1 @c This is part of the Emacs manual.
2 @c Copyright (C) 1985,86,87,93,94,95,97,99, 2000, 2001
3 @c Free Software Foundation, Inc.
4 @c See file emacs.texi for copying conditions.
5 @node Files, Buffers, Keyboard Macros, Top
9 The operating system stores data permanently in named @dfn{files}, so
10 most of the text you edit with Emacs comes from a file and is ultimately
13 To edit a file, you must tell Emacs to read the file and prepare a
14 buffer containing a copy of the file's text. This is called
15 @dfn{visiting} the file. Editing commands apply directly to text in the
16 buffer; that is, to the copy inside Emacs. Your changes appear in the
17 file itself only when you @dfn{save} the buffer back into the file.
19 In addition to visiting and saving files, Emacs can delete, copy,
20 rename, and append to files, keep multiple versions of them, and operate
24 * File Names:: How to type and edit file-name arguments.
25 * Visiting:: Visiting a file prepares Emacs to edit the file.
26 * Saving:: Saving makes your changes permanent.
27 * Reverting:: Reverting cancels all the changes not saved.
28 * Auto Save:: Auto Save periodically protects against loss of data.
29 * File Aliases:: Handling multiple names for one file.
30 * Version Control:: Version control systems (RCS, CVS and SCCS).
31 * Directories:: Creating, deleting, and listing file directories.
32 * Comparing Files:: Finding where two files differ.
33 * Misc File Ops:: Other things you can do on files.
34 * Compressed Files:: Accessing compressed files.
35 * File Archives:: Operating on tar, zip, jar etc. archive files.
36 * Remote Files:: Accessing files on other sites.
37 * Quoted File Names:: Quoting special characters in file names.
38 * File Name Cache:: Completion against a list of files you often use.
39 * File Conveniences:: Convenience Features for Finding Files.
46 Most Emacs commands that operate on a file require you to specify the
47 file name. (Saving and reverting are exceptions; the buffer knows which
48 file name to use for them.) You enter the file name using the
49 minibuffer (@pxref{Minibuffer}). @dfn{Completion} is available
50 (@pxref{Completion}) to make it easier to specify long file names. When
51 completing file names, Emacs ignores those whose file-name extensions
52 appear in the variable @code{completion-ignored-extensions}; see
53 @ref{Completion Options}.
55 For most operations, there is a @dfn{default file name} which is used
56 if you type just @key{RET} to enter an empty argument. Normally the
57 default file name is the name of the file visited in the current buffer;
58 this makes it easy to operate on that file with any of the Emacs file
61 @vindex default-directory
62 Each buffer has a default directory which is normally the same as the
63 directory of the file visited in that buffer. When you enter a file
64 name without a directory, the default directory is used. If you specify
65 a directory in a relative fashion, with a name that does not start with
66 a slash, it is interpreted with respect to the default directory. The
67 default directory is kept in the variable @code{default-directory},
68 which has a separate value in every buffer.
70 For example, if the default file name is @file{/u/rms/gnu/gnu.tasks} then
71 the default directory is @file{/u/rms/gnu/}. If you type just @samp{foo},
72 which does not specify a directory, it is short for @file{/u/rms/gnu/foo}.
73 @samp{../.login} would stand for @file{/u/rms/.login}. @samp{new/foo}
74 would stand for the file name @file{/u/rms/gnu/new/foo}.
78 The command @kbd{M-x pwd} displays the current buffer's default
79 directory, and the command @kbd{M-x cd} sets it (to a value read using
80 the minibuffer). A buffer's default directory changes only when the
81 @code{cd} command is used. A file-visiting buffer's default directory
82 is initialized to the directory of the file that is visited in that buffer. If
83 you create a buffer with @kbd{C-x b}, its default directory is copied
84 from that of the buffer that was current at the time.
86 @vindex insert-default-directory
87 The default directory actually appears in the minibuffer when the
88 minibuffer becomes active to read a file name. This serves two
89 purposes: it @emph{shows} you what the default is, so that you can type
90 a relative file name and know with certainty what it will mean, and it
91 allows you to @emph{edit} the default to specify a different directory.
92 This insertion of the default directory is inhibited if the variable
93 @code{insert-default-directory} is set to @code{nil}.
95 Note that it is legitimate to type an absolute file name after you
96 enter the minibuffer, ignoring the presence of the default directory
97 name as part of the text. The final minibuffer contents may look
98 invalid, but that is not so. For example, if the minibuffer starts out
99 with @samp{/usr/tmp/} and you add @samp{/x1/rms/foo}, you get
100 @samp{/usr/tmp//x1/rms/foo}; but Emacs ignores everything through the
101 first slash in the double slash; the result is @samp{/x1/rms/foo}.
102 @xref{Minibuffer File}.
104 @cindex environment variables in file names
105 @cindex expansion of environment variables
106 @cindex @code{$} in file names
107 @anchor{File Names with $}@samp{$} in a file name is used to
108 substitute an environment variable. The environment variable name
109 consists of all the alphanumeric characters after the @samp{$};
110 alternatively, it can be enclosed in braces after the @samp{$}. For
111 example, if you have used the shell command @command{export
112 FOO=rms/hacks} to set up an environment variable named @env{FOO}, then
113 you can use @file{/u/$FOO/test.c} or @file{/u/$@{FOO@}/test.c} as an
114 abbreviation for @file{/u/rms/hacks/test.c}. If the environment
115 variable is not defined, no substitution occurs: @file{/u/$notdefined}
116 stands for itself (assuming the environment variable @env{notdefined}
119 Note that shell commands to set environment variables affect Emacs
120 only when done before Emacs is started.
122 @cindex home directory shorthand
123 You can use the @file{~/} in a file name to mean your home directory,
124 or @file{~@var{user-id}/} to mean the home directory of a user whose
125 login name is @code{user-id}. (On DOS and Windows systems, where a user
126 doesn't have a home directory, Emacs substitutes @file{~/} with the
127 value of the environment variable @code{HOME}; see @ref{General
130 To access a file with @samp{$} in its name, if the @samp{$} causes
131 expansion, type @samp{$$}. This pair is converted to a single
132 @samp{$} at the same time as variable substitution is performed for a
133 single @samp{$}. Alternatively, quote the whole file name with
134 @samp{/:} (@pxref{Quoted File Names}). File names which begin with a
135 literal @samp{~} should also be quoted with @samp{/:}.
137 @findex substitute-in-file-name
138 The Lisp function that performs the substitution is called
139 @code{substitute-in-file-name}. The substitution is performed only on
140 file names read as such using the minibuffer.
142 You can include non-ASCII characters in file names if you set the
143 variable @code{file-name-coding-system} to a non-@code{nil} value.
144 @xref{Specify Coding}.
147 @section Visiting Files
148 @cindex visiting files
152 Visit a file (@code{find-file}).
154 Visit a file for viewing, without allowing changes to it
155 (@code{find-file-read-only}).
157 Visit a different file instead of the one visited last
158 (@code{find-alternate-file}).
160 Visit a file, in another window (@code{find-file-other-window}). Don't
161 alter what is displayed in the selected window.
163 Visit a file, in a new frame (@code{find-file-other-frame}). Don't
164 alter what is displayed in the selected frame.
165 @item M-x find-file-literally
166 Visit a file with no conversion of the contents.
169 @cindex files, visiting and saving
171 @dfn{Visiting} a file means copying its contents into an Emacs
172 buffer so you can edit them. Emacs makes a new buffer for each file
173 that you visit. We often say that this buffer ``is visiting'' that
174 file, or that the buffer's ``visited file'' is that file. Emacs
175 constructs the buffer name from the file name by throwing away the
176 directory, keeping just the name proper. For example, a file named
177 @file{/usr/rms/emacs.tex} would get a buffer named @samp{emacs.tex}.
178 If there is already a buffer with that name, Emacs constructs a unique
179 name---the normal method is to append @samp{<2>}, @samp{<3>}, and so
180 on, but you can select other methods (@pxref{Uniquify}).
182 Each window's mode line shows the name of the buffer that is being displayed
183 in that window, so you can always tell what buffer you are editing.
185 The changes you make with editing commands are made in the Emacs
186 buffer. They do not take effect in the file that you visited, or any
187 place permanent, until you @dfn{save} the buffer. Saving the buffer
188 means that Emacs writes the current contents of the buffer into its
189 visited file. @xref{Saving}.
191 @cindex modified (buffer)
192 If a buffer contains changes that have not been saved, we say the
193 buffer is @dfn{modified}. This is important because it implies that
194 some changes will be lost if the buffer is not saved. The mode line
195 displays two stars near the left margin to indicate that the buffer is
200 To visit a file, use the command @kbd{C-x C-f} (@code{find-file}). Follow
201 the command with the name of the file you wish to visit, terminated by a
204 The file name is read using the minibuffer (@pxref{Minibuffer}), with
205 defaulting and completion in the standard manner (@pxref{File Names}).
206 While in the minibuffer, you can abort @kbd{C-x C-f} by typing
207 @kbd{C-g}. File-name completion ignores certain filenames; for more
208 about this, see @ref{Completion Options}.
210 @cindex file selection dialog
211 When Emacs is built with a suitable GUI toolkit, it pops up the
212 standard File Selection dialog of that toolkit instead of prompting for
213 the file name in the minibuffer. On Unix and GNU/Linux platforms, Emacs
214 does that when built with LessTif and Motif toolkits; on MS-Windows, the
215 GUI version does that by default.
217 Your confirmation that @kbd{C-x C-f} has completed successfully is the
218 appearance of new text on the screen and a new buffer name in the mode
219 line. If the specified file does not exist and could not be created, or
220 cannot be read, then you get an error, with an error message displayed
223 If you visit a file that is already in Emacs, @kbd{C-x C-f} does not make
224 another copy. It selects the existing buffer containing that file.
225 However, before doing so, it checks that the file itself has not changed
226 since you visited or saved it last. If the file has changed, a warning
227 message is shown. @xref{Interlocking,,Simultaneous Editing}.
229 @cindex maximum buffer size exceeded, error message
230 Since Emacs reads the visited file in its entirety, files whose size
231 is larger than the maximum Emacs buffer size (@pxref{Buffers}) cannot be
232 visited; if you try, Emacs will display an error message saying that the
233 maximum buffer size has been exceeded.
235 @cindex creating files
236 What if you want to create a new file? Just visit it. Emacs displays
237 @samp{(New file)} in the echo area, but in other respects behaves as if
238 you had visited an existing empty file. If you make any changes and
239 save them, the file is created.
241 Emacs recognizes from the contents of a file which convention it uses
242 to separate lines---newline (used on GNU/Linux and on Unix),
243 carriage-return linefeed (used on Microsoft systems), or just
244 carriage-return (used on the Macintosh)---and automatically converts the
245 contents to the normal Emacs convention, which is that the newline
246 character separates lines. This is a part of the general feature of
247 coding system conversion (@pxref{Coding Systems}), and makes it possible
248 to edit files imported from different operating systems with
249 equal convenience. If you change the text and save the file, Emacs
250 performs the inverse conversion, changing newlines back into
251 carriage-return linefeed or just carriage-return if appropriate.
253 @vindex find-file-run-dired
254 If the file you specify is actually a directory, @kbd{C-x C-f} invokes
255 Dired, the Emacs directory browser, so that you can ``edit'' the contents
256 of the directory (@pxref{Dired}). Dired is a convenient way to delete,
257 look at, or operate on the files in the directory. However, if the
258 variable @code{find-file-run-dired} is @code{nil}, then it is an error
259 to try to visit a directory.
261 Files which are actually collections of other files, or @dfn{file
262 archives}, are visited in special modes which invoke a Dired-like
263 environment to allow operations on archive members. @xref{File
264 Archives}, for more about these features.
266 @cindex wildcard characters in file names
267 @vindex find-file-wildcards
268 If the file name you specify contains shell-style wildcard characters,
269 Emacs visits all the files that match it. Wildcards include @samp{?},
270 @samp{*}, and @samp{[@dots{}]} sequences. @xref{Quoted File Names}, for
271 information on how to visit a file whose name actually contains wildcard
272 characters. You can disable the wildcard feature by customizing
273 @code{find-file-wildcards}.
275 If you visit a file that the operating system won't let you modify,
276 or that is marked read-only, Emacs makes the buffer read-only too, so
277 that you won't go ahead and make changes that you'll have trouble
278 saving afterward. You can make the buffer writable with @kbd{C-x C-q}
279 (@code{toggle-read-only}). @xref{Misc Buffer}.
282 @findex find-file-read-only
283 If you want to visit a file as read-only in order to protect
284 yourself from entering changes accidentally, visit it with the command
285 @kbd{C-x C-r} (@code{find-file-read-only}) instead of @kbd{C-x C-f}.
288 @findex find-alternate-file
289 If you visit a nonexistent file unintentionally (because you typed the
290 wrong file name), use the @kbd{C-x C-v} command
291 (@code{find-alternate-file}) to visit the file you really wanted.
292 @kbd{C-x C-v} is similar to @kbd{C-x C-f}, but it kills the current
293 buffer (after first offering to save it if it is modified). When
294 @kbd{C-x C-v} reads the file name to visit, it inserts the entire
295 default file name in the buffer, with point just after the directory
296 part; this is convenient if you made a slight error in typing the name.
298 If you find a file which exists but cannot be read, @kbd{C-x C-f}
302 @findex find-file-other-window
303 @kbd{C-x 4 f} (@code{find-file-other-window}) is like @kbd{C-x C-f}
304 except that the buffer containing the specified file is selected in another
305 window. The window that was selected before @kbd{C-x 4 f} continues to
306 show the same buffer it was already showing. If this command is used when
307 only one window is being displayed, that window is split in two, with one
308 window showing the same buffer as before, and the other one showing the
309 newly requested file. @xref{Windows}.
312 @findex find-file-other-frame
313 @kbd{C-x 5 f} (@code{find-file-other-frame}) is similar, but opens a
314 new frame, or makes visible any existing frame showing the file you
315 seek. This feature is available only when you are using a window
316 system. @xref{Frames}.
318 @findex find-file-literally
319 If you wish to edit a file as a sequence of ASCII characters with no special
320 encoding or conversion, use the @kbd{M-x find-file-literally} command.
321 It visits a file, like @kbd{C-x C-f}, but does not do format conversion
322 (@pxref{Formatted Text}), character code conversion (@pxref{Coding
323 Systems}), or automatic uncompression (@pxref{Compressed Files}), and
324 does not add a final newline because of @code{require-final-newline}.
325 If you already have visited the same file in the usual (non-literal)
326 manner, this command asks you whether to visit it literally instead.
328 @vindex find-file-hook
329 @vindex find-file-not-found-functions
330 Two special hook variables allow extensions to modify the operation of
331 visiting files. Visiting a file that does not exist runs the functions
332 in the list @code{find-file-not-found-functions}; this variable holds a list
333 of functions, and the functions are called one by one (with no
334 arguments) until one of them returns non-@code{nil}. This is not a
335 normal hook, and the name ends in @samp{-functions} rather than @samp{-hook}
336 to indicate that fact.
338 Successful visiting of any file, whether existing or not, calls the
339 functions in the list @code{find-file-hook}, with no arguments.
340 This variable is a normal hook. In the case of a nonexistent file, the
341 @code{find-file-not-found-functions} are run first. @xref{Hooks}.
343 There are several ways to specify automatically the major mode for
344 editing the file (@pxref{Choosing Modes}), and to specify local
345 variables defined for that file (@pxref{File Variables}).
348 @section Saving Files
350 @dfn{Saving} a buffer in Emacs means writing its contents back into the file
351 that was visited in the buffer.
