1 \input texinfo @c -*-texinfo-*-
2 @comment %**start of header
3 @setfilename ../info/emacs-xtra
4 @settitle Specialized Emacs Features
8 @comment %**end of header
11 This manual describes specialized features of Emacs.
13 Copyright @copyright{} 2004, 2005, 2006 Free Software Foundation, Inc.
16 Permission is granted to copy, distribute and/or modify this document
17 under the terms of the GNU Free Documentation License, Version 1.2 or
18 any later version published by the Free Software Foundation; with no
19 Invariant Sections, with the Front-Cover texts being ``A GNU
20 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
21 license is included in the section entitled ``GNU Free Documentation
22 License'' in the Emacs manual.
24 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
25 this GNU Manual, like GNU software. Copies published by the Free
26 Software Foundation raise funds for GNU development.''
28 This document is part of a collection distributed under the GNU Free
29 Documentation License. If you want to distribute this document
30 separately from the collection, you can do so by adding a copy of the
31 license to the document, as described in section 6 of the license.
37 * Emacs-Xtra: (emacs-xtra). Specialized Emacs features.
41 @title Specialized Emacs Features
43 @vskip 0pt plus 1filll
51 @top Specialized Emacs Features
58 * Introduction:: What documentation belongs here?
59 * Autorevert:: Auto Reverting non-file buffers.
60 * Subdir Switches:: Subdirectory switches in Dired.
61 * Advanced Calendar/Diary Usage:: Advanced Calendar/Diary customization.
62 * Emerge:: A convenient way of merging two versions
64 * Picture Mode:: Editing pictures made up of characters
65 using the quarter-plane screen model.
67 * Advanced VC Usage:: Advanced VC (version control) features.
68 * Fortran:: Fortran mode and its special features.
74 @unnumbered Introduction
76 This manual contains detailed information about various features that
77 are too specialized to be included in the Emacs manual. It is
78 intended to be readable by anyone having a basic knowledge of Emacs.
79 However, certain sections may be intended for a more specialized
80 audience, such as Elisp authors. This should be clearly pointed out
81 at the beginning of these sections.
83 This manual is intended as a complement, rather than an alternative,
84 to other ways to gain a more detailed knowledge of Emacs than the
85 Emacs manual can provide, such as browsing packages using @kbd{C-h p},
86 accessing mode documentation using @kbd{C-h m} and browsing user
87 options using Custom. Also, certain packages, or collections of
88 related features, have their own manuals. The present manual is
89 mainly intended to be a collection of smaller specialized features,
90 too small to get their own manual.
92 Sections intended specifically for Elisp programmers can follow the
93 style of the Elisp manual. Other sections should follow the style of
97 @chapter Auto Reverting non-file Buffers
99 Normally Global Auto Revert Mode only reverts file buffers. There are
100 two ways to auto-revert certain non-file buffers: enabling Auto Revert
101 Mode in those buffers (using @kbd{M-x auto-revert-mode}) and setting
102 @code{global-auto-revert-non-file-buffers} to @code{t}. The latter
103 enables Auto Reverting for all types of buffers for which it is
104 implemented, that is, for the types of buffers listed in the menu
107 Like file buffers, non-file buffers should normally not revert while
108 you are working on them, or while they contain information that might
109 get lost after reverting. Therefore, they do not revert if they are
110 ``modified''. This can get tricky, because deciding when a non-file
111 buffer should be marked modified is usually more difficult than for
114 Another tricky detail is that, for efficiency reasons, Auto Revert
115 often does not try to detect all possible changes in the buffer, only
116 changes that are ``major'' or easy to detect. Hence, enabling
117 auto-reverting for a non-file buffer does not always guarantee that
118 all information in the buffer is up to date and does not necessarily
119 make manual reverts useless.
121 At the other extreme, certain buffers automatically auto-revert every
122 @code{auto-revert-interval} seconds. (This currently only applies to
123 the Buffer Menu.) In this case, Auto Revert does not print any
124 messages while reverting, even when @code{auto-revert-verbose} is
127 The details depend on the particular types of buffers and are
128 explained in the corresponding sections.
131 * Auto Reverting the Buffer Menu::
132 * Auto Reverting Dired::
133 * Supporting additional buffers::
136 @node Auto Reverting the Buffer Menu
137 @section Auto Reverting the Buffer Menu
139 If auto-reverting of non-file buffers is enabled, the Buffer Menu
140 automatically reverts every @code{auto-revert-interval} seconds,
141 whether there is a need for it or not. (It would probably take longer
142 to check whether there is a need than to actually revert.)
144 If the Buffer Menu inappropriately gets marked modified, just revert
145 it manually using @kbd{g} and auto-reverting will resume. However, if
146 you marked certain buffers to get deleted or to be displayed, you have
147 to be careful, because reverting erases all marks. The fact that
148 adding marks sets the buffer's modified flag prevents Auto Revert from
149 automatically erasing the marks.
151 @node Auto Reverting Dired
152 @section Auto Reverting Dired buffers
154 Auto-reverting Dired buffers currently works on GNU or Unix style
155 operating systems. It may not work satisfactorily on some other
158 Dired buffers only auto-revert when the file list of the buffer's main
159 directory changes. They do not auto-revert when information about a
160 particular file changes or when inserted subdirectories change. To be
161 sure that @emph{all} listed information is up to date, you have to
162 manually revert using @kbd{g}, @emph{even} if auto-reverting is
163 enabled in the Dired buffer. Sometimes, you might get the impression
164 that modifying or saving files listed in the main directory actually
165 does cause auto-reverting. This is because making changes to a file,
166 or saving it, very often causes changes in the directory itself, for
167 instance, through backup files or auto-save files. However, this is
170 If the Dired buffer is marked modified and there are no changes you
171 want to protect, then most of the time you can make auto-reverting
172 resume by manually reverting the buffer using @kbd{g}. There is one
173 exception. If you flag or mark files, you can safely revert the
174 buffer. This will not erase the flags or marks (unless the marked
175 file has been deleted, of course). However, the buffer will stay
176 modified, even after reverting, and auto-reverting will not resume.
177 This is because, if you flag or mark files, you may be working on the
178 buffer and you might not want the buffer to change without warning.
179 If you want auto-reverting to resume in the presence of marks and
180 flags, mark the buffer non-modified using @kbd{M-~}. However, adding,
181 deleting or changing marks or flags will mark it modified again.
183 Remote Dired buffers are not auto-reverted. Neither are Dired buffers
184 for which you used shell wildcards or file arguments to list only some
185 of the files. @samp{*Find*} and @samp{*Locate*} buffers do not
188 @node Supporting additional buffers
189 @section Adding Support for Auto-Reverting additional Buffers.
191 This section is intended for Elisp programmers who would like to add
192 support for auto-reverting new types of buffers.
194 To support auto-reverting the buffer must first of all have a
195 @code{revert-buffer-function}. @xref{Definition of
196 revert-buffer-function,, Reverting, elisp, the Emacs Lisp Reference Manual}.
198 In addition, it @emph{must} have a @code{buffer-stale-function}.
200 @defvar buffer-stale-function
201 The value of this variable is a function to check whether a non-file
202 buffer needs reverting. This should be a function with one optional
203 argument @var{noconfirm}. The function should return non-@code{nil}
204 if the buffer should be reverted. The buffer is current when this
207 While this function is mainly intended for use in auto-reverting, it
208 could be used for other purposes as well. For instance, if
209 auto-reverting is not enabled, it could be used to warn the user that
210 the buffer needs reverting. The idea behind the @var{noconfirm}
211 argument is that it should be @code{t} if the buffer is going to be
212 reverted without asking the user and @code{nil} if the function is
213 just going to be used to warn the user that the buffer is out of date.
214 In particular, for use in auto-reverting, @var{noconfirm} is @code{t}.
215 If the function is only going to be used for auto-reverting, you can
216 ignore the @var{noconfirm} argument.
218 If you just want to automatically auto-revert every
219 @code{auto-revert-interval} seconds, use:
222 (set (make-local-variable 'buffer-stale-function)
223 #'(lambda (&optional noconfirm) 'fast))
227 in the buffer's mode function.
229 The special return value @samp{fast} tells the caller that the need
230 for reverting was not checked, but that reverting the buffer is fast.
231 It also tells Auto Revert not to print any revert messages, even if
232 @code{auto-revert-verbose} is non-@code{nil}. This is important, as
233 getting revert messages every @code{auto-revert-interval} seconds can
234 be very annoying. The information provided by this return value could
235 also be useful if the function is consulted for purposes other than
239 Once the buffer has a @code{revert-buffer-function} and a
240 @code{buffer-stale-function}, several problems usually remain.
