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6bf7aab6 | 1 | @c This is part of the Emacs manual. |
259a88ca | 2 | @c Copyright (C) 1985,86,87,93,94,95,97,99, 2000 Free Software Foundation, Inc. |
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3 | @c See file emacs.texi for copying conditions. |
4 | @node Files, Buffers, Fixit, Top | |
5 | @chapter File Handling | |
6 | @cindex files | |
7 | ||
8 | The operating system stores data permanently in named @dfn{files}. So | |
9 | most of the text you edit with Emacs comes from a file and is ultimately | |
10 | stored in a file. | |
11 | ||
12 | To edit a file, you must tell Emacs to read the file and prepare a | |
13 | buffer containing a copy of the file's text. This is called | |
14 | @dfn{visiting} the file. Editing commands apply directly to text in the | |
15 | buffer; that is, to the copy inside Emacs. Your changes appear in the | |
16 | file itself only when you @dfn{save} the buffer back into the file. | |
17 | ||
18 | In addition to visiting and saving files, Emacs can delete, copy, | |
19 | rename, and append to files, keep multiple versions of them, and operate | |
20 | on file directories. | |
21 | ||
22 | @menu | |
23 | * File Names:: How to type and edit file-name arguments. | |
24 | * Visiting:: Visiting a file prepares Emacs to edit the file. | |
25 | * Saving:: Saving makes your changes permanent. | |
26 | * Reverting:: Reverting cancels all the changes not saved. | |
27 | * Auto Save:: Auto Save periodically protects against loss of data. | |
28 | * File Aliases:: Handling multiple names for one file. | |
29 | * Version Control:: Version control systems (RCS, CVS and SCCS). | |
30 | * Directories:: Creating, deleting, and listing file directories. | |
31 | * Comparing Files:: Finding where two files differ. | |
32 | * Misc File Ops:: Other things you can do on files. | |
33 | * Compressed Files:: Accessing compressed files. | |
259a88ca | 34 | * File Archives:: Operating on tar, zip, jar etc. archive files. |
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35 | * Remote Files:: Accessing files on other sites. |
36 | * Quoted File Names:: Quoting special characters in file names. | |
f02d86a3 | 37 | * File Name Cache:: Completion against a list of files you often use. |
9a98ef18 | 38 | * File Conveniences:: Convenience Features for Finding Files. |
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39 | @end menu |
40 | ||
41 | @node File Names | |
42 | @section File Names | |
43 | @cindex file names | |
44 | ||
45 | Most Emacs commands that operate on a file require you to specify the | |
46 | file name. (Saving and reverting are exceptions; the buffer knows which | |
47 | file name to use for them.) You enter the file name using the | |
48 | minibuffer (@pxref{Minibuffer}). @dfn{Completion} is available, to make | |
49 | it easier to specify long file names. @xref{Completion}. | |
50 | ||
51 | For most operations, there is a @dfn{default file name} which is used | |
52 | if you type just @key{RET} to enter an empty argument. Normally the | |
53 | default file name is the name of the file visited in the current buffer; | |
54 | this makes it easy to operate on that file with any of the Emacs file | |
55 | commands. | |
56 | ||
57 | @vindex default-directory | |
58 | Each buffer has a default directory, normally the same as the | |
59 | directory of the file visited in that buffer. When you enter a file | |
60 | name without a directory, the default directory is used. If you specify | |
61 | a directory in a relative fashion, with a name that does not start with | |
62 | a slash, it is interpreted with respect to the default directory. The | |
63 | default directory is kept in the variable @code{default-directory}, | |
64 | which has a separate value in every buffer. | |
65 | ||
66 | For example, if the default file name is @file{/u/rms/gnu/gnu.tasks} then | |
67 | the default directory is @file{/u/rms/gnu/}. If you type just @samp{foo}, | |
68 | which does not specify a directory, it is short for @file{/u/rms/gnu/foo}. | |
69 | @samp{../.login} would stand for @file{/u/rms/.login}. @samp{new/foo} | |
70 | would stand for the file name @file{/u/rms/gnu/new/foo}. | |
71 | ||
72 | @findex cd | |
73 | @findex pwd | |
74 | The command @kbd{M-x pwd} prints the current buffer's default | |
75 | directory, and the command @kbd{M-x cd} sets it (to a value read using | |
76 | the minibuffer). A buffer's default directory changes only when the | |
77 | @code{cd} command is used. A file-visiting buffer's default directory | |
78 | is initialized to the directory of the file that is visited there. If | |
79 | you create a buffer with @kbd{C-x b}, its default directory is copied | |
80 | from that of the buffer that was current at the time. | |
81 | ||
82 | @vindex insert-default-directory | |
83 | The default directory actually appears in the minibuffer when the | |
84 | minibuffer becomes active to read a file name. This serves two | |
85 | purposes: it @emph{shows} you what the default is, so that you can type | |
86 | a relative file name and know with certainty what it will mean, and it | |
87 | allows you to @emph{edit} the default to specify a different directory. | |
88 | This insertion of the default directory is inhibited if the variable | |
89 | @code{insert-default-directory} is set to @code{nil}. | |
90 | ||
91 | Note that it is legitimate to type an absolute file name after you | |
92 | enter the minibuffer, ignoring the presence of the default directory | |
93 | name as part of the text. The final minibuffer contents may look | |
94 | invalid, but that is not so. For example, if the minibuffer starts out | |
95 | with @samp{/usr/tmp/} and you add @samp{/x1/rms/foo}, you get | |
96 | @samp{/usr/tmp//x1/rms/foo}; but Emacs ignores everything through the | |
97 | first slash in the double slash; the result is @samp{/x1/rms/foo}. | |
98 | @xref{Minibuffer File}. | |
99 | ||
100 | @samp{$} in a file name is used to substitute environment variables. | |
f02d86a3 | 101 | For example, if you have used the shell command @command{export |
60a96371 | 102 | FOO=rms/hacks} to set up an environment variable named @env{FOO}, then |
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103 | you can use @file{/u/$FOO/test.c} or @file{/u/$@{FOO@}/test.c} as an |
104 | abbreviation for @file{/u/rms/hacks/test.c}. The environment variable | |
105 | name consists of all the alphanumeric characters after the @samp{$}; | |
106 | alternatively, it may be enclosed in braces after the @samp{$}. Note | |
107 | that shell commands to set environment variables affect Emacs only if | |
108 | done before Emacs is started. | |
109 | ||
110 | To access a file with @samp{$} in its name, type @samp{$$}. This pair | |
111 | is converted to a single @samp{$} at the same time as variable | |
112 | substitution is performed for single @samp{$}. Alternatively, quote the | |
113 | whole file name with @samp{/:} (@pxref{Quoted File Names}). | |
114 | ||
115 | @findex substitute-in-file-name | |
116 | The Lisp function that performs the substitution is called | |
117 | @code{substitute-in-file-name}. The substitution is performed only on | |
118 | file names read as such using the minibuffer. | |
119 | ||
120 | You can include non-ASCII characters in file names if you set the | |
121 | variable @code{file-name-coding-system} to a non-@code{nil} value. | |
122 | @xref{Specify Coding}. | |
123 | ||
124 | @node Visiting | |
125 | @section Visiting Files | |
126 | @cindex visiting files | |
127 | ||
128 | @c WideCommands | |
129 | @table @kbd | |
130 | @item C-x C-f | |
131 | Visit a file (@code{find-file}). | |
132 | @item C-x C-r | |
133 | Visit a file for viewing, without allowing changes to it | |
134 | (@code{find-file-read-only}). | |
135 | @item C-x C-v | |
136 | Visit a different file instead of the one visited last | |
137 | (@code{find-alternate-file}). | |
138 | @item C-x 4 f | |
139 | Visit a file, in another window (@code{find-file-other-window}). Don't | |
140 | alter what is displayed in the selected window. | |
141 | @item C-x 5 f | |
142 | Visit a file, in a new frame (@code{find-file-other-frame}). Don't | |
143 | alter what is displayed in the selected frame. | |
144 | @item M-x find-file-literally | |
145 | Visit a file with no conversion of the contents. | |
146 | @end table | |
147 | ||
148 | @cindex files, visiting and saving | |
149 | @cindex visiting files | |
150 | @cindex saving files | |
151 | @dfn{Visiting} a file means copying its contents into an Emacs buffer | |
152 | so you can edit them. Emacs makes a new buffer for each file that you | |
153 | visit. We say that this buffer is visiting the file that it was created | |
154 | to hold. Emacs constructs the buffer name from the file name by | |
155 | throwing away the directory, keeping just the name proper. For example, | |
156 | a file named @file{/usr/rms/emacs.tex} would get a buffer named | |
157 | @samp{emacs.tex}. If there is already a buffer with that name, a unique | |
158 | name is constructed by appending @samp{<2>}, @samp{<3>}, or so on, using | |
159 | the lowest number that makes a name that is not already in use. | |
160 | ||
161 | Each window's mode line shows the name of the buffer that is being displayed | |
162 | in that window, so you can always tell what buffer you are editing. | |
163 | ||
164 | The changes you make with editing commands are made in the Emacs | |
165 | buffer. They do not take effect in the file that you visited, or any | |
166 | place permanent, until you @dfn{save} the buffer. Saving the buffer | |
167 | means that Emacs writes the current contents of the buffer into its | |
168 | visited file. @xref{Saving}. | |
169 | ||
170 | @cindex modified (buffer) | |
171 | If a buffer contains changes that have not been saved, we say the | |
172 | buffer is @dfn{modified}. This is important because it implies that | |
173 | some changes will be lost if the buffer is not saved. The mode line | |
174 | displays two stars near the left margin to indicate that the buffer is | |
175 | modified. | |
176 | ||
177 | @kindex C-x C-f | |
178 | @findex find-file | |
179 | To visit a file, use the command @kbd{C-x C-f} (@code{find-file}). Follow | |
180 | the command with the name of the file you wish to visit, terminated by a | |
181 | @key{RET}. | |
182 | ||
183 | The file name is read using the minibuffer (@pxref{Minibuffer}), with | |
184 | defaulting and completion in the standard manner (@pxref{File Names}). | |
185 | While in the minibuffer, you can abort @kbd{C-x C-f} by typing @kbd{C-g}. | |
186 | ||
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187 | @cindex file selection dialog |
188 | When Emacs is built with a suitable GUI toolkit, it pops up the | |
189 | standard File Selection dialog of that toolkit instead of prompting for | |
190 | the file name in the minibuffer. On Unix and GNU/Linux platforms, Emacs | |
191 | does that when built with LessTif and Motif toolkits; on MS-Windows, the | |
192 | GUI version does that by default. | |
193 | ||
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194 | Your confirmation that @kbd{C-x C-f} has completed successfully is the |
195 | appearance of new text on the screen and a new buffer name in the mode | |
196 | line. If the specified file does not exist and could not be created, or | |
197 | cannot be read, then you get an error, with an error message displayed | |
198 | in the echo area. | |
199 | ||
200 | If you visit a file that is already in Emacs, @kbd{C-x C-f} does not make | |
201 | another copy. It selects the existing buffer containing that file. | |
202 | However, before doing so, it checks that the file itself has not changed | |
203 | since you visited or saved it last. If the file has changed, a warning | |
204 | message is printed. @xref{Interlocking,,Simultaneous Editing}. | |
205 | ||
206 | @cindex creating files | |
207 | What if you want to create a new file? Just visit it. Emacs prints | |
208 | @samp{(New File)} in the echo area, but in other respects behaves as if | |
209 | you had visited an existing empty file. If you make any changes and | |
210 | save them, the file is created. | |
211 | ||
212 | Emacs recognizes from the contents of a file which convention it uses | |
213 | to separate lines---newline (used on GNU/Linux and on Unix), | |
214 | carriage-return linefeed (used on Microsoft systems), or just | |
215 | carriage-return (used on the Macintosh)---and automatically converts the | |
216 | contents to the normal Emacs convention, which is that the newline | |
217 | character separates lines. This is a part of the general feature of | |
218 | coding system conversion (@pxref{Coding Systems}), and makes it possible | |
219 | to edit files imported from various different operating systems with | |
220 | equal convenience. If you change the text and save the file, Emacs | |
221 | performs the inverse conversion, changing newlines back into | |
222 | carriage-return linefeed or just carriage-return if appropriate. | |
223 | ||
224 | @vindex find-file-run-dired | |
225 | If the file you specify is actually a directory, @kbd{C-x C-f} invokes | |
226 | Dired, the Emacs directory browser, so that you can ``edit'' the contents | |
227 | of the directory (@pxref{Dired}). Dired is a convenient way to delete, | |
228 | look at, or operate on the files in the directory. However, if the | |
229 | variable @code{find-file-run-dired} is @code{nil}, then it is an error | |
230 | to try to visit a directory. | |
231 | ||
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232 | @cindex wildcard characters in file names |
233 | @vindex find-file-wildcards | |
f02d86a3 RS |
234 | If the file name you specify contains shell-style wildcard |
235 | characters, Emacs visits all the files that match it. Wildcards | |
236 | comprise @samp{?}, @samp{*} and @samp{[@dots{}]} sequences. | |
237 | @xref{Quoted File Names}, for how to visit a file whose name actually | |
238 | contains wildcard characters. You can disable the wildcard feature by | |
7ed32bd8 | 239 | customizing @code{find-file-wildcards}. |
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240 | |
241 | If you visit a file that the operating system won't let you modify, | |
242 | Emacs makes the buffer read-only, so that you won't go ahead and make | |
243 | changes that you'll have trouble saving afterward. You can make the | |
244 | buffer writable with @kbd{C-x C-q} (@code{vc-toggle-read-only}). | |
245 | @xref{Misc Buffer}. | |
246 | ||
247 | @kindex C-x C-r | |
248 | @findex find-file-read-only | |
249 | Occasionally you might want to visit a file as read-only in order to | |
250 | protect yourself from entering changes accidentally; do so by visiting | |
251 | the file with the command @kbd{C-x C-r} (@code{find-file-read-only}). | |
252 | ||
253 | @kindex C-x C-v | |
254 | @findex find-alternate-file | |
255 | If you visit a nonexistent file unintentionally (because you typed the | |
256 | wrong file name), use the @kbd{C-x C-v} command | |
257 | (@code{find-alternate-file}) to visit the file you really wanted. | |
258 | @kbd{C-x C-v} is similar to @kbd{C-x C-f}, but it kills the current | |
259 | buffer (after first offering to save it if it is modified). When it | |
260 | reads the file name to visit, it inserts the entire default file name in | |
261 | the buffer, with point just after the directory part; this is convenient | |
262 | if you made a slight error in typing the name. | |
263 | ||
264 | If you find a file which exists but cannot be read, @kbd{C-x C-f} | |
265 | signals an error. | |
266 | ||
267 | @kindex C-x 4 f | |
268 | @findex find-file-other-window | |
269 | @kbd{C-x 4 f} (@code{find-file-other-window}) is like @kbd{C-x C-f} | |
270 | except that the buffer containing the specified file is selected in another | |
271 | window. The window that was selected before @kbd{C-x 4 f} continues to | |
272 | show the same buffer it was already showing. If this command is used when | |
273 | only one window is being displayed, that window is split in two, with one | |
274 | window showing the same buffer as before, and the other one showing the | |
275 | newly requested file. @xref{Windows}. | |
276 | ||
277 | @kindex C-x 5 f | |
278 | @findex find-file-other-frame | |
279 | @kbd{C-x 5 f} (@code{find-file-other-frame}) is similar, but opens a | |
280 | new frame, or makes visible any existing frame showing the file you | |
281 | seek. This feature is available only when you are using a window | |
282 | system. @xref{Frames}. | |
283 | ||
284 | @findex find-file-literally | |
f02d86a3 | 285 | If you wish to edit a file as a sequence of ASCII characters with no special |
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286 | encoding or conversion, use the @kbd{M-x find-file-literally} command. |
287 | It visits a file, like @kbd{C-x C-f}, but does not do format conversion | |
288 | (@pxref{Formatted Text}), character code conversion (@pxref{Coding | |
4104194e GM |
289 | Systems}), or automatic uncompression (@pxref{Compressed Files}), and |
290 | does not add a final newline because of @code{require-final-newline}. | |
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291 | If you already have visited the same file in the usual (non-literal) |
292 | manner, this command asks you whether to visit it literally instead. | |
293 | ||
294 | @vindex find-file-hooks | |
295 | @vindex find-file-not-found-hooks | |
296 | Two special hook variables allow extensions to modify the operation of | |
297 | visiting files. Visiting a file that does not exist runs the functions | |
298 | in the list @code{find-file-not-found-hooks}; this variable holds a list | |
299 | of functions, and the functions are called one by one (with no | |
300 | arguments) until one of them returns non-@code{nil}. This is not a | |
301 | normal hook, and the name ends in @samp{-hooks} rather than @samp{-hook} | |
302 | to indicate that fact. | |
303 | ||
304 | Any visiting of a file, whether extant or not, expects | |
305 | @code{find-file-hooks} to contain a list of functions, and calls them | |
306 | all, one by one, with no arguments. This variable is really a normal | |
307 | hook, but it has an abnormal name for historical compatibility. In the | |
308 | case of a nonexistent file, the @code{find-file-not-found-hooks} are run | |
309 | first. @xref{Hooks}. | |
310 | ||
311 | There are several ways to specify automatically the major mode for | |
312 | editing the file (@pxref{Choosing Modes}), and to specify local | |
313 | variables defined for that file (@pxref{File Variables}). | |
314 | ||
315 | @node Saving | |
316 | @section Saving Files | |
317 | ||