355 Save the current buffer in its visited file on disk (@code{save-buffer}).
357 Save any or all buffers in their visited files (@code{save-some-buffers}).
359 Forget that the current buffer has been changed (@code{not-modified}).
360 With prefix argument (@kbd{C-u}), mark the current buffer as changed.
362 Save the current buffer as a specified file name (@code{write-file}).
363 @item M-x set-visited-file-name
364 Change the file name under which the current buffer will be saved.
369 When you wish to save the file and make your changes permanent, type
370 @kbd{C-x C-s} (@code{save-buffer}). After saving is finished, @kbd{C-x C-s}
371 displays a message like this:
374 Wrote /u/rms/gnu/gnu.tasks
378 If the selected buffer is not modified (no changes have been made in it
379 since the buffer was created or last saved), saving is not really done,
380 because it would have no effect. Instead, @kbd{C-x C-s} displays a message
381 like this in the echo area:
384 (No changes need to be saved)
388 @findex save-some-buffers
389 The command @kbd{C-x s} (@code{save-some-buffers}) offers to save any
390 or all modified buffers. It asks you what to do with each buffer. The
391 possible responses are analogous to those of @code{query-replace}:
395 Save this buffer and ask about the rest of the buffers.
397 Don't save this buffer, but ask about the rest of the buffers.
399 Save this buffer and all the rest with no more questions.
400 @c following generates acceptable underfull hbox
402 Terminate @code{save-some-buffers} without any more saving.
404 Save this buffer, then exit @code{save-some-buffers} without even asking
407 View the buffer that you are currently being asked about. When you exit
408 View mode, you get back to @code{save-some-buffers}, which asks the
411 Display a help message about these options.
414 @kbd{C-x C-c}, the key sequence to exit Emacs, invokes
415 @code{save-some-buffers} and therefore asks the same questions.
419 If you have changed a buffer but you do not want to save the changes,
420 you should take some action to prevent it. Otherwise, each time you use
421 @kbd{C-x s} or @kbd{C-x C-c}, you are liable to save this buffer by
422 mistake. One thing you can do is type @kbd{M-~} (@code{not-modified}),
423 which clears out the indication that the buffer is modified. If you do
424 this, none of the save commands will believe that the buffer needs to be
425 saved. (@samp{~} is often used as a mathematical symbol for `not'; thus
426 @kbd{M-~} is `not', metafied.) You could also use
427 @code{set-visited-file-name} (see below) to mark the buffer as visiting
428 a different file name, one which is not in use for anything important.
429 Alternatively, you can cancel all the changes made since the file was
430 visited or saved, by reading the text from the file again. This is
431 called @dfn{reverting}. @xref{Reverting}. You could also undo all the
432 changes by repeating the undo command @kbd{C-x u} until you have undone
433 all the changes; but reverting is easier.
435 @findex set-visited-file-name
436 @kbd{M-x set-visited-file-name} alters the name of the file that the
437 current buffer is visiting. It reads the new file name using the
438 minibuffer. Then it marks the buffer as visiting that file name, and
439 changes the buffer name correspondingly. @code{set-visited-file-name}
440 does not save the buffer in the newly visited file; it just alters the
441 records inside Emacs in case you do save later. It also marks the
442 buffer as ``modified'' so that @kbd{C-x C-s} in that buffer
447 If you wish to mark the buffer as visiting a different file and save it
448 right away, use @kbd{C-x C-w} (@code{write-file}). It is precisely
449 equivalent to @code{set-visited-file-name} followed by @kbd{C-x C-s}.
450 @kbd{C-x C-s} used on a buffer that is not visiting a file has the
451 same effect as @kbd{C-x C-w}; that is, it reads a file name, marks the
452 buffer as visiting that file, and saves it there. The default file name in
453 a buffer that is not visiting a file is made by combining the buffer name
454 with the buffer's default directory (@pxref{File Names}).
456 If the new file name implies a major mode, then @kbd{C-x C-w} switches
457 to that major mode, in most cases. The command
458 @code{set-visited-file-name} also does this. @xref{Choosing Modes}.
460 If Emacs is about to save a file and sees that the date of the latest
461 version on disk does not match what Emacs last read or wrote, Emacs
462 notifies you of this fact, because it probably indicates a problem caused
463 by simultaneous editing and requires your immediate attention.
464 @xref{Interlocking,, Simultaneous Editing}.
466 @vindex require-final-newline
467 If the value of the variable @code{require-final-newline} is @code{t},
468 Emacs silently puts a newline at the end of any file that doesn't
469 already end in one, every time a file is saved or written. If the value
470 is @code{nil}, Emacs leaves the end of the file unchanged; if it's
471 neither @code{nil} nor @code{t}, Emacs asks you whether to add a
472 newline. The default is @code{nil}.
475 * Backup:: How Emacs saves the old version of your file.
476 * Interlocking:: How Emacs protects against simultaneous editing
477 of one file by two users.
478 * Shadowing: File Shadowing.
479 Copying files to "shadows" automatically.
480 * Time Stamps:: Emacs can update time stamps on saved files.
484 @subsection Backup Files
486 @vindex make-backup-files
487 @vindex vc-make-backup-files
489 On most operating systems, rewriting a file automatically destroys all
490 record of what the file used to contain. Thus, saving a file from Emacs
491 throws away the old contents of the file---or it would, except that
492 Emacs carefully copies the old contents to another file, called the
493 @dfn{backup} file, before actually saving.
495 For most files, the variable @code{make-backup-files} determines
496 whether to make backup files. On most operating systems, its default
497 value is @code{t}, so that Emacs does write backup files.
499 For files managed by a version control system (@pxref{Version
500 Control}), the variable @code{vc-make-backup-files} determines whether
501 to make backup files. By default it is @code{nil}, since backup files
502 are redundant when you store all the previous versions in a version
503 control system. @xref{General VC Options}.
505 @vindex backup-enable-predicate
506 @vindex temporary-file-directory
507 @vindex small-temporary-file-directory
508 The default value of the @code{backup-enable-predicate} variable
509 prevents backup files being written for files in the directories used
510 for temporary files, specified by @code{temporary-file-directory} or
511 @code{small-temporary-file-directory}.
513 At your option, Emacs can keep either a single backup file or a series of
514 numbered backup files for each file that you edit.
516 Emacs makes a backup for a file only the first time the file is saved
517 from one buffer. No matter how many times you save a file, its backup file
518 continues to contain the contents from before the file was visited.
519 Normally this means that the backup file contains the contents from before
520 the current editing session; however, if you kill the buffer and then visit
521 the file again, a new backup file will be made by the next save.
523 You can also explicitly request making another backup file from a
524 buffer even though it has already been saved at least once. If you save
525 the buffer with @kbd{C-u C-x C-s}, the version thus saved will be made
526 into a backup file if you save the buffer again. @kbd{C-u C-u C-x C-s}
527 saves the buffer, but first makes the previous file contents into a new
528 backup file. @kbd{C-u C-u C-u C-x C-s} does both things: it makes a
529 backup from the previous contents, and arranges to make another from the
530 newly saved contents if you save again.
533 * Names: Backup Names. How backup files are named;
534 choosing single or numbered backup files.
535 * Deletion: Backup Deletion. Emacs deletes excess numbered backups.
536 * Copying: Backup Copying. Backups can be made by copying or renaming.
540 @subsubsection Single or Numbered Backups
542 If you choose to have a single backup file (this is the default),
543 the backup file's name is normally constructed by appending @samp{~} to the
544 file name being edited; thus, the backup file for @file{eval.c} would
547 @vindex make-backup-file-name-function
548 @vindex backup-directory-alist
549 You can change this behavior by defining the variable
550 @code{make-backup-file-name-function} to a suitable function.
551 Alternatively you can customize the variable
552 @code{backup-directory-alist} to specify that files matching certain
553 patterns should be backed up in specific directories.
555 A typical use is to add an element @code{("." . @var{dir})} to make
556 all backups in the directory with absolute name @var{dir}; Emacs
557 modifies the backup file names to avoid clashes between files with the
558 same names originating in different directories. Alternatively,
559 adding, say, @code{("." . ".~")} would make backups in the invisible
560 subdirectory @file{.~} of the original file's directory. Emacs
561 creates the directory, if necessary, to make the backup.
563 If access control stops Emacs from writing backup files under the usual
564 names, it writes the backup file as @file{%backup%~} in your home
565 directory. Only one such file can exist, so only the most recently
566 made such backup is available.
568 If you choose to have a series of numbered backup files, backup file
569 names contain @samp{.~}, the number, and another @samp{~} after the
570 original file name. Thus, the backup files of @file{eval.c} would be
571 called @file{eval.c.~1~}, @file{eval.c.~2~}, and so on, all the way
572 through names like @file{eval.c.~259~} and beyond. The variable
573 @code{backup-directory-alist} applies to numbered backups just as
576 @vindex version-control
577 The choice of single backup or numbered backups is controlled by the
578 variable @code{version-control}. Its possible values are
582 Make numbered backups.
584 Make numbered backups for files that have numbered backups already.
585 Otherwise, make single backups.
587 Never make numbered backups; always make single backups.
591 You can set @code{version-control} locally in an individual buffer to
592 control the making of backups for that buffer's file. For example,
593 Rmail mode locally sets @code{version-control} to @code{never} to make sure
594 that there is only one backup for an Rmail file. @xref{Locals}.
596 @cindex @env{VERSION_CONTROL} environment variable
597 If you set the environment variable @env{VERSION_CONTROL}, to tell
598 various GNU utilities what to do with backup files, Emacs also obeys the
599 environment variable by setting the Lisp variable @code{version-control}
600 accordingly at startup. If the environment variable's value is @samp{t}
601 or @samp{numbered}, then @code{version-control} becomes @code{t}; if the
602 value is @samp{nil} or @samp{existing}, then @code{version-control}
603 becomes @code{nil}; if it is @samp{never} or @samp{simple}, then
604 @code{version-control} becomes @code{never}.
606 @node Backup Deletion
607 @subsubsection Automatic Deletion of Backups
609 To prevent excessive consumption of disk space, Emacs can delete numbered
610 backup versions automatically. Generally Emacs keeps the first few backups
611 and the latest few backups, deleting any in between. This happens every
612 time a new backup is made.
614 @vindex kept-old-versions
615 @vindex kept-new-versions
616 The two variables @code{kept-old-versions} and
617 @code{kept-new-versions} control this deletion. Their values are,
618 respectively, the number of oldest (lowest-numbered) backups to keep
619 and the number of newest (highest-numbered) ones to keep, each time a
620 new backup is made. The backups in the middle (excluding those oldest
621 and newest) are the excess middle versions---those backups are
622 deleted. These variables' values are used when it is time to delete
623 excess versions, just after a new backup version is made; the newly
624 made backup is included in the count in @code{kept-new-versions}. By
625 default, both variables are 2.
627 @vindex delete-old-versions
628 If @code{delete-old-versions} is non-@code{nil}, Emacs deletes the
629 excess backup files silently. If it is @code{nil}, the default, Emacs
630 asks you whether it should delete the excess backup versions.
632 Dired's @kbd{.} (Period) command can also be used to delete old versions.
633 @xref{Dired Deletion}.
636 @subsubsection Copying vs.@: Renaming
638 Backup files can be made by copying the old file or by renaming it.
639 This makes a difference when the old file has multiple names (hard
640 links). If the old file is renamed into the backup file, then the
641 alternate names become names for the backup file. If the old file is
642 copied instead, then the alternate names remain names for the file
643 that you are editing, and the contents accessed by those names will be
646 The method of making a backup file may also affect the file's owner
647 and group. If copying is used, these do not change. If renaming is used,
648 you become the file's owner, and the file's group becomes the default
649 (different operating systems have different defaults for the group).
651 Having the owner change is usually a good idea, because then the owner
652 always shows who last edited the file. Also, the owners of the backups
653 show who produced those versions. Occasionally there is a file whose
654 owner should not change; it is a good idea for such files to contain
655 local variable lists to set @code{backup-by-copying-when-mismatch}
656 locally (@pxref{File Variables}).
658 @vindex backup-by-copying
659 @vindex backup-by-copying-when-linked
660 @vindex backup-by-copying-when-mismatch
661 @vindex backup-by-copying-when-privileged-mismatch
662 @cindex file ownership, and backup
663 @cindex backup, and user-id
664 The choice of renaming or copying is controlled by four variables.
665 Renaming is the default choice. If the variable
666 @code{backup-by-copying} is non-@code{nil}, copying is used. Otherwise,
667 if the variable @code{backup-by-copying-when-linked} is non-@code{nil},
668 then copying is used for files that have multiple names, but renaming
669 may still be used when the file being edited has only one name. If the
670 variable @code{backup-by-copying-when-mismatch} is non-@code{nil}, then
671 copying is used if renaming would cause the file's owner or group to
672 change. @code{backup-by-copying-when-mismatch} is @code{t} by default
673 if you start Emacs as the superuser. The fourth variable,
674 @code{backup-by-copying-when-privileged-mismatch}, gives the highest
675 numeric user-id for which @code{backup-by-copying-when-mismatch} will be
676 forced on. This is useful when low-numbered user-ids are assigned to
677 special system users, such as @code{root}, @code{bin}, @code{daemon},
678 etc., which must maintain ownership of files.
680 When a file is managed with a version control system (@pxref{Version
681 Control}), Emacs does not normally make backups in the usual way for
682 that file. But check-in and check-out are similar in some ways to
683 making backups. One unfortunate similarity is that these operations
684 typically break hard links, disconnecting the file name you visited from
685 any alternate names for the same file. This has nothing to do with
686 Emacs---the version control system does it.
689 @subsection Protection against Simultaneous Editing
692 @cindex simultaneous editing
693 Simultaneous editing occurs when two users visit the same file, both
694 make changes, and then both save them. If nobody were informed that
695 this was happening, whichever user saved first would later find that his
698 On some systems, Emacs notices immediately when the second user starts
699 to change the file, and issues an immediate warning. On all systems,
700 Emacs checks when you save the file, and warns if you are about to
701 overwrite another user's changes. You can prevent loss of the other
702 user's work by taking the proper corrective action instead of saving the
705 @findex ask-user-about-lock
706 @cindex locking files
707 When you make the first modification in an Emacs buffer that is
708 visiting a file, Emacs records that the file is @dfn{locked} by you.
709 (It does this by creating a symbolic link in the same directory with a
710 different name.) Emacs removes the lock when you save the changes. The
711 idea is that the file is locked whenever an Emacs buffer visiting it has
715 If you begin to modify the buffer while the visited file is locked by
716 someone else, this constitutes a @dfn{collision}. When Emacs detects a
717 collision, it asks you what to do, by calling the Lisp function
718 @code{ask-user-about-lock}. You can redefine this function for the sake
719 of customization. The standard definition of this function asks you a
720 question and accepts three possible answers:
724 Steal the lock. Whoever was already changing the file loses the lock,
725 and you gain the lock.
727 Proceed. Go ahead and edit the file despite its being locked by someone else.
729 Quit. This causes an error (@code{file-locked}), and the buffer
730 contents remain unchanged---the modification you were trying to make
731 does not actually take place.
734 Note that locking works on the basis of a file name; if a file has
735 multiple names, Emacs does not realize that the two names are the same file
736 and cannot prevent two users from editing it simultaneously under different
737 names. However, basing locking on names means that Emacs can interlock the
738 editing of new files that will not really exist until they are saved.
740 Some systems are not configured to allow Emacs to make locks, and
741 there are cases where lock files cannot be written. In these cases,
742 Emacs cannot detect trouble in advance, but it still can detect the
743 collision when you try to save a file and overwrite someone else's
746 If Emacs or the operating system crashes, this may leave behind lock
747 files which are stale, so you may occasionally get warnings about
748 spurious collisions. When you determine that the collision is spurious,
749 just use @kbd{p} to tell Emacs to go ahead anyway.
751 Every time Emacs saves a buffer, it first checks the last-modification
752 date of the existing file on disk to verify that it has not changed since the
753 file was last visited or saved. If the date does not match, it implies
754 that changes were made in the file in some other way, and these changes are
755 about to be lost if Emacs actually does save. To prevent this, Emacs
756 displays a warning message and asks for confirmation before saving.
757 Occasionally you will know why the file was changed and know that it does
758 not matter; then you can answer @kbd{yes} and proceed. Otherwise, you should
759 cancel the save with @kbd{C-g} and investigate the situation.
761 The first thing you should do when notified that simultaneous editing
762 has already taken place is to list the directory with @kbd{C-u C-x C-d}
763 (@pxref{Directories}). This shows the file's current author. You
764 should attempt to contact him to warn him not to continue editing.
