of numbered backups ultimately leads to a large number of | |
| 208 backup versions, which must then be deleted. XEmacs can do this | |
| 209 automatically or it can ask the user whether to delete them. | |
| 210 | |
| 211 @defopt kept-new-versions | |
| 212 The value of this variable is the number of newest versions to keep | |
| 213 when a new numbered backup is made. The newly made backup is included | |
| 214 in the count. The default value is 2. | |
| 215 @end defopt | |
| 216 | |
| 217 @defopt kept-old-versions | |
| 218 The value of this variable is the number of oldest versions to keep | |
| 219 when a new numbered backup is made. The default value is 2. | |
| 220 @end defopt | |
| 221 | |
| 222 If there are backups numbered 1, 2, 3, 5, and 7, and both of these | |
| 223 variables have the value 2, then the backups numbered 1 and 2 are kept | |
| 224 as old versions and those numbered 5 and 7 are kept as new versions; | |
| 225 backup version 3 is excess. The function @code{find-backup-file-name} | |
| 226 (@pxref{Backup Names}) is responsible for determining which backup | |
| 227 versions to delete, but does not delete them itself. | |
| 228 | |
| 359 | 229 @defopt delete-old-versions |
| 0 | 230 If this variable is non-@code{nil}, then saving a file deletes excess |
| 231 backup versions silently. Otherwise, it asks the user whether to delete | |
| 232 them. | |
| 233 @end defopt | |
| 234 | |
| 235 @defopt dired-kept-versions | |
| 236 This variable specifies how many of the newest backup versions to keep | |
| 237 in the Dired command @kbd{.} (@code{dired-clean-directory}). That's the | |
| 238 same thing @code{kept-new-versions} specifies when you make a new backup | |
| 239 file. The default value is 2. | |
| 240 @end defopt | |
| 241 | |
|
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242 @node Backup Names, , Numbered Backups, Backup Files |
| 0 | 243 @subsection Naming Backup Files |
| 244 | |
| 245 The functions in this section are documented mainly because you can | |
| 246 customize the naming conventions for backup files by redefining them. | |
| 247 If you change one, you probably need to change the rest. | |
| 248 | |
| 249 @defun backup-file-name-p filename | |
| 250 This function returns a non-@code{nil} value if @var{filename} is a | |
| 251 possible name for a backup file. A file with the name @var{filename} | |
| 252 need not exist; the function just checks the name. | |
| 253 | |
| 254 @smallexample | |
| 255 @group | |
| 256 (backup-file-name-p "foo") | |
| 257 @result{} nil | |
| 258 @end group | |
| 259 @group | |
| 260 (backup-file-name-p "foo~") | |
| 261 @result{} 3 | |
| 262 @end group | |
| 263 @end smallexample | |
| 264 | |
| 265 The standard definition of this function is as follows: | |
| 266 | |
| 267 @smallexample | |
| 268 @group | |
| 269 (defun backup-file-name-p (file) | |
| 270 "Return non-nil if FILE is a backup file \ | |
| 271 name (numeric or not)..." | |
| 272 (string-match "~$" file)) | |
| 273 @end group | |
| 274 @end smallexample | |
| 275 | |
| 276 @noindent | |
| 277 Thus, the function returns a non-@code{nil} value if the file name ends | |
| 278 with a @samp{~}. (We use a backslash to split the documentation | |
| 279 string's first line into two lines in the text, but produce just one | |
| 280 line in the string itself.) | |
| 281 | |
| 282 This simple expression is placed in a separate function to make it easy | |
| 283 to redefine for customization. | |
| 284 @end defun | |
| 285 | |
| 286 @defun make-backup-file-name filename | |
| 287 This function returns a string that is the name to use for a | |
| 288 non-numbered backup file for file @var{filename}. On Unix, this is just | |
| 289 @var{filename} with a tilde appended. | |
| 290 | |
| 291 The standard definition of this function is as follows: | |
| 292 | |
| 293 @smallexample | |
| 294 @group | |
| 295 (defun make-backup-file-name (file) | |
| 296 "Create the non-numeric backup file name for FILE. | |
| 297 @dots{}" | |
| 298 (concat file "~")) | |
| 299 @end group | |
| 300 @end smallexample | |
| 301 | |