318 | @dfn{Saving} a buffer in Emacs means writing its contents back into the file | |
319 | that was visited in the buffer. | |
320 | ||
321 | @table @kbd | |
322 | @item C-x C-s | |
323 | Save the current buffer in its visited file (@code{save-buffer}). | |
324 | @item C-x s | |
325 | Save any or all buffers in their visited files (@code{save-some-buffers}). | |
326 | @item M-~ | |
327 | Forget that the current buffer has been changed (@code{not-modified}). | |
db8eeecd | 328 | With prefix argument (@kbd{C-u}), mark the current buffer as changed. |
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329 | @item C-x C-w |
330 | Save the current buffer in a specified file (@code{write-file}). | |
331 | @item M-x set-visited-file-name | |
332 | Change file the name under which the current buffer will be saved. | |
333 | @end table | |
334 | ||
335 | @kindex C-x C-s | |
336 | @findex save-buffer | |
337 | When you wish to save the file and make your changes permanent, type | |
338 | @kbd{C-x C-s} (@code{save-buffer}). After saving is finished, @kbd{C-x C-s} | |
339 | displays a message like this: | |
340 | ||
341 | @example | |
342 | Wrote /u/rms/gnu/gnu.tasks | |
343 | @end example | |
344 | ||
345 | @noindent | |
346 | If the selected buffer is not modified (no changes have been made in it | |
347 | since the buffer was created or last saved), saving is not really done, | |
348 | because it would have no effect. Instead, @kbd{C-x C-s} displays a message | |
349 | like this in the echo area: | |
350 | ||
351 | @example | |
352 | (No changes need to be saved) | |
353 | @end example | |
354 | ||
355 | @kindex C-x s | |
356 | @findex save-some-buffers | |
357 | The command @kbd{C-x s} (@code{save-some-buffers}) offers to save any | |
358 | or all modified buffers. It asks you what to do with each buffer. The | |
359 | possible responses are analogous to those of @code{query-replace}: | |
360 | ||
361 | @table @kbd | |
362 | @item y | |
363 | Save this buffer and ask about the rest of the buffers. | |
364 | @item n | |
365 | Don't save this buffer, but ask about the rest of the buffers. | |
366 | @item ! | |
367 | Save this buffer and all the rest with no more questions. | |
368 | @c following generates acceptable underfull hbox | |
369 | @item @key{RET} | |
370 | Terminate @code{save-some-buffers} without any more saving. | |
371 | @item . | |
372 | Save this buffer, then exit @code{save-some-buffers} without even asking | |
373 | about other buffers. | |
374 | @item C-r | |
375 | View the buffer that you are currently being asked about. When you exit | |
376 | View mode, you get back to @code{save-some-buffers}, which asks the | |
377 | question again. | |
378 | @item C-h | |
379 | Display a help message about these options. | |
380 | @end table | |
381 | ||
382 | @kbd{C-x C-c}, the key sequence to exit Emacs, invokes | |
383 | @code{save-some-buffers} and therefore asks the same questions. | |
384 | ||
385 | @kindex M-~ | |
386 | @findex not-modified | |
387 | If you have changed a buffer but you do not want to save the changes, | |
388 | you should take some action to prevent it. Otherwise, each time you use | |
389 | @kbd{C-x s} or @kbd{C-x C-c}, you are liable to save this buffer by | |
390 | mistake. One thing you can do is type @kbd{M-~} (@code{not-modified}), | |
391 | which clears out the indication that the buffer is modified. If you do | |
392 | this, none of the save commands will believe that the buffer needs to be | |
393 | saved. (@samp{~} is often used as a mathematical symbol for `not'; thus | |
394 | @kbd{M-~} is `not', metafied.) You could also use | |
395 | @code{set-visited-file-name} (see below) to mark the buffer as visiting | |
396 | a different file name, one which is not in use for anything important. | |
397 | Alternatively, you can cancel all the changes made since the file was | |
398 | visited or saved, by reading the text from the file again. This is | |
399 | called @dfn{reverting}. @xref{Reverting}. You could also undo all the | |
400 | changes by repeating the undo command @kbd{C-x u} until you have undone | |
401 | all the changes; but reverting is easier. | |
402 | ||
403 | @findex set-visited-file-name | |
404 | @kbd{M-x set-visited-file-name} alters the name of the file that the | |
405 | current buffer is visiting. It reads the new file name using the | |
406 | minibuffer. Then it specifies the visited file name and changes the | |
407 | buffer name correspondingly (as long as the new name is not in use). | |
408 | @code{set-visited-file-name} does not save the buffer in the newly | |
409 | visited file; it just alters the records inside Emacs in case you do | |
410 | save later. It also marks the buffer as ``modified'' so that @kbd{C-x | |
411 | C-s} in that buffer @emph{will} save. | |
412 | ||
413 | @kindex C-x C-w | |
414 | @findex write-file | |
415 | If you wish to mark the buffer as visiting a different file and save it | |
416 | right away, use @kbd{C-x C-w} (@code{write-file}). It is precisely | |
417 | equivalent to @code{set-visited-file-name} followed by @kbd{C-x C-s}. | |
418 | @kbd{C-x C-s} used on a buffer that is not visiting a file has the | |
419 | same effect as @kbd{C-x C-w}; that is, it reads a file name, marks the | |
420 | buffer as visiting that file, and saves it there. The default file name in | |
421 | a buffer that is not visiting a file is made by combining the buffer name | |
422 | with the buffer's default directory. | |
423 | ||
424 | If the new file name implies a major mode, then @kbd{C-x C-w} switches | |
425 | to that major mode, in most cases. The command | |
426 | @code{set-visited-file-name} also does this. @xref{Choosing Modes}. | |
427 | ||
428 | If Emacs is about to save a file and sees that the date of the latest | |
429 | version on disk does not match what Emacs last read or wrote, Emacs | |
430 | notifies you of this fact, because it probably indicates a problem caused | |
431 | by simultaneous editing and requires your immediate attention. | |
432 | @xref{Interlocking,, Simultaneous Editing}. | |
433 | ||
434 | @vindex require-final-newline | |
435 | If the variable @code{require-final-newline} is non-@code{nil}, Emacs | |
436 | puts a newline at the end of any file that doesn't already end in one, | |
437 | every time a file is saved or written. The default is @code{nil}. | |
438 | ||
439 | @menu | |
440 | * Backup:: How Emacs saves the old version of your file. | |
441 | * Interlocking:: How Emacs protects against simultaneous editing | |
442 | of one file by two users. | |
f02d86a3 RS |
443 | * Shadowing: File Shadowing. |
444 | Copying files to `shadows' automatically. | |
9575b9ae | 445 | * Time Stamps:: Emacs can update time stamps on saved files. |
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446 | @end menu |
447 | ||
448 | @node Backup | |
449 | @subsection Backup Files | |
450 | @cindex backup file | |
451 | @vindex make-backup-files | |
452 | @vindex vc-make-backup-files | |
6bf7aab6 DL |
453 | |
454 | On most operating systems, rewriting a file automatically destroys all | |
455 | record of what the file used to contain. Thus, saving a file from Emacs | |
456 | throws away the old contents of the file---or it would, except that | |
457 | Emacs carefully copies the old contents to another file, called the | |
458 | @dfn{backup} file, before actually saving. | |
459 | ||
460 | For most files, the variable @code{make-backup-files} determines | |
461 | whether to make backup files. On most operating systems, its default | |
462 | value is @code{t}, so that Emacs does write backup files. | |
463 | ||
464 | For files managed by a version control system (@pxref{Version | |
465 | Control}), the variable @code{vc-make-backup-files} determines whether | |
466 | to make backup files. By default, it is @code{nil}, since backup files | |
467 | are redundant when you store all the previous versions in a version | |
468 | control system. @xref{VC Workfile Handling}. | |
469 | ||
9a98ef18 DL |
470 | @vindex backup-enable-predicate |
471 | @vindex temporary-file-directory | |
472 | @vindex small-temporary-file-directory | |
6bf7aab6 | 473 | The default value of the @code{backup-enable-predicate} variable |
f02d86a3 RS |
474 | prevents backup files being written for files in the directories used |
475 | for temporary files, specified by @code{temporary-file-directory} or | |
476 | @code{small-temporary-file-directory}. | |
6bf7aab6 DL |
477 | |
478 | At your option, Emacs can keep either a single backup file or a series of | |
479 | numbered backup files for each file that you edit. | |
480 | ||
481 | Emacs makes a backup for a file only the first time the file is saved | |
482 | from one buffer. No matter how many times you save a file, its backup file | |
483 | continues to contain the contents from before the file was visited. | |
484 | Normally this means that the backup file contains the contents from before | |
485 | the current editing session; however, if you kill the buffer and then visit | |
486 | the file again, a new backup file will be made by the next save. | |
487 | ||
488 | You can also explicitly request making another backup file from a | |
489 | buffer even though it has already been saved at least once. If you save | |
490 | the buffer with @kbd{C-u C-x C-s}, the version thus saved will be made | |
491 | into a backup file if you save the buffer again. @kbd{C-u C-u C-x C-s} | |
492 | saves the buffer, but first makes the previous file contents into a new | |
493 | backup file. @kbd{C-u C-u C-u C-x C-s} does both things: it makes a | |
494 | backup from the previous contents, and arranges to make another from the | |
495 | newly saved contents, if you save again. | |
496 | ||
497 | @menu | |
498 | * Names: Backup Names. How backup files are named; | |
499 | choosing single or numbered backup files. | |
500 | * Deletion: Backup Deletion. Emacs deletes excess numbered backups. | |
501 | * Copying: Backup Copying. Backups can be made by copying or renaming. | |
502 | @end menu | |
503 | ||
504 | @node Backup Names | |
505 | @subsubsection Single or Numbered Backups | |
506 | ||
507 | If you choose to have a single backup file (this is the default), | |
9a98ef18 | 508 | the backup file's name is normally constructed by appending @samp{~} to the |
6bf7aab6 DL |
509 | file name being edited; thus, the backup file for @file{eval.c} would |
510 | be @file{eval.c~}. | |
511 | ||
9a98ef18 DL |
512 | @vindex make-backup-file-name-function |
513 | @vindex backup-directory-alist | |
514 | You can change this behaviour by defining the variable | |
515 | @code{make-backup-file-name-function} to a suitable function. | |
516 | Alternatively you can customize the variable | |
f02d86a3 RS |
517 | @var{backup-directory-alist} to specify that files matching certain |
518 | patterns should be backed up in specific directories. | |
519 | ||
520 | A typical use is to add an element @code{("." . @var{dir})} to make | |
521 | all backups in the directory with absolute name @var{dir}; Emacs | |
522 | modifies the backup file names to avoid clashes between files with the | |
523 | same names originating in different directories. Alternatively, | |
524 | adding, say, @code{("." ".~")} would make backups in the invisible | |
525 | subdirectory @file{.~} of the original file's directory. Emacs | |
526 | creates the directory, if necessary, to make the backup. | |
527 | ||
528 | If access control stops Emacs from writing backup files under the usual | |
529 | names, it writes the backup file as @file{%backup%~} in your home | |
530 | directory. Only one such file can exist, so only the most recently | |
531 | made such backup is available. | |
9a98ef18 | 532 | |
6bf7aab6 | 533 | If you choose to have a series of numbered backup files, backup file |
f02d86a3 RS |
534 | names contain @samp{.~}, the number, and another @samp{~} after the |
535 | original file name. Thus, the backup files of @file{eval.c} would be | |
536 | called @file{eval.c.~1~}, @file{eval.c.~2~}, and so on, all the way | |
537 | through names like @file{eval.c.~259~} and beyond. The variable | |
538 | @code{backup-directory-alist} applies to numbered backups just as | |
539 | usual. | |
6bf7aab6 DL |
540 | |
541 | @vindex version-control | |
542 | The choice of single backup or numbered backups is controlled by the | |
543 | variable @code{version-control}. Its possible values are | |
544 | ||
545 | @table @code | |
546 | @item t | |
547 | Make numbered backups. | |
548 | @item nil | |
549 | Make numbered backups for files that have numbered backups already. | |
550 | Otherwise, make single backups. | |
551 | @item never | |
552 | Do not in any case make numbered backups; always make single backups. | |
553 | @end table | |
554 | ||
555 | @noindent | |
556 | You can set @code{version-control} locally in an individual buffer to | |
557 | control the making of backups for that buffer's file. For example, | |
558 | Rmail mode locally sets @code{version-control} to @code{never} to make sure | |
559 | that there is only one backup for an Rmail file. @xref{Locals}. | |
560 | ||
60a96371 GM |
561 | @cindex @env{VERSION_CONTROL} environment variable |
562 | If you set the environment variable @env{VERSION_CONTROL}, to tell | |
6bf7aab6 DL |
563 | various GNU utilities what to do with backup files, Emacs also obeys the |
564 | environment variable by setting the Lisp variable @code{version-control} | |
565 | accordingly at startup. If the environment variable's value is @samp{t} | |
566 | or @samp{numbered}, then @code{version-control} becomes @code{t}; if the | |
567 | value is @samp{nil} or @samp{existing}, then @code{version-control} | |
568 | becomes @code{nil}; if it is @samp{never} or @samp{simple}, then | |
569 | @code{version-control} becomes @code{never}. | |
570 | ||
571 | @node Backup Deletion | |
572 | @subsubsection Automatic Deletion of Backups | |
573 | ||
574 | To prevent unlimited consumption of disk space, Emacs can delete numbered | |
575 | backup versions automatically. Generally Emacs keeps the first few backups | |
576 | and the latest few backups, deleting any in between. This happens every | |
577 | time a new backup is made. | |
578 | ||
579 | @vindex kept-old-versions | |
580 | @vindex kept-new-versions | |
581 | The two variables @code{kept-old-versions} and | |
582 | @code{kept-new-versions} control this deletion. Their values are, | |
583 | respectively the number of oldest (lowest-numbered) backups to keep and | |
584 | the number of newest (highest-numbered) ones to keep, each time a new | |
585 | backup is made. Recall that these values are used just after a new | |
586 | backup version is made; that newly made backup is included in the count | |
587 | in @code{kept-new-versions}. By default, both variables are 2. | |
588 | ||
589 | @vindex delete-old-versions | |
590 | If @code{delete-old-versions} is non-@code{nil}, the excess | |
591 | middle versions are deleted without a murmur. If it is @code{nil}, the | |
592 | default, then you are asked whether the excess middle versions should | |
593 | really be deleted. | |
594 | ||
595 | Dired's @kbd{.} (Period) command can also be used to delete old versions. | |
596 | @xref{Dired Deletion}. | |
597 | ||
598 | @node Backup Copying | |
599 | @subsubsection Copying vs.@: Renaming | |
600 | ||
601 | Backup files can be made by copying the old file or by renaming it. This | |
602 | makes a difference when the old file has multiple names. If the old file | |
603 | is renamed into the backup file, then the alternate names become names for | |
604 | the backup file. If the old file is copied instead, then the alternate | |
605 | names remain names for the file that you are editing, and the contents | |
606 | accessed by those names will be the new contents. | |
607 | ||
608 | The method of making a backup file may also affect the file's owner | |
609 | and group. If copying is used, these do not change. If renaming is used, | |
610 | you become the file's owner, and the file's group becomes the default | |
611 | (different operating systems have different defaults for the group). | |
612 | ||
613 | Having the owner change is usually a good idea, because then the owner | |
614 | always shows who last edited the file. Also, the owners of the backups | |
615 | show who produced those versions. Occasionally there is a file whose | |
616 | owner should not change; it is a good idea for such files to contain | |
617 | local variable lists to set @code{backup-by-copying-when-mismatch} | |
618 | locally (@pxref{File Variables}). | |
619 | ||
620 | @vindex backup-by-copying | |
621 | @vindex backup-by-copying-when-linked | |
622 | @vindex backup-by-copying-when-mismatch | |
3c8b8db0 EZ |
623 | @vindex backup-by-copying-when-privileged-mismatch |
624 | @cindex file ownership, and backup | |
f02d86a3 | 625 | @cindex backup, and user-id |
3c8b8db0 | 626 | The choice of renaming or copying is controlled by four variables. |
6bf7aab6 DL |
627 | Renaming is the default choice. If the variable |
628 | @code{backup-by-copying} is non-@code{nil}, copying is used. Otherwise, | |
629 | if the variable @code{backup-by-copying-when-linked} is non-@code{nil}, | |
630 | then copying is used for files that have multiple names, but renaming | |
631 | may still be used when the file being edited has only one name. If the | |
632 | variable @code{backup-by-copying-when-mismatch} is non-@code{nil}, then | |
633 | copying is used if renaming would cause the file's owner or group to | |
634 | change. @code{backup-by-copying-when-mismatch} is @code{t} by default | |
3c8b8db0 EZ |
635 | if you start Emacs as the superuser. The fourth variable, |
636 | @code{backup-by-copying-when-privileged-mismatch}, gives the highest | |
f02d86a3 RS |
637 | numeric user-id for which @code{backup-by-copying-when-mismatch} will be |
638 | forced on. This is useful when low-numbered user-id are assigned to | |
3c8b8db0 EZ |
639 | special system users, such as @code{root}, @code{bin}, @code{daemon}, |
640 | etc., which must maintain ownership of files. | |
6bf7aab6 DL |
641 | |
642 | When a file is managed with a version control system (@pxref{Version | |
643 | Control}), Emacs does not normally make backups in the usual way for | |
644 | that file. But check-in and check-out are similar in some ways to | |
645 | making backups. One unfortunate similarity is that these operations | |
646 | typically break hard links, disconnecting the file name you visited from | |
647 | any alternate names for the same file. This has nothing to do with | |
648 | Emacs---the version control system does it. | |
649 | ||
650 | @node Interlocking | |
651 | @subsection Protection against Simultaneous Editing | |
652 | ||