765 Often the next step is to save the contents of your Emacs buffer under a
766 different name, and use @code{diff} to compare the two files.@refill
769 @subsection Shadowing Files
774 @item M-x shadow-initialize
775 Set up file shadowing.
776 @item M-x shadow-define-literal-group
777 Declare a single file to be shared between sites.
778 @item M-x shadow-define-regexp-group
779 Make all files that match each of a group of files be shared between hosts.
780 @item M-x shadow-define-cluster @key{RET} @var{name} @key{RET}
781 Define a shadow file cluster @var{name}.
782 @item M-x shadow-copy-files
783 Copy all pending shadow files.
784 @item M-x shadow-cancel
785 Cancel the instruction to shadow some files.
788 You can arrange to keep identical @dfn{shadow} copies of certain files
789 in more than one place---possibly on different machines. To do this,
790 first you must set up a @dfn{shadow file group}, which is a set of
791 identically-named files shared between a list of sites. The file
792 group is permanent and applies to further Emacs sessions as well as
793 the current one. Once the group is set up, every time you exit Emacs,
794 it will copy the file you edited to the other files in its group. You
795 can also do the copying without exiting Emacs, by typing @kbd{M-x
798 To set up a shadow file group, use @kbd{M-x
799 shadow-define-literal-group} or @kbd{M-x shadow-define-regexp-group}.
800 See their documentation strings for further information.
802 Before copying a file to its shadows, Emacs asks for confirmation.
803 You can answer ``no'' to bypass copying of this file, this time. If
804 you want to cancel the shadowing permanently for a certain file, use
805 @kbd{M-x shadow-cancel} to eliminate or change the shadow file group.
807 A @dfn{shadow cluster} is a group of hosts that share directories, so
808 that copying to or from one of them is sufficient to update the file
809 on all of them. Each shadow cluster has a name, and specifies the
810 network address of a primary host (the one we copy files to), and a
811 regular expression that matches the host names of all the other hosts
812 in the cluster. You can define a shadow cluster with @kbd{M-x
813 shadow-define-cluster}.
816 @subsection Updating Time Stamps Automatically
819 @cindex modification dates
820 @cindex locale, date format
822 You can arrange to put a time stamp in a file, so that it will be updated
823 automatically each time you edit and save the file. The time stamp
824 has to be in the first eight lines of the file, and you should
838 Then add the hook function @code{time-stamp} to the hook
839 @code{write-file-functions}; that hook function will automatically update
840 the time stamp, inserting the current date and time when you save the
841 file. You can also use the command @kbd{M-x time-stamp} to update the
842 time stamp manually. For other customizations, see the Custom group
843 @code{time-stamp}. Note that non-numeric fields in the time stamp are
844 formatted according to your locale setting (@pxref{Environment}).
847 @section Reverting a Buffer
848 @findex revert-buffer
849 @cindex drastic changes
850 @cindex reread a file
852 If you have made extensive changes to a file and then change your mind
853 about them, you can get rid of them by reading in the previous version
854 of the file. To do this, use @kbd{M-x revert-buffer}, which operates on
855 the current buffer. Since reverting a buffer unintentionally could lose
856 a lot of work, you must confirm this command with @kbd{yes}.
858 @code{revert-buffer} keeps point at the same distance (measured in
859 characters) from the beginning of the file. If the file was edited only
860 slightly, you will be at approximately the same piece of text after
861 reverting as before. If you have made drastic changes, the same value of
862 point in the old file may address a totally different piece of text.
864 Reverting marks the buffer as ``not modified'' until another change is
867 Some kinds of buffers whose contents reflect data bases other than files,
868 such as Dired buffers, can also be reverted. For them, reverting means
869 recalculating their contents from the appropriate data base. Buffers
870 created explicitly with @kbd{C-x b} cannot be reverted; @code{revert-buffer}
871 reports an error when asked to do so.
873 @vindex revert-without-query
874 When you edit a file that changes automatically and frequently---for
875 example, a log of output from a process that continues to run---it may be
876 useful for Emacs to revert the file without querying you, whenever you
877 visit the file again with @kbd{C-x C-f}.
879 To request this behavior, set the variable @code{revert-without-query}
880 to a list of regular expressions. When a file name matches one of these
881 regular expressions, @code{find-file} and @code{revert-buffer} will
882 revert it automatically if it has changed---provided the buffer itself
883 is not modified. (If you have edited the text, it would be wrong to
884 discard your changes.)
886 @cindex Global Auto-Revert mode
887 @cindex mode, Global Auto-Revert
888 @cindex Auto-Revert mode
889 @cindex mode, Auto-Revert
890 @findex global-auto-revert-mode
891 @findex auto-revert-mode
892 @vindex auto-revert-interval
893 You may find it useful to have Emacs revert files automatically when
894 they change. Two minor modes are available to do this. In Global
895 Auto-Revert mode, Emacs periodically checks all file buffers and
896 reverts any when the corresponding file has changed. The local
897 variant, Auto-Revert mode, applies only to buffers in which it was
898 activated. Checking the files is done at intervals determined by the
899 variable @code{auto-revert-interval}.
902 @section Auto-Saving: Protection Against Disasters
903 @cindex Auto Save mode
904 @cindex mode, Auto Save
907 Emacs saves all the visited files from time to time (based on counting
908 your keystrokes) without being asked. This is called @dfn{auto-saving}.
909 It prevents you from losing more than a limited amount of work if the
912 When Emacs determines that it is time for auto-saving, each buffer is
913 considered, and is auto-saved if auto-saving is turned on for it and it
914 has been changed since the last time it was auto-saved. The message
915 @samp{Auto-saving...} is displayed in the echo area during auto-saving,
916 if any files are actually auto-saved. Errors occurring during
917 auto-saving are caught so that they do not interfere with the execution
918 of commands you have been typing.
921 * Files: Auto Save Files. The file where auto-saved changes are
922 actually made until you save the file.
923 * Control: Auto Save Control. Controlling when and how often to auto-save.
924 * Recover:: Recovering text from auto-save files.
927 @node Auto Save Files
928 @subsection Auto-Save Files
930 Auto-saving does not normally save in the files that you visited, because
931 it can be very undesirable to save a program that is in an inconsistent
932 state when you have made half of a planned change. Instead, auto-saving
933 is done in a different file called the @dfn{auto-save file}, and the
934 visited file is changed only when you request saving explicitly (such as
937 Normally, the auto-save file name is made by appending @samp{#} to the
938 front and rear of the visited file name. Thus, a buffer visiting file
939 @file{foo.c} is auto-saved in a file @file{#foo.c#}. Most buffers that
940 are not visiting files are auto-saved only if you request it explicitly;
941 when they are auto-saved, the auto-save file name is made by appending
942 @samp{#} to the front and rear of buffer name, then
943 adding digits and letters at the end for uniqueness. For
944 example, the @samp{*mail*} buffer in which you compose messages to be
945 sent might auto-saved in a file named @file{#*mail*#704juu}. Auto-save file
946 names are made this way unless you reprogram parts of Emacs to do
947 something different (the functions @code{make-auto-save-file-name} and
948 @code{auto-save-file-name-p}). The file name to be used for auto-saving
949 in a buffer is calculated when auto-saving is turned on in that buffer.
951 @cindex auto-save for remote files
952 @vindex auto-save-file-name-transforms
953 The variable @code{auto-save-file-name-transforms} allows a degree
954 of control over the auto-save file name. It lets you specify a series
955 of regular expressions and replacements to transform the auto save
956 file name. The default value puts the auto-save files for remote
957 files (@pxref{Remote Files}) into the temporary file directory on the
960 When you delete a substantial part of the text in a large buffer, auto
961 save turns off temporarily in that buffer. This is because if you
962 deleted the text unintentionally, you might find the auto-save file more
963 useful if it contains the deleted text. To reenable auto-saving after
964 this happens, save the buffer with @kbd{C-x C-s}, or use @kbd{C-u 1 M-x
967 @vindex auto-save-visited-file-name
968 If you want auto-saving to be done in the visited file rather than
969 in a separate auto-save file, set the variable
970 @code{auto-save-visited-file-name} to a non-@code{nil} value. In this
971 mode, there is no real difference between auto-saving and explicit
974 @vindex delete-auto-save-files
975 A buffer's auto-save file is deleted when you save the buffer in its
976 visited file. To inhibit this, set the variable @code{delete-auto-save-files}
977 to @code{nil}. Changing the visited file name with @kbd{C-x C-w} or
978 @code{set-visited-file-name} renames any auto-save file to go with
979 the new visited name.
981 @node Auto Save Control
982 @subsection Controlling Auto-Saving
984 @vindex auto-save-default
985 @findex auto-save-mode
986 Each time you visit a file, auto-saving is turned on for that file's
987 buffer if the variable @code{auto-save-default} is non-@code{nil} (but not
988 in batch mode; @pxref{Entering Emacs}). The default for this variable is
989 @code{t}, so auto-saving is the usual practice for file-visiting buffers.
990 Auto-saving can be turned on or off for any existing buffer with the
991 command @kbd{M-x auto-save-mode}. Like other minor mode commands, @kbd{M-x
992 auto-save-mode} turns auto-saving on with a positive argument, off with a
993 zero or negative argument; with no argument, it toggles.
995 @vindex auto-save-interval
996 Emacs does auto-saving periodically based on counting how many characters
997 you have typed since the last time auto-saving was done. The variable
998 @code{auto-save-interval} specifies how many characters there are between
999 auto-saves. By default, it is 300. Emacs doesn't accept values that are
1000 too small: if you customize @code{auto-save-interval} to a value less
1001 than 20, Emacs will behave as if the value is 20.
1003 @vindex auto-save-timeout
1004 Auto-saving also takes place when you stop typing for a while. The
1005 variable @code{auto-save-timeout} says how many seconds Emacs should
1006 wait before it does an auto save (and perhaps also a garbage
1007 collection). (The actual time period is longer if the current buffer is
1008 long; this is a heuristic which aims to keep out of your way when you
1009 are editing long buffers, in which auto-save takes an appreciable amount
1010 of time.) Auto-saving during idle periods accomplishes two things:
1011 first, it makes sure all your work is saved if you go away from the
1012 terminal for a while; second, it may avoid some auto-saving while you
1013 are actually typing.
1015 Emacs also does auto-saving whenever it gets a fatal error. This
1016 includes killing the Emacs job with a shell command such as @samp{kill
1017 %emacs}, or disconnecting a phone line or network connection.
1019 @findex do-auto-save
1020 You can request an auto-save explicitly with the command @kbd{M-x
1024 @subsection Recovering Data from Auto-Saves
1026 @findex recover-file
1027 You can use the contents of an auto-save file to recover from a loss
1028 of data with the command @kbd{M-x recover-file @key{RET} @var{file}
1029 @key{RET}}. This visits @var{file} and then (after your confirmation)
1030 restores the contents from its auto-save file @file{#@var{file}#}.
1031 You can then save with @kbd{C-x C-s} to put the recovered text into
1032 @var{file} itself. For example, to recover file @file{foo.c} from its
1033 auto-save file @file{#foo.c#}, do:@refill
1036 M-x recover-file @key{RET} foo.c @key{RET}
1041 Before asking for confirmation, @kbd{M-x recover-file} displays a
1042 directory listing describing the specified file and the auto-save file,
1043 so you can compare their sizes and dates. If the auto-save file
1044 is older, @kbd{M-x recover-file} does not offer to read it.
1046 @findex recover-session
1047 If Emacs or the computer crashes, you can recover all the files you
1048 were editing from their auto save files with the command @kbd{M-x
1049 recover-session}. This first shows you a list of recorded interrupted
1050 sessions. Move point to the one you choose, and type @kbd{C-c C-c}.
1052 Then @code{recover-session} asks about each of the files that were
1053 being edited during that session, asking whether to recover that file.
1054 If you answer @kbd{y}, it calls @code{recover-file}, which works in its
1055 normal fashion. It shows the dates of the original file and its
1056 auto-save file, and asks once again whether to recover that file.
1058 When @code{recover-session} is done, the files you've chosen to
1059 recover are present in Emacs buffers. You should then save them. Only
1060 this---saving them---updates the files themselves.
1062 @vindex auto-save-list-file-prefix
1063 Emacs records interrupted sessions for later recovery in files named
1064 @file{~/.emacs.d/auto-save-list/.saves-@var{pid}-@var{hostname}}. All
1065 of this name except @file{@var{pid}-@var{hostname}} comes from the
1066 value of @code{auto-save-list-file-prefix}. You can record sessions
1067 in a different place by customizing that variable. If you set
1068 @code{auto-save-list-file-prefix} to @code{nil} in your @file{.emacs}
1069 file, sessions are not recorded for recovery.
1072 @section File Name Aliases
1074 Symbolic links and hard links both make it possible for several file
1075 names to refer to the same file. Hard links are alternate names that
1076 refer directly to the file; all the names are equally valid, and no one
1077 of them is preferred. By contrast, a symbolic link is a kind of defined
1078 alias: when @file{foo} is a symbolic link to @file{bar}, you can use
1079 either name to refer to the file, but @file{bar} is the real name, while
1080 @file{foo} is just an alias. More complex cases occur when symbolic
1081 links point to directories.
1083 If you visit two names for the same file, normally Emacs makes
1084 two different buffers, but it warns you about the situation.
1086 @vindex find-file-existing-other-name
1087 @vindex find-file-suppress-same-file-warnings
1088 Normally, if you visit a file which Emacs is already visiting under
1089 a different name, Emacs displays a message in the echo area and uses
1090 the existing buffer visiting that file. This can happen on systems
1091 that support symbolic links, or if you use a long file name on a
1092 system that truncates long file names. You can suppress the message by
1093 setting the variable @code{find-file-suppress-same-file-warnings} to a
1094 non-@code{nil} value. You can disable this feature entirely by setting
1095 the variable @code{find-file-existing-other-name} to @code{nil}: then
1096 if you visit the same file under two different names, you get a separate
1097 buffer for each file name.
1099 @vindex find-file-visit-truename
1100 @cindex truenames of files
1101 @cindex file truenames
1102 If the variable @code{find-file-visit-truename} is non-@code{nil},
1103 then the file name recorded for a buffer is the file's @dfn{truename}
1104 (made by replacing all symbolic links with their target names), rather
1105 than the name you specify. Setting @code{find-file-visit-truename} also
1106 implies the effect of @code{find-file-existing-other-name}.
1108 @node Version Control
1109 @section Version Control
1110 @cindex version control
1112 @dfn{Version control systems} are packages that can record multiple
1113 versions of a source file, usually storing the unchanged parts of the
1114 file just once. Version control systems also record history information
1115 such as the creation time of each version, who created it, and a
1116 description of what was changed in that version.
1118 The Emacs version control interface is called VC. Its commands work
1119 with three version control systems---RCS, CVS, and SCCS. The GNU
1120 project recommends RCS and CVS, which are free software and available
1121 from the Free Software Foundation. We also have free software to
1122 replace SCCS, known as CSSC; if you are using SCCS and don't want to
1123 make the incompatible change to RCS or CVS, you can switch to CSSC.
1126 * Introduction to VC:: How version control works in general.
1127 * VC Mode Line:: How the mode line shows version control status.
1128 * Basic VC Editing:: How to edit a file under version control.
1129 * Old Versions:: Examining and comparing old versions.
1130 * Secondary VC Commands:: The commands used a little less frequently.
1131 * Branches:: Multiple lines of development.
1132 * Remote Repositories:: Efficient access to remote CVS servers.
1133 * Snapshots:: Sets of file versions treated as a unit.
1134 * Miscellaneous VC:: Various other commands and features of VC.
1135 * Customizing VC:: Variables that change VC's behavior.
1138 @node Introduction to VC
1139 @subsection Introduction to Version Control
1141 VC allows you to use a version control system from within Emacs,
1142 integrating the version control operations smoothly with editing. VC
1143 provides a uniform interface to version control, so that regardless of
1144 which version control system is in use, you can use it the same way.
1146 This section provides a general overview of version control, and
1147 describes the version control systems that VC supports. You can skip
1148 this section if you are already familiar with the version control system
1152 * Version Systems:: Supported version control back-end systems.