242 The buffer will only auto-revert if it is marked unmodified. Hence,
243 you will have to make sure that various functions mark the buffer
244 modified if and only if either the buffer contains information that
245 might be lost by reverting or there is reason to believe that the user
246 might be inconvenienced by auto-reverting, because he is actively
247 working on the buffer. The user can always override this by manually
248 adjusting the modified status of the buffer. To support this, calling
249 the @code{revert-buffer-function} on a buffer that is marked
250 unmodified should always keep the buffer marked unmodified.
252 It is important to assure that point does not continuously jump around
253 as a consequence of auto-reverting. Of course, moving point might be
254 inevitable if the buffer radically changes.
256 You should make sure that the @code{revert-buffer-function} does not
257 print messages that unnecessarily duplicate Auto Revert's own messages
258 if @code{auto-revert-verbose} is @code{t} and effectively override a
259 @code{nil} value for @code{auto-revert-verbose}. Hence, adapting a
260 mode for auto-reverting often involves getting rid of such messages.
261 This is especially important for buffers that automatically
262 auto-revert every @code{auto-revert-interval} seconds.
264 Also, you may want to update the documentation string of
265 @code{global-auto-revert-non-file-buffers}.
268 Finally, you should add a node to this chapter's menu. This node
271 Finally, you should add a section to this chapter. This section
273 should at the very least make clear whether enabling auto-reverting
274 for the buffer reliably assures that all information in the buffer is
275 completely up to date (or will be after @code{auto-revert-interval}
278 @node Subdir Switches
279 @chapter Subdirectory Switches in Dired
281 You can insert subdirectories with specified @code{ls} switches in
282 Dired buffers, using @kbd{C-u i}. You can change the @code{ls}
283 switches of an already inserted subdirectory using @kbd{C-u l}.
285 In Emacs versions 22.1 and later, Dired remembers the switches, so
286 that reverting the buffer will not change them back to the main
287 directory's switches. Deleting a subdirectory forgets about its
290 Using @code{dired-undo} (usually bound to @kbd{C-_} and @kbd{C-x u})
291 to reinsert or delete subdirectories, that were inserted with explicit
292 switches, can bypass Dired's machinery for remembering (or forgetting)
293 switches. Deleting a subdirectory using @code{dired-undo} does not
294 forget its switches. When later reinserted using @kbd{i}, it will be
295 reinserted using its old switches. Using @code{dired-undo} to
296 reinsert a subdirectory that was deleted using the regular
297 Dired commands (not @code{dired-undo}) will originally insert it with
298 its old switches. However, reverting the buffer will relist it using
299 the buffer's default switches. If any of this yields problems, you
300 can easily correct the situation using @kbd{C-u i} or @kbd{C-u l}.
302 Dired does not remember the @code{R} switch. Inserting a subdirectory
303 with switches that include the @code{R} switch is equivalent with
304 inserting each of its subdirectories using all remaining switches.
305 For instance, updating or killing a subdirectory that was inserted
306 with the @code{R} switch will not update or kill its subdirectories.
308 The buffer's default switches do not affect subdirectories that were
309 inserted using explicitly specified switches. In particular,
310 commands such as @kbd{s}, that change the buffer's switches do not
311 affect such subdirectories. (They do affect subdirectories without
312 explicitly assigned switches, however.)
314 You can make Dired forget about all subdirectory switches and relist
315 all subdirectories with the buffer's default switches using
316 @kbd{M-x dired-reset-subdir-switches}. This also reverts the Dired buffer.
319 @c Moved here from the Emacs Lisp Reference Manual, 2005-03-26.
320 @node Advanced Calendar/Diary Usage
321 @chapter Customizing the Calendar and Diary
323 There are many customizations that you can use to make the calendar and
324 diary suit your personal tastes.
327 * Calendar Customizing:: Defaults you can set.
328 * Holiday Customizing:: Defining your own holidays.
329 * Date Display Format:: Changing the format.
330 * Time Display Format:: Changing the format.
331 * Daylight Savings:: Changing the default.
332 * Diary Customizing:: Defaults you can set.
333 * Hebrew/Islamic Entries:: How to obtain them.
334 * Fancy Diary Display:: Enhancing the diary display, sorting entries,
335 using included diary files.
336 * Sexp Diary Entries:: Fancy things you can do.
339 @node Calendar Customizing
340 @section Customizing the Calendar
341 @vindex calendar-holiday-marker
342 @vindex diary-entry-marker
343 The variable @code{calendar-holiday-marker} specifies how to mark a
344 date as being a holiday. Its value may be a single-character string
345 to insert next to the date, or a face name to use for displaying the
346 date. Likewise, the variable @code{diary-entry-marker} specifies how
347 to mark a date that has diary entries. The calendar creates faces
348 named @code{holiday-face} and @code{diary-face} for these purposes;
349 those symbols are the default values of these variables.
351 @vindex calendar-load-hook
352 The variable @code{calendar-load-hook} is a normal hook run when the
353 calendar package is first loaded (before actually starting to display
356 @vindex initial-calendar-window-hook
357 Starting the calendar runs the normal hook
358 @code{initial-calendar-window-hook}. Recomputation of the calendar
359 display does not run this hook. But if you leave the calendar with the
360 @kbd{q} command and reenter it, the hook runs again.@refill
362 @vindex today-visible-calendar-hook
363 The variable @code{today-visible-calendar-hook} is a normal hook run
364 after the calendar buffer has been prepared with the calendar when the
365 current date is visible in the window. One use of this hook is to
366 replace today's date with asterisks; to do that, use the hook function
367 @code{calendar-star-date}.
369 @findex calendar-star-date
371 (add-hook 'today-visible-calendar-hook 'calendar-star-date)
375 Another standard hook function marks the current date, either by
376 changing its face or by adding an asterisk. Here's how to use it:
378 @findex calendar-mark-today
380 (add-hook 'today-visible-calendar-hook 'calendar-mark-today)
384 @vindex calendar-today-marker
385 The variable @code{calendar-today-marker} specifies how to mark
386 today's date. Its value should be a single-character string to insert
387 next to the date or a face name to use for displaying the date. A
388 face named @code{calendar-today-face} is provided for this purpose;
389 that symbol is the default for this variable.
391 @vindex today-invisible-calendar-hook
393 A similar normal hook, @code{today-invisible-calendar-hook} is run if
394 the current date is @emph{not} visible in the window.
396 @vindex calendar-move-hook
397 Each of the calendar cursor motion commands runs the hook
398 @code{calendar-move-hook} after it moves the cursor.
400 @node Holiday Customizing
401 @section Customizing the Holidays
403 @vindex calendar-holidays
404 @vindex christian-holidays
405 @vindex hebrew-holidays
406 @vindex islamic-holidays
407 Emacs knows about holidays defined by entries on one of several lists.
408 You can customize these lists of holidays to your own needs, adding or
409 deleting holidays. The lists of holidays that Emacs uses are for
410 general holidays (@code{general-holidays}), local holidays
411 (@code{local-holidays}), Christian holidays (@code{christian-holidays}),
412 Hebrew (Jewish) holidays (@code{hebrew-holidays}), Islamic (Muslim)
413 holidays (@code{islamic-holidays}), and other holidays
414 (@code{other-holidays}).
416 @vindex general-holidays
417 The general holidays are, by default, holidays common throughout the
418 United States. To eliminate these holidays, set @code{general-holidays}
421 @vindex local-holidays
422 There are no default local holidays (but sites may supply some). You
423 can set the variable @code{local-holidays} to any list of holidays, as
426 @vindex all-christian-calendar-holidays
427 @vindex all-hebrew-calendar-holidays
428 @vindex all-islamic-calendar-holidays
429 By default, Emacs does not include all the holidays of the religions
430 that it knows, only those commonly found in secular calendars. For a
431 more extensive collection of religious holidays, you can set any (or
432 all) of the variables @code{all-christian-calendar-holidays},
433 @code{all-hebrew-calendar-holidays}, or
434 @code{all-islamic-calendar-holidays} to @code{t}. If you want to
435 eliminate the religious holidays, set any or all of the corresponding
436 variables @code{christian-holidays}, @code{hebrew-holidays}, and
437 @code{islamic-holidays} to @code{nil}.@refill
439 @vindex other-holidays
440 You can set the variable @code{other-holidays} to any list of
441 holidays. This list, normally empty, is intended for individual use.
443 @cindex holiday forms
444 Each of the lists (@code{general-holidays}, @code{local-holidays},
445 @code{christian-holidays}, @code{hebrew-holidays},
446 @code{islamic-holidays}, and @code{other-holidays}) is a list of
447 @dfn{holiday forms}, each holiday form describing a holiday (or
448 sometimes a list of holidays).