653 | @cindex file dates | |
654 | @cindex simultaneous editing | |
655 | Simultaneous editing occurs when two users visit the same file, both | |
656 | make changes, and then both save them. If nobody were informed that | |
657 | this was happening, whichever user saved first would later find that his | |
658 | changes were lost. | |
659 | ||
660 | On some systems, Emacs notices immediately when the second user starts | |
661 | to change the file, and issues an immediate warning. On all systems, | |
662 | Emacs checks when you save the file, and warns if you are about to | |
663 | overwrite another user's changes. You can prevent loss of the other | |
664 | user's work by taking the proper corrective action instead of saving the | |
665 | file. | |
666 | ||
667 | @findex ask-user-about-lock | |
668 | @cindex locking files | |
669 | When you make the first modification in an Emacs buffer that is | |
670 | visiting a file, Emacs records that the file is @dfn{locked} by you. | |
671 | (It does this by creating a symbolic link in the same directory with a | |
672 | different name.) Emacs removes the lock when you save the changes. The | |
673 | idea is that the file is locked whenever an Emacs buffer visiting it has | |
674 | unsaved changes. | |
675 | ||
676 | @cindex collision | |
677 | If you begin to modify the buffer while the visited file is locked by | |
678 | someone else, this constitutes a @dfn{collision}. When Emacs detects a | |
679 | collision, it asks you what to do, by calling the Lisp function | |
680 | @code{ask-user-about-lock}. You can redefine this function for the sake | |
681 | of customization. The standard definition of this function asks you a | |
682 | question and accepts three possible answers: | |
683 | ||
684 | @table @kbd | |
685 | @item s | |
686 | Steal the lock. Whoever was already changing the file loses the lock, | |
687 | and you gain the lock. | |
688 | @item p | |
689 | Proceed. Go ahead and edit the file despite its being locked by someone else. | |
690 | @item q | |
691 | Quit. This causes an error (@code{file-locked}) and the modification you | |
692 | were trying to make in the buffer does not actually take place. | |
693 | @end table | |
694 | ||
695 | Note that locking works on the basis of a file name; if a file has | |
696 | multiple names, Emacs does not realize that the two names are the same file | |
697 | and cannot prevent two users from editing it simultaneously under different | |
698 | names. However, basing locking on names means that Emacs can interlock the | |
699 | editing of new files that will not really exist until they are saved. | |
700 | ||
701 | Some systems are not configured to allow Emacs to make locks, and | |
702 | there are cases where lock files cannot be written. In these cases, | |
703 | Emacs cannot detect trouble in advance, but it still can detect the | |
704 | collision when you try to save a file and overwrite someone else's | |
705 | changes. | |
706 | ||
707 | If Emacs or the operating system crashes, this may leave behind lock | |
708 | files which are stale. So you may occasionally get warnings about | |
709 | spurious collisions. When you determine that the collision is spurious, | |
710 | just use @kbd{p} to tell Emacs to go ahead anyway. | |
711 | ||
712 | Every time Emacs saves a buffer, it first checks the last-modification | |
713 | date of the existing file on disk to verify that it has not changed since the | |
714 | file was last visited or saved. If the date does not match, it implies | |
715 | that changes were made in the file in some other way, and these changes are | |
716 | about to be lost if Emacs actually does save. To prevent this, Emacs | |
717 | prints a warning message and asks for confirmation before saving. | |
718 | Occasionally you will know why the file was changed and know that it does | |
719 | not matter; then you can answer @kbd{yes} and proceed. Otherwise, you should | |
720 | cancel the save with @kbd{C-g} and investigate the situation. | |
721 | ||
722 | The first thing you should do when notified that simultaneous editing | |
723 | has already taken place is to list the directory with @kbd{C-u C-x C-d} | |
724 | (@pxref{Directories}). This shows the file's current author. You | |
725 | should attempt to contact him to warn him not to continue editing. | |
726 | Often the next step is to save the contents of your Emacs buffer under a | |
727 | different name, and use @code{diff} to compare the two files.@refill | |
728 | ||
fa474484 DL |
729 | @node File Shadowing |
730 | @subsection Shadowing Files | |
731 | @cindex shadow files | |
732 | @cindex file shadows | |
733 | ||
734 | @table @kbd | |
735 | @item M-x shadow-initialize | |
736 | Set up file shadowing. | |
fa474484 DL |
737 | @item M-x shadow-define-literal-group |
738 | Declare a single file to be shared between sites. | |
f02d86a3 RS |
739 | @item M-x shadow-define-regexp-group |
740 | Make all files that match each of a group of files be shared between hosts. | |
741 | @item M-x shadow-define-cluster @key{RET} @var{name} @key{RET} | |
742 | Define a shadow file cluster @var{name}. | |
fa474484 DL |
743 | @item M-x shadow-copy-files |
744 | Copy all pending shadow files. | |
f02d86a3 RS |
745 | @item M-x shadow-cancel |
746 | Cancel the instruction to shadow some files. | |
fa474484 DL |
747 | @end table |
748 | ||
f02d86a3 RS |
749 | You can arrange to keep identical @dfn{shadow} copies of certain files |
750 | in more than one place---possibly on different machines. To do this, | |
751 | first you must set up a @dfn{shadow file group}, which is a set of | |
752 | identically-named files shared between a list of sites. The file | |
753 | group is permanent and applies to further Emacs sessions as well as | |
754 | the current one. Once the group is set up, every time you exit Emacs, | |
755 | it will copy the file you edited to the other files in its group. You | |
756 | can also do the copying without exiting Emacs, by typing @kbd{M-x | |
757 | shadow-copy-files}. | |
758 | ||
759 | To set up a file group, use @kbd{M-x shadow-define-literal-group} or | |
760 | @kbd{M-x shadow-define-regexp-group}. See their documentation strings | |
761 | for further information. | |
762 | ||
763 | Before copying a file to its shadows, Emacs asks for confirmation. | |
764 | You can answer ``no'' to bypass copying of this file, this time. If | |
765 | you want to cancel the shadowing permanently for a certain file, use | |
766 | @kbd{M-x shadow-cancel} to eliminate or change the shadow file group. | |
767 | ||
768 | A @dfn{shadow cluster} is a group of hosts that share directories, so | |
769 | that copying to or from one of them is sufficient to update the file | |
770 | on all of them. Each shadow cluster has a name, and specifies the | |
771 | network address of a primary host (the one we copy files to), and a | |
772 | regular expression that matches the hostnames of all the other hosts | |
773 | in the cluster. You can define a shadow cluster with @kbd{M-x | |
774 | shadow-define-cluster}. | |
fa474484 | 775 | |
9575b9ae DL |
776 | @node Time Stamps |
777 | @subsection Updating Time Stamps Automatically | |
778 | @findex time-stamp | |
779 | @cindex time stamps | |
780 | @cindex modification dates | |
940f14b4 | 781 | @cindex locale, date format |
9575b9ae | 782 | |
f02d86a3 RS |
783 | You can arrange put a time stamp in a file, so that it will be updated |
784 | automatically each time you edit and save the file. The time stamp | |
785 | has to be in the first eight lines of the file, and you should | |
786 | insert it like this: | |
787 | ||
9575b9ae DL |
788 | @example |
789 | Time-stamp: <> | |
790 | @end example | |
f02d86a3 | 791 | |
9575b9ae | 792 | @noindent |
f02d86a3 RS |
793 | or like this: |
794 | ||
9575b9ae DL |
795 | @example |
796 | Time-stamp: "" | |
797 | @end example | |
9575b9ae | 798 | |
f02d86a3 RS |
799 | Then add the hook function @code{time-stamp} to the hook |
800 | @code{write-file-hooks}; that hook function will automatically update | |
801 | the time stamp, inserting the current date and time when you save the | |
802 | file. You can also use the command @kbd{M-x time-stamp} to update the | |
803 | time stamp manually. For other customizations, see the Custom group | |
804 | @code{time-stamp}. Note that non-numeric fields in the time stamp are | |
805 | formatted according to your locale setting (@pxref{Environment}). | |
9575b9ae | 806 | |
6bf7aab6 DL |
807 | @node Reverting |
808 | @section Reverting a Buffer | |
809 | @findex revert-buffer | |
810 | @cindex drastic changes | |
811 | ||
812 | If you have made extensive changes to a file and then change your mind | |
813 | about them, you can get rid of them by reading in the previous version | |
814 | of the file. To do this, use @kbd{M-x revert-buffer}, which operates on | |
815 | the current buffer. Since reverting a buffer unintentionally could lose | |
816 | a lot of work, you must confirm this command with @kbd{yes}. | |
817 | ||
818 | @code{revert-buffer} keeps point at the same distance (measured in | |
819 | characters) from the beginning of the file. If the file was edited only | |
820 | slightly, you will be at approximately the same piece of text after | |
821 | reverting as before. If you have made drastic changes, the same value of | |
822 | point in the old file may address a totally different piece of text. | |
823 | ||
824 | Reverting marks the buffer as ``not modified'' until another change is | |
825 | made. | |
826 | ||
827 | Some kinds of buffers whose contents reflect data bases other than files, | |
828 | such as Dired buffers, can also be reverted. For them, reverting means | |
829 | recalculating their contents from the appropriate data base. Buffers | |
830 | created explicitly with @kbd{C-x b} cannot be reverted; @code{revert-buffer} | |
831 | reports an error when asked to do so. | |
832 | ||
833 | @vindex revert-without-query | |
834 | When you edit a file that changes automatically and frequently---for | |
835 | example, a log of output from a process that continues to run---it may be | |
836 | useful for Emacs to revert the file without querying you, whenever you | |
837 | visit the file again with @kbd{C-x C-f}. | |
838 | ||
839 | To request this behavior, set the variable @code{revert-without-query} | |
840 | to a list of regular expressions. When a file name matches one of these | |
841 | regular expressions, @code{find-file} and @code{revert-buffer} will | |
842 | revert it automatically if it has changed---provided the buffer itself | |
843 | is not modified. (If you have edited the text, it would be wrong to | |
844 | discard your changes.) | |
845 | ||
846 | @node Auto Save | |
847 | @section Auto-Saving: Protection Against Disasters | |
848 | @cindex Auto Save mode | |
849 | @cindex mode, Auto Save | |
850 | @cindex crashes | |
851 | ||
852 | Emacs saves all the visited files from time to time (based on counting | |
853 | your keystrokes) without being asked. This is called @dfn{auto-saving}. | |
854 | It prevents you from losing more than a limited amount of work if the | |
855 | system crashes. | |
856 | ||
857 | When Emacs determines that it is time for auto-saving, each buffer is | |
858 | considered, and is auto-saved if auto-saving is turned on for it and it | |
859 | has been changed since the last time it was auto-saved. The message | |
860 | @samp{Auto-saving...} is displayed in the echo area during auto-saving, | |
861 | if any files are actually auto-saved. Errors occurring during | |
862 | auto-saving are caught so that they do not interfere with the execution | |
863 | of commands you have been typing. | |
864 | ||
865 | @menu | |
866 | * Files: Auto Save Files. The file where auto-saved changes are | |
867 | actually made until you save the file. | |
868 | * Control: Auto Save Control. Controlling when and how often to auto-save. | |
869 | * Recover:: Recovering text from auto-save files. | |
870 | @end menu | |
871 | ||
872 | @node Auto Save Files | |
873 | @subsection Auto-Save Files | |
874 | ||
875 | Auto-saving does not normally save in the files that you visited, because | |
876 | it can be very undesirable to save a program that is in an inconsistent | |
877 | state when you have made half of a planned change. Instead, auto-saving | |
878 | is done in a different file called the @dfn{auto-save file}, and the | |
879 | visited file is changed only when you request saving explicitly (such as | |
880 | with @kbd{C-x C-s}). | |
881 | ||
882 | Normally, the auto-save file name is made by appending @samp{#} to the | |
883 | front and rear of the visited file name. Thus, a buffer visiting file | |
884 | @file{foo.c} is auto-saved in a file @file{#foo.c#}. Most buffers that | |
885 | are not visiting files are auto-saved only if you request it explicitly; | |
886 | when they are auto-saved, the auto-save file name is made by appending | |
887 | @samp{#%} to the front and @samp{#} to the rear of buffer name. For | |
888 | example, the @samp{*mail*} buffer in which you compose messages to be | |
889 | sent is auto-saved in a file named @file{#%*mail*#}. Auto-save file | |
890 | names are made this way unless you reprogram parts of Emacs to do | |
891 | something different (the functions @code{make-auto-save-file-name} and | |
892 | @code{auto-save-file-name-p}). The file name to be used for auto-saving | |
893 | in a buffer is calculated when auto-saving is turned on in that buffer. | |
894 | ||
895 | When you delete a substantial part of the text in a large buffer, auto | |
896 | save turns off temporarily in that buffer. This is because if you | |
897 | deleted the text unintentionally, you might find the auto-save file more | |
898 | useful if it contains the deleted text. To reenable auto-saving after | |
899 | this happens, save the buffer with @kbd{C-x C-s}, or use @kbd{C-u 1 M-x | |
900 | auto-save}. | |
901 | ||
902 | @vindex auto-save-visited-file-name | |
903 | If you want auto-saving to be done in the visited file, set the variable | |
904 | @code{auto-save-visited-file-name} to be non-@code{nil}. In this mode, | |
905 | there is really no difference between auto-saving and explicit saving. | |
906 | ||
907 | @vindex delete-auto-save-files | |
908 | A buffer's auto-save file is deleted when you save the buffer in its | |
909 | visited file. To inhibit this, set the variable @code{delete-auto-save-files} | |
910 | to @code{nil}. Changing the visited file name with @kbd{C-x C-w} or | |
911 | @code{set-visited-file-name} renames any auto-save file to go with | |
912 | the new visited name. | |
913 | ||
914 | @node Auto Save Control | |
915 | @subsection Controlling Auto-Saving | |
916 | ||
917 | @vindex auto-save-default | |
918 | @findex auto-save-mode | |
919 | Each time you visit a file, auto-saving is turned on for that file's | |
920 | buffer if the variable @code{auto-save-default} is non-@code{nil} (but not | |
921 | in batch mode; @pxref{Entering Emacs}). The default for this variable is | |
922 | @code{t}, so auto-saving is the usual practice for file-visiting buffers. | |
923 | Auto-saving can be turned on or off for any existing buffer with the | |
924 | command @kbd{M-x auto-save-mode}. Like other minor mode commands, @kbd{M-x | |
925 | auto-save-mode} turns auto-saving on with a positive argument, off with a | |
926 | zero or negative argument; with no argument, it toggles. | |
927 | ||
928 | @vindex auto-save-interval | |
929 | Emacs does auto-saving periodically based on counting how many characters | |
930 | you have typed since the last time auto-saving was done. The variable | |
931 | @code{auto-save-interval} specifies how many characters there are between | |
932 | auto-saves. By default, it is 300. | |
933 | ||
934 | @vindex auto-save-timeout | |
935 | Auto-saving also takes place when you stop typing for a while. The | |
936 | variable @code{auto-save-timeout} says how many seconds Emacs should | |
937 | wait before it does an auto save (and perhaps also a garbage | |
938 | collection). (The actual time period is longer if the current buffer is | |
939 | long; this is a heuristic which aims to keep out of your way when you | |
940 | are editing long buffers, in which auto-save takes an appreciable amount | |
941 | of time.) Auto-saving during idle periods accomplishes two things: | |
942 | first, it makes sure all your work is saved if you go away from the | |
943 | terminal for a while; second, it may avoid some auto-saving while you | |
944 | are actually typing. | |
945 | ||
946 | Emacs also does auto-saving whenever it gets a fatal error. This | |
947 | includes killing the Emacs job with a shell command such as @samp{kill | |
948 | %emacs}, or disconnecting a phone line or network connection. | |
949 | ||
950 | @findex do-auto-save | |
951 | You can request an auto-save explicitly with the command @kbd{M-x | |
952 | do-auto-save}. | |
953 | ||
954 | @node Recover | |
955 | @subsection Recovering Data from Auto-Saves | |
956 | ||
957 | @findex recover-file | |
958 | You can use the contents of an auto-save file to recover from a loss | |
959 | of data with the command @kbd{M-x recover-file @key{RET} @var{file} | |
960 | @key{RET}}. This visits @var{file} and then (after your confirmation) | |
961 | restores the contents from its auto-save file @file{#@var{file}#}. | |
962 | You can then save with @kbd{C-x C-s} to put the recovered text into | |
963 | @var{file} itself. For example, to recover file @file{foo.c} from its | |
964 | auto-save file @file{#foo.c#}, do:@refill | |
965 | ||
966 | @example | |
967 | M-x recover-file @key{RET} foo.c @key{RET} | |
968 | yes @key{RET} | |
969 | C-x C-s | |
970 | @end example | |
971 | ||
972 | Before asking for confirmation, @kbd{M-x recover-file} displays a | |
973 | directory listing describing the specified file and the auto-save file, | |
974 | so you can compare their sizes and dates. If the auto-save file | |
975 | is older, @kbd{M-x recover-file} does not offer to read it. | |
976 | ||
977 | @findex recover-session | |
978 | If Emacs or the computer crashes, you can recover all the files you | |
979 | were editing from their auto save files with the command @kbd{M-x | |
980 | recover-session}. This first shows you a list of recorded interrupted | |
981 | sessions. Move point to the one you choose, and type @kbd{C-c C-c}. | |
982 | ||
983 | Then @code{recover-session} asks about each of the files that were | |
984 | being edited during that session, asking whether to recover that file. | |
985 | If you answer @kbd{y}, it calls @code{recover-file}, which works in its | |
986 | normal fashion. It shows the dates of the original file and its | |