1153 * VC Concepts:: Words and concepts related to version control.
1154 * Types of Log File:: The per-file VC log in contrast to the ChangeLog.
1157 @node Version Systems
1158 @subsubsection Supported Version Control Systems
1161 @cindex back end (version control)
1162 VC currently works with three different version control systems or
1163 ``back ends'': RCS, CVS, and SCCS.
1165 RCS is a free version control system that is available from the Free
1166 Software Foundation. It is perhaps the most mature of the supported
1167 back ends, and the VC commands are conceptually closest to RCS. Almost
1168 everything you can do with RCS can be done through VC.
1171 CVS is built on top of RCS, and extends the features of RCS, allowing
1172 for more sophisticated release management, and concurrent multi-user
1173 development. VC supports basic editing operations under CVS, but for
1174 some less common tasks you still need to call CVS from the command line.
1175 Note also that before using CVS you must set up a repository, which is a
1176 subject too complex to treat here.
1179 SCCS is a proprietary but widely used version control system. In
1180 terms of capabilities, it is the weakest of the three that VC
1181 supports. VC compensates for certain features missing in SCCS
1182 (snapshots, for example) by implementing them itself, but some other VC
1183 features, such as multiple branches, are not available with SCCS. You
1184 should use SCCS only if for some reason you cannot use RCS.
1187 @subsubsection Concepts of Version Control
1190 @cindex registered file
1191 When a file is under version control, we also say that it is
1192 @dfn{registered} in the version control system. Each registered file
1193 has a corresponding @dfn{master file} which represents the file's
1194 present state plus its change history---enough to reconstruct the
1195 current version or any earlier version. Usually the master file also
1196 records a @dfn{log entry} for each version, describing in words what was
1197 changed in that version.
1200 @cindex checking out files
1201 The file that is maintained under version control is sometimes called
1202 the @dfn{work file} corresponding to its master file. You edit the work
1203 file and make changes in it, as you would with an ordinary file. (With
1204 SCCS and RCS, you must @dfn{lock} the file before you start to edit it.)
1205 After you are done with a set of changes, you @dfn{check the file in},
1206 which records the changes in the master file, along with a log entry for
1209 With CVS, there are usually multiple work files corresponding to a
1210 single master file---often each user has his own copy. It is also
1211 possible to use RCS in this way, but this is not the usual way to use
1214 @cindex locking and version control
1215 A version control system typically has some mechanism to coordinate
1216 between users who want to change the same file. One method is
1217 @dfn{locking} (analogous to the locking that Emacs uses to detect
1218 simultaneous editing of a file, but distinct from it). The other method
1219 is to merge your changes with other people's changes when you check them
1222 With version control locking, work files are normally read-only so
1223 that you cannot change them. You ask the version control system to make
1224 a work file writable for you by locking it; only one user can do
1225 this at any given time. When you check in your changes, that unlocks
1226 the file, making the work file read-only again. This allows other users
1227 to lock the file to make further changes. SCCS always uses locking, and
1230 The other alternative for RCS is to let each user modify the work file
1231 at any time. In this mode, locking is not required, but it is
1232 permitted; check-in is still the way to record a new version.
1234 CVS normally allows each user to modify his own copy of the work file
1235 at any time, but requires merging with changes from other users at
1236 check-in time. However, CVS can also be set up to require locking.
1237 (@pxref{CVS Options}).
1239 @node Types of Log File
1240 @subsubsection Types of Log File
1241 @cindex types of log file
1242 @cindex log File, types of
1243 @cindex version control log
1245 GNU projects under a revision control system generally possess
1246 @emph{two} types of log for changes. One is the per-file log
1247 maintained by the revision control system: each time you check in a
1248 change, you must fill out a @dfn{log entry} for the change (@pxref{Log
1249 Buffer}). This kind of log is called the @dfn{version control log},
1250 also the @dfn{revision control log}, @dfn{RCS log}, or @dfn{CVS log}.
1252 The other kind of log is the change log file, typically a file called
1253 @file{ChangeLog}. It provides a chronological record of all changes
1254 to a large portion of a program---one directory and its
1255 subdirectories. A small program would use one @file{ChangeLog} file;
1256 a large program may well merit a @file{ChangeLog} file in each major
1257 directory. @xref{Change Log}.
1259 When you use version control, you can use just the per-file log if you
1260 wish, or you can use both kinds of logs. When you use both, you
1261 typically want to write just one entry for each change. You can write
1262 the entry in @file{ChangeLog}, then copy it to the log buffer when you
1263 check in the change. Or you can write the entry in the log buffer
1264 while checking in the change, and later use the @kbd{C-x v a} command
1265 to copy it to @file{ChangeLog} (@pxref{Change Logs and VC}).
1268 @subsection Version Control and the Mode Line
1270 When you visit a file that is under version control, Emacs indicates
1271 this on the mode line. For example, @samp{RCS-1.3} says that RCS is
1272 used for that file, and the current version is 1.3.
1274 The character between the back-end name and the version number
1275 indicates the version control status of the file. @samp{-} means that
1276 the work file is not locked (if locking is in use), or not modified (if
1277 locking is not in use). @samp{:} indicates that the file is locked, or
1278 that it is modified. If the file is locked by some other user (for
1279 instance, @samp{jim}), that is displayed as @samp{RCS:jim:1.3}.
1281 @node Basic VC Editing
1282 @subsection Basic Editing under Version Control
1284 The principal VC command is an all-purpose command that performs
1285 either locking or check-in, depending on the situation.
1289 Perform the next logical version control operation on this file.
1292 @findex vc-next-action
1294 The precise action of this command depends on the state of the file,
1295 and whether the version control system uses locking or not. SCCS and
1296 RCS normally use locking; CVS normally does not use locking.
1298 @findex vc-toggle-read-only
1299 @kindex C-x C-q @r{(Version Control)}
1300 As a special convenience that is particularly useful for files with
1301 locking, you can let Emacs check a file in or out whenever you change
1302 its read-only flag. This means, for example, that you cannot
1303 accidentally edit a file without properly checking it out first. To
1304 achieve this, bind the key @kbd{C-x C-q} to @kbd{vc-toggle-read-only}
1305 in your @file{~/.emacs} file. (@xref{Init Rebinding}.)
1308 * VC with Locking:: RCS in its default mode, SCCS, and optionally CVS.
1309 * Without Locking:: Without locking: default mode for CVS.
1310 * Advanced C-x v v:: Advanced features available with a prefix argument.
1311 * Log Buffer:: Features available in log entry buffers.
1314 @node VC with Locking
1315 @subsubsection Basic Version Control with Locking
1317 If locking is used for the file (as with SCCS, and RCS in its default
1318 mode), @kbd{C-x v v} can either lock a file or check it in:
1322 If the file is not locked, @kbd{C-x v v} locks it, and
1323 makes it writable so that you can change it.
1326 If the file is locked by you, and contains changes, @kbd{C-x v v} checks
1327 in the changes. In order to do this, it first reads the log entry
1328 for the new version. @xref{Log Buffer}.
1331 If the file is locked by you, but you have not changed it since you
1332 locked it, @kbd{C-x v v} releases the lock and makes the file read-only
1336 If the file is locked by some other user, @kbd{C-x v v} asks you whether
1337 you want to ``steal the lock'' from that user. If you say yes, the file
1338 becomes locked by you, but a message is sent to the person who had
1339 formerly locked the file, to inform him of what has happened.
1342 These rules also apply when you use CVS in locking mode, except
1343 that there is no such thing as stealing a lock.
1345 @node Without Locking
1346 @subsubsection Basic Version Control without Locking
1348 When there is no locking---the default for CVS---work files are always
1349 writable; you do not need to do anything before you begin to edit a
1350 file. The status indicator on the mode line is @samp{-} if the file is
1351 unmodified; it flips to @samp{:} as soon as you save any changes in the
1354 Here is what @kbd{C-x v v} does when using CVS:
1358 If some other user has checked in changes into the master file, Emacs
1359 asks you whether you want to merge those changes into your own work
1360 file. You must do this before you can check in your own changes. (To
1361 pick up any recent changes from the master file @emph{without} trying
1362 to commit your own changes, type @kbd{C-x v m @key{RET}}.)
1366 If there are no new changes in the master file, but you have made
1367 modifications in your work file, @kbd{C-x v v} checks in your changes.
1368 In order to do this, it first reads the log entry for the new version.
1372 If the file is not modified, the @kbd{C-x v v} does nothing.
1375 These rules also apply when you use RCS in the mode that does not
1376 require locking, except that automatic merging of changes from the
1377 master file is not implemented. Unfortunately, this means that nothing
1378 informs you if another user has checked in changes in the same file
1379 since you began editing it, and when this happens, his changes will be
1380 effectively removed when you check in your version (though they will
1381 remain in the master file, so they will not be entirely lost). You must
1382 therefore verify the current version is unchanged, before you check in your
1383 changes. We hope to eliminate this risk and provide automatic merging
1384 with RCS in a future Emacs version.
1386 In addition, locking is possible with RCS even in this mode, although
1387 it is not required; @kbd{C-x v v} with an unmodified file locks the
1388 file, just as it does with RCS in its normal (locking) mode.
1390 @node Advanced C-x v v
1391 @subsubsection Advanced Control in @kbd{C-x v v}
1393 @cindex version number to check in/out
1394 When you give a prefix argument to @code{vc-next-action} (@kbd{C-u
1395 C-x v v}), it still performs the next logical version control
1396 operation, but accepts additional arguments to specify precisely how
1397 to do the operation.
1401 If the file is modified (or locked), you can specify the version
1402 number to use for the new version that you check in. This is one way
1403 to create a new branch (@pxref{Branches}).
1406 If the file is not modified (and unlocked), you can specify the
1407 version to select; this lets you start working from an older version,
1408 or on another branch. If you do not enter any version, that takes you
1409 to the highest version on the current branch; therefore @kbd{C-u C-x
1410 v v @key{RET}} is a convenient way to get the latest version of a file from
1414 @cindex specific version control system
1415 Instead of the version number, you can also specify the name of a
1416 version control system. This is useful when one file is being managed
1417 with two version control systems at the same time (@pxref{Local
1422 @subsubsection Features of the Log Entry Buffer
1424 When you check in changes, @kbd{C-x v v} first reads a log entry. It
1425 pops up a buffer called @samp{*VC-Log*} for you to enter the log entry.
1426 When you are finished, type @kbd{C-c C-c} in the @samp{*VC-Log*} buffer.
1427 That is when check-in really happens.
1429 To abort check-in, just @strong{don't} type @kbd{C-c C-c} in that
1430 buffer. You can switch buffers and do other editing. As long as you
1431 don't try to check in another file, the entry you were editing remains
1432 in the @samp{*VC-Log*} buffer, and you can go back to that buffer at any
1433 time to complete the check-in.
1435 If you change several source files for the same reason, it is often
1436 convenient to specify the same log entry for many of the files. To do
1437 this, use the history of previous log entries. The commands @kbd{M-n},
1438 @kbd{M-p}, @kbd{M-s} and @kbd{M-r} for doing this work just like the
1439 minibuffer history commands (except that these versions are used outside
1442 @vindex vc-log-mode-hook
1443 Each time you check in a file, the log entry buffer is put into VC Log
1444 mode, which involves running two hooks: @code{text-mode-hook} and
1445 @code{vc-log-mode-hook}. @xref{Hooks}.
1448 @subsection Examining And Comparing Old Versions
1450 One of the convenient features of version control is the ability
1451 to examine any version of a file, or compare two versions.
1454 @item C-x v ~ @var{version} @key{RET}
1455 Examine version @var{version} of the visited file, in a buffer of its
1459 Compare the current buffer contents with the latest checked-in version
1462 @item C-u C-x v = @var{file} @key{RET} @var{oldvers} @key{RET} @var{newvers} @key{RET}
1463 Compare the specified two versions of @var{file}.
1466 Display the result of the CVS annotate command using colors.
1469 @findex vc-version-other-window
1471 To examine an old version in its entirety, visit the file and then type
1472 @kbd{C-x v ~ @var{version} @key{RET}} (@code{vc-version-other-window}).
1473 This puts the text of version @var{version} in a file named
1474 @file{@var{filename}.~@var{version}~}, and visits it in its own buffer
1475 in a separate window. (In RCS, you can also select an old version
1476 and create a branch from it. @xref{Branches}.)
1480 It is usually more convenient to compare two versions of the file,
1481 with the command @kbd{C-x v =} (@code{vc-diff}). Plain @kbd{C-x v =}
1482 compares the current buffer contents (saving them in the file if
1483 necessary) with the last checked-in version of the file. @kbd{C-u C-x
1484 v =}, with a numeric argument, reads a file name and two version
1485 numbers, then compares those versions of the specified file. Both
1486 forms display the output in a special buffer in another window.
1488 You can specify a checked-in version by its number; an empty input
1489 specifies the current contents of the work file (which may be different
1490 from all the checked-in versions). You can also specify a snapshot name
1491 (@pxref{Snapshots}) instead of one or both version numbers.
1493 If you supply a directory name instead of the name of a registered
1494 file, this command compares the two specified versions of all registered
1495 files in that directory and its subdirectories.
1497 @vindex vc-diff-switches
1498 @vindex vc-rcs-diff-switches
1499 @kbd{C-x v =} works by running a variant of the @code{diff} utility
1500 designed to work with the version control system in use. When you
1501 invoke @code{diff} this way, in addition to the options specified by
1502 @code{diff-switches} (@pxref{Comparing Files}), it receives those
1503 specified by @code{vc-diff-switches}, plus those specified for the
1504 specific back end by @code{vc-@var{backend}-diff-switches}. For
1505 instance, when the version control back end is RCS, @code{diff} uses
1506 the options in @code{vc-rcs-diff-switches}. The
1507 @samp{vc@dots{}diff-switches} variables are @code{nil} by default.
1509 Unlike the @kbd{M-x diff} command, @kbd{C-x v =} does not try to
1510 locate the changes in the old and new versions. This is because
1511 normally one or both versions do not exist as files when you compare
1512 them; they exist only in the records of the master file.
1513 @xref{Comparing Files}, for more information about @kbd{M-x diff}.
1517 For CVS-controlled files, you can display the result of the CVS
1518 annotate command, using colors to enhance the visual appearance. Use
1519 the command @kbd{M-x vc-annotate} to do this. It creates a new buffer
1520 to display file's text, colored to show how old each part is. Text
1521 colored red is new, blue means old, and intermediate colors indicate
1522 intermediate ages. By default, the time scale is 360 days, so that
1523 everything more than one year old is shown in blue.
1525 When you give a prefix argument to this command, it uses the
1526 minibuffer to read two arguments: which version number to display and
1527 annotate (instead of the current file contents), and a stretch factor
1528 for the time scale. A stretch factor of 0.1 means that the color
1529 range from red to blue spans the past 36 days instead of 360 days. A
1530 stretch factor greater than 1 means the color range spans more than a
1533 @node Secondary VC Commands
1534 @subsection The Secondary Commands of VC
1536 This section explains the secondary commands of VC; those that you might
1540 * Registering:: Putting a file under version control.
1541 * VC Status:: Viewing the VC status of files.
1542 * VC Undo:: Cancelling changes before or after check-in.
1543 * VC Dired Mode:: Listing files managed by version control.
1544 * VC Dired Commands:: Commands to use in a VC Dired buffer.
1548 @subsubsection Registering a File for Version Control
1552 You can put any file under version control by simply visiting it, and
1553 then typing @w{@kbd{C-x v i}} (@code{vc-register}).
1557 Register the visited file for version control.
1560 To register the file, Emacs must choose which version control system
1561 to use for it. If the file's directory already contains files
1562 registered in a version control system, Emacs uses that system. If
1563 there is more than one system in use for a directory, Emacs uses the one
1564 that appears first in @code{vc-handled-backends} (@pxref{Customizing VC}).
1565 On the other hand, if there are no files already registered,
1566 Emacs uses the first system from @code{vc-handled-backends} that could
1567 register the file---for example, you cannot register a file under CVS if
1568 its directory is not already part of a CVS tree.