450 Here is a table of the possible kinds of holiday form. Day numbers
451 and month numbers count starting from 1, but ``dayname'' numbers
452 count Sunday as 0. The element @var{string} is always the
453 name of the holiday, as a string.
456 @item (holiday-fixed @var{month} @var{day} @var{string})
457 A fixed date on the Gregorian calendar.
459 @item (holiday-float @var{month} @var{dayname} @var{k} @var{string})
460 The @var{k}th @var{dayname} in @var{month} on the Gregorian calendar
461 (@var{dayname}=0 for Sunday, and so on); negative @var{k} means count back
462 from the end of the month.
464 @item (holiday-hebrew @var{month} @var{day} @var{string})
465 A fixed date on the Hebrew calendar.
467 @item (holiday-islamic @var{month} @var{day} @var{string})
468 A fixed date on the Islamic calendar.
470 @item (holiday-julian @var{month} @var{day} @var{string})
471 A fixed date on the Julian calendar.
473 @item (holiday-sexp @var{sexp} @var{string})
474 A date calculated by the Lisp expression @var{sexp}. The expression
475 should use the variable @code{year} to compute and return the date of a
476 holiday, or @code{nil} if the holiday doesn't happen this year. The
477 value of @var{sexp} must represent the date as a list of the form
478 @code{(@var{month} @var{day} @var{year})}.
480 @item (if @var{condition} @var{holiday-form})
481 A holiday that happens only if @var{condition} is true.
483 @item (@var{function} @r{[}@var{args}@r{]})
484 A list of dates calculated by the function @var{function}, called with
485 arguments @var{args}.
488 For example, suppose you want to add Bastille Day, celebrated in
489 France on July 14. You can do this as follows:
492 (setq other-holidays '((holiday-fixed 7 14 "Bastille Day")))
496 The holiday form @code{(holiday-fixed 7 14 "Bastille Day")} specifies the
497 fourteenth day of the seventh month (July).
499 Many holidays occur on a specific day of the week, at a specific time
500 of month. Here is a holiday form describing Hurricane Supplication Day,
501 celebrated in the Virgin Islands on the fourth Monday in August:
504 (holiday-float 8 1 4 "Hurricane Supplication Day")
508 Here the 8 specifies August, the 1 specifies Monday (Sunday is 0,
509 Tuesday is 2, and so on), and the 4 specifies the fourth occurrence in
510 the month (1 specifies the first occurrence, 2 the second occurrence,
511 @minus{}1 the last occurrence, @minus{}2 the second-to-last occurrence, and
514 You can specify holidays that occur on fixed days of the Hebrew,
515 Islamic, and Julian calendars too. For example,
519 '((holiday-hebrew 10 2 "Last day of Hanukkah")
520 (holiday-islamic 3 12 "Mohammed's Birthday")
521 (holiday-julian 4 2 "Jefferson's Birthday")))
525 adds the last day of Hanukkah (since the Hebrew months are numbered with
526 1 starting from Nisan), the Islamic feast celebrating Mohammed's
527 birthday (since the Islamic months are numbered from 1 starting with
528 Muharram), and Thomas Jefferson's birthday, which is 2 April 1743 on the
531 To include a holiday conditionally, use either Emacs Lisp's @code{if} or the
532 @code{holiday-sexp} form. For example, American presidential elections
533 occur on the first Tuesday after the first Monday in November of years
537 (holiday-sexp '(if (= 0 (% year 4))
538 (calendar-gregorian-from-absolute
539 (1+ (calendar-dayname-on-or-before
540 1 (+ 6 (calendar-absolute-from-gregorian
541 (list 11 1 year)))))))
542 "US Presidential Election")
549 (if (= 0 (% displayed-year 4))
551 (extract-calendar-day
552 (calendar-gregorian-from-absolute
553 (1+ (calendar-dayname-on-or-before
554 1 (+ 6 (calendar-absolute-from-gregorian
555 (list 11 1 displayed-year)))))))
556 "US Presidential Election"))
559 Some holidays just don't fit into any of these forms because special
560 calculations are involved in their determination. In such cases you
561 must write a Lisp function to do the calculation. To include eclipses,
562 for example, add @code{(eclipses)} to @code{other-holidays}
563 and write an Emacs Lisp function @code{eclipses} that returns a
564 (possibly empty) list of the relevant Gregorian dates among the range
565 visible in the calendar window, with descriptive strings, like this:
568 (((6 27 1991) "Lunar Eclipse") ((7 11 1991) "Solar Eclipse") ... )
571 @node Date Display Format
572 @section Date Display Format
573 @vindex calendar-date-display-form
575 You can customize the manner of displaying dates in the diary, in mode
576 lines, and in messages by setting @code{calendar-date-display-form}.
577 This variable holds a list of expressions that can involve the variables
578 @code{month}, @code{day}, and @code{year}, which are all numbers in
579 string form, and @code{monthname} and @code{dayname}, which are both
580 alphabetic strings. In the American style, the default value of this
584 ((if dayname (concat dayname ", ")) monthname " " day ", " year)
588 while in the European style this value is the default:
591 ((if dayname (concat dayname ", ")) day " " monthname " " year)
595 The ISO standard date representation is this:
598 (year "-" month "-" day)
602 This specifies a typical American format:
605 (month "/" day "/" (substring year -2))
608 @node Time Display Format
609 @section Time Display Format
610 @vindex calendar-time-display-form
612 The calendar and diary by default display times of day in the
613 conventional American style with the hours from 1 through 12, minutes,
614 and either @samp{am} or @samp{pm}. If you prefer the European style,
615 also known in the US as military, in which the hours go from 00 to 23,
616 you can alter the variable @code{calendar-time-display-form}. This
617 variable is a list of expressions that can involve the variables
618 @code{12-hours}, @code{24-hours}, and @code{minutes}, which are all
619 numbers in string form, and @code{am-pm} and @code{time-zone}, which are
620 both alphabetic strings. The default value of
621 @code{calendar-time-display-form} is as follows:
624 (12-hours ":" minutes am-pm
625 (if time-zone " (") time-zone (if time-zone ")"))
629 Here is a value that provides European style times:
632 (24-hours ":" minutes
633 (if time-zone " (") time-zone (if time-zone ")"))
636 @node Daylight Savings
637 @section Daylight Savings Time
638 @cindex daylight savings time
640 Emacs understands the difference between standard time and daylight
641 savings time---the times given for sunrise, sunset, solstices,
642 equinoxes, and the phases of the moon take that into account. The rules
643 for daylight savings time vary from place to place and have also varied
644 historically from year to year. To do the job properly, Emacs needs to
645 know which rules to use.
647 Some operating systems keep track of the rules that apply to the place
648 where you are; on these systems, Emacs gets the information it needs
649 from the system automatically. If some or all of this information is
650 missing, Emacs fills in the gaps with the rules currently used in
651 Cambridge, Massachusetts, which is the center of GNU's world.
654 @vindex calendar-daylight-savings-starts
655 @vindex calendar-daylight-savings-ends
656 If the default choice of rules is not appropriate for your location,
657 you can tell Emacs the rules to use by setting the variables
658 @code{calendar-daylight-savings-starts} and
659 @code{calendar-daylight-savings-ends}. Their values should be Lisp
660 expressions that refer to the variable @code{year}, and evaluate to the
661 Gregorian date on which daylight savings time starts or (respectively)
662 ends, in the form of a list @code{(@var{month} @var{day} @var{year})}.
663 The values should be @code{nil} if your area does not use daylight
666 Emacs uses these expressions to determine the start and end dates of
667 daylight savings time as holidays and for correcting times of day in the
668 solar and lunar calculations.
670 The values for Cambridge, Massachusetts are as follows:
674 (calendar-nth-named-day 1 0 4 year)
675 (calendar-nth-named-day -1 0 10 year)
680 i.e., the first 0th day (Sunday) of the fourth month (April) in
681 the year specified by @code{year}, and the last Sunday of the tenth month
682 (October) of that year. If daylight savings time were
683 changed to start on October 1, you would set
684 @code{calendar-daylight-savings-starts} to this:
690 For a more complex example, suppose daylight savings time begins on
691 the first of Nisan on the Hebrew calendar. You should set
692 @code{calendar-daylight-savings-starts} to this value:
695 (calendar-gregorian-from-absolute
696 (calendar-absolute-from-hebrew
697 (list 1 1 (+ year 3760))))
701 because Nisan is the first month in the Hebrew calendar and the Hebrew
702 year differs from the Gregorian year by 3760 at Nisan.