987 | auto-save file, and asks once again whether to recover that file. | |
988 | ||
989 | When @code{recover-session} is done, the files you've chosen to | |
990 | recover are present in Emacs buffers. You should then save them. Only | |
991 | this---saving them---updates the files themselves. | |
992 | ||
993 | @vindex auto-save-list-file-prefix | |
f02d86a3 | 994 | Emacs records interrupted sessions for later recovery in files named |
fa474484 | 995 | @file{~/.emacs.d/auto-save-list/.saves-@var{pid}-@var{hostname}}. The |
826f3788 | 996 | @samp{~/.emacs.d/auto-save-list/.saves-} portion of these names comes |
f02d86a3 RS |
997 | from the value of @code{auto-save-list-file-prefix}. You can record |
998 | sessions in a different place by customizing that variable. If you | |
999 | set @code{auto-save-list-file-prefix} to @code{nil} in your | |
1000 | @file{.emacs} file, sessions are not recorded for recovery. | |
6bf7aab6 DL |
1001 | |
1002 | @node File Aliases | |
1003 | @section File Name Aliases | |
1004 | ||
1005 | Symbolic links and hard links both make it possible for several file | |
1006 | names to refer to the same file. Hard links are alternate names that | |
1007 | refer directly to the file; all the names are equally valid, and no one | |
1008 | of them is preferred. By contrast, a symbolic link is a kind of defined | |
1009 | alias: when @file{foo} is a symbolic link to @file{bar}, you can use | |
1010 | either name to refer to the file, but @file{bar} is the real name, while | |
1011 | @file{foo} is just an alias. More complex cases occur when symbolic | |
1012 | links point to directories. | |
1013 | ||
1014 | If you visit two names for the same file, normally Emacs makes | |
1015 | two different buffers, but it warns you about the situation. | |
1016 | ||
4295d0b2 | 1017 | @vindex find-file-existing-other-name |
f02d86a3 RS |
1018 | Normally, if you visit a file which Emacs is already visiting under |
1019 | a different name, Emacs displays a message in the echo area and uses | |
1020 | the existing buffer visiting that file. This can happen on systems | |
1021 | that support symbolic links, or if you use a long file name on a | |
1022 | system that truncates long file names. You can disable this feature | |
1023 | by setting the variable @code{find-file-existing-other-name} to | |
1024 | @code{nil}. Then if you visit the same file under two different names, | |
1025 | you get a separate buffer for each file name. | |
6bf7aab6 DL |
1026 | |
1027 | @vindex find-file-visit-truename | |
1028 | @cindex truenames of files | |
1029 | @cindex file truenames | |
1030 | If the variable @code{find-file-visit-truename} is non-@code{nil}, | |
1031 | then the file name recorded for a buffer is the file's @dfn{truename} | |
1032 | (made by replacing all symbolic links with their target names), rather | |
1033 | than the name you specify. Setting @code{find-file-visit-truename} also | |
1034 | implies the effect of @code{find-file-existing-other-name}. | |
1035 | ||
1036 | @node Version Control | |
1037 | @section Version Control | |
1038 | @cindex version control | |
1039 | ||
1040 | @dfn{Version control systems} are packages that can record multiple | |
1041 | versions of a source file, usually storing the unchanged parts of the | |
1042 | file just once. Version control systems also record history information | |
1043 | such as the creation time of each version, who created it, and a | |
1044 | description of what was changed in that version. | |
1045 | ||
1046 | The Emacs version control interface is called VC. Its commands work | |
f02d86a3 RS |
1047 | with three version control systems---RCS, CVS and SCCS. The GNU |
1048 | project recommends RCS and CVS, which are free software and available | |
1049 | from the Free Software Foundation. We also have free software to | |
1050 | replace SCCS, known as CSSC; if you are using SCCS and don't want to | |
1051 | make the incompatible change to RCS or CVS, you can switch to CSSC. | |
6bf7aab6 DL |
1052 | |
1053 | @menu | |
1054 | * Introduction to VC:: How version control works in general. | |
1055 | * VC Mode Line:: How the mode line shows version control status. | |
1056 | * Basic VC Editing:: How to edit a file under version control. | |
1057 | * Old Versions:: Examining and comparing old versions. | |
1058 | * Secondary VC Commands:: The commands used a little less frequently. | |
1059 | * Branches:: Multiple lines of development. | |
1060 | * Snapshots:: Sets of file versions treated as a unit. | |
1061 | * Miscellaneous VC:: Various other commands and features of VC. | |
1062 | * Customizing VC:: Variables that change VC's behavior. | |
1063 | @end menu | |
1064 | ||
1065 | @node Introduction to VC | |
1066 | @subsection Introduction to Version Control | |
1067 | ||
1068 | VC allows you to use a version control system from within Emacs, | |
1069 | integrating the version control operations smoothly with editing. VC | |
1070 | provides a uniform interface to version control, so that regardless of | |
1071 | which version control system is in use, you can use it the same way. | |
1072 | ||
1073 | This section provides a general overview of version control, and | |
1074 | describes the version control systems that VC supports. You can skip | |
1075 | this section if you are already familiar with the version control system | |
1076 | you want to use. | |
1077 | ||
1078 | @menu | |
1079 | * Version Systems:: Supported version control back-end systems. | |
1080 | * VC Concepts:: Words and concepts related to version control. | |
1081 | @end menu | |
1082 | ||
1083 | @node Version Systems | |
1084 | @subsubsection Supported Version Control Systems | |
1085 | ||
1086 | @cindex RCS | |
1087 | @cindex back end (version control) | |
1088 | VC currently works with three different version control systems or | |
1089 | ``back ends'': RCS, CVS, and SCCS. | |
1090 | ||
1091 | RCS is a free version control system that is available from the Free | |
1092 | Software Foundation. It is perhaps the most mature of the supported | |
1093 | back ends, and the VC commands are conceptually closest to RCS. Almost | |
1094 | everything you can do with RCS can be done through VC. | |
1095 | ||
1096 | @cindex CVS | |
1097 | CVS is built on top of RCS, and extends the features of RCS, allowing | |
1098 | for more sophisticated release management, and concurrent multi-user | |
1099 | development. VC supports basic editing operations under CVS, but for | |
1100 | some less common tasks you still need to call CVS from the command line. | |
1101 | Note also that before using CVS you must set up a repository, which is a | |
1102 | subject too complex to treat here. | |
1103 | ||
1104 | @cindex SCCS | |
1105 | SCCS is a proprietary but widely used version control system. In | |
1106 | terms of capabilities, it is the weakest of the three that VC | |
1107 | supports. VC compensates for certain features missing in SCCS | |
1108 | (snapshots, for example) by implementing them itself, but some other VC | |
1109 | features, such as multiple branches, are not available with SCCS. You | |
1110 | should use SCCS only if for some reason you cannot use RCS. | |
1111 | ||
1112 | @node VC Concepts | |
1113 | @subsubsection Concepts of Version Control | |
1114 | ||
1115 | @cindex master file | |
1116 | @cindex registered file | |
1117 | When a file is under version control, we also say that it is | |
1118 | @dfn{registered} in the version control system. Each registered file | |
1119 | has a corresponding @dfn{master file} which represents the file's | |
1120 | present state plus its change history---enough to reconstruct the | |
1121 | current version or any earlier version. Usually the master file also | |
1122 | records a @dfn{log entry} for each version, describing in words what was | |
1123 | changed in that version. | |
1124 | ||
1125 | @cindex work file | |
1126 | @cindex checking out files | |
1127 | The file that is maintained under version control is sometimes called | |
1128 | the @dfn{work file} corresponding to its master file. You edit the work | |
1129 | file and make changes in it, as you would with an ordinary file. (With | |
1130 | SCCS and RCS, you must @dfn{lock} the file before you start to edit it.) | |
1131 | After you are done with a set of changes, you @dfn{check the file in}, | |
1132 | which records the changes in the master file, along with a log entry for | |
1133 | them. | |
1134 | ||
1135 | With CVS, there are usually multiple work files corresponding to a | |
1136 | single master file---often each user has his own copy. It is also | |
1137 | possible to use RCS in this way, but this is not the usual way to use | |
1138 | RCS. | |
1139 | ||
1140 | @cindex locking and version control | |
1141 | A version control system typically has some mechanism to coordinate | |
1142 | between users who want to change the same file. One method is | |
1143 | @dfn{locking} (analogous to the locking that Emacs uses to detect | |
1144 | simultaneous editing of a file, but distinct from it). The other method | |
1145 | is to merge your changes with other people's changes when you check them | |
1146 | in. | |
1147 | ||
1148 | With version control locking, work files are normally read-only so | |
1149 | that you cannot change them. You ask the version control system to make | |
1150 | a work file writable for you by locking it; only one user can do | |
1151 | this at any given time. When you check in your changes, that unlocks | |
1152 | the file, making the work file read-only again. This allows other users | |
1153 | to lock the file to make further changes. SCCS always uses locking, and | |
1154 | RCS normally does. | |
1155 | ||
1156 | The other alternative for RCS is to let each user modify the work file | |
1157 | at any time. In this mode, locking is not required, but it is | |
1158 | permitted; check-in is still the way to record a new version. | |
1159 | ||
1160 | CVS normally allows each user to modify his own copy of the work file | |
1161 | at any time, but requires merging with changes from other users at | |
1162 | check-in time. However, CVS can also be set up to require locking. | |
1163 | (@pxref{Backend Options}). | |
1164 | ||
1165 | @node VC Mode Line | |
1166 | @subsection Version Control and the Mode Line | |
1167 | ||
1168 | When you visit a file that is under version control, Emacs indicates | |
1169 | this on the mode line. For example, @samp{RCS-1.3} says that RCS is | |
1170 | used for that file, and the current version is 1.3. | |
1171 | ||
1172 | The character between the back-end name and the version number | |
1173 | indicates the version control status of the file. @samp{-} means that | |
1174 | the work file is not locked (if locking is in use), or not modified (if | |
1175 | locking is not in use). @samp{:} indicates that the file is locked, or | |
1176 | that it is modified. If the file is locked by some other user (for | |
1177 | instance, @samp{jim}), that is displayed as @samp{RCS:jim:1.3}. | |
1178 | ||
1179 | @node Basic VC Editing | |
1180 | @subsection Basic Editing under Version Control | |
1181 | ||
1182 | The principal VC command is an all-purpose command that performs | |
1183 | either locking or check-in, depending on the situation. | |
1184 | ||
1185 | @table @kbd | |
1186 | @item C-x C-q | |
1187 | @itemx C-x v v | |
1188 | Perform the next logical version control operation on this file. | |
1189 | @end table | |
1190 | ||
1191 | @findex vc-next-action | |
1192 | @findex vc-toggle-read-only | |
1193 | @kindex C-x v v | |
1194 | @kindex C-x C-q @r{(Version Control)} | |
1195 | Strictly speaking, the command for this job is @code{vc-next-action}, | |
1196 | bound to @kbd{C-x v v}. However, the normal meaning of @kbd{C-x C-q} is | |
1197 | to make a read-only buffer writable, or vice versa; we have extended it | |
1198 | to do the same job properly for files managed by version control, by | |
1199 | performing the appropriate version control operations. When you type | |
1200 | @kbd{C-x C-q} on a registered file, it acts like @kbd{C-x v v}. | |
1201 | ||
1202 | The precise action of this command depends on the state of the file, | |
1203 | and whether the version control system uses locking or not. SCCS and | |
1204 | RCS normally use locking; CVS normally does not use locking. | |
1205 | ||
1206 | @menu | |
1207 | * VC with Locking:: RCS in its default mode, SCCS, and optionally CVS. | |
1208 | * Without Locking:: Without locking: default mode for CVS. | |
1209 | * Log Buffer:: Features available in log entry buffers. | |
1210 | @end menu | |
1211 | ||
1212 | @node VC with Locking | |
1213 | @subsubsection Basic Version Control with Locking | |
1214 | ||
1215 | If locking is used for the file (as with SCCS, and RCS in its default | |
1216 | mode), @kbd{C-x C-q} can either lock a file or check it in: | |
1217 | ||
1218 | @itemize @bullet | |
1219 | @item | |
1220 | If the file is not locked, @kbd{C-x C-q} locks it, and | |
1221 | makes it writable so that you can change it. | |
1222 | ||
1223 | @item | |
1224 | If the file is locked by you, and contains changes, @kbd{C-x C-q} checks | |
1225 | in the changes. In order to do this, it first reads the log entry | |
1226 | for the new version. @xref{Log Buffer}. | |
1227 | ||
1228 | @item | |
1229 | If the file is locked by you, but you have not changed it since you | |
1230 | locked it, @kbd{C-x C-q} releases the lock and makes the file read-only | |
1231 | again. | |
1232 | ||
1233 | @item | |
1234 | If the file is locked by some other user, @kbd{C-x C-q} asks you whether | |
1235 | you want to ``steal the lock'' from that user. If you say yes, the file | |
1236 | becomes locked by you, but a message is sent to the person who had | |
1237 | formerly locked the file, to inform him of what has happened. | |
1238 | @end itemize | |
1239 | ||
1240 | These rules also apply when you use CVS in locking mode, except | |
1241 | that there is no such thing as stealing a lock. | |
1242 | ||
1243 | @node Without Locking | |
1244 | @subsubsection Basic Version Control without Locking | |
1245 | ||
1246 | When there is no locking---the default for CVS---work files are always | |
1247 | writable; you do not need to do anything before you begin to edit a | |
1248 | file. The status indicator on the mode line is @samp{-} if the file is | |
1249 | unmodified; it flips to @samp{:} as soon as you save any changes in the | |
1250 | work file. | |
1251 | ||
1252 | Here is what @kbd{C-x C-q} does when using CVS: | |
1253 | ||
1254 | @itemize @bullet | |
1255 | @item | |
1256 | If some other user has checked in changes into the master file, | |
1257 | Emacs asks you whether you want to merge those changes into your own | |
1258 | work file (@pxref{Merging}). You must do this before you can check in | |
1259 | your own changes. | |
1260 | ||
1261 | @item | |
1262 | If there are no new changes in the master file, but you have made | |
1263 | modifications in your work file, @kbd{C-x C-q} checks in your changes. | |
1264 | In order to do this, it first reads the log entry for the new version. | |
1265 | @xref{Log Buffer}. | |
1266 | ||
1267 | @item | |
1268 | If the file is not modified, the @kbd{C-x C-q} does nothing. | |
1269 | @end itemize | |
1270 | ||
1271 | These rules also apply when you use RCS in the mode that does not | |
1272 | require locking, except that automatic merging of changes from the | |
1273 | master file is not implemented. Unfortunately, this means that nothing | |
1274 | informs you if another user has checked in changes in the same file | |
1275 | since you began editing it, and when this happens, his changes will be | |
1276 | effectively removed when you check in your version (though they will | |
1277 | remain in the master file, so they will not be entirely lost). You must | |
1278 | therefore verify the current version is unchanged, before you check in your | |
1279 | changes. We hope to eliminate this risk and provide automatic merging | |
1280 | with RCS in a future Emacs version. | |
1281 | ||
1282 | In addition, locking is possible with RCS even in this mode, although | |
1283 | it is not required; @kbd{C-x C-q} with an unmodified file locks the | |
1284 | file, just as it does with RCS in its normal (locking) mode. | |
1285 | ||
1286 | @node Log Buffer | |
1287 | @subsubsection Features of the Log Entry Buffer | |
1288 | ||
1289 | When you check in changes, @kbd{C-x C-q} first reads a log entry. It | |
1290 | pops up a buffer called @samp{*VC-Log*} for you to enter the log entry. | |
1291 | When you are finished, type @kbd{C-c C-c} in the @samp{*VC-Log*} buffer. | |
1292 | That is when check-in really happens. | |
1293 | ||
1294 | To abort check-in, just @strong{don't} type @kbd{C-c C-c} in that | |
1295 | buffer. You can switch buffers and do other editing. As long as you | |
1296 | don't try to check in another file, the entry you were editing remains | |
1297 | in the @samp{*VC-Log*} buffer, and you can go back to that buffer at any | |
1298 | time to complete the check-in. | |
1299 | ||
1300 | If you change several source files for the same reason, it is often | |
1301 | convenient to specify the same log entry for many of the files. To do | |
1302 | this, use the history of previous log entries. The commands @kbd{M-n}, | |
1303 | @kbd{M-p}, @kbd{M-s} and @kbd{M-r} for doing this work just like the | |
1304 | minibuffer history commands (except that these versions are used outside | |
1305 | the minibuffer). | |
1306 | ||
1307 | @vindex vc-log-mode-hook | |
1308 | Each time you check in a file, the log entry buffer is put into VC Log | |
1309 | mode, which involves running two hooks: @code{text-mode-hook} and | |
1310 | @code{vc-log-mode-hook}. @xref{Hooks}. | |
1311 | ||
1312 | @node Old Versions | |
1313 | @subsection Examining And Comparing Old Versions | |
1314 | ||
1315 | One of the convenient features of version control is the ability | |
1316 | to examine any version of a file, or compare two versions. | |
1317 | ||
1318 | @table @kbd | |
1319 | @item C-x v ~ @var{version} @key{RET} | |
1320 | Examine version @var{version} of the visited file, in a buffer of its | |
1321 | own. | |
1322 | ||
1323 | @item C-x v = | |
1324 | Compare the current buffer contents with the latest checked-in version | |
1325 | of the file. | |
1326 | ||
1327 | @item C-u C-x v = @var{file} @key{RET} @var{oldvers} @key{RET} @var{newvers} @key{RET} | |
1328 | Compare the specified two versions of @var{file}. | |
1329 | ||
1330 | @item C-x v g | |
1331 | Display the result of the CVS annotate command using colors. | |
1332 | @end table | |
1333 | ||
1334 | @findex vc-version-other-window | |
1335 | @kindex C-x v ~ | |
1336 | To examine an old version in toto, visit the file and then type | |