| 302 You can change the backup-file naming convention by redefining this | |
| 303 function. The following example redefines @code{make-backup-file-name} | |
| 304 to prepend a @samp{.} in addition to appending a tilde: | |
| 305 | |
| 306 @smallexample | |
| 307 @group | |
| 308 (defun make-backup-file-name (filename) | |
| 309 (concat "." filename "~")) | |
| 310 @end group | |
| 311 | |
| 312 @group | |
| 313 (make-backup-file-name "backups.texi") | |
| 314 @result{} ".backups.texi~" | |
| 315 @end group | |
| 316 @end smallexample | |
| 317 @end defun | |
| 318 | |
| 319 @defun find-backup-file-name filename | |
| 320 This function computes the file name for a new backup file for | |
| 321 @var{filename}. It may also propose certain existing backup files for | |
| 322 deletion. @code{find-backup-file-name} returns a list whose @sc{car} is | |
| 323 the name for the new backup file and whose @sc{cdr} is a list of backup | |
| 324 files whose deletion is proposed. | |
| 325 | |
| 326 Two variables, @code{kept-old-versions} and @code{kept-new-versions}, | |
| 327 determine which backup versions should be kept. This function keeps | |
| 328 those versions by excluding them from the @sc{cdr} of the value. | |
| 329 @xref{Numbered Backups}. | |
| 330 | |
| 331 In this example, the value says that @file{~rms/foo.~5~} is the name | |
| 332 to use for the new backup file, and @file{~rms/foo.~3~} is an ``excess'' | |
| 333 version that the caller should consider deleting now. | |
| 334 | |
| 335 @smallexample | |
| 336 @group | |
| 337 (find-backup-file-name "~rms/foo") | |
| 338 @result{} ("~rms/foo.~5~" "~rms/foo.~3~") | |
| 339 @end group | |
| 340 @end smallexample | |
| 341 @end defun | |
| 342 | |
| 343 @c Emacs 19 feature | |
| 344 @defun file-newest-backup filename | |
| 345 This function returns the name of the most recent backup file for | |
| 346 @var{filename}, or @code{nil} if that file has no backup files. | |
| 347 | |
| 348 Some file comparison commands use this function so that they can | |
| 349 automatically compare a file with its most recent backup. | |
| 444 | 350 @end defun |
| 0 | 351 |
|
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352 @node Auto-Saving, Reverting, Backup Files, Backups and Auto-Saving |
| 0 | 353 @section Auto-Saving |
| 354 @cindex auto-saving | |
| 355 | |
| 356 XEmacs periodically saves all files that you are visiting; this is | |
| 357 called @dfn{auto-saving}. Auto-saving prevents you from losing more | |
| 358 than a limited amount of work if the system crashes. By default, | |
| 359 auto-saves happen every 300 keystrokes, or after around 30 seconds of | |
| 1288 | 360 idle time. @xref{Auto Save, Auto-Save, Auto-Saving: Protection Against |
| 361 Disasters, xemacs, The XEmacs User's Manual}, for information on | |
| 446 | 362 auto-save for users. Here we describe the functions used to implement |
| 363 auto-saving and the variables that control them. | |
| 0 | 364 |
| 365 @defvar buffer-auto-save-file-name | |
| 366 This buffer-local variable is the name of the file used for | |
| 367 auto-saving the current buffer. It is @code{nil} if the buffer | |
| 368 should not be auto-saved. | |
| 369 | |
| 370 @example | |
| 371 @group | |
| 372 buffer-auto-save-file-name | |
| 373 => "/xcssun/users/rms/lewis/#files.texi#" | |
| 374 @end group | |
| 375 @end example | |
| 376 @end defvar | |
| 377 | |
| 378 @deffn Command auto-save-mode arg | |
| 379 When used interactively without an argument, this command is a toggle | |
| 380 switch: it turns on auto-saving of the current buffer if it is off, and | |
| 381 vice-versa. With an argument @var{arg}, the command turns auto-saving | |
| 382 on if the value of @var{arg} is @code{t}, a nonempty list, or a positive | |
| 383 integer. Otherwise, it turns auto-saving off. | |
| 384 @end deffn | |
| 385 | |
| 386 @defun auto-save-file-name-p filename | |
| 387 This function returns a non-@code{nil} value if @var{filename} is a | |
| 388 string that could be the name of an auto-save file. It works based on | |
| 389 knowledge of the naming convention for auto-save files: a name that | |