704 If there is no daylight savings time at your location, or if you want
705 all times in standard time, set @code{calendar-daylight-savings-starts}
706 and @code{calendar-daylight-savings-ends} to @code{nil}.
708 @vindex calendar-daylight-time-offset
709 The variable @code{calendar-daylight-time-offset} specifies the
710 difference between daylight savings time and standard time, measured in
711 minutes. The value for Cambridge is 60.
713 @vindex calendar-daylight-savings-starts-time
714 @vindex calendar-daylight-savings-ends-time
715 The variable @code{calendar-daylight-savings-starts-time} and the
716 variable @code{calendar-daylight-savings-ends-time} specify the number
717 of minutes after midnight local time when the transition to and from
718 daylight savings time should occur. For Cambridge, both variables'
721 @node Diary Customizing
722 @section Customizing the Diary
724 @vindex holidays-in-diary-buffer
725 Ordinarily, the mode line of the diary buffer window indicates any
726 holidays that fall on the date of the diary entries. The process of
727 checking for holidays can take several seconds, so including holiday
728 information delays the display of the diary buffer noticeably. If you'd
729 prefer to have a faster display of the diary buffer but without the
730 holiday information, set the variable @code{holidays-in-diary-buffer} to
733 @vindex number-of-diary-entries
734 The variable @code{number-of-diary-entries} controls the number of
735 days of diary entries to be displayed at one time. It affects the
736 initial display when @code{view-diary-entries-initially} is @code{t}, as
737 well as the command @kbd{M-x diary}. For example, the default value is
738 1, which says to display only the current day's diary entries. If the
739 value is 2, both the current day's and the next day's entries are
740 displayed. The value can also be a vector of seven elements: for
741 example, if the value is @code{[0 2 2 2 2 4 1]} then no diary entries
742 appear on Sunday, the current date's and the next day's diary entries
743 appear Monday through Thursday, Friday through Monday's entries appear
744 on Friday, while on Saturday only that day's entries appear.
746 @vindex print-diary-entries-hook
747 @findex print-diary-entries
748 The variable @code{print-diary-entries-hook} is a normal hook run
749 after preparation of a temporary buffer containing just the diary
750 entries currently visible in the diary buffer. (The other, irrelevant
751 diary entries are really absent from the temporary buffer; in the diary
752 buffer, they are merely hidden.) The default value of this hook does
753 the printing with the command @code{lpr-buffer}. If you want to use a
754 different command to do the printing, just change the value of this
755 hook. Other uses might include, for example, rearranging the lines into
756 order by day and time.
758 @vindex diary-date-forms
759 You can customize the form of dates in your diary file, if neither the
760 standard American nor European styles suits your needs, by setting the
761 variable @code{diary-date-forms}. This variable is a list of patterns
762 for recognizing a date. Each date pattern is a list whose elements may
763 be regular expressions (@pxref{Regular Expressions,,, elisp, the Emacs
764 Lisp Reference Manual}) or the symbols @code{month}, @code{day},
765 @code{year}, @code{monthname}, and @code{dayname}. All these elements
766 serve as patterns that match certain kinds of text in the diary file.
767 In order for the date pattern, as a whole, to match, all of its elements
768 must match consecutively.
770 A regular expression in a date pattern matches in its usual fashion,
771 using the standard syntax table altered so that @samp{*} is a word
774 The symbols @code{month}, @code{day}, @code{year}, @code{monthname},
775 and @code{dayname} match the month number, day number, year number,
776 month name, and day name of the date being considered. The symbols that
777 match numbers allow leading zeros; those that match names allow
778 three-letter abbreviations and capitalization. All the symbols can
779 match @samp{*}; since @samp{*} in a diary entry means ``any day'', ``any
780 month'', and so on, it should match regardless of the date being
783 The default value of @code{diary-date-forms} in the American style is
787 ((month "/" day "[^/0-9]")
788 (month "/" day "/" year "[^0-9]")
789 (monthname " *" day "[^,0-9]")
790 (monthname " *" day ", *" year "[^0-9]")
794 The date patterns in the list must be @emph{mutually exclusive} and
795 must not match any portion of the diary entry itself, just the date and
796 one character of whitespace. If, to be mutually exclusive, the pattern
797 must match a portion of the diary entry text---beyond the whitespace
798 that ends the date---then the first element of the date pattern
799 @emph{must} be @code{backup}. This causes the date recognizer to back
800 up to the beginning of the current word of the diary entry, after
801 finishing the match. Even if you use @code{backup}, the date pattern
802 must absolutely not match more than a portion of the first word of the
803 diary entry. The default value of @code{diary-date-forms} in the
804 European style is this list:
807 ((day "/" month "[^/0-9]")
808 (day "/" month "/" year "[^0-9]")
809 (backup day " *" monthname "\\W+\\<[^*0-9]")
810 (day " *" monthname " *" year "[^0-9]")
815 Notice the use of @code{backup} in the third pattern, because it needs
816 to match part of a word beyond the date itself to distinguish it from
819 @node Hebrew/Islamic Entries
820 @section Hebrew- and Islamic-Date Diary Entries
822 Your diary file can have entries based on Hebrew or Islamic dates, as
823 well as entries based on the world-standard Gregorian calendar.
824 However, because recognition of such entries is time-consuming and most
825 people don't use them, you must explicitly enable their use. If you
826 want the diary to recognize Hebrew-date diary entries, for example,
829 @vindex nongregorian-diary-listing-hook
830 @vindex nongregorian-diary-marking-hook
831 @findex list-hebrew-diary-entries
832 @findex mark-hebrew-diary-entries
834 (add-hook 'nongregorian-diary-listing-hook 'list-hebrew-diary-entries)
835 (add-hook 'nongregorian-diary-marking-hook 'mark-hebrew-diary-entries)
839 If you want Islamic-date entries, do this:
841 @findex list-islamic-diary-entries
842 @findex mark-islamic-diary-entries
844 (add-hook 'nongregorian-diary-listing-hook 'list-islamic-diary-entries)
845 (add-hook 'nongregorian-diary-marking-hook 'mark-islamic-diary-entries)
848 Hebrew- and Islamic-date diary entries have the same formats as
849 Gregorian-date diary entries, except that @samp{H} precedes a Hebrew
850 date and @samp{I} precedes an Islamic date. Moreover, because the
851 Hebrew and Islamic month names are not uniquely specified by the first
852 three letters, you may not abbreviate them. For example, a diary entry
853 for the Hebrew date Heshvan 25 could look like this:
856 HHeshvan 25 Happy Hebrew birthday!
860 and would appear in the diary for any date that corresponds to Heshvan 25
861 on the Hebrew calendar. And here is an Islamic-date diary entry that matches
865 IDhu al-Qada 25 Happy Islamic birthday!
868 As with Gregorian-date diary entries, Hebrew- and Islamic-date entries
869 are nonmarking if they are preceded with an ampersand (@samp{&}).
871 Here is a table of commands used in the calendar to create diary entries
872 that match the selected date and other dates that are similar in the Hebrew
877 Add a diary entry for the Hebrew date corresponding to the selected date
878 (@code{insert-hebrew-diary-entry}).
880 Add a diary entry for the day of the Hebrew month corresponding to the
881 selected date (@code{insert-monthly-hebrew-diary-entry}). This diary
882 entry matches any date that has the same Hebrew day-within-month as the
885 Add a diary entry for the day of the Hebrew year corresponding to the
886 selected date (@code{insert-yearly-hebrew-diary-entry}). This diary
887 entry matches any date which has the same Hebrew month and day-within-month
888 as the selected date.
890 Add a diary entry for the Islamic date corresponding to the selected date
891 (@code{insert-islamic-diary-entry}).
893 Add a diary entry for the day of the Islamic month corresponding to the
894 selected date (@code{insert-monthly-islamic-diary-entry}).
896 Add a diary entry for the day of the Islamic year corresponding to the
897 selected date (@code{insert-yearly-islamic-diary-entry}).