1337 | @kbd{C-x v ~ @var{version} @key{RET}} (@code{vc-version-other-window}). | |
1338 | This puts the text of version @var{version} in a file named | |
1339 | @file{@var{filename}.~@var{version}~}, and visits it in its own buffer | |
1340 | in a separate window. (In RCS, you can also select an old version | |
1341 | and create a branch from it. @xref{Branches}.) | |
1342 | ||
1343 | @findex vc-diff | |
1344 | @kindex C-x v = | |
1345 | But usually it is more convenient to compare two versions of the file, | |
1346 | with the command @kbd{C-x v =} (@code{vc-diff}). Plain @kbd{C-x v =} | |
1347 | compares the current buffer contents (saving them in the file if | |
1348 | necessary) with the last checked-in version of the file. @kbd{C-u C-x v | |
1349 | =}, with a numeric argument, reads a file name and two version numbers, | |
1350 | then compares those versions of the specified file. | |
1351 | ||
1352 | If you supply a directory name instead of the name of a registered | |
1353 | file, this command compares the two specified versions of all registered | |
1354 | files in that directory and its subdirectories. | |
1355 | ||
1356 | You can specify a checked-in version by its number; an empty input | |
1357 | specifies the current contents of the work file (which may be different | |
1358 | from all the checked-in versions). You can also specify a snapshot name | |
1359 | (@pxref{Snapshots}) instead of one or both version numbers. | |
1360 | ||
1361 | This command works by running the @code{diff} utility, getting the | |
1362 | options from the variable @code{diff-switches}. It displays the output | |
1363 | in a special buffer in another window. Unlike the @kbd{M-x diff} | |
1364 | command, @kbd{C-x v =} does not try to locate the changes in the old and | |
1365 | new versions. This is because normally one or both versions do not | |
1366 | exist as files when you compare them; they exist only in the records of | |
1367 | the master file. @xref{Comparing Files}, for more information about | |
1368 | @kbd{M-x diff}. | |
1369 | ||
1370 | @findex vc-annotate | |
1371 | @kindex C-x v g | |
1372 | For CVS-controlled files, you can display the result of the CVS | |
1373 | annotate command, using colors to enhance the visual appearance. Use | |
1374 | the command @kbd{M-x vc-annotate} to do this. Red means new, blue means | |
1375 | old, and intermediate colors indicate intermediate ages. A prefix | |
1376 | argument @var{n} specifies a stretch factor for the time scale; it makes | |
1377 | each color cover a period @var{n} times as long. | |
1378 | ||
1379 | @node Secondary VC Commands | |
1380 | @subsection The Secondary Commands of VC | |
1381 | ||
1382 | This section explains the secondary commands of VC; those that you might | |
1383 | use once a day. | |
1384 | ||
1385 | @menu | |
1386 | * Registering:: Putting a file under version control. | |
1387 | * VC Status:: Viewing the VC status of files. | |
1388 | * VC Undo:: Cancelling changes before or after check-in. | |
1389 | * VC Dired Mode:: Listing files managed by version control. | |
1390 | * VC Dired Commands:: Commands to use in a VC Dired buffer. | |
1391 | @end menu | |
1392 | ||
1393 | @node Registering | |
1394 | @subsubsection Registering a File for Version Control | |
1395 | ||
1396 | @kindex C-x v i | |
1397 | @findex vc-register | |
1398 | You can put any file under version control by simply visiting it, and | |
1399 | then typing @w{@kbd{C-x v i}} (@code{vc-register}). | |
1400 | ||
1401 | @table @kbd | |
1402 | @item C-x v i | |
1403 | Register the visited file for version control. | |
1404 | @end table | |
1405 | ||
1406 | @vindex vc-default-back-end | |
1407 | To register the file, Emacs must choose which version control system | |
1408 | to use for it. You can specify your choice explicitly by setting | |
1409 | @code{vc-default-back-end} to @code{RCS}, @code{CVS} or @code{SCCS}. | |
1410 | Otherwise, if there is a subdirectory named @file{RCS}, @file{SCCS}, or | |
1411 | @file{CVS}, Emacs uses the corresponding version control system. In the | |
1412 | absence of any specification, the default choice is RCS if RCS is | |
1413 | installed, otherwise SCCS. | |
1414 | ||
1415 | If locking is in use, @kbd{C-x v i} leaves the file unlocked and | |
1416 | read-only. Type @kbd{C-x C-q} if you wish to start editing it. After | |
1417 | registering a file with CVS, you must subsequently commit the initial | |
1418 | version by typing @kbd{C-x C-q}. | |
1419 | ||
1420 | @vindex vc-default-init-version | |
1421 | The initial version number for a newly registered file is 1.1, by | |
1422 | default. You can specify a different default by setting the variable | |
1423 | @code{vc-default-init-version}, or you can give @kbd{C-x v i} a numeric | |
1424 | argument; then it reads the initial version number for this particular | |
1425 | file using the minibuffer. | |
1426 | ||
1427 | @vindex vc-initial-comment | |
1428 | If @code{vc-initial-comment} is non-@code{nil}, @kbd{C-x v i} reads an | |
1429 | initial comment to describe the purpose of this source file. Reading | |
1430 | the initial comment works like reading a log entry (@pxref{Log Buffer}). | |
1431 | ||
1432 | @node VC Status | |
1433 | @subsubsection VC Status Commands | |
1434 | ||
1435 | @table @kbd | |
1436 | @item C-x v l | |
1437 | Display version control state and change history. | |
1438 | @end table | |
1439 | ||
1440 | @kindex C-x v l | |
1441 | @findex vc-print-log | |
1442 | To view the detailed version control status and history of a file, | |
1443 | type @kbd{C-x v l} (@code{vc-print-log}). It displays the history of | |
1444 | changes to the current file, including the text of the log entries. The | |
1445 | output appears in a separate window. | |
1446 | ||
1447 | @node VC Undo | |
1448 | @subsubsection Undoing Version Control Actions | |
1449 | ||
1450 | @table @kbd | |
1451 | @item C-x v u | |
1452 | Revert the buffer and the file to the last checked-in version. | |
1453 | ||
1454 | @item C-x v c | |
1455 | Remove the last-entered change from the master for the visited file. | |
1456 | This undoes your last check-in. | |
1457 | @end table | |
1458 | ||
1459 | @kindex C-x v u | |
1460 | @findex vc-revert-buffer | |
1461 | If you want to discard your current set of changes and revert to the | |
1462 | last version checked in, use @kbd{C-x v u} (@code{vc-revert-buffer}). | |
1463 | This leaves the file unlocked; if locking is in use, you must first lock | |
1464 | the file again before you change it again. @kbd{C-x v u} requires | |
1465 | confirmation, unless it sees that you haven't made any changes since the | |
1466 | last checked-in version. | |
1467 | ||
1468 | @kbd{C-x v u} is also the command to unlock a file if you lock it and | |
1469 | then decide not to change it. | |
1470 | ||
1471 | @kindex C-x v c | |
1472 | @findex vc-cancel-version | |
1473 | To cancel a change that you already checked in, use @kbd{C-x v c} | |
1474 | (@code{vc-cancel-version}). This command discards all record of the | |
1475 | most recent checked-in version. @kbd{C-x v c} also offers to revert | |
1476 | your work file and buffer to the previous version (the one that precedes | |
1477 | the version that is deleted). | |
1478 | ||
1479 | If you answer @kbd{no}, VC keeps your changes in the buffer, and locks | |
1480 | the file. The no-revert option is useful when you have checked in a | |
1481 | change and then discover a trivial error in it; you can cancel the | |
1482 | erroneous check-in, fix the error, and check the file in again. | |
1483 | ||
1484 | When @kbd{C-x v c} does not revert the buffer, it unexpands all | |
1485 | version control headers in the buffer instead (@pxref{Version Headers}). | |
1486 | This is because the buffer no longer corresponds to any existing | |
1487 | version. If you check it in again, the check-in process will expand the | |
1488 | headers properly for the new version number. | |
1489 | ||
1490 | However, it is impossible to unexpand the RCS @samp{@w{$}Log$} header | |
1491 | automatically. If you use that header feature, you have to unexpand it | |
1492 | by hand---by deleting the entry for the version that you just canceled. | |
1493 | ||
1494 | Be careful when invoking @kbd{C-x v c}, as it is easy to lose a lot of | |
1495 | work with it. To help you be careful, this command always requires | |
1496 | confirmation with @kbd{yes}. Note also that this command is disabled | |
1497 | under CVS, because canceling versions is very dangerous and discouraged | |
1498 | with CVS. | |
1499 | ||
1500 | @node VC Dired Mode | |
1501 | @subsubsection Dired under VC | |
1502 | ||
fa474484 DL |
1503 | @cindex PCL-CVS |
1504 | @pindex cvs | |
1505 | @cindex CVS Dired Mode | |
f02d86a3 RS |
1506 | The VC Dired Mode described here works with all the version control |
1507 | systems that VC supports. Another more powerful facility, designed | |
1508 | specifically for CVS, is called PCL-CVS. @xref{Top, , About PCL-CVS, | |
1509 | pcl-cvs, PCL-CVS --- The Emacs Front-End to CVS}. | |
fa474484 | 1510 | |
6bf7aab6 DL |
1511 | @kindex C-x v d |
1512 | @findex vc-directory | |
1513 | When you are working on a large program, it is often useful to find | |
1514 | out which files have changed within an entire directory tree, or to view | |
1515 | the status of all files under version control at once, and to perform | |
1516 | version control operations on collections of files. You can use the | |
1517 | command @kbd{C-x v d} (@code{vc-directory}) to make a directory listing | |
1518 | that includes only files relevant for version control. | |
1519 | ||
1520 | @vindex vc-dired-terse-display | |
1521 | @kbd{C-x v d} creates a buffer which uses VC Dired Mode. This looks | |
1522 | much like an ordinary Dired buffer (@pxref{Dired}); however, normally it | |
1523 | shows only the noteworthy files (those locked or not up-to-date). This | |
1524 | is called @dfn{terse display}. If you set the variable | |
1525 | @code{vc-dired-terse-display} to @code{nil}, then VC Dired shows all | |
1526 | relevant files---those managed under version control, plus all | |
1527 | subdirectories (@dfn{full display}). The command @kbd{v t} in a VC | |
1528 | Dired buffer toggles between terse display and full display (@pxref{VC | |
1529 | Dired Commands}). | |
1530 | ||
1531 | @vindex vc-dired-recurse | |
1532 | By default, VC Dired produces a recursive listing of noteworthy or | |
1533 | relevant files at or below the given directory. You can change this by | |
1534 | setting the variable @code{vc-dired-recurse} to @code{nil}; then VC | |
1535 | Dired shows only the files in the given directory. | |
1536 | ||
1537 | The line for an individual file shows the version control state in the | |
1538 | place of the hard link count, owner, group, and size of the file. If | |
1539 | the file is unmodified, in sync with the master file, the version | |
1540 | control state shown is blank. Otherwise it consists of text in | |
1541 | parentheses. Under RCS and SCCS, the name of the user locking the file | |
1542 | is shown; under CVS, an abbreviated version of the @samp{cvs status} | |
1543 | output is used. Here is an example using RCS: | |
1544 | ||
1545 | @smallexample | |
1546 | @group | |
1547 | /home/jim/project: | |
1548 | ||
1549 | -rw-r--r-- (jim) Apr 2 23:39 file1 | |
1550 | -r--r--r-- Apr 5 20:21 file2 | |
1551 | @end group | |
1552 | @end smallexample | |
1553 | ||
1554 | @noindent | |
1555 | The files @samp{file1} and @samp{file2} are under version control, | |
1556 | @samp{file1} is locked by user jim, and @samp{file2} is unlocked. | |
1557 | ||
1558 | Here is an example using CVS: | |
1559 | ||
1560 | @smallexample | |
1561 | @group | |
1562 | /home/joe/develop: | |
1563 | ||
1564 | -rw-r--r-- (modified) Aug 2 1997 file1.c | |
1565 | -rw-r--r-- Apr 4 20:09 file2.c | |
1566 | -rw-r--r-- (merge) Sep 13 1996 file3.c | |
1567 | @end group | |
1568 | @end smallexample | |
1569 | ||
1570 | Here @samp{file1.c} is modified with respect to the repository, and | |
1571 | @samp{file2.c} is not. @samp{file3.c} is modified, but other changes | |
1572 | have also been checked in to the repository---you need to merge them | |
1573 | with the work file before you can check it in. | |
1574 | ||
1575 | @vindex vc-directory-exclusion-list | |
1576 | When VC Dired displays subdirectories (in the ``full'' display mode), | |
1577 | it omits some that should never contain any files under version control. | |
1578 | By default, this includes Version Control subdirectories such as | |
1579 | @samp{RCS} and @samp{CVS}; you can customize this by setting the | |
1580 | variable @code{vc-directory-exclusion-list}. | |
1581 | ||
1582 | You can fine-tune VC Dired's format by typing @kbd{C-u C-x v d}---as in | |
1583 | ordinary Dired, that allows you to specify additional switches for the | |
1584 | @samp{ls} command. | |
1585 | ||
1586 | @node VC Dired Commands | |
1587 | @subsubsection VC Dired Commands | |
1588 | ||
1589 | All the usual Dired commands work normally in VC Dired mode, except | |
1590 | for @kbd{v}, which is redefined as the version control prefix. You can | |
1591 | invoke VC commands such as @code{vc-diff} and @code{vc-print-log} by | |
1592 | typing @kbd{v =}, or @kbd{v l}, and so on. Most of these commands apply | |
1593 | to the file name on the current line. | |
1594 | ||
1595 | The command @kbd{v v} (@code{vc-next-action}) operates on all the | |
1596 | marked files, so that you can lock or check in several files at once. | |
1597 | If it operates on more than one file, it handles each file according to | |
1598 | its current state; thus, it might lock one file, but check in another | |
1599 | file. This could be confusing; it is up to you to avoid confusing | |
1600 | behavior by marking a set of files that are in a similar state. | |
1601 | ||
1602 | If any files call for check-in, @kbd{v v} reads a single log entry, | |
1603 | then uses it for all the files being checked in. This is convenient for | |
1604 | registering or checking in several files at once, as part of the same | |
1605 | change. | |
1606 | ||
1607 | @findex vc-dired-toggle-terse-mode | |
1608 | @findex vc-dired-mark-locked | |
1609 | You can toggle between terse display (only locked files, or files not | |
1610 | up-to-date) and full display at any time by typing @kbd{v t} | |
1611 | @code{vc-dired-toggle-terse-mode}. There is also a special command | |
1612 | @kbd{* l} (@code{vc-dired-mark-locked}), which marks all files currently | |
1613 | locked (or, with CVS, all files not up-to-date). Thus, typing @kbd{* l | |
1614 | t k} is another way to delete from the buffer all files except those | |
1615 | currently locked. | |
1616 | ||
1617 | @node Branches | |
1618 | @subsection Multiple Branches of a File | |
1619 | @cindex branch (version control) | |
1620 | @cindex trunk (version control) | |
1621 | ||
1622 | One use of version control is to maintain multiple ``current'' | |
1623 | versions of a file. For example, you might have different versions of a | |
1624 | program in which you are gradually adding various unfinished new | |
1625 | features. Each such independent line of development is called a | |
1626 | @dfn{branch}. VC allows you to create branches, switch between | |
1627 | different branches, and merge changes from one branch to another. | |
1628 | Please note, however, that branches are only supported for RCS at the | |
1629 | moment. | |
1630 | ||
1631 | A file's main line of development is usually called the @dfn{trunk}. | |
1632 | The versions on the trunk are normally numbered 1.1, 1.2, 1.3, etc. At | |
1633 | any such version, you can start an independent branch. A branch | |
1634 | starting at version 1.2 would have version number 1.2.1.1, and consecutive | |
1635 | versions on this branch would have numbers 1.2.1.2, 1.2.1.3, 1.2.1.4, | |
1636 | and so on. If there is a second branch also starting at version 1.2, it | |
1637 | would consist of versions 1.2.2.1, 1.2.2.2, 1.2.2.3, etc. | |
1638 | ||
1639 | @cindex head version | |
1640 | If you omit the final component of a version number, that is called a | |
1641 | @dfn{branch number}. It refers to the highest existing version on that | |
1642 | branch---the @dfn{head version} of that branch. The branches in the | |
1643 | example above have branch numbers 1.2.1 and 1.2.2. | |
1644 | ||
1645 | @menu | |
1646 | * Switching Branches:: How to get to another existing branch. | |
1647 | * Creating Branches:: How to start a new branch. | |
1648 | * Merging:: Transferring changes between branches. | |
1649 | * Multi-User Branching:: Multiple users working at multiple branches | |
1650 | in parallel. | |
1651 | @end menu | |
1652 | ||
1653 | @node Switching Branches | |
1654 | @subsubsection Switching between Branches | |
1655 | ||
1656 | To switch between branches, type @kbd{C-u C-x C-q} and specify the | |
1657 | version number you want to select. This version is then visited | |
1658 | @emph{unlocked} (write-protected), so you can examine it before locking | |
1659 | it. Switching branches in this way is allowed only when the file is not | |
1660 | locked. | |
1661 | ||
1662 | You can omit the minor version number, thus giving only the branch | |
1663 | number; this takes you to the head version on the chosen branch. If you | |
1664 | only type @key{RET}, Emacs goes to the highest version on the trunk. | |
1665 | ||
1666 | After you have switched to any branch (including the main branch), you | |
1667 | stay on it for subsequent VC commands, until you explicitly select some | |
1668 | other branch. | |
1669 | ||
1670 | @node Creating Branches | |
1671 | @subsubsection Creating New Branches | |
1672 | ||
1673 | To create a new branch from a head version (one that is the latest in | |
1674 | the branch that contains it), first select that version if necessary, | |
1675 | lock it with @kbd{C-x C-q}, and make whatever changes you want. Then, | |
1676 | when you check in the changes, use @kbd{C-u C-x C-q}. This lets you | |
1677 | specify the version number for the new version. You should specify a | |
1678 | suitable branch number for a branch starting at the current version. | |
1679 | For example, if the current version is 2.5, the branch number should be | |
1680 | 2.5.1, 2.5.2, and so on, depending on the number of existing branches at | |
1681 | that point. | |
1682 | ||
1683 | To create a new branch at an older version (one that is no longer the | |
1684 | head of a branch), first select that version (@pxref{Switching | |
1685 | Branches}), then lock it with @kbd{C-x C-q}. You'll be asked to | |
1686 | confirm, when you lock the old version, that you really mean to create a | |