| 390 begins and ends with hash marks (@samp{#}) is a possible auto-save file | |
| 391 name. The argument @var{filename} should not contain a directory part. | |
| 392 | |
| 393 @example | |
| 394 @group | |
| 395 (make-auto-save-file-name) | |
| 396 @result{} "/xcssun/users/rms/lewis/#files.texi#" | |
| 397 @end group | |
| 398 @group | |
| 399 (auto-save-file-name-p "#files.texi#") | |
| 400 @result{} 0 | |
| 401 @end group | |
| 402 @group | |
| 403 (auto-save-file-name-p "files.texi") | |
| 404 @result{} nil | |
| 405 @end group | |
| 406 @end example | |
| 407 | |
| 408 The standard definition of this function is as follows: | |
| 409 | |
| 410 @example | |
| 411 @group | |
| 412 (defun auto-save-file-name-p (filename) | |
| 413 "Return non-nil if FILENAME can be yielded by..." | |
| 414 (string-match "^#.*#$" filename)) | |
| 415 @end group | |
| 416 @end example | |
| 417 | |
| 418 This function exists so that you can customize it if you wish to | |
| 419 change the naming convention for auto-save files. If you redefine it, | |
| 420 be sure to redefine the function @code{make-auto-save-file-name} | |
| 421 correspondingly. | |
| 422 @end defun | |
| 423 | |
| 444 | 424 @defun make-auto-save-file-name &optional filename |
| 0 | 425 This function returns the file name to use for auto-saving the current |
| 426 buffer. This is just the file name with hash marks (@samp{#}) appended | |
| 427 and prepended to it. This function does not look at the variable | |
| 428 @code{auto-save-visited-file-name} (described below); you should check | |
| 429 that before calling this function. | |
| 430 | |
| 431 @example | |
| 432 @group | |
| 433 (make-auto-save-file-name) | |
| 434 @result{} "/xcssun/users/rms/lewis/#backup.texi#" | |
| 435 @end group | |
| 436 @end example | |
| 437 | |
| 438 The standard definition of this function is as follows: | |
| 439 | |
| 440 @example | |
| 441 @group | |
| 442 (defun make-auto-save-file-name () | |
| 443 "Return file name to use for auto-saves \ | |
| 444 of current buffer. | |
| 445 @dots{}" | |
| 446 (if buffer-file-name | |
| 447 @end group | |
| 448 @group | |
| 449 (concat | |
| 450 (file-name-directory buffer-file-name) | |
| 451 "#" | |
| 452 (file-name-nondirectory buffer-file-name) | |
| 453 "#") | |
| 454 (expand-file-name | |
| 455 (concat "#%" (buffer-name) "#")))) | |
| 456 @end group | |
| 457 @end example | |
| 458 | |
| 459 This exists as a separate function so that you can redefine it to | |
| 460 customize the naming convention for auto-save files. Be sure to | |
| 461 change @code{auto-save-file-name-p} in a corresponding way. | |
| 462 @end defun | |
| 463 | |
| 464 @defvar auto-save-visited-file-name | |
| 465 If this variable is non-@code{nil}, XEmacs auto-saves buffers in | |
| 466 the files they are visiting. That is, the auto-save is done in the same | |
| 467 file that you are editing. Normally, this variable is @code{nil}, so | |
| 468 auto-save files have distinct names that are created by | |
| 469 @code{make-auto-save-file-name}. | |
| 470 | |
| 471 When you change the value of this variable, the value does not take | |
| 472 effect until the next time auto-save mode is reenabled in any given | |
| 473 buffer. If auto-save mode is already enabled, auto-saves continue to go | |
| 474 in the same file name until @code{auto-save-mode} is called again. | |
| 475 @end defvar | |
| 476 | |
| 477 @defun recent-auto-save-p | |
| 478 This function returns @code{t} if the current buffer has been | |
| 479 auto-saved since the last time it was read in or saved. | |
| 480 @end defun | |
| 481 | |
| 482 @defun set-buffer-auto-saved | |
| 483 This function marks the current buffer as auto-saved. The buffer will | |
| 484 not be auto-saved again until the buffer text is changed again. The | |
| 485 function returns @code{nil}. | |
| 486 @end defun | |
| 487 | |
| 488 @defopt auto-save-interval | |
| 489 The value of this variable is the number of characters that XEmacs | |
| 490 reads from the keyboard between auto-saves. Each time this many more | |
| 491 characters are read, auto-saving is done for all buffers in which it is | |