1570 With the default value of @code{vc-handled-backends}, this means
1571 that Emacs uses RCS if there are any files under RCS control, CVS if
1572 there are any files under CVS, SCCS if any files are under SCCS, or
1573 RCS as the ultimate default.
1575 If locking is in use, @kbd{C-x v i} leaves the file unlocked and
1576 read-only. Type @kbd{C-x v v} if you wish to start editing it. After
1577 registering a file with CVS, you must subsequently commit the initial
1578 version by typing @kbd{C-x v v}.
1580 @vindex vc-default-init-version
1581 @cindex initial version number to register
1582 The initial version number for a newly registered file is 1.1, by
1583 default. You can specify a different default by setting the variable
1584 @code{vc-default-init-version}, or you can give @kbd{C-x v i} a numeric
1585 argument; then it reads the initial version number for this particular
1586 file using the minibuffer.
1588 @vindex vc-initial-comment
1589 If @code{vc-initial-comment} is non-@code{nil}, @kbd{C-x v i} reads an
1590 initial comment to describe the purpose of this source file. Reading
1591 the initial comment works like reading a log entry (@pxref{Log Buffer}).
1594 @subsubsection VC Status Commands
1598 Display version control state and change history.
1602 @findex vc-print-log
1603 To view the detailed version control status and history of a file,
1604 type @kbd{C-x v l} (@code{vc-print-log}). It displays the history of
1605 changes to the current file, including the text of the log entries. The
1606 output appears in a separate window.
1609 @subsubsection Undoing Version Control Actions
1613 Revert the buffer and the file to the last checked-in version.
1616 Remove the last-entered change from the master for the visited file.
1617 This undoes your last check-in.
1621 @findex vc-revert-buffer
1622 If you want to discard your current set of changes and revert to the
1623 last version checked in, use @kbd{C-x v u} (@code{vc-revert-buffer}).
1624 This leaves the file unlocked; if locking is in use, you must first lock
1625 the file again before you change it again. @kbd{C-x v u} requires
1626 confirmation, unless it sees that you haven't made any changes since the
1627 last checked-in version.
1629 @kbd{C-x v u} is also the command to unlock a file if you lock it and
1630 then decide not to change it.
1633 @findex vc-cancel-version
1634 To cancel a change that you already checked in, use @kbd{C-x v c}
1635 (@code{vc-cancel-version}). This command discards all record of the
1636 most recent checked-in version. @kbd{C-x v c} also offers to revert
1637 your work file and buffer to the previous version (the one that precedes
1638 the version that is deleted).
1640 If you answer @kbd{no}, VC keeps your changes in the buffer, and locks
1641 the file. The no-revert option is useful when you have checked in a
1642 change and then discover a trivial error in it; you can cancel the
1643 erroneous check-in, fix the error, and check the file in again.
1645 When @kbd{C-x v c} does not revert the buffer, it unexpands all
1646 version control headers in the buffer instead (@pxref{Version Headers}).
1647 This is because the buffer no longer corresponds to any existing
1648 version. If you check it in again, the check-in process will expand the
1649 headers properly for the new version number.
1651 However, it is impossible to unexpand the RCS @samp{@w{$}Log$} header
1652 automatically. If you use that header feature, you have to unexpand it
1653 by hand---by deleting the entry for the version that you just canceled.
1655 Be careful when invoking @kbd{C-x v c}, as it is easy to lose a lot of
1656 work with it. To help you be careful, this command always requires
1657 confirmation with @kbd{yes}. Note also that this command is disabled
1658 under CVS, because canceling versions is very dangerous and discouraged
1662 @subsubsection Dired under VC
1666 @cindex CVS Dired Mode
1667 The VC Dired Mode described here works with all the version control
1668 systems that VC supports. Another more powerful facility, designed
1669 specifically for CVS, is called PCL-CVS. @xref{Top, , About PCL-CVS,
1670 pcl-cvs, PCL-CVS --- The Emacs Front-End to CVS}.
1673 @findex vc-directory
1674 When you are working on a large program, it is often useful to find
1675 out which files have changed within an entire directory tree, or to view
1676 the status of all files under version control at once, and to perform
1677 version control operations on collections of files. You can use the
1678 command @kbd{C-x v d} (@code{vc-directory}) to make a directory listing
1679 that includes only files relevant for version control.
1681 @vindex vc-dired-terse-display
1682 @kbd{C-x v d} creates a buffer which uses VC Dired Mode. This looks
1683 much like an ordinary Dired buffer (@pxref{Dired}); however, normally it
1684 shows only the noteworthy files (those locked or not up-to-date). This
1685 is called @dfn{terse display}. If you set the variable
1686 @code{vc-dired-terse-display} to @code{nil}, then VC Dired shows all
1687 relevant files---those managed under version control, plus all
1688 subdirectories (@dfn{full display}). The command @kbd{v t} in a VC
1689 Dired buffer toggles between terse display and full display (@pxref{VC
1692 @vindex vc-dired-recurse
1693 By default, VC Dired produces a recursive listing of noteworthy or
1694 relevant files at or below the given directory. You can change this by
1695 setting the variable @code{vc-dired-recurse} to @code{nil}; then VC
1696 Dired shows only the files in the given directory.
1698 The line for an individual file shows the version control state in the
1699 place of the hard link count, owner, group, and size of the file. If
1700 the file is unmodified, in sync with the master file, the version
1701 control state shown is blank. Otherwise it consists of text in
1702 parentheses. Under RCS and SCCS, the name of the user locking the file
1703 is shown; under CVS, an abbreviated version of the @samp{cvs status}
1704 output is used. Here is an example using RCS:
1710 -rw-r--r-- (jim) Apr 2 23:39 file1
1711 -r--r--r-- Apr 5 20:21 file2
1716 The files @samp{file1} and @samp{file2} are under version control,
1717 @samp{file1} is locked by user jim, and @samp{file2} is unlocked.
1719 Here is an example using CVS:
1725 -rw-r--r-- (modified) Aug 2 1997 file1.c
1726 -rw-r--r-- Apr 4 20:09 file2.c
1727 -rw-r--r-- (merge) Sep 13 1996 file3.c
1731 Here @samp{file1.c} is modified with respect to the repository, and
1732 @samp{file2.c} is not. @samp{file3.c} is modified, but other changes
1733 have also been checked in to the repository---you need to merge them
1734 with the work file before you can check it in.
1736 @vindex vc-directory-exclusion-list
1737 When VC Dired displays subdirectories (in the ``full'' display mode),
1738 it omits some that should never contain any files under version control.
1739 By default, this includes Version Control subdirectories such as
1740 @samp{RCS} and @samp{CVS}; you can customize this by setting the
1741 variable @code{vc-directory-exclusion-list}.
1743 You can fine-tune VC Dired's format by typing @kbd{C-u C-x v d}---as in
1744 ordinary Dired, that allows you to specify additional switches for the
1747 @node VC Dired Commands
1748 @subsubsection VC Dired Commands
1750 All the usual Dired commands work normally in VC Dired mode, except
1751 for @kbd{v}, which is redefined as the version control prefix. You can
1752 invoke VC commands such as @code{vc-diff} and @code{vc-print-log} by
1753 typing @kbd{v =}, or @kbd{v l}, and so on. Most of these commands apply
1754 to the file name on the current line.
1756 The command @kbd{v v} (@code{vc-next-action}) operates on all the
1757 marked files, so that you can lock or check in several files at once.
1758 If it operates on more than one file, it handles each file according to
1759 its current state; thus, it might lock one file, but check in another
1760 file. This could be confusing; it is up to you to avoid confusing
1761 behavior by marking a set of files that are in a similar state.
1763 If any files call for check-in, @kbd{v v} reads a single log entry,
1764 then uses it for all the files being checked in. This is convenient for
1765 registering or checking in several files at once, as part of the same
1768 @findex vc-dired-toggle-terse-mode
1769 @findex vc-dired-mark-locked
1770 You can toggle between terse display (only locked files, or files not
1771 up-to-date) and full display at any time by typing @kbd{v t}
1772 (@code{vc-dired-toggle-terse-mode}). There is also a special command
1773 @kbd{* l} (@code{vc-dired-mark-locked}), which marks all files currently
1774 locked (or, with CVS, all files not up-to-date). Thus, typing @kbd{* l
1775 t k} is another way to delete from the buffer all files except those
1779 @subsection Multiple Branches of a File
1780 @cindex branch (version control)
1781 @cindex trunk (version control)
1783 One use of version control is to maintain multiple ``current''
1784 versions of a file. For example, you might have different versions of a
1785 program in which you are gradually adding various unfinished new
1786 features. Each such independent line of development is called a
1787 @dfn{branch}. VC allows you to create branches, switch between
1788 different branches, and merge changes from one branch to another.
1789 Please note, however, that branches are only supported for RCS at the
1792 A file's main line of development is usually called the @dfn{trunk}.
1793 The versions on the trunk are normally numbered 1.1, 1.2, 1.3, etc. At
1794 any such version, you can start an independent branch. A branch
1795 starting at version 1.2 would have version number 1.2.1.1, and consecutive
1796 versions on this branch would have numbers 1.2.1.2, 1.2.1.3, 1.2.1.4,
1797 and so on. If there is a second branch also starting at version 1.2, it
1798 would consist of versions 1.2.2.1, 1.2.2.2, 1.2.2.3, etc.
1800 @cindex head version
1801 If you omit the final component of a version number, that is called a
1802 @dfn{branch number}. It refers to the highest existing version on that
1803 branch---the @dfn{head version} of that branch. The branches in the
1804 example above have branch numbers 1.2.1 and 1.2.2.
1807 * Switching Branches:: How to get to another existing branch.
1808 * Creating Branches:: How to start a new branch.
1809 * Merging:: Transferring changes between branches.
1810 * Multi-User Branching:: Multiple users working at multiple branches
1814 @node Switching Branches
1815 @subsubsection Switching between Branches
1817 To switch between branches, type @kbd{C-u C-x v v} and specify the
1818 version number you want to select. This version is then visited
1819 @emph{unlocked} (write-protected), so you can examine it before locking
1820 it. Switching branches in this way is allowed only when the file is not
1823 You can omit the minor version number, thus giving only the branch
1824 number; this takes you to the head version on the chosen branch. If you
1825 only type @key{RET}, Emacs goes to the highest version on the trunk.
1827 After you have switched to any branch (including the main branch), you
1828 stay on it for subsequent VC commands, until you explicitly select some
1831 @node Creating Branches
1832 @subsubsection Creating New Branches
1834 To create a new branch from a head version (one that is the latest in
1835 the branch that contains it), first select that version if necessary,
1836 lock it with @kbd{C-x v v}, and make whatever changes you want. Then,
1837 when you check in the changes, use @kbd{C-u C-x v v}. This lets you
1838 specify the version number for the new version. You should specify a
1839 suitable branch number for a branch starting at the current version.
1840 For example, if the current version is 2.5, the branch number should be
1841 2.5.1, 2.5.2, and so on, depending on the number of existing branches at
1844 To create a new branch at an older version (one that is no longer the
1845 head of a branch), first select that version (@pxref{Switching
1846 Branches}), then lock it with @kbd{C-x v v}. You'll be asked to
1847 confirm, when you lock the old version, that you really mean to create a
1848 new branch---if you say no, you'll be offered a chance to lock the
1849 latest version instead.
1851 Then make your changes and type @kbd{C-x v v} again to check in a new
1852 version. This automatically creates a new branch starting from the
1853 selected version. You need not specially request a new branch, because
1854 that's the only way to add a new version at a point that is not the head
1857 After the branch is created, you ``stay'' on it. That means that
1858 subsequent check-ins create new versions on that branch. To leave the
1859 branch, you must explicitly select a different version with @kbd{C-u C-x
1860 v v}. To transfer changes from one branch to another, use the merge
1861 command, described in the next section.
1864 @subsubsection Merging Branches
1866 @cindex merging changes
1867 When you have finished the changes on a certain branch, you will
1868 often want to incorporate them into the file's main line of development
1869 (the trunk). This is not a trivial operation, because development might
1870 also have proceeded on the trunk, so that you must @dfn{merge} the
1871 changes into a file that has already been changed otherwise. VC allows
1872 you to do this (and other things) with the @code{vc-merge} command.
1875 @item C-x v m (vc-merge)
1876 Merge changes into the work file.
1881 @kbd{C-x v m} (@code{vc-merge}) takes a set of changes and merges it
1882 into the current version of the work file. It firsts asks you in the
1883 minibuffer where the changes should come from. If you just type
1884 @key{RET}, Emacs merges any changes that were made on the same branch
1885 since you checked the file out (we call this @dfn{merging the news}).
1886 This is the common way to pick up recent changes from the repository,
1887 regardless of whether you have already changed the file yourself.
1889 You can also enter a branch number or a pair of version numbers in
1890 the minibuffer. Then @kbd{C-x v m} finds the changes from that
1891 branch, or the differences between the two versions you specified, and
1892 merges them into the current version of the current file.
1894 As an example, suppose that you have finished a certain feature on
1895 branch 1.3.1. In the meantime, development on the trunk has proceeded
1896 to version 1.5. To merge the changes from the branch to the trunk,
1897 first go to the head version of the trunk, by typing @kbd{C-u C-x v v
1898 @key{RET}}. Version 1.5 is now current. If locking is used for the file,
1899 type @kbd{C-x v v} to lock version 1.5 so that you can change it. Next,
1900 type @kbd{C-x v m 1.3.1 @key{RET}}. This takes the entire set of changes on
1901 branch 1.3.1 (relative to version 1.3, where the branch started, up to
1902 the last version on the branch) and merges it into the current version
1903 of the work file. You can now check in the changed file, thus creating
1904 version 1.6 containing the changes from the branch.
1906 It is possible to do further editing after merging the branch, before
1907 the next check-in. But it is usually wiser to check in the merged
1908 version, then lock it and make the further changes. This will keep
1909 a better record of the history of changes.
1912 @cindex resolving conflicts
1913 When you merge changes into a file that has itself been modified, the
1914 changes might overlap. We call this situation a @dfn{conflict}, and
1915 reconciling the conflicting changes is called @dfn{resolving a
1918 Whenever conflicts occur during merging, VC detects them, tells you
1919 about them in the echo area, and asks whether you want help in merging.
1920 If you say yes, it starts an Ediff session (@pxref{Top,
1921 Ediff, Ediff, ediff, The Ediff Manual}).
1923 If you say no, the conflicting changes are both inserted into the
1924 file, surrounded by @dfn{conflict markers}. The example below shows how
1925 a conflict region looks; the file is called @samp{name} and the current
1926 master file version with user B's changes in it is 1.11.
1928 @c @w here is so CVS won't think this is a conflict.
1932 @var{User A's version}
1934 @var{User B's version}
1939 @cindex vc-resolve-conflicts
1940 Then you can resolve the conflicts by editing the file manually. Or
1941 you can type @code{M-x vc-resolve-conflicts} after visiting the file.
1942 This starts an Ediff session, as described above. Don't forget to
1943 check in the merged version afterwards.
1945 @node Multi-User Branching
1946 @subsubsection Multi-User Branching
1948 It is often useful for multiple developers to work simultaneously on
1949 different branches of a file. CVS allows this by default; for RCS, it
1950 is possible if you create multiple source directories. Each source
1951 directory should have a link named @file{RCS} which points to a common
1952 directory of RCS master files. Then each source directory can have its
1953 own choice of selected versions, but all share the same common RCS
1956 This technique works reliably and automatically, provided that the
1957 source files contain RCS version headers (@pxref{Version Headers}). The
1958 headers enable Emacs to be sure, at all times, which version number is
1959 present in the work file.
1961 If the files do not have version headers, you must instead tell Emacs
1962 explicitly in each session which branch you are working on. To do this,
1963 first find the file, then type @kbd{C-u C-x v v} and specify the correct
1964 branch number. This ensures that Emacs knows which branch it is using
1965 during this particular editing session.
1967 @node Remote Repositories
1968 @subsection Remote Repositories
1969 @cindex remote repositories (CVS)
1971 A common way of using CVS is to set up a central CVS repository on
1972 some Internet host, then have each developer check out a personal
1973 working copy of the files on his local machine. Committing changes to
1974 the repository, and picking up changes from other users into one's own
1975 working area, then works by direct interactions with the CVS server.