900 @findex insert-hebrew-diary-entry
901 @findex insert-monthly-hebrew-diary-entry
902 @findex insert-yearly-hebrew-diary-entry
903 @findex insert-islamic-diary-entry
904 @findex insert-monthly-islamic-diary-entry
905 @findex insert-yearly-islamic-diary-entry
906 These commands work much like the corresponding commands for ordinary
907 diary entries: they apply to the date that point is on in the calendar
908 window, and what they do is insert just the date portion of a diary entry
909 at the end of your diary file. You must then insert the rest of the
912 @node Fancy Diary Display
913 @section Fancy Diary Display
914 @vindex diary-display-hook
915 @findex simple-diary-display
917 Diary display works by preparing the diary buffer and then running the
918 hook @code{diary-display-hook}. The default value of this hook
919 (@code{simple-diary-display}) hides the irrelevant diary entries and
920 then displays the buffer. However, if you specify the hook as follows,
923 @findex fancy-diary-display
925 (add-hook 'diary-display-hook 'fancy-diary-display)
929 this enables fancy diary display. It displays diary entries and
930 holidays by copying them into a special buffer that exists only for the
931 sake of display. Copying to a separate buffer provides an opportunity
932 to change the displayed text to make it prettier---for example, to sort
933 the entries by the dates they apply to.
935 As with simple diary display, you can print a hard copy of the buffer
936 with @code{print-diary-entries}. To print a hard copy of a day-by-day
937 diary for a week, position point on Sunday of that week, type
938 @kbd{7 d}, and then do @kbd{M-x print-diary-entries}. As usual, the
939 inclusion of the holidays slows down the display slightly; you can speed
940 things up by setting the variable @code{holidays-in-diary-buffer} to
943 @vindex diary-list-include-blanks
944 Ordinarily, the fancy diary buffer does not show days for which there are
945 no diary entries, even if that day is a holiday. If you want such days to be
946 shown in the fancy diary buffer, set the variable
947 @code{diary-list-include-blanks} to @code{t}.@refill
949 @cindex sorting diary entries
950 If you use the fancy diary display, you can use the normal hook
951 @code{list-diary-entries-hook} to sort each day's diary entries by their
952 time of day. Here's how:
954 @findex sort-diary-entries
956 (add-hook 'list-diary-entries-hook 'sort-diary-entries t)
960 For each day, this sorts diary entries that begin with a recognizable
961 time of day according to their times. Diary entries without times come
962 first within each day.
964 Fancy diary display also has the ability to process included diary
965 files. This permits a group of people to share a diary file for events
966 that apply to all of them. Lines in the diary file of this form:
969 #include "@var{filename}"
973 includes the diary entries from the file @var{filename} in the fancy
974 diary buffer. The include mechanism is recursive, so that included files
975 can include other files, and so on; you must be careful not to have a
976 cycle of inclusions, of course. Here is how to enable the include
979 @vindex list-diary-entries-hook
980 @vindex mark-diary-entries-hook
981 @findex include-other-diary-files
982 @findex mark-included-diary-files
984 (add-hook 'list-diary-entries-hook 'include-other-diary-files)
985 (add-hook 'mark-diary-entries-hook 'mark-included-diary-files)
988 The include mechanism works only with the fancy diary display, because
989 ordinary diary display shows the entries directly from your diary file.
991 @node Sexp Diary Entries
992 @section Sexp Entries and the Fancy Diary Display
993 @cindex sexp diary entries
995 Sexp diary entries allow you to do more than just have complicated
996 conditions under which a diary entry applies. If you use the fancy
997 diary display, sexp entries can generate the text of the entry depending
998 on the date itself. For example, an anniversary diary entry can insert
999 the number of years since the anniversary date into the text of the
1000 diary entry. Thus the @samp{%d} in this dairy entry:
1002 @findex diary-anniversary
1004 %%(diary-anniversary 10 31 1948) Arthur's birthday (%d years old)
1008 gets replaced by the age, so on October 31, 1990 the entry appears in
1009 the fancy diary buffer like this:
1012 Arthur's birthday (42 years old)
1016 If the diary file instead contains this entry:
1019 %%(diary-anniversary 10 31 1948) Arthur's %d%s birthday
1023 the entry in the fancy diary buffer for October 31, 1990 appears like this:
1026 Arthur's 42nd birthday
1029 Similarly, cyclic diary entries can interpolate the number of repetitions
1032 @findex diary-cyclic
1034 %%(diary-cyclic 50 1 1 1990) Renew medication (%d%s time)
1041 Renew medication (5th time)
1045 in the fancy diary display on September 8, 1990.
1047 There is an early reminder diary sexp that includes its entry in the
1048 diary not only on the date of occurrence, but also on earlier dates.
1049 For example, if you want a reminder a week before your anniversary, you
1052 @findex diary-remind
1054 %%(diary-remind '(diary-anniversary 12 22 1968) 7) Ed's anniversary
1058 and the fancy diary will show
1063 both on December 15 and on December 22.
1066 The function @code{diary-date} applies to dates described by a month,
1067 day, year combination, each of which can be an integer, a list of
1068 integers, or @code{t}. The value @code{t} means all values. For
1072 %%(diary-date '(10 11 12) 22 t) Rake leaves
1076 causes the fancy diary to show
1083 on October 22, November 22, and December 22 of every year.
1086 The function @code{diary-float} allows you to describe diary entries
1087 that apply to dates like the third Friday of November, or the last
1088 Tuesday in April. The parameters are the @var{month}, @var{dayname},
1089 and an index @var{n}. The entry appears on the @var{n}th @var{dayname}
1090 of @var{month}, where @var{dayname}=0 means Sunday, 1 means Monday, and
1091 so on. If @var{n} is negative it counts backward from the end of
1092 @var{month}. The value of @var{month} can be a list of months, a single
1093 month, or @code{t} to specify all months. You can also use an optional
1094 parameter @var{day} to specify the @var{n}th @var{dayname} of
1095 @var{month} on or after/before @var{day}; the value of @var{day} defaults
1096 to 1 if @var{n} is positive and to the last day of @var{month} if
1097 @var{n} is negative. For example,
1100 %%(diary-float t 1 -1) Pay rent
1104 causes the fancy diary to show
1111 on the last Monday of every month.
1113 The generality of sexp diary entries lets you specify any diary
1114 entry that you can describe algorithmically. A sexp diary entry
1115 contains an expression that computes whether the entry applies to any
1116 given date. If its value is non-@code{nil}, the entry applies to that
1117 date; otherwise, it does not. The expression can use the variable
1118 @code{date} to find the date being considered; its value is a list
1119 (@var{month} @var{day} @var{year}) that refers to the Gregorian
1122 The sexp diary entry applies to a date when the expression's value
1123 is non-@code{nil}, but some values have more specific meanings. If
1124 the value is a string, that string is a description of the event which
1125 occurs on that date. The value can also have the form
1126 @code{(@var{mark} . @var{string})}; then @var{mark} specifies how to
1127 mark the date in the calendar, and @var{string} is the description of
1128 the event. If @var{mark} is a single-character string, that character
1129 appears next to the date in the calendar. If @var{mark} is a face
1130 name, the date is displayed in that face. If @var{mark} is
1131 @code{nil}, that specifies no particular highlighting for the date.
1133 Suppose you get paid on the 21st of the month if it is a weekday, and
1134 on the Friday before if the 21st is on a weekend. Here is how to write
1135 a sexp diary entry that matches those dates:
1138 &%%(let ((dayname (calendar-day-of-week date))
1139 (day (car (cdr date))))
1140 (or (and (= day 21) (memq dayname '(1 2 3 4 5)))
1141 (and (memq day '(19 20)) (= dayname 5)))
1142 ) Pay check deposited
1145 The following sexp diary entries take advantage of the ability (in the fancy
1146 diary display) to concoct diary entries whose text varies based on the date:
1148 @findex diary-sunrise-sunset
1149 @findex diary-phases-of-moon
1150 @findex diary-day-of-year
1151 @findex diary-iso-date
1152 @findex diary-julian-date
1153 @findex diary-astro-day-number
1154 @findex diary-hebrew-date
1155 @findex diary-islamic-date
1156 @findex diary-french-date
1157 @findex diary-mayan-date
1159 @item %%(diary-sunrise-sunset)
1160 Make a diary entry for the local times of today's sunrise and sunset.
1161 @item %%(diary-phases-of-moon)
1162 Make a diary entry for the phases (quarters) of the moon.
1163 @item %%(diary-day-of-year)
1164 Make a diary entry with today's day number in the current year and the number
1165 of days remaining in the current year.
1166 @item %%(diary-iso-date)
1167 Make a diary entry with today's equivalent ISO commercial date.
1168 @item %%(diary-julian-date)
1169 Make a diary entry with today's equivalent date on the Julian calendar.
1170 @item %%(diary-astro-day-number)
1171 Make a diary entry with today's equivalent astronomical (Julian) day number.
1172 @item %%(diary-hebrew-date)
1173 Make a diary entry with today's equivalent date on the Hebrew calendar.
1174 @item %%(diary-islamic-date)
1175 Make a diary entry with today's equivalent date on the Islamic calendar.
1176 @item %%(diary-french-date)
1177 Make a diary entry with today's equivalent date on the French Revolutionary
1179 @item %%(diary-mayan-date)
1180 Make a diary entry with today's equivalent date on the Mayan calendar.
1184 Thus including the diary entry
1187 &%%(diary-hebrew-date)
1191 causes every day's diary display to contain the equivalent date on the
1192 Hebrew calendar, if you are using the fancy diary display. (With simple
1193 diary display, the line @samp{&%%(diary-hebrew-date)} appears in the
1194 diary for any date, but does nothing particularly useful.)