| 492 enabled. | |
| 493 @end defopt | |
| 494 | |
| 495 @defopt auto-save-timeout | |
| 496 The value of this variable is the number of seconds of idle time that | |
| 497 should cause auto-saving. Each time the user pauses for this long, | |
| 498 XEmacs auto-saves any buffers that need it. (Actually, the specified | |
| 499 timeout is multiplied by a factor depending on the size of the current | |
| 500 buffer.) | |
| 501 @end defopt | |
| 502 | |
| 503 @defvar auto-save-hook | |
| 504 This normal hook is run whenever an auto-save is about to happen. | |
| 505 @end defvar | |
| 506 | |
| 507 @defopt auto-save-default | |
| 508 If this variable is non-@code{nil}, buffers that are visiting files | |
| 509 have auto-saving enabled by default. Otherwise, they do not. | |
| 510 @end defopt | |
| 511 | |
| 512 @deffn Command do-auto-save &optional no-message current-only | |
| 513 This function auto-saves all buffers that need to be auto-saved. It | |
| 514 saves all buffers for which auto-saving is enabled and that have been | |
| 515 changed since the previous auto-save. | |
| 516 | |
| 517 Normally, if any buffers are auto-saved, a message that says | |
| 518 @samp{Auto-saving...} is displayed in the echo area while auto-saving is | |
| 519 going on. However, if @var{no-message} is non-@code{nil}, the message | |
| 520 is inhibited. | |
| 521 | |
| 522 If @var{current-only} is non-@code{nil}, only the current buffer | |
| 523 is auto-saved. | |
| 524 @end deffn | |
| 525 | |
| 526 @defun delete-auto-save-file-if-necessary | |
| 527 This function deletes the current buffer's auto-save file if | |
| 528 @code{delete-auto-save-files} is non-@code{nil}. It is called every | |
| 529 time a buffer is saved. | |
| 530 @end defun | |
| 531 | |
| 532 @defvar delete-auto-save-files | |
| 533 This variable is used by the function | |
| 534 @code{delete-auto-save-file-if-necessary}. If it is non-@code{nil}, | |
| 535 Emacs deletes auto-save files when a true save is done (in the visited | |
| 536 file). This saves disk space and unclutters your directory. | |
| 537 @end defvar | |
| 538 | |
| 539 @defun rename-auto-save-file | |
| 540 This function adjusts the current buffer's auto-save file name if the | |
| 541 visited file name has changed. It also renames an existing auto-save | |
| 542 file. If the visited file name has not changed, this function does | |
| 543 nothing. | |
| 544 @end defun | |
| 545 | |
| 546 @defvar buffer-saved-size | |
| 547 The value of this buffer-local variable is the length of the current | |
| 548 buffer as of the last time it was read in, saved, or auto-saved. This is | |
| 549 used to detect a substantial decrease in size, and turn off auto-saving | |
| 550 in response. | |
| 551 | |
| 552 If it is -1, that means auto-saving is temporarily shut off in this | |
| 553 buffer due to a substantial deletion. Explicitly saving the buffer | |
| 554 stores a positive value in this variable, thus reenabling auto-saving. | |
| 555 Turning auto-save mode off or on also alters this variable. | |
| 556 @end defvar | |
| 557 | |
| 558 @defvar auto-save-list-file-name | |
| 559 This variable (if non-@code{nil}) specifies a file for recording the | |
| 560 names of all the auto-save files. Each time XEmacs does auto-saving, it | |
| 561 writes two lines into this file for each buffer that has auto-saving | |
| 562 enabled. The first line gives the name of the visited file (it's empty | |
| 563 if the buffer has none), and the second gives the name of the auto-save | |
| 564 file. | |
| 565 | |
| 566 If XEmacs exits normally, it deletes this file. If XEmacs crashes, you | |
| 567 can look in the file to find all the auto-save files that might contain | |
| 568 work that was otherwise lost. The @code{recover-session} command uses | |
| 569 these files. | |
| 570 | |
| 571 The default name for this file is in your home directory and starts with | |
| 572 @samp{.saves-}. It also contains the XEmacs process @sc{id} and the host | |
| 573 name. | |
| 574 @end defvar | |
| 575 | |
|
5791
9fae6227ede5