1687 | new branch---if you say no, you'll be offered a chance to lock the | |
1688 | latest version instead. | |
1689 | ||
1690 | Then make your changes and type @kbd{C-x C-q} again to check in a new | |
1691 | version. This automatically creates a new branch starting from the | |
1692 | selected version. You need not specially request a new branch, because | |
1693 | that's the only way to add a new version at a point that is not the head | |
1694 | of a branch. | |
1695 | ||
1696 | After the branch is created, you ``stay'' on it. That means that | |
1697 | subsequent check-ins create new versions on that branch. To leave the | |
1698 | branch, you must explicitly select a different version with @kbd{C-u C-x | |
1699 | C-q}. To transfer changes from one branch to another, use the merge | |
1700 | command, described in the next section. | |
1701 | ||
1702 | @node Merging | |
1703 | @subsubsection Merging Branches | |
1704 | ||
1705 | @cindex merging changes | |
1706 | When you have finished the changes on a certain branch, you will | |
1707 | often want to incorporate them into the file's main line of development | |
1708 | (the trunk). This is not a trivial operation, because development might | |
1709 | also have proceeded on the trunk, so that you must @dfn{merge} the | |
1710 | changes into a file that has already been changed otherwise. VC allows | |
1711 | you to do this (and other things) with the @code{vc-merge} command. | |
1712 | ||
1713 | @table @kbd | |
1714 | @item C-x v m (vc-merge) | |
1715 | Merge changes into the work file. | |
1716 | @end table | |
1717 | ||
1718 | @kindex C-x v m | |
1719 | @findex vc-merge | |
1720 | @kbd{C-x v m} (@code{vc-merge}) takes a set of changes and merges it | |
1721 | into the current version of the work file. It first asks you for a | |
1722 | branch number or a pair of version numbers in the minibuffer. Then it | |
1723 | finds the changes from that branch, or between the two versions you | |
1724 | specified, and merges them into the current version of the current file. | |
1725 | ||
1726 | As an example, suppose that you have finished a certain feature on | |
1727 | branch 1.3.1. In the meantime, development on the trunk has proceeded | |
1728 | to version 1.5. To merge the changes from the branch to the trunk, | |
1729 | first go to the head version of the trunk, by typing @kbd{C-u C-x C-q | |
1730 | RET}. Version 1.5 is now current. If locking is used for the file, | |
1731 | type @kbd{C-x C-q} to lock version 1.5 so that you can change it. Next, | |
1732 | type @kbd{C-x v m 1.3.1 RET}. This takes the entire set of changes on | |
1733 | branch 1.3.1 (relative to version 1.3, where the branch started, up to | |
1734 | the last version on the branch) and merges it into the current version | |
1735 | of the work file. You can now check in the changed file, thus creating | |
1736 | version 1.6 containing the changes from the branch. | |
1737 | ||
1738 | It is possible to do further editing after merging the branch, before | |
1739 | the next check-in. But it is usually wiser to check in the merged | |
1740 | version, then lock it and make the further changes. This will keep | |
1741 | a better record of the history of changes. | |
1742 | ||
1743 | @cindex conflicts | |
1744 | @cindex resolving conflicts | |
1745 | When you merge changes into a file that has itself been modified, the | |
1746 | changes might overlap. We call this situation a @dfn{conflict}, and | |
1747 | reconciling the conflicting changes is called @dfn{resolving a | |
1748 | conflict}. | |
1749 | ||
1750 | Whenever conflicts occur during merging, VC detects them, tells you | |
1751 | about them in the echo area, and asks whether you want help in merging. | |
1752 | If you say yes, it starts an Ediff session (@pxref{Top, | |
1753 | Ediff, Ediff, ediff, The Ediff Manual}). | |
1754 | ||
1755 | If you say no, the conflicting changes are both inserted into the | |
1756 | file, surrounded by @dfn{conflict markers}. The example below shows how | |
1757 | a conflict region looks; the file is called @samp{name} and the current | |
1758 | master file version with user B's changes in it is 1.11. | |
1759 | ||
1760 | @c @w here is so CVS won't think this is a conflict. | |
1761 | @smallexample | |
1762 | @group | |
1763 | @w{<}<<<<<< name | |
1764 | @var{User A's version} | |
1765 | ======= | |
1766 | @var{User B's version} | |
1767 | @w{>}>>>>>> 1.11 | |
1768 | @end group | |
1769 | @end smallexample | |
1770 | ||
1771 | @cindex vc-resolve-conflicts | |
1772 | Then you can resolve the conflicts by editing the file manually. Or | |
1773 | you can type @code{M-x vc-resolve-conflicts} after visiting the file. | |
1774 | This starts an Ediff session, as described above. | |
1775 | ||
1776 | @node Multi-User Branching | |
1777 | @subsubsection Multi-User Branching | |
1778 | ||
1779 | It is often useful for multiple developers to work simultaneously on | |
1780 | different branches of a file. CVS allows this by default; for RCS, it | |
1781 | is possible if you create multiple source directories. Each source | |
1782 | directory should have a link named @file{RCS} which points to a common | |
1783 | directory of RCS master files. Then each source directory can have its | |
1784 | own choice of selected versions, but all share the same common RCS | |
1785 | records. | |
1786 | ||
1787 | This technique works reliably and automatically, provided that the | |
1788 | source files contain RCS version headers (@pxref{Version Headers}). The | |
1789 | headers enable Emacs to be sure, at all times, which version number is | |
1790 | present in the work file. | |
1791 | ||
1792 | If the files do not have version headers, you must instead tell Emacs | |
1793 | explicitly in each session which branch you are working on. To do this, | |
1794 | first find the file, then type @kbd{C-u C-x C-q} and specify the correct | |
1795 | branch number. This ensures that Emacs knows which branch it is using | |
1796 | during this particular editing session. | |
1797 | ||
1798 | @node Snapshots | |
1799 | @subsection Snapshots | |
1800 | @cindex snapshots and version control | |
1801 | ||
1802 | A @dfn{snapshot} is a named set of file versions (one for each | |
1803 | registered file) that you can treat as a unit. One important kind of | |
1804 | snapshot is a @dfn{release}, a (theoretically) stable version of the | |
1805 | system that is ready for distribution to users. | |
1806 | ||
1807 | @menu | |
1808 | * Making Snapshots:: The snapshot facilities. | |
1809 | * Snapshot Caveats:: Things to be careful of when using snapshots. | |
1810 | @end menu | |
1811 | ||
1812 | @node Making Snapshots | |
1813 | @subsubsection Making and Using Snapshots | |
1814 | ||
1815 | There are two basic commands for snapshots; one makes a | |
1816 | snapshot with a given name, the other retrieves a named snapshot. | |
1817 | ||
1818 | @table @code | |
1819 | @kindex C-x v s | |
1820 | @findex vc-create-snapshot | |
1821 | @item C-x v s @var{name} @key{RET} | |
1822 | Define the last saved versions of every registered file in or under the | |
1823 | current directory as a snapshot named @var{name} | |
1824 | (@code{vc-create-snapshot}). | |
1825 | ||
1826 | @kindex C-x v r | |
1827 | @findex vc-retrieve-snapshot | |
1828 | @item C-x v r @var{name} @key{RET} | |
1829 | For all registered files at or below the current directory level, select | |
1830 | whatever versions correspond to the snapshot @var{name} | |
1831 | (@code{vc-retrieve-snapshot}). | |
1832 | ||
1833 | This command reports an error if any files are locked at or below the | |
1834 | current directory, without changing anything; this is to avoid | |
1835 | overwriting work in progress. | |
1836 | @end table | |
1837 | ||
1838 | A snapshot uses a very small amount of resources---just enough to record | |
1839 | the list of file names and which version belongs to the snapshot. Thus, | |
1840 | you need not hesitate to create snapshots whenever they are useful. | |
1841 | ||
1842 | You can give a snapshot name as an argument to @kbd{C-x v =} or | |
1843 | @kbd{C-x v ~} (@pxref{Old Versions}). Thus, you can use it to compare a | |
1844 | snapshot against the current files, or two snapshots against each other, | |
1845 | or a snapshot against a named version. | |
1846 | ||
1847 | @node Snapshot Caveats | |
1848 | @subsubsection Snapshot Caveats | |
1849 | ||
1850 | @cindex named configurations (RCS) | |
1851 | VC's snapshot facilities are modeled on RCS's named-configuration | |
1852 | support. They use RCS's native facilities for this, so under VC | |
1853 | snapshots made using RCS are visible even when you bypass VC. | |
1854 | ||
1855 | @c worded verbosely to avoid overfull hbox. | |
1856 | For SCCS, VC implements snapshots itself. The files it uses contain | |
1857 | name/file/version-number triples. These snapshots are visible only | |
1858 | through VC. | |
1859 | ||
1860 | A snapshot is a set of checked-in versions. So make sure that all the | |
1861 | files are checked in and not locked when you make a snapshot. | |
1862 | ||
1863 | File renaming and deletion can create some difficulties with snapshots. | |
1864 | This is not a VC-specific problem, but a general design issue in version | |
1865 | control systems that no one has solved very well yet. | |
1866 | ||
1867 | If you rename a registered file, you need to rename its master along | |
1868 | with it (the command @code{vc-rename-file} does this automatically). If | |
1869 | you are using SCCS, you must also update the records of the snapshot, to | |
1870 | mention the file by its new name (@code{vc-rename-file} does this, | |
1871 | too). An old snapshot that refers to a master file that no longer | |
1872 | exists under the recorded name is invalid; VC can no longer retrieve | |
1873 | it. It would be beyond the scope of this manual to explain enough about | |
1874 | RCS and SCCS to explain how to update the snapshots by hand. | |
1875 | ||
1876 | Using @code{vc-rename-file} makes the snapshot remain valid for | |
1877 | retrieval, but it does not solve all problems. For example, some of the | |
1878 | files in the program probably refer to others by name. At the very | |
1879 | least, the makefile probably mentions the file that you renamed. If you | |
1880 | retrieve an old snapshot, the renamed file is retrieved under its new | |
1881 | name, which is not the name that the makefile expects. So the program | |
1882 | won't really work as retrieved. | |
1883 | ||
1884 | @node Miscellaneous VC | |
1885 | @subsection Miscellaneous Commands and Features of VC | |
1886 | ||
1887 | This section explains the less-frequently-used features of VC. | |
1888 | ||
1889 | @menu | |
1890 | * Change Logs and VC:: Generating a change log file from log entries. | |
1891 | * Renaming and VC:: A command to rename both the source and master | |
1892 | file correctly. | |
1893 | * Version Headers:: Inserting version control headers into working files. | |
1894 | @end menu | |
1895 | ||
1896 | @node Change Logs and VC | |
1897 | @subsubsection Change Logs and VC | |
1898 | ||
1899 | If you use RCS or CVS for a program and also maintain a change log | |
1900 | file for it (@pxref{Change Log}), you can generate change log entries | |
1901 | automatically from the version control log entries: | |
1902 | ||
1903 | @table @kbd | |
1904 | @item C-x v a | |
1905 | @kindex C-x v a | |
1906 | @findex vc-update-change-log | |
1907 | Visit the current directory's change log file and, for registered files | |
1908 | in that directory, create new entries for versions checked in since the | |
1909 | most recent entry in the change log file. | |
1910 | (@code{vc-update-change-log}). | |
1911 | ||
1912 | This command works with RCS or CVS only, not with SCCS. | |
1913 | ||
1914 | @item C-u C-x v a | |
1915 | As above, but only find entries for the current buffer's file. | |
1916 | ||
1917 | @item M-1 C-x v a | |
1918 | As above, but find entries for all the currently visited files that are | |
1919 | maintained with version control. This works only with RCS, and it puts | |
1920 | all entries in the log for the default directory, which may not be | |
1921 | appropriate. | |
1922 | @end table | |
1923 | ||
1924 | For example, suppose the first line of @file{ChangeLog} is dated | |
1925 | 1999-04-10, and that the only check-in since then was by Nathaniel | |
1926 | Bowditch to @file{rcs2log} on 1999-05-22 with log text @samp{Ignore log | |
1927 | messages that start with `#'.}. Then @kbd{C-x v a} visits | |
1928 | @file{ChangeLog} and inserts text like this: | |
1929 | ||
1930 | @iftex | |
1931 | @medbreak | |
1932 | @end iftex | |
1933 | @smallexample | |
1934 | @group | |
1935 | 1999-05-22 Nathaniel Bowditch <nat@@apn.org> | |
1936 | ||
1937 | * rcs2log: Ignore log messages that start with `#'. | |
1938 | @end group | |
1939 | @end smallexample | |
1940 | @iftex | |
1941 | @medbreak | |
1942 | @end iftex | |
1943 | ||
1944 | @noindent | |
1945 | You can then edit the new change log entry further as you wish. | |
1946 | ||
1947 | Unfortunately, timestamps in ChangeLog files are only dates, so some | |
1948 | of the new change log entry may duplicate what's already in ChangeLog. | |
1949 | You will have to remove these duplicates by hand. | |
1950 | ||
1951 | Normally, the log entry for file @file{foo} is displayed as @samp{* | |
1952 | foo: @var{text of log entry}}. The @samp{:} after @file{foo} is omitted | |
1953 | if the text of the log entry starts with @w{@samp{(@var{functionname}): | |
1954 | }}. For example, if the log entry for @file{vc.el} is | |
1955 | @samp{(vc-do-command): Check call-process status.}, then the text in | |
1956 | @file{ChangeLog} looks like this: | |
1957 | ||
1958 | @iftex | |
1959 | @medbreak | |
1960 | @end iftex | |
1961 | @smallexample | |
1962 | @group | |
1963 | 1999-05-06 Nathaniel Bowditch <nat@@apn.org> | |
1964 | ||
1965 | * vc.el (vc-do-command): Check call-process status. | |
1966 | @end group | |
1967 | @end smallexample | |
1968 | @iftex | |
1969 | @medbreak | |
1970 | @end iftex | |
1971 | ||
1972 | When @kbd{C-x v a} adds several change log entries at once, it groups | |
1973 | related log entries together if they all are checked in by the same | |
1974 | author at nearly the same time. If the log entries for several such | |
1975 | files all have the same text, it coalesces them into a single entry. | |
1976 | For example, suppose the most recent check-ins have the following log | |
1977 | entries: | |
1978 | ||
1979 | @flushleft | |
1980 | @bullet{} For @file{vc.texinfo}: @samp{Fix expansion typos.} | |
1981 | @bullet{} For @file{vc.el}: @samp{Don't call expand-file-name.} | |
1982 | @bullet{} For @file{vc-hooks.el}: @samp{Don't call expand-file-name.} | |
1983 | @end flushleft | |
1984 | ||
1985 | @noindent | |
1986 | They appear like this in @file{ChangeLog}: | |
1987 | ||
1988 | @iftex | |
1989 | @medbreak | |
1990 | @end iftex | |
1991 | @smallexample | |
1992 | @group | |
1993 | 1999-04-01 Nathaniel Bowditch <nat@@apn.org> | |
1994 | ||
1995 | * vc.texinfo: Fix expansion typos. | |
1996 | ||
1997 | * vc.el, vc-hooks.el: Don't call expand-file-name. | |
1998 | @end group | |
1999 | @end smallexample | |
2000 | @iftex | |
2001 | @medbreak | |
2002 | @end iftex | |
2003 | ||
2004 | Normally, @kbd{C-x v a} separates log entries by a blank line, but you | |
2005 | can mark several related log entries to be clumped together (without an | |
2006 | intervening blank line) by starting the text of each related log entry | |
2007 | with a label of the form @w{@samp{@{@var{clumpname}@} }}. The label | |
2008 | itself is not copied to @file{ChangeLog}. For example, suppose the log | |
2009 | entries are: | |
2010 | ||
2011 | @flushleft | |
2012 | @bullet{} For @file{vc.texinfo}: @samp{@{expand@} Fix expansion typos.} | |
2013 | @bullet{} For @file{vc.el}: @samp{@{expand@} Don't call expand-file-name.} | |
2014 | @bullet{} For @file{vc-hooks.el}: @samp{@{expand@} Don't call expand-file-name.} | |
2015 | @end flushleft | |
2016 | ||
2017 | @noindent | |
2018 | Then the text in @file{ChangeLog} looks like this: | |
2019 | ||
2020 | @iftex | |
2021 | @medbreak | |
2022 | @end iftex | |
2023 | @smallexample | |
2024 | @group | |
2025 | 1999-04-01 Nathaniel Bowditch <nat@@apn.org> | |
2026 | ||
2027 | * vc.texinfo: Fix expansion typos. | |
2028 | * vc.el, vc-hooks.el: Don't call expand-file-name. | |
2029 | @end group | |
2030 | @end smallexample | |
2031 | @iftex | |
2032 | @medbreak | |
2033 | @end iftex | |
2034 | ||
2035 | A log entry whose text begins with @samp{#} is not copied to | |
2036 | @file{ChangeLog}. For example, if you merely fix some misspellings in | |
2037 | comments, you can log the change with an entry beginning with @samp{#} | |
2038 | to avoid putting such trivia into @file{ChangeLog}. | |
2039 | ||
2040 | @node Renaming and VC | |
2041 | @subsubsection Renaming VC Work Files and Master Files | |
2042 | ||
2043 | @findex vc-rename-file | |
2044 | When you rename a registered file, you must also rename its master | |
2045 | file correspondingly to get proper results. Use @code{vc-rename-file} | |
2046 | to rename the source file as you specify, and rename its master file | |
2047 | accordingly. It also updates any snapshots (@pxref{Snapshots}) that | |
2048 | mention the file, so that they use the new name; despite this, the | |
2049 | snapshot thus modified may not completely work (@pxref{Snapshot | |
2050 | Caveats}). | |
2051 | ||
2052 | You cannot use @code{vc-rename-file} on a file that is locked by | |
2053 | someone else. | |
2054 | ||
2055 | @node Version Headers | |
2056 | @subsubsection Inserting Version Control Headers | |
2057 | ||
2058 | Sometimes it is convenient to put version identification strings | |
2059 | directly into working files. Certain special strings called | |
2060 | @dfn{version headers} are replaced in each successive version by the | |
2061 | number of that version. | |
2062 | ||
2063 | If you are using RCS, and version headers are present in your working | |
2064 | files, Emacs can use them to determine the current version and the | |
2065 | locking state of the files. This is more reliable than referring to the | |
2066 | master files, which is done when there are no version headers. Note | |
2067 | that in a multi-branch environment, version headers are necessary to | |
2068 | make VC behave correctly (@pxref{Multi-User Branching}). | |
2069 | ||
2070 | Searching for version headers is controlled by the variable | |
2071 | @code{vc-consult-headers}. If it is non-@code{nil}, Emacs searches for | |
2072 | headers to determine the version number you are editing. Setting it to | |
2073 | @code{nil} disables this feature. | |