1196 These functions can be used to construct sexp diary entries based on
1197 the Hebrew calendar in certain standard ways:
1200 @findex diary-rosh-hodesh
1201 @cindex parasha, weekly
1202 @findex diary-parasha
1203 @cindex candle lighting times
1204 @findex diary-sabbath-candles
1208 @findex diary-yahrzeit
1210 @item %%(diary-rosh-hodesh)
1211 Make a diary entry that tells the occurrence and ritual announcement of each
1213 @item %%(diary-parasha)
1214 Make a Saturday diary entry that tells the weekly synagogue scripture reading.
1215 @item %%(diary-sabbath-candles)
1216 Make a Friday diary entry that tells the @emph{local time} of Sabbath
1218 @item %%(diary-omer)
1219 Make a diary entry that gives the omer count, when appropriate.
1220 @item %%(diary-yahrzeit @var{month} @var{day} @var{year}) @var{name}
1221 Make a diary entry marking the anniversary of a date of death. The date
1222 is the @emph{Gregorian} (civil) date of death. The diary entry appears
1223 on the proper Hebrew calendar anniversary and on the day before. (In
1224 the European style, the order of the parameters is changed to @var{day},
1225 @var{month}, @var{year}.)
1228 All the functions documented above take an optional argument
1229 @var{mark} which specifies how to mark the date in the calendar display.
1230 If one of these functions decides that it applies to a certain date,
1231 it returns a value that contains @var{mark}.
1234 @chapter Merging Files with Emerge
1236 @cindex merging files
1238 It's not unusual for programmers to get their signals crossed and
1239 modify the same program in two different directions. To recover from
1240 this confusion, you need to merge the two versions. Emerge makes this
1241 easier. For other ways to compare files, see @ref{Comparing Files,,,
1242 emacs, the Emacs Manual} and @ref{Top, Ediff,, ediff, The Ediff
1246 * Overview of Emerge:: How to start Emerge. Basic concepts.
1247 * Submodes of Emerge:: Fast mode vs. Edit mode.
1248 Skip Prefers mode and Auto Advance mode.
1249 * State of Difference:: You do the merge by specifying state A or B
1250 for each difference.
1251 * Merge Commands:: Commands for selecting a difference,
1252 changing states of differences, etc.
1253 * Exiting Emerge:: What to do when you've finished the merge.
1254 * Combining in Emerge:: How to keep both alternatives for a difference.
1255 * Fine Points of Emerge:: Misc.
1258 @node Overview of Emerge
1259 @section Overview of Emerge
1261 To start Emerge, run one of these four commands:
1264 @item M-x emerge-files
1265 @findex emerge-files
1266 Merge two specified files.
1268 @item M-x emerge-files-with-ancestor
1269 @findex emerge-files-with-ancestor
1270 Merge two specified files, with reference to a common ancestor.
1272 @item M-x emerge-buffers
1273 @findex emerge-buffers
1276 @item M-x emerge-buffers-with-ancestor
1277 @findex emerge-buffers-with-ancestor
1278 Merge two buffers with reference to a common ancestor in a third
1282 @cindex merge buffer (Emerge)
1283 @cindex A and B buffers (Emerge)
1284 The Emerge commands compare two files or buffers, and display the
1285 comparison in three buffers: one for each input text (the @dfn{A buffer}
1286 and the @dfn{B buffer}), and one (the @dfn{merge buffer}) where merging
1287 takes place. The merge buffer shows the full merged text, not just the
1288 differences. Wherever the two input texts differ, you can choose which
1289 one of them to include in the merge buffer.
1291 The Emerge commands that take input from existing buffers use only
1292 the accessible portions of those buffers, if they are narrowed.
1293 @xref{Narrowing,,, emacs, the Emacs Manual}.
1296 If a common ancestor version is available, from which the two texts to
1297 be merged were both derived, Emerge can use it to guess which
1298 alternative is right. Wherever one current version agrees with the
1299 ancestor, Emerge presumes that the other current version is a deliberate
1300 change which should be kept in the merged version. Use the
1301 @samp{with-ancestor} commands if you want to specify a common ancestor
1302 text. These commands read three file or buffer names---variant A,
1303 variant B, and the common ancestor.
1305 After the comparison is done and the buffers are prepared, the
1306 interactive merging starts. You control the merging by typing special
1307 @dfn{merge commands} in the merge buffer (@pxref{Merge Commands}).
1308 For each run of differences between the input texts, you can choose
1309 which one of them to keep, or edit them both together.
1311 The merge buffer uses a special major mode, Emerge mode, with commands
1312 for making these choices. But you can also edit the buffer with
1313 ordinary Emacs commands.
1315 At any given time, the attention of Emerge is focused on one
1316 particular difference, called the @dfn{selected} difference. This
1317 difference is marked off in the three buffers like this:
1320 vvvvvvvvvvvvvvvvvvvv
1321 @var{text that differs}
1322 ^^^^^^^^^^^^^^^^^^^^
1326 Emerge numbers all the differences sequentially and the mode
1327 line always shows the number of the selected difference.
1329 Normally, the merge buffer starts out with the A version of the text.
1330 But when the A version of a difference agrees with the common ancestor,
1331 then the B version is initially preferred for that difference.
1333 Emerge leaves the merged text in the merge buffer when you exit. At
1334 that point, you can save it in a file with @kbd{C-x C-w}. If you give a
1335 numeric argument to @code{emerge-files} or
1336 @code{emerge-files-with-ancestor}, it reads the name of the output file
1337 using the minibuffer. (This is the last file name those commands read.)
1338 Then exiting from Emerge saves the merged text in the output file.
1340 Normally, Emerge commands save the output buffer in its file when you
1341 exit. If you abort Emerge with @kbd{C-]}, the Emerge command does not
1342 save the output buffer, but you can save it yourself if you wish.
1344 @node Submodes of Emerge
1345 @section Submodes of Emerge
1347 You can choose between two modes for giving merge commands: Fast mode
1348 and Edit mode. In Fast mode, basic merge commands are single
1349 characters, but ordinary Emacs commands are disabled. This is
1350 convenient if you use only merge commands. In Edit mode, all merge
1351 commands start with the prefix key @kbd{C-c C-c}, and the normal Emacs
1352 commands are also available. This allows editing the merge buffer, but
1353 slows down Emerge operations.
1355 Use @kbd{e} to switch to Edit mode, and @kbd{C-c C-c f} to switch to
1356 Fast mode. The mode line indicates Edit and Fast modes with @samp{E}
1359 Emerge has two additional submodes that affect how particular merge
1360 commands work: Auto Advance mode and Skip Prefers mode.
1362 If Auto Advance mode is in effect, the @kbd{a} and @kbd{b} commands
1363 advance to the next difference. This lets you go through the merge
1364 faster as long as you simply choose one of the alternatives from the
1365 input. The mode line indicates Auto Advance mode with @samp{A}.
1367 If Skip Prefers mode is in effect, the @kbd{n} and @kbd{p} commands
1368 skip over differences in states prefer-A and prefer-B (@pxref{State of
1369 Difference}). Thus you see only differences for which neither version
1370 is presumed ``correct.'' The mode line indicates Skip Prefers mode with
1373 @findex emerge-auto-advance-mode
1374 @findex emerge-skip-prefers-mode
1375 Use the command @kbd{s a} (@code{emerge-auto-advance-mode}) to set or
1376 clear Auto Advance mode. Use @kbd{s s}
1377 (@code{emerge-skip-prefers-mode}) to set or clear Skip Prefers mode.
1378 These commands turn on the mode with a positive argument, turns it off
1379 with a negative or zero argument, and toggle the mode with no argument.
1381 @node State of Difference
1382 @section State of a Difference
1384 In the merge buffer, a difference is marked with lines of @samp{v} and
1385 @samp{^} characters. Each difference has one of these seven states:
1389 The difference is showing the A version. The @kbd{a} command always
1390 produces this state; the mode line indicates it with @samp{A}.
1393 The difference is showing the B version. The @kbd{b} command always
1394 produces this state; the mode line indicates it with @samp{B}.