1977 One difficulty is that access to the CVS server is often slow, and
1978 that developers might need to work off-line as well. VC is designed
1979 to reduce the amount of network interaction necessary.
1982 * Version Backups:: Keeping local copies of repository versions.
1983 * Local Version Control:: Using another version system for local editing.
1986 @node Version Backups
1987 @subsubsection Version Backups
1988 @cindex version backups
1990 @cindex automatic version backups
1991 When VC sees that the CVS repository for a file is on a remote
1992 machine, it automatically makes local backups of unmodified versions
1993 of the file---@dfn{automatic version backups}. This means that you
1994 can compare the file to the repository version (@kbd{C-x v =}), or
1995 revert to that version (@kbd{C-x v u}), without any network
1998 The local copy of the unmodified file is called a @dfn{version
1999 backup} to indicate that it corresponds exactly to a version that is
2000 stored in the repository. Note that version backups are not the same
2001 as ordinary Emacs backup files (@pxref{Backup}). But they follow a
2002 similar naming convention.
2004 For a file that comes from a remote CVS repository, VC makes a
2005 version backup whenever you save the first changes to the file, and
2006 removes it after you have committed your modified version to the
2007 repository. You can disable the making of automatic version backups by
2008 setting @code{vc-cvs-stay-local} to @code{nil} (@pxref{CVS Options}).
2010 @cindex manual version backups
2011 The name of the automatic version backup for version @var{version}
2012 of file @var{file} is @code{@var{file}.~@var{version}.~}. This is
2013 almost the same as the name used by @kbd{C-x v ~} (@pxref{Old
2014 Versions}), the only difference being the additional dot (@samp{.})
2015 after the version number. This similarity is intentional, because
2016 both kinds of files store the same kind of information. The file made
2017 by @kbd{C-x v ~} acts as a @dfn{manual version backup}.
2019 All the VC commands that operate on old versions of a file can use
2020 both kinds of version backups. For instance, @kbd{C-x v ~} uses
2021 either an automatic or a manual version backup, if possible, to get
2022 the contents of the version you request. Likewise, @kbd{C-x v =} and
2023 @kbd{C-x v u} use either an automatic or a manual version backup, if
2024 one of them exists, to get the contents of a version to compare or
2025 revert to. If you changed a file outside of Emacs, so that no
2026 automatic version backup was created for the previous text, you can
2027 create a manual backup of that version using @kbd{C-x v ~}, and thus
2028 obtain the benefit of the local copy for Emacs commands.
2030 The only difference in Emacs's handling of manual and automatic
2031 version backups, once they exist, is that Emacs deletes automatic
2032 version backups when you commit to the repository. By contrast,
2033 manual version backups remain until you delete them.
2035 @node Local Version Control
2036 @subsubsection Local Version Control
2037 @cindex local version control
2038 @cindex local back end (version control)
2040 When you make many changes to a file that comes from a remote
2041 repository, it can be convenient to have version control on your local
2042 machine as well. You can then record intermediate versions, revert to
2043 a previous state, etc., before you actually commit your changes to the
2046 VC lets you do this by putting a file under a second, local version
2047 control system, so that the file is effectively registered in two
2048 systems at the same time. For the description here, we will assume
2049 that the remote system is CVS, and you use RCS locally, although the
2050 mechanism works with any combination of version control systems
2053 To make it work with other back ends, you must make sure that the
2054 ``more local'' back end comes before the ``more remote'' back end in
2055 the setting of @code{vc-handled-backends} (@pxref{Customizing VC}). By
2056 default, this variable is set up so that you can use remote CVS and
2057 local RCS as described here.
2059 To start using local RCS for a file that comes from a remote CVS
2060 server, you must @emph{register the file in RCS}, by typing @kbd{C-u
2061 C-x v v rcs @key{RET}}. (In other words, use @code{vc-next-action} with a
2062 prefix argument, and specify RCS as the back end.)
2064 You can do this at any time; it does not matter whether you have
2065 already modified the file with respect to the version in the CVS
2066 repository. If possible, VC tries to make the RCS master start with
2067 the unmodified repository version, then checks in any local changes
2068 as a new version. This works if you have not made any changes yet, or
2069 if the unmodified repository version exists locally as a version
2070 backup (@pxref{Version Backups}). If the unmodified version is not
2071 available locally, the RCS master starts with the modified version;
2072 the only drawback to this is that you cannot compare your changes
2073 locally to what is stored in the repository.
2075 The version number of the RCS master is derived from the current CVS
2076 version, starting a branch from it. For example, if the current CVS
2077 version is 1.23, the local RCS branch will be 1.23.1. Version 1.23 in
2078 the RCS master will be identical to version 1.23 under CVS; your first
2079 changes are checked in as 1.23.1.1. (If the unmodified file is not
2080 available locally, VC will check in the modified file twice, both as
2081 1.23 and 1.23.1.1, to make the revision numbers consistent.)
2083 If you do not use locking under CVS (the default), locking is also
2084 disabled for RCS, so that editing under RCS works exactly as under
2087 When you are done with local editing, you can commit the final version
2088 back to the CVS repository by typing @kbd{C-u C-x v v cvs @key{RET}}.
2089 This initializes the log entry buffer (@pxref{Log Buffer}) to contain
2090 all the log entries you have recorded in the RCS master; you can edit
2091 them as you wish, and then commit in CVS by typing @kbd{C-c C-c}. If
2092 the commit is successful, VC removes the RCS master, so that the file
2093 is once again registered under CVS only. (The RCS master is not
2094 actually deleted, just renamed by appending @samp{~} to the name, so
2095 that you can refer to it later if you wish.)
2097 While using local RCS, you can pick up recent changes from the CVS
2098 repository into your local file, or commit some of your changes back
2099 to CVS, without terminating local RCS version control. To do this,
2100 switch to the CVS back end temporarily, with the @kbd{C-x v b} command:
2104 Switch to another back end that the current file is registered
2105 under (@code{vc-switch-backend}).
2107 @item C-u C-x v b @var{backend} @key{RET}
2108 Switch to @var{backend} for the current file.
2112 @findex vc-switch-backend
2113 @kbd{C-x v b} does not change the buffer contents, or any files; it
2114 only changes VC's perspective on how to handle the file. Any
2115 subsequent VC commands for that file will operate on the back end that
2116 is currently selected.
2118 If the current file is registered in more than one back end, typing
2119 @kbd{C-x v b} ``cycles'' through all of these back ends. With a
2120 prefix argument, it asks for the back end to use in the minibuffer.
2122 Thus, if you are using local RCS, and you want to pick up some recent
2123 changes in the file from remote CVS, first visit the file, then type
2124 @kbd{C-x v b} to switch to CVS, and finally use @kbd{C-x v m
2125 @key{RET}} to merge the news (@pxref{Merging}). You can then switch
2126 back to RCS by typing @kbd{C-x v b} again, and continue to edit
2129 But if you do this, the revision numbers in the RCS master no longer
2130 correspond to those of CVS. Technically, this is not a problem, but
2131 it can become difficult to keep track of what is in the CVS repository
2132 and what is not. So we suggest that you return from time to time to
2133 CVS-only operation, using @kbd{C-u C-x v v cvs @key{RET}}.
2136 @subsection Snapshots
2137 @cindex snapshots and version control
2139 A @dfn{snapshot} is a named set of file versions (one for each
2140 registered file) that you can treat as a unit. One important kind of
2141 snapshot is a @dfn{release}, a (theoretically) stable version of the
2142 system that is ready for distribution to users.
2145 * Making Snapshots:: The snapshot facilities.
2146 * Snapshot Caveats:: Things to be careful of when using snapshots.
2149 @node Making Snapshots
2150 @subsubsection Making and Using Snapshots
2152 There are two basic commands for snapshots; one makes a
2153 snapshot with a given name, the other retrieves a named snapshot.
2157 @findex vc-create-snapshot
2158 @item C-x v s @var{name} @key{RET}
2159 Define the last saved versions of every registered file in or under the
2160 current directory as a snapshot named @var{name}
2161 (@code{vc-create-snapshot}).
2164 @findex vc-retrieve-snapshot
2165 @item C-x v r @var{name} @key{RET}
2166 For all registered files at or below the current directory level, select
2167 whatever versions correspond to the snapshot @var{name}
2168 (@code{vc-retrieve-snapshot}).
2170 This command reports an error if any files are locked at or below the
2171 current directory, without changing anything; this is to avoid
2172 overwriting work in progress.
2175 A snapshot uses a very small amount of resources---just enough to record
2176 the list of file names and which version belongs to the snapshot. Thus,
2177 you need not hesitate to create snapshots whenever they are useful.
2179 You can give a snapshot name as an argument to @kbd{C-x v =} or
2180 @kbd{C-x v ~} (@pxref{Old Versions}). Thus, you can use it to compare a
2181 snapshot against the current files, or two snapshots against each other,
2182 or a snapshot against a named version.
2184 @node Snapshot Caveats
2185 @subsubsection Snapshot Caveats
2187 @cindex named configurations (RCS)
2188 VC's snapshot facilities are modeled on RCS's named-configuration
2189 support. They use RCS's native facilities for this, so under VC
2190 snapshots made using RCS are visible even when you bypass VC.
2192 @c worded verbosely to avoid overfull hbox.
2193 For SCCS, VC implements snapshots itself. The files it uses contain
2194 name/file/version-number triples. These snapshots are visible only
2197 A snapshot is a set of checked-in versions. So make sure that all the
2198 files are checked in and not locked when you make a snapshot.
2200 File renaming and deletion can create some difficulties with snapshots.
2201 This is not a VC-specific problem, but a general design issue in version
2202 control systems that no one has solved very well yet.
2204 If you rename a registered file, you need to rename its master along
2205 with it (the command @code{vc-rename-file} does this automatically). If
2206 you are using SCCS, you must also update the records of the snapshot, to
2207 mention the file by its new name (@code{vc-rename-file} does this,
2208 too). An old snapshot that refers to a master file that no longer
2209 exists under the recorded name is invalid; VC can no longer retrieve
2210 it. It would be beyond the scope of this manual to explain enough about
2211 RCS and SCCS to explain how to update the snapshots by hand.
2213 Using @code{vc-rename-file} makes the snapshot remain valid for
2214 retrieval, but it does not solve all problems. For example, some of the
2215 files in your program probably refer to others by name. At the very
2216 least, the makefile probably mentions the file that you renamed. If you
2217 retrieve an old snapshot, the renamed file is retrieved under its new
2218 name, which is not the name that the makefile expects. So the program
2219 won't really work as retrieved.
2221 @node Miscellaneous VC
2222 @subsection Miscellaneous Commands and Features of VC
2224 This section explains the less-frequently-used features of VC.
2227 * Change Logs and VC:: Generating a change log file from log entries.
2228 * Renaming and VC:: A command to rename both the source and master
2230 * Version Headers:: Inserting version control headers into working files.
2233 @node Change Logs and VC
2234 @subsubsection Change Logs and VC
2236 If you use RCS or CVS for a program and also maintain a change log
2237 file for it (@pxref{Change Log}), you can generate change log entries
2238 automatically from the version control log entries:
2243 @findex vc-update-change-log
2244 Visit the current directory's change log file and, for registered files
2245 in that directory, create new entries for versions checked in since the
2246 most recent entry in the change log file.
2247 (@code{vc-update-change-log}).
2249 This command works with RCS or CVS only, not with SCCS.
2252 As above, but only find entries for the current buffer's file.
2255 As above, but find entries for all the currently visited files that are
2256 maintained with version control. This works only with RCS, and it puts
2257 all entries in the log for the default directory, which may not be
2261 For example, suppose the first line of @file{ChangeLog} is dated
2262 1999-04-10, and that the only check-in since then was by Nathaniel
2263 Bowditch to @file{rcs2log} on 1999-05-22 with log text @samp{Ignore log
2264 messages that start with `#'.}. Then @kbd{C-x v a} visits
2265 @file{ChangeLog} and inserts text like this:
2272 1999-05-22 Nathaniel Bowditch <nat@@apn.org>
2274 * rcs2log: Ignore log messages that start with `#'.
2282 You can then edit the new change log entry further as you wish.
2284 Some of the new change log entries may duplicate what's already in
2285 ChangeLog. You will have to remove these duplicates by hand.
2287 Normally, the log entry for file @file{foo} is displayed as @samp{*
2288 foo: @var{text of log entry}}. The @samp{:} after @file{foo} is omitted
2289 if the text of the log entry starts with @w{@samp{(@var{functionname}):
2290 }}. For example, if the log entry for @file{vc.el} is
2291 @samp{(vc-do-command): Check call-process status.}, then the text in
2292 @file{ChangeLog} looks like this:
2299 1999-05-06 Nathaniel Bowditch <nat@@apn.org>
2301 * vc.el (vc-do-command): Check call-process status.
2308 When @kbd{C-x v a} adds several change log entries at once, it groups
2309 related log entries together if they all are checked in by the same
2310 author at nearly the same time. If the log entries for several such
2311 files all have the same text, it coalesces them into a single entry.
2312 For example, suppose the most recent check-ins have the following log
2316 @bullet{} For @file{vc.texinfo}: @samp{Fix expansion typos.}
2317 @bullet{} For @file{vc.el}: @samp{Don't call expand-file-name.}
2318 @bullet{} For @file{vc-hooks.el}: @samp{Don't call expand-file-name.}
2322 They appear like this in @file{ChangeLog}:
2329 1999-04-01 Nathaniel Bowditch <nat@@apn.org>
2331 * vc.texinfo: Fix expansion typos.
2333 * vc.el, vc-hooks.el: Don't call expand-file-name.
2340 Normally, @kbd{C-x v a} separates log entries by a blank line, but you
2341 can mark several related log entries to be clumped together (without an
2342 intervening blank line) by starting the text of each related log entry
2343 with a label of the form @w{@samp{@{@var{clumpname}@} }}. The label
2344 itself is not copied to @file{ChangeLog}. For example, suppose the log
2348 @bullet{} For @file{vc.texinfo}: @samp{@{expand@} Fix expansion typos.}
2349 @bullet{} For @file{vc.el}: @samp{@{expand@} Don't call expand-file-name.}
2350 @bullet{} For @file{vc-hooks.el}: @samp{@{expand@} Don't call expand-file-name.}
2354 Then the text in @file{ChangeLog} looks like this:
2361 1999-04-01 Nathaniel Bowditch <nat@@apn.org>
2363 * vc.texinfo: Fix expansion typos.
2364 * vc.el, vc-hooks.el: Don't call expand-file-name.
2371 A log entry whose text begins with @samp{#} is not copied to
2372 @file{ChangeLog}. For example, if you merely fix some misspellings in
2373 comments, you can log the change with an entry beginning with @samp{#}
2374 to avoid putting such trivia into @file{ChangeLog}.
2376 @node Renaming and VC
2377 @subsubsection Renaming VC Work Files and Master Files
2379 @findex vc-rename-file
2380 When you rename a registered file, you must also rename its master
2381 file correspondingly to get proper results. Use @code{vc-rename-file}
2382 to rename the source file as you specify, and rename its master file
2383 accordingly. It also updates any snapshots (@pxref{Snapshots}) that
2384 mention the file, so that they use the new name; despite this, the
2385 snapshot thus modified may not completely work (@pxref{Snapshot
2388 You cannot use @code{vc-rename-file} on a file that is locked by
2391 @node Version Headers
2392 @subsubsection Inserting Version Control Headers
2394 Sometimes it is convenient to put version identification strings
2395 directly into working files. Certain special strings called
2396 @dfn{version headers} are replaced in each successive version by the
2397 number of that version.
2399 If you are using RCS, and version headers are present in your working
2400 files, Emacs can use them to determine the current version and the
2401 locking state of the files. This is more reliable than referring to the
2402 master files, which is done when there are no version headers. Note
2403 that in a multi-branch environment, version headers are necessary to
2404 make VC behave correctly (@pxref{Multi-User Branching}).
2406 Searching for version headers is controlled by the variable
2407 @code{vc-consult-headers}. If it is non-@code{nil} (the default),
2408 Emacs searches for headers to determine the version number you are
2409 editing. Setting it to @code{nil} disables this feature.