2074 | ||
2075 | @kindex C-x v h | |
2076 | @findex vc-insert-headers | |
2077 | You can use the @kbd{C-x v h} command (@code{vc-insert-headers}) to | |
2078 | insert a suitable header string. | |
2079 | ||
2080 | @table @kbd | |
2081 | @item C-x v h | |
2082 | Insert headers in a file for use with your version-control system. | |
2083 | @end table | |
2084 | ||
2085 | @vindex vc-header-alist | |
2086 | The default header string is @samp{@w{$}Id$} for RCS and | |
2087 | @samp{@w{%}W%} for SCCS. You can specify other headers to insert by | |
2088 | setting the variable @code{vc-header-alist}. Its value is a list of | |
2089 | elements of the form @code{(@var{program} . @var{string})} where | |
2090 | @var{program} is @code{RCS} or @code{SCCS} and @var{string} is the | |
2091 | string to use. | |
2092 | ||
2093 | Instead of a single string, you can specify a list of strings; then | |
2094 | each string in the list is inserted as a separate header on a line of | |
2095 | its own. | |
2096 | ||
2097 | It is often necessary to use ``superfluous'' backslashes when writing | |
2098 | the strings that you put in this variable. This is to prevent the | |
2099 | string in the constant from being interpreted as a header itself if the | |
2100 | Emacs Lisp file containing it is maintained with version control. | |
2101 | ||
2102 | @vindex vc-comment-alist | |
2103 | Each header is inserted surrounded by tabs, inside comment delimiters, | |
2104 | on a new line at point. Normally the ordinary comment | |
2105 | start and comment end strings of the current mode are used, but for | |
2106 | certain modes, there are special comment delimiters for this purpose; | |
2107 | the variable @code{vc-comment-alist} specifies them. Each element of | |
2108 | this list has the form @code{(@var{mode} @var{starter} @var{ender})}. | |
2109 | ||
2110 | @vindex vc-static-header-alist | |
2111 | The variable @code{vc-static-header-alist} specifies further strings | |
2112 | to add based on the name of the buffer. Its value should be a list of | |
2113 | elements of the form @code{(@var{regexp} . @var{format})}. Whenever | |
2114 | @var{regexp} matches the buffer name, @var{format} is inserted as part | |
2115 | of the header. A header line is inserted for each element that matches | |
2116 | the buffer name, and for each string specified by | |
2117 | @code{vc-header-alist}. The header line is made by processing the | |
2118 | string from @code{vc-header-alist} with the format taken from the | |
2119 | element. The default value for @code{vc-static-header-alist} is as follows: | |
2120 | ||
2121 | @example | |
2122 | @group | |
2123 | (("\\.c$" . | |
2124 | "\n#ifndef lint\nstatic char vcid[] = \"\%s\";\n\ | |
2125 | #endif /* lint */\n")) | |
2126 | @end group | |
2127 | @end example | |
2128 | ||
2129 | @noindent | |
2130 | It specifies insertion of text of this form: | |
2131 | ||
2132 | @example | |
2133 | @group | |
2134 | ||
2135 | #ifndef lint | |
2136 | static char vcid[] = "@var{string}"; | |
2137 | #endif /* lint */ | |
2138 | @end group | |
2139 | @end example | |
2140 | ||
2141 | @noindent | |
2142 | Note that the text above starts with a blank line. | |
2143 | ||
2144 | If you use more than one version header in a file, put them close | |
2145 | together in the file. The mechanism in @code{revert-buffer} that | |
2146 | preserves markers may not handle markers positioned between two version | |
2147 | headers. | |
2148 | ||
2149 | @node Customizing VC | |
2150 | @subsection Customizing VC | |
2151 | ||
2152 | There are many ways of customizing VC. The options you can set fall | |
2153 | into four categories, described in the following sections. | |
2154 | ||
2155 | @menu | |
2156 | * Backend Options:: Customizing the back-end to your needs. | |
2157 | * VC Workfile Handling:: Various options concerning working files. | |
2158 | * VC Status Retrieval:: How VC finds the version control status of a file, | |
2159 | and how to customize this. | |
2160 | * VC Command Execution:: Which commands VC should run, and how. | |
2161 | @end menu | |
2162 | ||
2163 | @node Backend Options | |
2164 | @subsubsection Options for VC Backends | |
2165 | ||
f02d86a3 RS |
2166 | @vindex vc-handled-backends |
2167 | By default, VC detects automatically which files are managed by RCS, | |
2168 | which by CVS, and which by SCCS, and it tries to do the right thing in | |
2169 | all three cases. If you want VC to ignore one or more of these | |
2170 | backends, set @code{vc-handled-backends} to the list of backends that | |
2171 | @emph{should} be handled. | |
2172 | ||
6bf7aab6 DL |
2173 | @cindex backend options (VC) |
2174 | @cindex locking under version control | |
2175 | You can tell RCS and CVS whether to use locking for a file or not | |
2176 | (@pxref{VC Concepts}, for a description of locking). VC automatically | |
2177 | recognizes what you have chosen, and behaves accordingly. | |
2178 | ||
2179 | @cindex non-strict locking (RCS) | |
2180 | @cindex locking, non-strict (RCS) | |
2181 | For RCS, the default is to use locking, but there is a mode called | |
2182 | @dfn{non-strict locking} in which you can check-in changes without | |
2183 | locking the file first. Use @samp{rcs -U} to switch to non-strict | |
2184 | locking for a particular file, see the @samp{rcs} manpage for details. | |
2185 | ||
2186 | @cindex locking (CVS) | |
2187 | Under CVS, the default is not to use locking; anyone can change a work | |
2188 | file at any time. However, there are ways to restrict this, resulting | |
2189 | in behavior that resembles locking. | |
2190 | ||
2191 | @cindex CVSREAD environment variable (CVS) | |
60a96371 | 2192 | For one thing, you can set the @env{CVSREAD} environment variable to |
6bf7aab6 DL |
2193 | an arbitrary value. If this variable is defined, CVS makes your work |
2194 | files read-only by default. In Emacs, you must type @kbd{C-x C-q} to | |
2195 | make the file writeable, so that editing works in fact similar as if | |
2196 | locking was used. Note however, that no actual locking is performed, so | |
2197 | several users can make their files writeable at the same time. When | |
60a96371 | 2198 | setting @env{CVSREAD} for the first time, make sure to check out all |
6bf7aab6 DL |
2199 | your modules anew, so that the file protections are set correctly. |
2200 | ||
2201 | @cindex cvs watch feature | |
2202 | @cindex watching files (CVS) | |
2203 | Another way to achieve something similar to locking is to use the | |
2204 | @dfn{watch} feature of CVS. If a file is being watched, CVS makes it | |
2205 | read-only by default, and you must also use @kbd{C-x C-q} in Emacs to | |
2206 | make it writable. VC calls @code{cvs edit} to make the file writeable, | |
2207 | and CVS takes care to notify other developers of the fact that you | |
2208 | intend to change the file. See the CVS documentation for details on | |
2209 | using the watch feature. | |
2210 | ||
6bf7aab6 DL |
2211 | @node VC Workfile Handling |
2212 | @subsubsection VC Workfile Handling | |
2213 | ||
2214 | @vindex vc-make-backup-files | |
2215 | Emacs normally does not save backup files for source files that are | |
2216 | maintained with version control. If you want to make backup files even | |
2217 | for files that use version control, set the variable | |
2218 | @code{vc-make-backup-files} to a non-@code{nil} value. | |
2219 | ||
2220 | @vindex vc-keep-workfiles | |
2221 | Normally the work file exists all the time, whether it is locked or | |
2222 | not. If you set @code{vc-keep-workfiles} to @code{nil}, then checking | |
2223 | in a new version with @kbd{C-x C-q} deletes the work file; but any | |
2224 | attempt to visit the file with Emacs creates it again. (With CVS, work | |
2225 | files are always kept.) | |
2226 | ||
2227 | @vindex vc-follow-symlinks | |
2228 | Editing a version-controlled file through a symbolic link can be | |
2229 | dangerous. It bypasses the version control system---you can edit the | |
2230 | file without locking it, and fail to check your changes in. Also, | |
2231 | your changes might overwrite those of another user. To protect against | |
2232 | this, VC checks each symbolic link that you visit, to see if it points | |
2233 | to a file under version control. | |
2234 | ||
2235 | The variable @code{vc-follow-symlinks} controls what to do when a | |
2236 | symbolic link points to a version-controlled file. If it is @code{nil}, | |
2237 | VC only displays a warning message. If it is @code{t}, VC automatically | |
2238 | follows the link, and visits the real file instead, telling you about | |
2239 | this in the echo area. If the value is @code{ask} (the default), VC | |
2240 | asks you each time whether to follow the link. | |
2241 | ||
2242 | @node VC Status Retrieval | |
2243 | @subsubsection VC Status Retrieval | |
2244 | @c There is no need to tell users about vc-master-templates. | |
2245 | ||
2246 | When deducing the locked/unlocked state of a file, VC first looks for | |
2247 | an RCS version header string in the file (@pxref{Version Headers}). If | |
2248 | there is no header string, or if you are using SCCS, VC normally looks | |
2249 | at the file permissions of the work file; this is fast. But there might | |
2250 | be situations when the file permissions cannot be trusted. In this case | |
2251 | the master file has to be consulted, which is rather expensive. Also | |
2252 | the master file can only tell you @emph{if} there's any lock on the | |
2253 | file, but not whether your work file really contains that locked | |
2254 | version. | |
2255 | ||
2256 | @vindex vc-consult-headers | |
2257 | You can tell VC not to use version headers to determine lock status by | |
2258 | setting @code{vc-consult-headers} to @code{nil}. VC then always uses | |
2259 | the file permissions (if it can trust them), or else checks the master | |
2260 | file. | |
2261 | ||
2262 | @vindex vc-mistrust-permissions | |
2263 | You can specify the criterion for whether to trust the file | |
2264 | permissions by setting the variable @code{vc-mistrust-permissions}. Its | |
2265 | value can be @code{t} (always mistrust the file permissions and check | |
2266 | the master file), @code{nil} (always trust the file permissions), or a | |
2267 | function of one argument which makes the decision. The argument is the | |
2268 | directory name of the @file{RCS}, @file{CVS} or @file{SCCS} | |
2269 | subdirectory. A non-@code{nil} value from the function says to mistrust | |
2270 | the file permissions. If you find that the file permissions of work | |
2271 | files are changed erroneously, set @code{vc-mistrust-permissions} to | |
2272 | @code{t}. Then VC always checks the master file to determine the file's | |
2273 | status. | |
2274 | ||
2275 | @node VC Command Execution | |
2276 | @subsubsection VC Command Execution | |
2277 | ||
2278 | @vindex vc-suppress-confirm | |
2279 | If @code{vc-suppress-confirm} is non-@code{nil}, then @kbd{C-x C-q} | |
2280 | and @kbd{C-x v i} can save the current buffer without asking, and | |
2281 | @kbd{C-x v u} also operates without asking for confirmation. (This | |
2282 | variable does not affect @kbd{C-x v c}; that operation is so drastic | |
2283 | that it should always ask for confirmation.) | |
2284 | ||
2285 | @vindex vc-command-messages | |
2286 | VC mode does much of its work by running the shell commands for RCS, | |
2287 | CVS and SCCS. If @code{vc-command-messages} is non-@code{nil}, VC | |
2288 | displays messages to indicate which shell commands it runs, and | |
2289 | additional messages when the commands finish. | |
2290 | ||
2291 | @vindex vc-path | |
2292 | You can specify additional directories to search for version control | |
2293 | programs by setting the variable @code{vc-path}. These directories are | |
2294 | searched before the usual search path. But the proper files are usually | |
2295 | found automatically. | |
2296 | ||
2297 | @node Directories | |
2298 | @section File Directories | |
2299 | ||
2300 | @cindex file directory | |
2301 | @cindex directory listing | |
2302 | The file system groups files into @dfn{directories}. A @dfn{directory | |
2303 | listing} is a list of all the files in a directory. Emacs provides | |
2304 | commands to create and delete directories, and to make directory | |
2305 | listings in brief format (file names only) and verbose format (sizes, | |
2306 | dates, and authors included). There is also a directory browser called | |
2307 | Dired; see @ref{Dired}. | |
2308 | ||
2309 | @table @kbd | |
2310 | @item C-x C-d @var{dir-or-pattern} @key{RET} | |
2311 | Display a brief directory listing (@code{list-directory}). | |
2312 | @item C-u C-x C-d @var{dir-or-pattern} @key{RET} | |
2313 | Display a verbose directory listing. | |
2314 | @item M-x make-directory @key{RET} @var{dirname} @key{RET} | |
2315 | Create a new directory named @var{dirname}. | |
2316 | @item M-x delete-directory @key{RET} @var{dirname} @key{RET} | |
2317 | Delete the directory named @var{dirname}. It must be empty, | |
2318 | or you get an error. | |
2319 | @end table | |
2320 | ||
2321 | @findex list-directory | |
2322 | @kindex C-x C-d | |
2323 | The command to display a directory listing is @kbd{C-x C-d} | |
2324 | (@code{list-directory}). It reads using the minibuffer a file name | |
2325 | which is either a directory to be listed or a wildcard-containing | |
2326 | pattern for the files to be listed. For example, | |
2327 | ||
2328 | @example | |
2329 | C-x C-d /u2/emacs/etc @key{RET} | |
2330 | @end example | |
2331 | ||
2332 | @noindent | |
2333 | lists all the files in directory @file{/u2/emacs/etc}. Here is an | |
2334 | example of specifying a file name pattern: | |
2335 | ||
2336 | @example | |
2337 | C-x C-d /u2/emacs/src/*.c @key{RET} | |
2338 | @end example | |
2339 | ||
2340 | Normally, @kbd{C-x C-d} prints a brief directory listing containing | |
2341 | just file names. A numeric argument (regardless of value) tells it to | |
2342 | make a verbose listing including sizes, dates, and authors (like | |
2343 | @samp{ls -l}). | |
2344 | ||
2345 | @vindex list-directory-brief-switches | |
2346 | @vindex list-directory-verbose-switches | |
2347 | The text of a directory listing is obtained by running @code{ls} in an | |
2348 | inferior process. Two Emacs variables control the switches passed to | |
2349 | @code{ls}: @code{list-directory-brief-switches} is a string giving the | |
2350 | switches to use in brief listings (@code{"-CF"} by default), and | |
2351 | @code{list-directory-verbose-switches} is a string giving the switches to | |
2352 | use in a verbose listing (@code{"-l"} by default). | |
2353 | ||
2354 | @node Comparing Files | |
2355 | @section Comparing Files | |
2356 | @cindex comparing files | |
2357 | ||
2358 | @findex diff | |
2359 | @vindex diff-switches | |
2360 | The command @kbd{M-x diff} compares two files, displaying the | |
2361 | differences in an Emacs buffer named @samp{*Diff*}. It works by running | |
2362 | the @code{diff} program, using options taken from the variable | |
2363 | @code{diff-switches}, whose value should be a string. | |
2364 | ||
2365 | The buffer @samp{*Diff*} has Compilation mode as its major mode, so | |
2366 | you can use @kbd{C-x `} to visit successive changed locations in the two | |
2367 | source files. You can also move to a particular hunk of changes and | |
2368 | type @key{RET} or @kbd{C-c C-c}, or click @kbd{Mouse-2} on it, to move | |
2369 | to the corresponding source location. You can also use the other | |
2370 | special commands of Compilation mode: @key{SPC} and @key{DEL} for | |
2371 | scrolling, and @kbd{M-p} and @kbd{M-n} for cursor motion. | |
2372 | @xref{Compilation}. | |
2373 | ||
2374 | @findex diff-backup | |
2375 | The command @kbd{M-x diff-backup} compares a specified file with its most | |
2376 | recent backup. If you specify the name of a backup file, | |
2377 | @code{diff-backup} compares it with the source file that it is a backup | |
2378 | of. | |
2379 | ||
2380 | @findex compare-windows | |
2381 | The command @kbd{M-x compare-windows} compares the text in the current | |
2382 | window with that in the next window. Comparison starts at point in each | |
2383 | window, and each starting position is pushed on the mark ring in its | |
2384 | respective buffer. Then point moves forward in each window, a character | |
2385 | at a time, until a mismatch between the two windows is reached. Then | |
2386 | the command is finished. For more information about windows in Emacs, | |
2387 | @ref{Windows}. | |
2388 | ||
2389 | @vindex compare-ignore-case | |
2390 | With a numeric argument, @code{compare-windows} ignores changes in | |
2391 | whitespace. If the variable @code{compare-ignore-case} is | |
2392 | non-@code{nil}, it ignores differences in case as well. | |
2393 | ||
fa474484 DL |
2394 | @findex diff-mode |
2395 | @cindex diffs | |
2396 | @cindex patches | |
2397 | @cindex Diff mode | |
f02d86a3 RS |
2398 | Differences between versions of files are often distributed as |
2399 | @dfn{patches}, which are the output from @command{diff} or a version | |
2400 | control system that uses @command{diff}. @kbd{M-x diff-mode} turns on | |
2401 | Diff mode, a major mode for viewing and editing patches, either as | |
2402 | ``unified diffs'' or ``context diffs.'' | |
fa474484 DL |
2403 | |
2404 | @cindex Smerge mode | |
2405 | @findex smerge-mode | |
2406 | @cindex failed merges | |
2407 | @cindex merges, failed | |
2408 | @pindex diff3 | |
f02d86a3 RS |
2409 | You can use @kbd{M-x smerge-mode} to turn on Smerge mode, a minor |
2410 | mode for editing output from the @command{diff3} program. This is | |
2411 | typically the result of a failed merge from a version control system | |
2412 | ``update'' outside VC, due to conflicting changes to a file. Smerge | |
2413 | mode provides commands to resolve conflicts by selecting specific | |
2414 | changes. | |
2415 | ||
2416 | See also @ref{Emerge}, and @ref{Top,,, ediff, The Ediff Manual}, for | |
2417 | convenient facilities for merging two similar files. | |
6bf7aab6 DL |
2418 | |
2419 | @node Misc File Ops | |
2420 | @section Miscellaneous File Operations | |
2421 | ||
2422 | Emacs has commands for performing many other operations on files. | |
2423 | All operate on one file; they do not accept wildcard file names. | |
2424 | ||
2425 | @findex view-file | |
2426 | @cindex viewing | |
2427 | @cindex View mode | |
2428 | @cindex mode, View | |
2429 | @kbd{M-x view-file} allows you to scan or read a file by sequential | |
2430 | screenfuls. It reads a file name argument using the minibuffer. After | |
2431 | reading the file into an Emacs buffer, @code{view-file} displays the | |