1398 The difference is showing the A or the B state by default, because you
1399 haven't made a choice. All differences start in the default-A state
1400 (and thus the merge buffer is a copy of the A buffer), except those for
1401 which one alternative is ``preferred'' (see below).
1403 When you select a difference, its state changes from default-A or
1404 default-B to plain A or B. Thus, the selected difference never has
1405 state default-A or default-B, and these states are never displayed in
1408 The command @kbd{d a} chooses default-A as the default state, and @kbd{d
1409 b} chooses default-B. This chosen default applies to all differences
1410 which you haven't ever selected and for which no alternative is preferred.
1411 If you are moving through the merge sequentially, the differences you
1412 haven't selected are those following the selected one. Thus, while
1413 moving sequentially, you can effectively make the A version the default
1414 for some sections of the merge buffer and the B version the default for
1415 others by using @kbd{d a} and @kbd{d b} between sections.
1419 The difference is showing the A or B state because it is
1420 @dfn{preferred}. This means that you haven't made an explicit choice,
1421 but one alternative seems likely to be right because the other
1422 alternative agrees with the common ancestor. Thus, where the A buffer
1423 agrees with the common ancestor, the B version is preferred, because
1424 chances are it is the one that was actually changed.
1426 These two states are displayed in the mode line as @samp{A*} and @samp{B*}.
1429 The difference is showing a combination of the A and B states, as a
1430 result of the @kbd{x c} or @kbd{x C} commands.
1432 Once a difference is in this state, the @kbd{a} and @kbd{b} commands
1433 don't do anything to it unless you give them a numeric argument.
1435 The mode line displays this state as @samp{comb}.
1438 @node Merge Commands
1439 @section Merge Commands
1441 Here are the Merge commands for Fast mode; in Edit mode, precede them
1446 Select the previous difference.
1449 Select the next difference.
1452 Choose the A version of this difference.
1455 Choose the B version of this difference.
1458 Select difference number @var{n}.
1461 Select the difference containing point. You can use this command in the
1462 merge buffer or in the A or B buffer.
1465 Quit---finish the merge.
1468 Abort---exit merging and do not save the output.
1471 Go into Fast mode. (In Edit mode, this is actually @kbd{C-c C-c f}.)
1477 Recenter (like @kbd{C-l}) all three windows.
1480 Specify part of a prefix numeric argument.
1483 Also specify part of a prefix numeric argument.
1486 Choose the A version as the default from here down in
1490 Choose the B version as the default from here down in
1494 Copy the A version of this difference into the kill ring.
1497 Copy the B version of this difference into the kill ring.
1500 Insert the A version of this difference at point.
1503 Insert the B version of this difference at point.
1506 Put point and mark around the difference.
1509 Scroll all three windows down (like @kbd{M-v}).
1512 Scroll all three windows up (like @kbd{C-v}).
1515 Scroll all three windows left (like @kbd{C-x <}).
1518 Scroll all three windows right (like @kbd{C-x >}).
1521 Reset horizontal scroll on all three windows.
1524 Shrink the merge window to one line. (Use @kbd{C-u l} to restore it
1528 Combine the two versions of this difference (@pxref{Combining in
1532 Show the names of the files/buffers Emerge is operating on, in a Help
1533 window. (Use @kbd{C-u l} to restore windows.)
1536 Join this difference with the following one.
1537 (@kbd{C-u x j} joins this difference with the previous one.)
1540 Split this difference into two differences. Before you use this
1541 command, position point in each of the three buffers at the place where
1542 you want to split the difference.
1545 Trim identical lines off the top and bottom of the difference.
1546 Such lines occur when the A and B versions are
1547 identical but differ from the ancestor version.
1550 @node Exiting Emerge
1551 @section Exiting Emerge
1553 The @kbd{q} command (@code{emerge-quit}) finishes the merge, storing
1554 the results into the output file if you specified one. It restores the
1555 A and B buffers to their proper contents, or kills them if they were
1556 created by Emerge and you haven't changed them. It also disables the
1557 Emerge commands in the merge buffer, since executing them later could
1558 damage the contents of the various buffers.
1560 @kbd{C-]} aborts the merge. This means exiting without writing the
1561 output file. If you didn't specify an output file, then there is no
1562 real difference between aborting and finishing the merge.
1564 If the Emerge command was called from another Lisp program, then its
1565 return value is @code{t} for successful completion, or @code{nil} if you
1568 @node Combining in Emerge
1569 @section Combining the Two Versions
1571 Sometimes you want to keep @emph{both} alternatives for a particular
1572 difference. To do this, use @kbd{x c}, which edits the merge buffer
1578 @var{version from A buffer}
1580 @var{version from B buffer}
1581 #endif /* not NEW */
1586 @vindex emerge-combine-versions-template
1587 While this example shows C preprocessor conditionals delimiting the two
1588 alternative versions, you can specify the strings to use by setting
1589 the variable @code{emerge-combine-versions-template} to a string of your
1590 choice. In the string, @samp{%a} says where to put version A, and
1591 @samp{%b} says where to put version B. The default setting, which
1592 produces the results shown above, looks like this:
1596 "#ifdef NEW\n%a#else /* not NEW */\n%b#endif /* not NEW */\n"
1600 @node Fine Points of Emerge
1601 @section Fine Points of Emerge
1603 During the merge, you mustn't try to edit the A and B buffers yourself.
1604 Emerge modifies them temporarily, but ultimately puts them back the way
1607 You can have any number of merges going at once---just don't use any one
1608 buffer as input to more than one merge at once, since the temporary
1609 changes made in these buffers would get in each other's way.
1611 Starting Emerge can take a long time because it needs to compare the
1612 files fully. Emacs can't do anything else until @code{diff} finishes.
1613 Perhaps in the future someone will change Emerge to do the comparison in
1614 the background when the input files are large---then you could keep on
1615 doing other things with Emacs until Emerge is ready to accept
1618 @vindex emerge-startup-hook
1619 After setting up the merge, Emerge runs the hook
1620 @code{emerge-startup-hook}. @xref{Hooks,,, emacs, the Emacs Manual}.
1623 @chapter Editing Pictures
1625 @cindex making pictures out of text characters
1626 @findex edit-picture
1628 To edit a picture made out of text characters (for example, a picture
1629 of the division of a register into fields, as a comment in a program),
1630 use the command @kbd{M-x edit-picture} to enter Picture mode.
1632 In Picture mode, editing is based on the @dfn{quarter-plane} model of
1633 text, according to which the text characters lie studded on an area that
1634 stretches infinitely far to the right and downward. The concept of the end
1635 of a line does not exist in this model; the most you can say is where the
1636 last nonblank character on the line is found.
1638 Of course, Emacs really always considers text as a sequence of
1639 characters, and lines really do have ends. But Picture mode replaces
1640 the most frequently-used commands with variants that simulate the
1641 quarter-plane model of text. They do this by inserting spaces or by
1642 converting tabs to spaces.
1644 Most of the basic editing commands of Emacs are redefined by Picture mode
1645 to do essentially the same thing but in a quarter-plane way. In addition,
1646 Picture mode defines various keys starting with the @kbd{C-c} prefix to
1647 run special picture editing commands.
1649 One of these keys, @kbd{C-c C-c}, is particularly important. Often a
1650 picture is part of a larger file that is usually edited in some other
1651 major mode. @kbd{M-x edit-picture} records the name of the previous
1652 major mode so you can use the @kbd{C-c C-c} command
1653 (@code{picture-mode-exit}) later to go back to that mode. @kbd{C-c C-c}
1654 also deletes spaces from the ends of lines, unless given a numeric
1657 The special commands of Picture mode all work in other modes (provided
1658 the @file{picture} library is loaded), but are not bound to keys except
1659 in Picture mode. The descriptions below talk of moving ``one column''
1660 and so on, but all the picture mode commands handle numeric arguments as
1661 their normal equivalents do.
1663 @vindex picture-mode-hook
1664 Turning on Picture mode runs the hook @code{picture-mode-hook}.
1665 Additional extensions to Picture mode can be found in
1669 * Basic Picture:: Basic concepts and simple commands of Picture Mode.
1670 * Insert in Picture:: Controlling direction of cursor motion
1671 after "self-inserting" characters.
1672 * Tabs in Picture:: Various features for tab stops and indentation.
1673 * Rectangles in Picture:: Clearing and superimposing rectangles.