2412 @findex vc-insert-headers
2413 You can use the @kbd{C-x v h} command (@code{vc-insert-headers}) to
2414 insert a suitable header string.
2418 Insert headers in a file for use with your version-control system.
2421 @vindex vc-header-alist
2422 The default header string is @samp{@w{$}Id$} for RCS and
2423 @samp{@w{%}W%} for SCCS. You can specify other headers to insert by
2424 setting the variable @code{vc-header-alist}. Its value is a list of
2425 elements of the form @code{(@var{program} . @var{string})} where
2426 @var{program} is @code{RCS} or @code{SCCS} and @var{string} is the
2429 Instead of a single string, you can specify a list of strings; then
2430 each string in the list is inserted as a separate header on a line of
2433 It is often necessary to use ``superfluous'' backslashes when
2434 writing the strings that you put in this variable. For instance, you
2435 might write @code{"$Id\$"} rather than @code{"$Id@w{$}"}. The extra
2436 backslash prevents the string constant from being interpreted as a
2437 header, if the Emacs Lisp file containing it is maintained with
2440 @vindex vc-comment-alist
2441 Each header is inserted surrounded by tabs, inside comment delimiters,
2442 on a new line at point. Normally the ordinary comment
2443 start and comment end strings of the current mode are used, but for
2444 certain modes, there are special comment delimiters for this purpose;
2445 the variable @code{vc-comment-alist} specifies them. Each element of
2446 this list has the form @code{(@var{mode} @var{starter} @var{ender})}.
2448 @vindex vc-static-header-alist
2449 The variable @code{vc-static-header-alist} specifies further strings
2450 to add based on the name of the buffer. Its value should be a list of
2451 elements of the form @code{(@var{regexp} . @var{format})}. Whenever
2452 @var{regexp} matches the buffer name, @var{format} is inserted as part
2453 of the header. A header line is inserted for each element that matches
2454 the buffer name, and for each string specified by
2455 @code{vc-header-alist}. The header line is made by processing the
2456 string from @code{vc-header-alist} with the format taken from the
2457 element. The default value for @code{vc-static-header-alist} is as follows:
2462 "\n#ifndef lint\nstatic char vcid[] = \"\%s\";\n\
2463 #endif /* lint */\n"))
2468 It specifies insertion of text of this form:
2474 static char vcid[] = "@var{string}";
2480 Note that the text above starts with a blank line.
2482 If you use more than one version header in a file, put them close
2483 together in the file. The mechanism in @code{revert-buffer} that
2484 preserves markers may not handle markers positioned between two version
2487 @node Customizing VC
2488 @subsection Customizing VC
2490 @vindex vc-handled-backends
2491 The variable @code{vc-handled-backends} determines which version
2492 control systems VC should handle. The default value is @code{(RCS CVS
2493 SCCS)}, so it contains all three version systems that are currently
2494 supported. If you want VC to ignore one or more of these systems,
2495 exclude its name from the list.
2497 The order of systems in the list is significant: when you visit a file
2498 registered in more than one system (@pxref{Local Version Control}),
2499 VC uses the system that comes first in @code{vc-handled-backends} by
2500 default. The order is also significant when you register a file for
2501 the first time, @pxref{Registering} for details.
2504 * General VC Options:: Options that apply to multiple back ends.
2505 * RCS and SCCS:: Options for RCS and SCCS.
2506 * CVS Options:: Options for CVS.
2509 @node General VC Options
2510 @subsubsection General Options
2512 @vindex vc-make-backup-files
2513 Emacs normally does not save backup files for source files that are
2514 maintained with version control. If you want to make backup files even
2515 for files that use version control, set the variable
2516 @code{vc-make-backup-files} to a non-@code{nil} value.
2518 @vindex vc-keep-workfiles
2519 Normally the work file exists all the time, whether it is locked or
2520 not. If you set @code{vc-keep-workfiles} to @code{nil}, then checking
2521 in a new version with @kbd{C-x v v} deletes the work file; but any
2522 attempt to visit the file with Emacs creates it again. (With CVS, work
2523 files are always kept.)
2525 @vindex vc-follow-symlinks
2526 Editing a version-controlled file through a symbolic link can be
2527 dangerous. It bypasses the version control system---you can edit the
2528 file without locking it, and fail to check your changes in. Also,
2529 your changes might overwrite those of another user. To protect against
2530 this, VC checks each symbolic link that you visit, to see if it points
2531 to a file under version control.
2533 The variable @code{vc-follow-symlinks} controls what to do when a
2534 symbolic link points to a version-controlled file. If it is @code{nil},
2535 VC only displays a warning message. If it is @code{t}, VC automatically
2536 follows the link, and visits the real file instead, telling you about
2537 this in the echo area. If the value is @code{ask} (the default), VC
2538 asks you each time whether to follow the link.
2540 @vindex vc-suppress-confirm
2541 If @code{vc-suppress-confirm} is non-@code{nil}, then @kbd{C-x v v}
2542 and @kbd{C-x v i} can save the current buffer without asking, and
2543 @kbd{C-x v u} also operates without asking for confirmation. (This
2544 variable does not affect @kbd{C-x v c}; that operation is so drastic
2545 that it should always ask for confirmation.)
2547 @vindex vc-command-messages
2548 VC mode does much of its work by running the shell commands for RCS,
2549 CVS and SCCS. If @code{vc-command-messages} is non-@code{nil}, VC
2550 displays messages to indicate which shell commands it runs, and
2551 additional messages when the commands finish.
2554 You can specify additional directories to search for version control
2555 programs by setting the variable @code{vc-path}. These directories
2556 are searched before the usual search path. It is rarely necessary to
2557 set this variable, because VC normally finds the proper files
2561 @subsubsection Options for RCS and SCCS
2563 @cindex non-strict locking (RCS)
2564 @cindex locking, non-strict (RCS)
2565 By default, RCS uses locking to coordinate the activities of several
2566 users, but there is a mode called @dfn{non-strict locking} in which
2567 you can check-in changes without locking the file first. Use
2568 @samp{rcs -U} to switch to non-strict locking for a particular file,
2569 see the @code{rcs} manual page for details.
2571 When deducing the version control state of an RCS file, VC first
2572 looks for an RCS version header string in the file (@pxref{Version
2573 Headers}). If there is no header string, VC normally looks at the
2574 file permissions of the work file; this is fast. But there might be
2575 situations when the file permissions cannot be trusted. In this case
2576 the master file has to be consulted, which is rather expensive. Also
2577 the master file can only tell you @emph{if} there's any lock on the
2578 file, but not whether your work file really contains that locked
2581 @vindex vc-consult-headers
2582 You can tell VC not to use version headers to determine the file
2583 status by setting @code{vc-consult-headers} to @code{nil}. VC then
2584 always uses the file permissions (if it is supposed to trust them), or
2585 else checks the master file.
2587 @vindex vc-mistrust-permissions
2588 You can specify the criterion for whether to trust the file
2589 permissions by setting the variable @code{vc-mistrust-permissions}.
2590 Its value can be @code{t} (always mistrust the file permissions and
2591 check the master file), @code{nil} (always trust the file
2592 permissions), or a function of one argument which makes the decision.
2593 The argument is the directory name of the @file{RCS} subdirectory. A
2594 non-@code{nil} value from the function says to mistrust the file
2595 permissions. If you find that the file permissions of work files are
2596 changed erroneously, set @code{vc-mistrust-permissions} to @code{t}.
2597 Then VC always checks the master file to determine the file's status.
2599 VC determines the version control state of files under SCCS much as
2600 with RCS. It does not consider SCCS version headers, though. Thus,
2601 the variable @code{vc-mistrust-permissions} affects SCCS use, but
2602 @code{vc-consult-headers} does not.
2605 @subsubsection Options specific for CVS
2607 @cindex locking (CVS)
2608 By default, CVS does not use locking to coordinate the activities of
2609 several users; anyone can change a work file at any time. However,
2610 there are ways to restrict this, resulting in behavior that resembles
2613 @cindex CVSREAD environment variable (CVS)
2614 For one thing, you can set the @env{CVSREAD} environment variable
2615 (the value you use makes no difference). If this variable is defined,
2616 CVS makes your work files read-only by default. In Emacs, you must
2617 type @kbd{C-x v v} to make the file writable, so that editing works
2618 in fact similar as if locking was used. Note however, that no actual
2619 locking is performed, so several users can make their files writable
2620 at the same time. When setting @env{CVSREAD} for the first time, make
2621 sure to check out all your modules anew, so that the file protections
2624 @cindex cvs watch feature
2625 @cindex watching files (CVS)
2626 Another way to achieve something similar to locking is to use the
2627 @dfn{watch} feature of CVS. If a file is being watched, CVS makes it
2628 read-only by default, and you must also use @kbd{C-x v v} in Emacs to
2629 make it writable. VC calls @code{cvs edit} to make the file writable,
2630 and CVS takes care to notify other developers of the fact that you
2631 intend to change the file. See the CVS documentation for details on
2632 using the watch feature.
2634 @vindex vc-cvs-stay-local
2635 @cindex remote repositories (CVS)
2636 When a file's repository is on a remote machine, VC tries to keep
2637 network interactions to a minimum. This is controlled by the variable
2638 @code{vc-cvs-stay-local}. If it is @code{t} (the default), then VC uses
2639 only the entry in the local CVS subdirectory to determine the file's
2640 state (and possibly information returned by previous CVS commands). One
2641 consequence of this is that when you have modified a file, and somebody
2642 else has already checked in other changes to the file, you are not
2643 notified of it until you actually try to commit. (But you can try to
2644 pick up any recent changes from the repository first, using @kbd{C-x v m
2645 @key{RET}}, @pxref{Merging}).
2647 @vindex vc-cvs-global-switches
2648 The variable @code{vc-cvs-global-switches} should be a string
2649 specifying switches to pass to CVS for all CVS operations.
2651 When @code{vc-cvs-stay-local} is @code{t}, VC also makes local
2652 version backups, so that simple diff and revert operations are
2653 completely local (@pxref{Version Backups}).
2655 On the other hand, if you set @code{vc-cvs-stay-local} to @code{nil},
2656 then VC queries the remote repository @emph{before} it decides what to
2657 do in @code{vc-next-action} (@kbd{C-x v v}), just as it does for local
2658 repositories. It also does not make any version backups.
2660 You can also set @code{vc-cvs-stay-local} to a regular expression
2661 that is matched against the repository host name; VC then stays local
2662 only for repositories from hosts that match the pattern.
2665 @section File Directories
2667 @cindex file directory
2668 @cindex directory listing
2669 The file system groups files into @dfn{directories}. A @dfn{directory
2670 listing} is a list of all the files in a directory. Emacs provides
2671 commands to create and delete directories, and to make directory
2672 listings in brief format (file names only) and verbose format (sizes,
2673 dates, and authors included). There is also a directory browser called
2674 Dired; see @ref{Dired}.
2677 @item C-x C-d @var{dir-or-pattern} @key{RET}
2678 Display a brief directory listing (@code{list-directory}).
2679 @item C-u C-x C-d @var{dir-or-pattern} @key{RET}
2680 Display a verbose directory listing.
2681 @item M-x make-directory @key{RET} @var{dirname} @key{RET}
2682 Create a new directory named @var{dirname}.
2683 @item M-x delete-directory @key{RET} @var{dirname} @key{RET}
2684 Delete the directory named @var{dirname}. It must be empty,
2685 or you get an error.
2688 @findex list-directory
2690 The command to display a directory listing is @kbd{C-x C-d}
2691 (@code{list-directory}). It reads using the minibuffer a file name
2692 which is either a directory to be listed or a wildcard-containing
2693 pattern for the files to be listed. For example,
2696 C-x C-d /u2/emacs/etc @key{RET}
2700 lists all the files in directory @file{/u2/emacs/etc}. Here is an
2701 example of specifying a file name pattern:
2704 C-x C-d /u2/emacs/src/*.c @key{RET}
2707 Normally, @kbd{C-x C-d} displays a brief directory listing containing
2708 just file names. A numeric argument (regardless of value) tells it to
2709 make a verbose listing including sizes, dates, and owners (like
2712 @vindex list-directory-brief-switches
2713 @vindex list-directory-verbose-switches
2714 The text of a directory listing is mostly obtained by running
2715 @code{ls} in an inferior process. Two Emacs variables control the
2716 switches passed to @code{ls}: @code{list-directory-brief-switches} is
2717 a string giving the switches to use in brief listings (@code{"-CF"} by
2718 default), and @code{list-directory-verbose-switches} is a string
2719 giving the switches to use in a verbose listing (@code{"-l"} by
2722 @vindex directory-free-space-program
2723 @vindex directory-free-space-args
2724 Emacs adds information about the amount of free space on the disk
2725 that contains the directory. To do this, it runs the program
2726 specified by @code{directory-free-space-program} with arguments
2727 @code{directory-free-space-args}.
2729 @node Comparing Files
2730 @section Comparing Files
2731 @cindex comparing files
2734 @vindex diff-switches
2735 The command @kbd{M-x diff} compares two files, displaying the
2736 differences in an Emacs buffer named @samp{*diff*}. It works by
2737 running the @code{diff} program, using options taken from the variable
2738 @code{diff-switches}. The value of @code{diff-switches} should be a
2739 string; the default is @code{"-c"} to specify a context diff.
2741 The buffer @samp{*diff*} has Compilation mode as its major mode, so
2742 you can use @kbd{C-x `} to visit successive changed locations in the two
2743 source files. You can also move to a particular hunk of changes and
2744 type @key{RET} or @kbd{C-c C-c}, or click @kbd{Mouse-2} on it, to move
2745 to the corresponding source location. You can also use the other
2746 special commands of Compilation mode: @key{SPC} and @key{DEL} for
2747 scrolling, and @kbd{M-p} and @kbd{M-n} for cursor motion.
2751 The command @kbd{M-x diff-backup} compares a specified file with its most
2752 recent backup. If you specify the name of a backup file,
2753 @code{diff-backup} compares it with the source file that it is a backup
2756 @findex compare-windows
2757 The command @kbd{M-x compare-windows} compares the text in the current
2758 window with that in the next window. Comparison starts at point in each
2759 window, and each starting position is pushed on the mark ring in its
2760 respective buffer. Then point moves forward in each window, a character
2761 at a time, until a mismatch between the two windows is reached. Then
2762 the command is finished. For more information about windows in Emacs,
2765 @vindex compare-ignore-case
2766 With a numeric argument, @code{compare-windows} ignores changes in
2767 whitespace. If the variable @code{compare-ignore-case} is
2768 non-@code{nil}, it ignores differences in case as well.
2774 Differences between versions of files are often distributed as
2775 @dfn{patches}, which are the output from @command{diff} or a version
2776 control system that uses @command{diff}. @kbd{M-x diff-mode} turns on
2777 Diff mode, a major mode for viewing and editing patches, either as
2778 ``unified diffs'' or ``context diffs.''
2782 @cindex failed merges
2783 @cindex merges, failed
2784 @cindex comparing 3 files (@code{diff3})
2785 You can use @kbd{M-x smerge-mode} to turn on Smerge mode, a minor
2786 mode for editing output from the @command{diff3} program. This is
2787 typically the result of a failed merge from a version control system
2788 ``update'' outside VC, due to conflicting changes to a file. Smerge
2789 mode provides commands to resolve conflicts by selecting specific
2792 See also @ref{Emerge}, and @ref{Top,,, ediff, The Ediff Manual}, for
2793 convenient facilities for merging two similar files.
2796 @section Miscellaneous File Operations
2798 Emacs has commands for performing many other operations on files.
2799 All operate on one file; they do not accept wildcard file names.
2805 @kbd{M-x view-file} allows you to scan or read a file by sequential
2806 screenfuls. It reads a file name argument using the minibuffer. After
2807 reading the file into an Emacs buffer, @code{view-file} displays the
2808 beginning. You can then type @key{SPC} to scroll forward one windowful,
2809 or @key{DEL} to scroll backward. Various other commands are provided
2810 for moving around in the file, but none for changing it; type @kbd{?}
2811 while viewing for a list of them. They are mostly the same as normal
2812 Emacs cursor motion commands. To exit from viewing, type @kbd{q}.
2813 The commands for viewing are defined by a special major mode called View
2816 A related command, @kbd{M-x view-buffer}, views a buffer already present
2817 in Emacs. @xref{Misc Buffer}.