2432 | beginning. You can then type @key{SPC} to scroll forward one windowful, | |
2433 | or @key{DEL} to scroll backward. Various other commands are provided | |
2434 | for moving around in the file, but none for changing it; type @kbd{?} | |
2435 | while viewing for a list of them. They are mostly the same as normal | |
2436 | Emacs cursor motion commands. To exit from viewing, type @kbd{q}. | |
2437 | The commands for viewing are defined by a special major mode called View | |
2438 | mode. | |
2439 | ||
2440 | A related command, @kbd{M-x view-buffer}, views a buffer already present | |
2441 | in Emacs. @xref{Misc Buffer}. | |
2442 | ||
2443 | @findex insert-file | |
2444 | @kbd{M-x insert-file} inserts a copy of the contents of the specified | |
2445 | file into the current buffer at point, leaving point unchanged before the | |
2446 | contents and the mark after them. | |
2447 | ||
2448 | @findex write-region | |
2449 | @kbd{M-x write-region} is the inverse of @kbd{M-x insert-file}; it | |
2450 | copies the contents of the region into the specified file. @kbd{M-x | |
2451 | append-to-file} adds the text of the region to the end of the specified | |
2452 | file. @xref{Accumulating Text}. | |
2453 | ||
2454 | @findex delete-file | |
2455 | @cindex deletion (of files) | |
2456 | @kbd{M-x delete-file} deletes the specified file, like the @code{rm} | |
2457 | command in the shell. If you are deleting many files in one directory, it | |
2458 | may be more convenient to use Dired (@pxref{Dired}). | |
2459 | ||
2460 | @findex rename-file | |
2461 | @kbd{M-x rename-file} reads two file names @var{old} and @var{new} using | |
2462 | the minibuffer, then renames file @var{old} as @var{new}. If a file named | |
2463 | @var{new} already exists, you must confirm with @kbd{yes} or renaming is not | |
2464 | done; this is because renaming causes the old meaning of the name @var{new} | |
2465 | to be lost. If @var{old} and @var{new} are on different file systems, the | |
2466 | file @var{old} is copied and deleted. | |
2467 | ||
2468 | @findex add-name-to-file | |
2469 | The similar command @kbd{M-x add-name-to-file} is used to add an | |
2470 | additional name to an existing file without removing its old name. | |
2471 | The new name must belong on the same file system that the file is on. | |
2472 | ||
2473 | @findex copy-file | |
2474 | @cindex copying files | |
2475 | @kbd{M-x copy-file} reads the file @var{old} and writes a new file named | |
2476 | @var{new} with the same contents. Confirmation is required if a file named | |
2477 | @var{new} already exists, because copying has the consequence of overwriting | |
2478 | the old contents of the file @var{new}. | |
2479 | ||
2480 | @findex make-symbolic-link | |
2481 | @kbd{M-x make-symbolic-link} reads two file names @var{target} and | |
2482 | @var{linkname}, then creates a symbolic link named @var{linkname} and | |
2483 | pointing at @var{target}. The effect is that future attempts to open file | |
2484 | @var{linkname} will refer to whatever file is named @var{target} at the | |
2485 | time the opening is done, or will get an error if the name @var{target} is | |
2486 | not in use at that time. This command does not expand the argument | |
2487 | @var{target}, so that it allows you to specify a relative name | |
2488 | as the target of the link. | |
2489 | ||
2490 | Confirmation is required when creating the link if @var{linkname} is | |
2491 | in use. Note that not all systems support symbolic links. | |
2492 | ||
2493 | @node Compressed Files | |
2494 | @section Accessing Compressed Files | |
2495 | @cindex compression | |
2496 | @cindex uncompression | |
2497 | @cindex Auto Compression mode | |
2498 | @cindex mode, Auto Compression | |
2499 | @pindex gzip | |
2500 | ||
2501 | @findex auto-compression-mode | |
259a88ca | 2502 | @vindex auto-compression-mode |
6bf7aab6 DL |
2503 | Emacs comes with a library that can automatically uncompress |
2504 | compressed files when you visit them, and automatically recompress them | |
2505 | if you alter them and save them. To enable this feature, type the | |
259a88ca DL |
2506 | command @kbd{M-x auto-compression-mode}. You can enable it permanently |
2507 | by customizing the option @var{auto-compression-mode}. | |
6bf7aab6 DL |
2508 | |
2509 | When automatic compression (which implies automatic uncompression as | |
2510 | well) is enabled, Emacs recognizes compressed files by their file names. | |
2511 | File names ending in @samp{.gz} indicate a file compressed with | |
2512 | @code{gzip}. Other endings indicate other compression programs. | |
2513 | ||
2514 | Automatic uncompression and compression apply to all the operations in | |
2515 | which Emacs uses the contents of a file. This includes visiting it, | |
2516 | saving it, inserting its contents into a buffer, loading it, and byte | |
2517 | compiling it. | |
2518 | ||
259a88ca DL |
2519 | @node File Archives |
2520 | @section File Archives | |
2521 | @cindex mode, tar | |
2522 | @cindex Tar mode | |
259a88ca | 2523 | @pindex tar |
259a88ca | 2524 | |
f02d86a3 RS |
2525 | A file whose name ends in @samp{.tar} is normally an @dfn{archive} |
2526 | made by the @code{tar} program. Emacs views these files in a special | |
2527 | mode called Tar mode which provides a Dired-like list of the contents | |
2528 | (@pxref{Dired}). You can move around through the list just as you | |
2529 | would in Dired, and visit the subfiles contained in the archive. | |
2530 | However, not all Dired commands are available in Tar mode. | |
2531 | ||
2532 | If you enable Auto Compression mode (@pxref{Compressed Files}), then | |
2533 | Tar mode is used also for compressed archives---files with extensions | |
2534 | @samp{.tgz}, @code{.tar.Z} and @code{.tar.gz}. | |
259a88ca | 2535 | |
366f22ff | 2536 | The keys @kbd{e}, @kbd{f} and @kbd{RET} all extract a component file |
259a88ca | 2537 | into its own buffer. You can edit it there and when you save the buffer |
366f22ff EZ |
2538 | the edited version will replace the version in the Tar buffer. @kbd{v} |
2539 | extracts a file into a buffer in View mode. @kbd{o} extracts the file | |
2540 | and displays it in another window, so you could edit the file and | |
2541 | operate on the archive simultaneously. @kbd{d} marks a file for | |
2542 | deletion when you later use @kbd{x}, and @kbd{u} unmarks a file, as in | |
2543 | Dired. @kbd{C} copies a file from the archive to disk and @kbd{R} | |
2544 | renames a file. @kbd{g} reverts the buffer from the archive on disk. | |
2545 | ||
2546 | The keys @kbd{M}, @kbd{G}, and @kbd{O} change the file's permission | |
2547 | bits, group, and owner, respectively. | |
2548 | ||
2549 | If your display supports colors and the mouse, moving the mouse | |
2550 | pointer across a file name highlights that file name, indicating that | |
2551 | you can click on it. Clicking @kbd{Mouse-2} on the highlighted file | |
2552 | name extracts the file into a buffer and displays that buffer. | |
2553 | ||
2554 | Saving the Tar buffer writes a new version of the archive to disk with | |
259a88ca DL |
2555 | the changes you made to the components. |
2556 | ||
f02d86a3 RS |
2557 | You don't need the @code{tar} program to use Tar mode---Emacs reads |
2558 | the archives directly. However, accessing compressed archives | |
2559 | requires the appropriate uncompression program. | |
fa474484 | 2560 | |
366f22ff EZ |
2561 | @cindex Archive mode |
2562 | @cindex mode, archive | |
259a88ca DL |
2563 | @cindex @code{arc} |
2564 | @cindex @code{jar} | |
2565 | @cindex @code{zip} | |
2566 | @cindex @code{lzh} | |
2567 | @cindex @code{zoo} | |
259a88ca DL |
2568 | @pindex arc |
2569 | @pindex jar | |
2570 | @pindex zip | |
2571 | @pindex lzh | |
2572 | @pindex zoo | |
2573 | @cindex Java class archives | |
366f22ff EZ |
2574 | @cindex unzip archives |
2575 | A separate but similar Archive mode is used for archives produced by | |
f02d86a3 RS |
2576 | the programs @code{arc}, @code{jar}, @code{lzh}, @code{zip}, and |
2577 | @code{zoo}, which have extensions corresponding to the program names. | |
366f22ff | 2578 | |
f02d86a3 RS |
2579 | The keybindings of Archive mode are similar to those in Tar mode, |
2580 | with the addition of the @kbd{m} key which marks a file for subsequent | |
366f22ff | 2581 | operations, and @kbd{M-@key{DEL}} which unmarks all the marked files. |
f02d86a3 RS |
2582 | Also, the @kbd{a} key toggles the display of detailed file |
2583 | information, for those archive types where it won't fit in a single | |
2584 | line. Operations such as renaming a subfile, or changing its mode or | |
2585 | owner, are supported only for some of the archive formats. | |
366f22ff | 2586 | |
f02d86a3 RS |
2587 | Unlike Tar mode, Archive mode runs the archiving program to unpack |
2588 | and repack archives. Details of the program names and their options | |
2589 | can be set in the @samp{Archive} Customize group. However, you don't | |
2590 | need these programs to the archive table of contents, only to extract | |
2591 | or manipulate the subfiles in the archive. | |
259a88ca | 2592 | |
6bf7aab6 DL |
2593 | @node Remote Files |
2594 | @section Remote Files | |
2595 | ||
2596 | @cindex FTP | |
2597 | @cindex remote file access | |
2598 | You can refer to files on other machines using a special file name syntax: | |
2599 | ||
2600 | @example | |
2601 | @group | |
2602 | /@var{host}:@var{filename} | |
2603 | /@var{user}@@@var{host}:@var{filename} | |
4f36dd62 | 2604 | /@var{user}@@@var{host}#@var{port}:@var{filename} |
6bf7aab6 DL |
2605 | @end group |
2606 | @end example | |
2607 | ||
2608 | @noindent | |
2609 | When you do this, Emacs uses the FTP program to read and write files on | |
2610 | the specified host. It logs in through FTP using your user name or the | |
2611 | name @var{user}. It may ask you for a password from time to time; this | |
4f36dd62 DL |
2612 | is used for logging in on @var{host}. The form using @var{port} allows |
2613 | you to access servers running on a non-default TCP port. | |
6bf7aab6 | 2614 | |
436b2c06 EZ |
2615 | @cindex backups for remote files |
2616 | @vindex ange-ftp-make-backup-files | |
2617 | If you want to disable backups for remote files, set the variable | |
2618 | @code{ange-ftp-make-backup-files} to @code{nil}. | |
2619 | ||
6bf7aab6 DL |
2620 | @cindex ange-ftp |
2621 | @vindex ange-ftp-default-user | |
436b2c06 | 2622 | @cindex user name for remote file access |
6bf7aab6 DL |
2623 | Normally, if you do not specify a user name in a remote file name, |
2624 | that means to use your own user name. But if you set the variable | |
2625 | @code{ange-ftp-default-user} to a string, that string is used instead. | |
2626 | (The Emacs package that implements FTP file access is called | |
2627 | @code{ange-ftp}.) | |
2628 | ||
436b2c06 EZ |
2629 | @cindex anonymous FTP |
2630 | @vindex ange-ftp-generate-anonymous-password | |
2631 | To visit files accessible by anonymous FTP, you use special user | |
2632 | names ``anonymous'' or ``ftp''. Passwords for these user names are | |
2633 | handled specially. The variable | |
2634 | @code{ange-ftp-generate-anonymous-password} controls what happens: if | |
2635 | the value of this variable is a string, then that string is used as | |
2636 | the password; if non-@code{nil} (the default), then the value of | |
2637 | @code{user-mail-address} is used; if @code{nil}, the user is prompted | |
2638 | for a password as normal. | |
2639 | ||
2640 | @cindex firewall, and accessing remote files | |
2641 | @cindex gateway, and remote file access with @code{ange-ftp} | |
2642 | @vindex ange-ftp-smart-gateway | |
2643 | @vindex ange-ftp-gateway-host | |
2644 | Sometimes you may be unable to access files on a remote machine | |
f02d86a3 RS |
2645 | because a @dfn{firewall} in between blocks the connection for security |
2646 | reasons. If you can log in on a @dfn{gateway} machine from which the | |
2647 | target files @emph{are} accessible, and whose FTP server supports | |
2648 | gatewaying features, you can still use remote file names; all you have | |
2649 | to do is specify the name of the gateway machine by setting the | |
2650 | variable @code{ange-ftp-gateway-host}, and set | |
2651 | @code{ange-ftp-smart-gateway} to @code{t}. Otherwise you may be able | |
2652 | to make remote file names work, but the procedure is complex. You can | |
2653 | read the instructions by typing @kbd{M-x finder-commentary @key{RET} | |
2654 | ange-ftp @key{RET}}. | |
436b2c06 | 2655 | |
6bf7aab6 | 2656 | @vindex file-name-handler-alist |
f02d86a3 | 2657 | @cindex disabling remote files |
4f36dd62 DL |
2658 | You can entirely turn off the FTP file name feature by removing the |
2659 | entries @var{ange-ftp-completion-hook-function} and | |
2660 | @var{ange-ftp-hook-function} from the variable | |
7ed32bd8 DL |
2661 | @code{file-name-handler-alist}. You can turn off the feature in |
2662 | individual cases by quoting the file name with @samp{/:} (@pxref{Quoted | |
2663 | File Names}). | |
6bf7aab6 DL |
2664 | |
2665 | @node Quoted File Names | |
2666 | @section Quoted File Names | |
2667 | ||
2668 | @cindex quoting file names | |
2669 | You can @dfn{quote} an absolute file name to prevent special | |
2670 | characters and syntax in it from having their special effects. | |
2671 | The way to do this is to add @samp{/:} at the beginning. | |
2672 | ||
2673 | For example, you can quote a local file name which appears remote, to | |
2674 | prevent it from being treated as a remote file name. Thus, if you have | |
2675 | a directory named @file{/foo:} and a file named @file{bar} in it, you | |
2676 | can refer to that file in Emacs as @samp{/:/foo:/bar}. | |
2677 | ||
2678 | @samp{/:} can also prevent @samp{~} from being treated as a special | |
2679 | character for a user's home directory. For example, @file{/:/tmp/~hack} | |
2680 | refers to a file whose name is @file{~hack} in directory @file{/tmp}. | |
2681 | ||
2682 | Likewise, quoting with @samp{/:} is one way to enter in the minibuffer | |
2683 | a file name that contains @samp{$}. However, the @samp{/:} must be at | |
2684 | the beginning of the buffer in order to quote @samp{$}. | |
2685 | ||
7ed32bd8 | 2686 | @cindex wildcard characters in file names |
6bf7aab6 DL |
2687 | You can also quote wildcard characters with @samp{/:}, for visiting. |
2688 | For example, @file{/:/tmp/foo*bar} visits the file @file{/tmp/foo*bar}. | |
2689 | However, in most cases you can simply type the wildcard characters for | |
2690 | themselves. For example, if the only file name in @file{/tmp} that | |
2691 | starts with @samp{foo} and ends with @samp{bar} is @file{foo*bar}, then | |
2692 | specifying @file{/tmp/foo*bar} will visit just @file{/tmp/foo*bar}. | |
7ed32bd8 | 2693 | Another way is to specify @file{/tmp/foo[*]bar}. |
9a98ef18 | 2694 | |
f02d86a3 RS |
2695 | @node File Name Cache |
2696 | @section File Name Cache | |
2697 | ||
2698 | @cindex file name caching | |
2699 | @cindex cache of file names | |
2700 | @pindex find | |
2701 | @kindex C-@key{TAB} | |
2702 | @findex file-cache-minibuffer-complete | |
2703 | You can use the @dfn{file name cache} to make it easy to locate a | |
2704 | file by name, without having to remember exactly where it is located. | |
2705 | When typing a file name in the minibuffer, @kbd{C-@key{tab}} | |
2706 | (@code{file-cache-minibuffer-complete}) completes it using the file | |
2707 | name cache. If you repeat @kbd{C-@key{tab}}, that cycles through the | |
2708 | possible completions of what you had originally typed. Note that the | |
2709 | @kbd{C-@key{tab}} character cannot be typed on most text-only | |
2710 | terminals. | |
2711 | ||
2712 | The file name cache does not fill up automatically. Instead, you | |
2713 | load file names into the cache using these commands: | |
9a98ef18 | 2714 | |
f02d86a3 | 2715 | @findex file-cache-add-directory |
fa474484 | 2716 | @table @kbd |
fa474484 | 2717 | @item M-x file-cache-add-directory @key{RET} @var{directory} @key{RET} |
f02d86a3 RS |
2718 | Add each file name in @var{directory} to the file name cache. |
2719 | @item M-x file-cache-add-directory-using-find @key{RET} @var{directory} @key{RET} | |
2720 | Add each file name in @var{directory} and all of its nested | |
2721 | subdirectories to the file name cache. | |
2722 | @item M-x file-cache-add-directory-using-locate @key{RET} @var{directory} @key{RET} | |
2723 | Add each file name in @var{directory} and all of its nested | |
2724 | subdirectories to the file name cache, using @command{locate} to find | |
2725 | them all. | |
2726 | @item M-x file-cache-add-directory-list @key{RET} @var{variable} @key{RET} | |
2727 | Add each file name in each directory listed in @var{variable} | |
2728 | to the file name cache. @var{variable} should be a Lisp variable | |
2729 | such as @code{load-path} or @code{exec-path}, whose value is a list | |
2730 | of directory names. | |
2731 | @item M-x file-cache-clear-cache @key{RET} | |
2732 | Clear the cache; that is, remove all file names from it. | |
fa474484 | 2733 | @end table |
9a98ef18 | 2734 | |
f02d86a3 RS |
2735 | @node File Conveniences |
2736 | @section Convenience Features for Finding Files | |
fa474484 DL |
2737 | |
2738 | @findex recentf-mode | |
2739 | @vindex recentf-mode | |
2740 | @findex recentf-save-list | |
2741 | @findex recentf-edit-list | |
f02d86a3 RS |
2742 | If you enable Recentf mode, with @kbd{M-x recentf-mode}, the |
2743 | @samp{Files} menu includes a submenu containing a list of recently | |
2744 | opened files. @kbd{M-x recentf-save-list} saves the current | |
2745 | recent-file-list to a file, and @kbd{M-x recentf-edit-list} edits it. | |
0d7a07f3 DL |
2746 | |
2747 | @findex auto-image-file-mode | |
2748 | @findex mode, auto-image-file | |
2749 | @cindex images, visiting | |
2750 | @cindex visiting image files | |
2751 | @vindex image-file-name-regexps | |
2752 | @vindex image-file-name-extensions | |
f02d86a3 RS |
2753 | When Auto-image-file minor mode is enabled, visiting an image file |
2754 | displays it as an image, not as text. Likewise, inserting an image | |
2755 | file into a buffer inserts it as an image. This works only when Emacs | |
2756 | can display the relevant image type. The variables | |
2757 | @code{image-file-name-extensions} or @code{image-file-name-regexps} | |
2758 | control which file names are recognized as containing images. | |
2759 | ||
2760 | The @kbd{M-x ffap} command generalizes @code{find-file} with more | |
2761 | powerful heuristic defaults (@pxref{FFAP}), often based on the text at | |
2762 | point. Partial Completion mode offers other features extending | |
2763 | @code{find-file}, which can be used with @code{ffap}. | |
2764 | @xref{Completion Options}. |