Silence texinfo 5.2 warnings, primarily by adding next, prev, and up
Jerry James <james@xemacs.org>
parents:
1710
diff
changeset
|
576 @node Reverting, , Auto-Saving, Backups and Auto-Saving |
| 0 | 577 @section Reverting |
| 578 | |
| 579 If you have made extensive changes to a file and then change your mind | |
| 580 about them, you can get rid of them by reading in the previous version | |
| 581 of the file with the @code{revert-buffer} command. @xref{Reverting, , | |
| 1710 | 582 Reverting a Buffer, xemacs, The XEmacs User's Manual}. |
| 0 | 583 |
| 444 | 584 @deffn Command revert-buffer &optional check-auto-save noconfirm preserve-modes |
| 0 | 585 This command replaces the buffer text with the text of the visited |
| 586 file on disk. This action undoes all changes since the file was visited | |
| 587 or saved. | |
| 588 | |
| 589 If the argument @var{check-auto-save} is non-@code{nil}, and the | |
| 590 latest auto-save file is more recent than the visited file, | |
| 591 @code{revert-buffer} asks the user whether to use that instead. | |
| 592 Otherwise, it always uses the text of the visited file itself. | |
| 593 Interactively, @var{check-auto-save} is set if there is a numeric prefix | |
| 594 argument. | |
| 595 | |
| 596 Normally, @code{revert-buffer} asks for confirmation before it changes | |
| 597 the buffer; but if the argument @var{noconfirm} is non-@code{nil}, | |
| 598 @code{revert-buffer} does not ask for confirmation. | |
| 599 | |
| 444 | 600 Optional third argument @var{preserve-modes} non-@code{nil} means don't |
| 601 alter the files modes. Normally we reinitialize them using | |
| 602 @code{normal-mode}. | |
| 603 | |
| 0 | 604 Reverting tries to preserve marker positions in the buffer by using the |
| 605 replacement feature of @code{insert-file-contents}. If the buffer | |
| 606 contents and the file contents are identical before the revert | |
| 607 operation, reverting preserves all the markers. If they are not | |
| 608 identical, reverting does change the buffer; then it preserves the | |
| 609 markers in the unchanged text (if any) at the beginning and end of the | |
| 610 buffer. Preserving any additional markers would be problematical. | |
| 611 @end deffn | |
| 612 | |
| 613 You can customize how @code{revert-buffer} does its work by setting | |
| 614 these variables---typically, as buffer-local variables. | |
| 615 | |
| 616 @defvar revert-buffer-function | |
| 617 The value of this variable is the function to use to revert this buffer. | |
| 618 If non-@code{nil}, it is called as a function with no arguments to do | |
| 619 the work of reverting. If the value is @code{nil}, reverting works the | |
| 620 usual way. | |
| 621 | |
| 622 Modes such as Dired mode, in which the text being edited does not | |
| 623 consist of a file's contents but can be regenerated in some other | |
| 624 fashion, give this variable a buffer-local value that is a function to | |
| 625 regenerate the contents. | |
| 626 @end defvar | |
| 627 | |
| 628 @defvar revert-buffer-insert-file-contents-function | |
| 629 The value of this variable, if non-@code{nil}, is the function to use to | |
| 630 insert the updated contents when reverting this buffer. The function | |
| 631 receives two arguments: first the file name to use; second, @code{t} if | |
| 632 the user has asked to read the auto-save file. | |
| 633 @end defvar | |
| 634 | |
| 635 @defvar before-revert-hook | |
| 636 This normal hook is run by @code{revert-buffer} before actually | |
| 637 inserting the modified contents---but only if | |
| 638 @code{revert-buffer-function} is @code{nil}. | |
| 639 | |
| 640 Font Lock mode uses this hook to record that the buffer contents are no | |
| 641 longer fontified. | |
| 642 @end defvar | |
| 643 | |
| 644 @defvar after-revert-hook | |
| 645 This normal hook is run by @code{revert-buffer} after actually inserting | |
| 646 the modified contents---but only if @code{revert-buffer-function} is | |
| 647 @code{nil}. | |
| 648 | |
| 649 Font Lock mode uses this hook to recompute the fonts for the updated | |
| 650 buffer contents. | |
| 651 @end defvar | |
| 652 |