2821 @kbd{M-x insert-file} (also @kbd{C-x i}) inserts a copy of the
2822 contents of the specified file into the current buffer at point,
2823 leaving point unchanged before the contents and the mark after them.
2825 @findex write-region
2826 @kbd{M-x write-region} is the inverse of @kbd{M-x insert-file}; it
2827 copies the contents of the region into the specified file. @kbd{M-x
2828 append-to-file} adds the text of the region to the end of the specified
2829 file. @xref{Accumulating Text}.
2832 @cindex deletion (of files)
2833 @kbd{M-x delete-file} deletes the specified file, like the @code{rm}
2834 command in the shell. If you are deleting many files in one directory, it
2835 may be more convenient to use Dired (@pxref{Dired}).
2838 @kbd{M-x rename-file} reads two file names @var{old} and @var{new} using
2839 the minibuffer, then renames file @var{old} as @var{new}. If the file name
2840 @var{new} already exists, you must confirm with @kbd{yes} or renaming is not
2841 done; this is because renaming causes the old meaning of the name @var{new}
2842 to be lost. If @var{old} and @var{new} are on different file systems, the
2843 file @var{old} is copied and deleted.
2845 @findex add-name-to-file
2846 @cindex hard links (creation)
2847 The similar command @kbd{M-x add-name-to-file} is used to add an
2848 additional name to an existing file without removing its old name.
2849 The new name is created as a ``hard link'' to the existing file.
2850 The new name must belong on the same file system that the file is on.
2851 On Windows, this command works only if the file resides in an NTFS
2852 file system. On MS-DOS, it works by copying the file.
2855 @cindex copying files
2856 @kbd{M-x copy-file} reads the file @var{old} and writes a new file named
2857 @var{new} with the same contents. Confirmation is required if a file named
2858 @var{new} already exists, because copying has the consequence of overwriting
2859 the old contents of the file @var{new}.
2861 @findex make-symbolic-link
2862 @kbd{M-x make-symbolic-link} reads two file names @var{target} and
2863 @var{linkname}, then creates a symbolic link named @var{linkname}, which
2864 points at @var{target}. The effect is that future attempts to open file
2865 @var{linkname} will refer to whatever file is named @var{target} at the
2866 time the opening is done, or will get an error if the name @var{target} is
2867 not in use at that time. This command does not expand the argument
2868 @var{target}, so that it allows you to specify a relative name
2869 as the target of the link.
2871 Confirmation is required when creating the link if @var{linkname} is
2872 in use. Note that not all systems support symbolic links; on systems
2873 that don't support them, this command is not defined.
2875 @node Compressed Files
2876 @section Accessing Compressed Files
2878 @cindex uncompression
2879 @cindex Auto Compression mode
2880 @cindex mode, Auto Compression
2883 @findex auto-compression-mode
2884 @vindex auto-compression-mode
2885 Emacs comes with a library that can automatically uncompress
2886 compressed files when you visit them, and automatically recompress them
2887 if you alter them and save them. To enable this feature, type the
2888 command @kbd{M-x auto-compression-mode}. You can enable it permanently
2889 by customizing the option @code{auto-compression-mode}.
2891 When automatic compression (which implies automatic uncompression as
2892 well) is enabled, Emacs recognizes compressed files by their file names.
2893 File names ending in @samp{.gz} indicate a file compressed with
2894 @code{gzip}. Other endings indicate other compression programs.
2896 Automatic uncompression and compression apply to all the operations in
2897 which Emacs uses the contents of a file. This includes visiting it,
2898 saving it, inserting its contents into a buffer, loading it, and byte
2902 @section File Archives
2905 @cindex file archives
2907 A file whose name ends in @samp{.tar} is normally an @dfn{archive}
2908 made by the @code{tar} program. Emacs views these files in a special
2909 mode called Tar mode which provides a Dired-like list of the contents
2910 (@pxref{Dired}). You can move around through the list just as you
2911 would in Dired, and visit the subfiles contained in the archive.
2912 However, not all Dired commands are available in Tar mode.
2914 If you enable Auto Compression mode (@pxref{Compressed Files}), then
2915 Tar mode is used also for compressed archives---files with extensions
2916 @samp{.tgz}, @code{.tar.Z} and @code{.tar.gz}.
2918 The keys @kbd{e}, @kbd{f} and @key{RET} all extract a component file
2919 into its own buffer. You can edit it there and when you save the buffer
2920 the edited version will replace the version in the Tar buffer. @kbd{v}
2921 extracts a file into a buffer in View mode. @kbd{o} extracts the file
2922 and displays it in another window, so you could edit the file and
2923 operate on the archive simultaneously. @kbd{d} marks a file for
2924 deletion when you later use @kbd{x}, and @kbd{u} unmarks a file, as in
2925 Dired. @kbd{C} copies a file from the archive to disk and @kbd{R}
2926 renames a file. @kbd{g} reverts the buffer from the archive on disk.
2928 The keys @kbd{M}, @kbd{G}, and @kbd{O} change the file's permission
2929 bits, group, and owner, respectively.
2931 If your display supports colors and the mouse, moving the mouse
2932 pointer across a file name highlights that file name, indicating that
2933 you can click on it. Clicking @kbd{Mouse-2} on the highlighted file
2934 name extracts the file into a buffer and displays that buffer.
2936 Saving the Tar buffer writes a new version of the archive to disk with
2937 the changes you made to the components.
2939 You don't need the @code{tar} program to use Tar mode---Emacs reads
2940 the archives directly. However, accessing compressed archives
2941 requires the appropriate uncompression program.
2943 @cindex Archive mode
2944 @cindex mode, archive
2955 @cindex Java class archives
2956 @cindex unzip archives
2957 A separate but similar Archive mode is used for archives produced by
2958 the programs @code{arc}, @code{jar}, @code{lzh}, @code{zip}, and
2959 @code{zoo}, which have extensions corresponding to the program names.
2961 The key bindings of Archive mode are similar to those in Tar mode,
2962 with the addition of the @kbd{m} key which marks a file for subsequent
2963 operations, and @kbd{M-@key{DEL}} which unmarks all the marked files.
2964 Also, the @kbd{a} key toggles the display of detailed file
2965 information, for those archive types where it won't fit in a single
2966 line. Operations such as renaming a subfile, or changing its mode or
2967 owner, are supported only for some of the archive formats.
2969 Unlike Tar mode, Archive mode runs the archiving program to unpack
2970 and repack archives. Details of the program names and their options
2971 can be set in the @samp{Archive} Customize group. However, you don't
2972 need these programs to look at the archive table of contents, only to
2973 extract or manipulate the subfiles in the archive.
2976 @section Remote Files
2980 @cindex remote file access
2981 You can refer to files on other machines using a special file name
2986 /@var{host}:@var{filename}
2987 /@var{user}@@@var{host}:@var{filename}
2988 /@var{user}@@@var{host}#@var{port}:@var{filename}
2989 /@var{method}:@var{user}@@@var{host}:@var{filename}
2990 /@var{method}:@var{user}@@@var{host}#@var{port}:@var{filename}
2995 When you do this, Emacs may use the FTP program to access files on the
2996 remote host, or Emacs may use a remote-login program (such as
2997 @command{ssh}, @command{rlogin}, or @command{telnet}) to do this.
2999 You can always specify in the file name which method should be used to
3000 access the remote files, for example
3001 @file{/ftp:@var{user}@@@var{host}:@var{filename}} uses FTP, whereas
3002 @file{/ssh:@var{user}@@@var{host}:@var{filename}} uses @command{ssh}.
3003 When you don't specify a method in the file name, Emacs determines a
3004 default method according to the following rules:
3008 If the host name starts with @samp{ftp.} (with dot), then Emacs assumes
3009 the @command{ftp} method.
3011 If the user name is @samp{ftp} or @samp{anonymous}, then Emacs assumes
3012 the @command{ftp} method.
3014 Otherwise, Emacs assumes the @command{ssh} method.
3018 Remote file access through FTP is handled by the Ange-FTP package, which
3019 is documented in the following. Remote file access through the other
3020 methods is handled by the Tramp package, which has its own manual.
3021 @xref{Top, The Tramp Manual,, tramp, The Tramp Manual}.
3023 When the Ange-FTP package is used, Emacs logs in through FTP using your
3024 user name or the name @var{user}. It may ask you for a password from
3025 time to time; this is used for logging in on @var{host}. The form using
3026 @var{port} allows you to access servers running on a non-default TCP
3029 @cindex backups for remote files
3030 @vindex ange-ftp-make-backup-files
3031 If you want to disable backups for remote files, set the variable
3032 @code{ange-ftp-make-backup-files} to @code{nil}.
3034 By default, the auto-save files (@pxref{Auto Save Files}) for remote
3035 files are made in the temporary file directory on the local machine.
3036 This is achieved using the variable @code{auto-save-file-name-transforms}.
3039 @vindex ange-ftp-default-user
3040 @cindex user name for remote file access
3041 Normally, if you do not specify a user name in a remote file name,
3042 that means to use your own user name. But if you set the variable
3043 @code{ange-ftp-default-user} to a string, that string is used instead.
3044 (The Emacs package that implements FTP file access is called
3047 @cindex anonymous FTP
3048 @vindex ange-ftp-generate-anonymous-password
3049 To visit files accessible by anonymous FTP, you use special user
3050 names @samp{anonymous} or @samp{ftp}. Passwords for these user names
3051 are handled specially. The variable
3052 @code{ange-ftp-generate-anonymous-password} controls what happens: if
3053 the value of this variable is a string, then that string is used as
3054 the password; if non-@code{nil} (the default), then the value of
3055 @code{user-mail-address} is used; if @code{nil}, the user is prompted
3056 for a password as normal.
3058 @cindex firewall, and accessing remote files
3059 @cindex gateway, and remote file access with @code{ange-ftp}
3060 @vindex ange-ftp-smart-gateway
3061 @vindex ange-ftp-gateway-host
3062 Sometimes you may be unable to access files on a remote machine
3063 because a @dfn{firewall} in between blocks the connection for security
3064 reasons. If you can log in on a @dfn{gateway} machine from which the
3065 target files @emph{are} accessible, and whose FTP server supports
3066 gatewaying features, you can still use remote file names; all you have
3067 to do is specify the name of the gateway machine by setting the
3068 variable @code{ange-ftp-gateway-host}, and set
3069 @code{ange-ftp-smart-gateway} to @code{t}. Otherwise you may be able
3070 to make remote file names work, but the procedure is complex. You can
3071 read the instructions by typing @kbd{M-x finder-commentary @key{RET}
3072 ange-ftp @key{RET}}.
3074 @vindex file-name-handler-alist
3075 @cindex disabling remote files
3076 You can entirely turn off the FTP file name feature by removing the
3077 entries @code{ange-ftp-completion-hook-function} and
3078 @code{ange-ftp-hook-function} from the variable
3079 @code{file-name-handler-alist}. You can turn off the feature in
3080 individual cases by quoting the file name with @samp{/:} (@pxref{Quoted
3083 @node Quoted File Names
3084 @section Quoted File Names
3086 @cindex quoting file names
3087 You can @dfn{quote} an absolute file name to prevent special
3088 characters and syntax in it from having their special effects.
3089 The way to do this is to add @samp{/:} at the beginning.
3091 For example, you can quote a local file name which appears remote, to
3092 prevent it from being treated as a remote file name. Thus, if you have
3093 a directory named @file{/foo:} and a file named @file{bar} in it, you
3094 can refer to that file in Emacs as @samp{/:/foo:/bar}.
3096 @samp{/:} can also prevent @samp{~} from being treated as a special
3097 character for a user's home directory. For example, @file{/:/tmp/~hack}
3098 refers to a file whose name is @file{~hack} in directory @file{/tmp}.
3100 Quoting with @samp{/:} is also a way to enter in the minibuffer a
3101 file name that contains @samp{$}. In order for this to work, the
3102 @samp{/:} must be at the beginning of the minibuffer contents. (You
3103 can also double each @samp{$}; see @ref{File Names with $}.)
3105 You can also quote wildcard characters with @samp{/:}, for visiting.
3106 For example, @file{/:/tmp/foo*bar} visits the file
3107 @file{/tmp/foo*bar}.
3109 Another method of getting the same result is to enter
3110 @file{/tmp/foo[*]bar}, which is a wildcard specification that matches
3111 only @file{/tmp/foo*bar}. However, in many cases there is no need to
3112 quote the wildcard characters because even unquoted they give the
3113 right result. For example, if the only file name in @file{/tmp} that
3114 starts with @samp{foo} and ends with @samp{bar} is @file{foo*bar},
3115 then specifying @file{/tmp/foo*bar} will visit only
3116 @file{/tmp/foo*bar}.
3118 @node File Name Cache
3119 @section File Name Cache
3121 @cindex file name caching
3122 @cindex cache of file names
3125 @findex file-cache-minibuffer-complete
3126 You can use the @dfn{file name cache} to make it easy to locate a
3127 file by name, without having to remember exactly where it is located.
3128 When typing a file name in the minibuffer, @kbd{C-@key{tab}}
3129 (@code{file-cache-minibuffer-complete}) completes it using the file
3130 name cache. If you repeat @kbd{C-@key{tab}}, that cycles through the
3131 possible completions of what you had originally typed. Note that the
3132 @kbd{C-@key{tab}} character cannot be typed on most text-only
3135 The file name cache does not fill up automatically. Instead, you
3136 load file names into the cache using these commands:
3138 @findex file-cache-add-directory
3140 @item M-x file-cache-add-directory @key{RET} @var{directory} @key{RET}
3141 Add each file name in @var{directory} to the file name cache.
3142 @item M-x file-cache-add-directory-using-find @key{RET} @var{directory} @key{RET}
3143 Add each file name in @var{directory} and all of its nested
3144 subdirectories to the file name cache.
3145 @item M-x file-cache-add-directory-using-locate @key{RET} @var{directory} @key{RET}
3146 Add each file name in @var{directory} and all of its nested
3147 subdirectories to the file name cache, using @command{locate} to find
3149 @item M-x file-cache-add-directory-list @key{RET} @var{variable} @key{RET}
3150 Add each file name in each directory listed in @var{variable}
3151 to the file name cache. @var{variable} should be a Lisp variable
3152 such as @code{load-path} or @code{exec-path}, whose value is a list
3154 @item M-x file-cache-clear-cache @key{RET}
3155 Clear the cache; that is, remove all file names from it.
3158 @node File Conveniences
3159 @section Convenience Features for Finding Files
3161 @findex recentf-mode
3162 @vindex recentf-mode
3163 @findex recentf-save-list
3164 @findex recentf-edit-list
3165 If you enable Recentf mode, with @kbd{M-x recentf-mode}, the
3166 @samp{File} menu includes a submenu containing a list of recently
3167 opened files. @kbd{M-x recentf-save-list} saves the current
3168 @code{recent-file-list} to a file, and @kbd{M-x recentf-edit-list}
3171 @findex auto-image-file-mode
3172 @findex mode, auto-image-file
3173 @cindex images, visiting
3174 @cindex visiting image files
3175 @vindex image-file-name-regexps
3176 @vindex image-file-name-extensions
3177 When Auto-image-file minor mode is enabled, visiting an image file
3178 displays it as an image, not as text. Likewise, inserting an image
3179 file into a buffer inserts it as an image. This works only when Emacs
3180 can display the relevant image type. The variables
3181 @code{image-file-name-extensions} or @code{image-file-name-regexps}
3182 control which file names are recognized as containing images.
3184 The @kbd{M-x ffap} command generalizes @code{find-file} with more
3185 powerful heuristic defaults (@pxref{FFAP}), often based on the text at
3186 point. Partial Completion mode offers other features extending
3187 @code{find-file}, which can be used with @code{ffap}.
3188 @xref{Completion Options}.
3191 arch-tag: 768d32cb-e15a-4cc1-b7bf-62c00ee12250