1677 @section Basic Editing in Picture Mode
1679 @findex picture-forward-column
1680 @findex picture-backward-column
1681 @findex picture-move-down
1682 @findex picture-move-up
1683 @cindex editing in Picture mode
1685 Most keys do the same thing in Picture mode that they usually do, but
1686 do it in a quarter-plane style. For example, @kbd{C-f} is rebound to
1687 run @code{picture-forward-column}, a command which moves point one
1688 column to the right, inserting a space if necessary so that the actual
1689 end of the line makes no difference. @kbd{C-b} is rebound to run
1690 @code{picture-backward-column}, which always moves point left one
1691 column, converting a tab to multiple spaces if necessary. @kbd{C-n} and
1692 @kbd{C-p} are rebound to run @code{picture-move-down} and
1693 @code{picture-move-up}, which can either insert spaces or convert tabs
1694 as necessary to make sure that point stays in exactly the same column.
1695 @kbd{C-e} runs @code{picture-end-of-line}, which moves to after the last
1696 nonblank character on the line. There is no need to change @kbd{C-a},
1697 as the choice of screen model does not affect beginnings of
1700 @findex picture-newline
1701 Insertion of text is adapted to the quarter-plane screen model
1702 through the use of Overwrite mode (@pxref{Minor Modes,,, emacs, the
1703 Emacs Manual}.) Self-inserting characters replace existing text,
1704 column by column, rather than pushing existing text to the right.
1705 @key{RET} runs @code{picture-newline}, which just moves to the
1706 beginning of the following line so that new text will replace that
1709 @findex picture-backward-clear-column
1710 @findex picture-clear-column
1711 @findex picture-clear-line
1712 In Picture mode, the commands that normally delete or kill text,
1713 instead erase text (replacing it with spaces). @key{DEL}
1714 (@code{picture-backward-clear-column}) replaces the preceding
1715 character with a space rather than removing it; this moves point
1716 backwards. @kbd{C-d} (@code{picture-clear-column}) replaces the next
1717 character or characters with spaces, but does not move point. (If you
1718 want to clear characters to spaces and move forward over them, use
1719 @key{SPC}.) @kbd{C-k} (@code{picture-clear-line}) really kills the
1720 contents of lines, but does not delete the newlines from the buffer.
1722 @findex picture-open-line
1723 To do actual insertion, you must use special commands. @kbd{C-o}
1724 (@code{picture-open-line}) creates a blank line after the current
1725 line; it never splits a line. @kbd{C-M-o} (@code{split-line}) makes
1726 sense in Picture mode, so it is not changed. @kbd{C-j}
1727 (@code{picture-duplicate-line}) inserts another line with the same
1728 contents below the current line.
1730 @kindex C-c C-d @r{(Picture mode)}
1731 To do actual deletion in Picture mode, use @kbd{C-w}, @kbd{C-c C-d}
1732 (which is defined as @code{delete-char}, as @kbd{C-d} is in other
1733 modes), or one of the picture rectangle commands (@pxref{Rectangles in
1736 @node Insert in Picture
1737 @section Controlling Motion after Insert
1739 @findex picture-movement-up
1740 @findex picture-movement-down
1741 @findex picture-movement-left
1742 @findex picture-movement-right
1743 @findex picture-movement-nw
1744 @findex picture-movement-ne
1745 @findex picture-movement-sw
1746 @findex picture-movement-se
1747 @kindex C-c < @r{(Picture mode)}
1748 @kindex C-c > @r{(Picture mode)}
1749 @kindex C-c ^ @r{(Picture mode)}
1750 @kindex C-c . @r{(Picture mode)}
1751 @kindex C-c ` @r{(Picture mode)}
1752 @kindex C-c ' @r{(Picture mode)}
1753 @kindex C-c / @r{(Picture mode)}
1754 @kindex C-c \ @r{(Picture mode)}
1755 Since ``self-inserting'' characters in Picture mode overwrite and move
1756 point, there is no essential restriction on how point should be moved.
1757 Normally point moves right, but you can specify any of the eight
1758 orthogonal or diagonal directions for motion after a ``self-inserting''
1759 character. This is useful for drawing lines in the buffer.
1763 @itemx C-c @key{LEFT}
1764 Move left after insertion (@code{picture-movement-left}).
1766 @itemx C-c @key{RIGHT}
1767 Move right after insertion (@code{picture-movement-right}).
1770 Move up after insertion (@code{picture-movement-up}).
1772 @itemx C-c @key{DOWN}
1773 Move down after insertion (@code{picture-movement-down}).
1775 @itemx C-c @key{HOME}
1776 Move up and left (``northwest'') after insertion (@code{picture-movement-nw}).
1778 @itemx C-c @key{PAGEUP}
1779 Move up and right (``northeast'') after insertion
1780 (@code{picture-movement-ne}).
1782 @itemx C-c @key{END}
1783 Move down and left (``southwest'') after insertion
1784 @*(@code{picture-movement-sw}).
1786 @itemx C-c @key{PAGEDOWN}
1787 Move down and right (``southeast'') after insertion
1788 @*(@code{picture-movement-se}).
1791 @kindex C-c C-f @r{(Picture mode)}
1792 @kindex C-c C-b @r{(Picture mode)}
1793 @findex picture-motion
1794 @findex picture-motion-reverse
1795 Two motion commands move based on the current Picture insertion
1796 direction. The command @kbd{C-c C-f} (@code{picture-motion}) moves in the
1797 same direction as motion after ``insertion'' currently does, while @kbd{C-c
1798 C-b} (@code{picture-motion-reverse}) moves in the opposite direction.
1800 @node Tabs in Picture
1801 @section Picture Mode Tabs
1803 @kindex M-TAB @r{(Picture mode)}
1804 @findex picture-tab-search
1805 @vindex picture-tab-chars
1806 Two kinds of tab-like action are provided in Picture mode. Use
1807 @kbd{M-@key{TAB}} (@code{picture-tab-search}) for context-based tabbing.
1808 With no argument, it moves to a point underneath the next
1809 ``interesting'' character that follows whitespace in the previous
1810 nonblank line. ``Next'' here means ``appearing at a horizontal position
1811 greater than the one point starts out at.'' With an argument, as in
1812 @kbd{C-u M-@key{TAB}}, this command moves to the next such interesting
1813 character in the current line. @kbd{M-@key{TAB}} does not change the
1814 text; it only moves point. ``Interesting'' characters are defined by
1815 the variable @code{picture-tab-chars}, which should define a set of
1816 characters. The syntax for this variable is like the syntax used inside
1817 of @samp{[@dots{}]} in a regular expression---but without the @samp{[}
1818 and the @samp{]}. Its default value is @code{"!-~"}.
1821 @key{TAB} itself runs @code{picture-tab}, which operates based on the
1822 current tab stop settings; it is the Picture mode equivalent of
1823 @code{tab-to-tab-stop}. Normally it just moves point, but with a numeric
1824 argument it clears the text that it moves over.
1826 @kindex C-c TAB @r{(Picture mode)}
1827 @findex picture-set-tab-stops
1828 The context-based and tab-stop-based forms of tabbing are brought
1829 together by the command @kbd{C-c @key{TAB}} (@code{picture-set-tab-stops}).
1830 This command sets the tab stops to the positions which @kbd{M-@key{TAB}}
1831 would consider significant in the current line. The use of this command,
1832 together with @key{TAB}, can get the effect of context-based tabbing. But
1833 @kbd{M-@key{TAB}} is more convenient in the cases where it is sufficient.
1835 It may be convenient to prevent use of actual tab characters in
1836 pictures. For example, this prevents @kbd{C-x @key{TAB}} from messing
1837 up the picture. You can do this by setting the variable
1838 @code{indent-tabs-mode} to @code{nil}.
1840 @node Rectangles in Picture
1841 @section Picture Mode Rectangle Commands
1842 @cindex rectangles and Picture mode
1843 @cindex Picture mode and rectangles
1845 Picture mode defines commands for working on rectangular pieces of
1846 the text in ways that fit with the quarter-plane model. The standard
1847 rectangle commands may also be useful. @xref{Rectangles,,, emacs, the
1852 Clear out the region-rectangle with spaces
1853 (@code{picture-clear-rectangle}). With argument, delete the text.
1854 @item C-c C-w @var{r}
1855 Similar, but save rectangle contents in register @var{r} first
1856 (@code{picture-clear-rectangle-to-register}).
1858 Copy last killed rectangle into the buffer by overwriting, with upper
1859 left corner at point (@code{picture-yank-rectangle}). With argument,
1861 @item C-c C-x @var{r}
1862 Similar, but use the rectangle in register @var{r}
1863 (@code{picture-yank-rectangle-from-register}).
1866 @kindex C-c C-k @r{(Picture mode)}
1867 @kindex C-c C-w @r{(Picture mode)}
1868 @findex picture-clear-rectangle
1869 @findex picture-clear-rectangle-to-register
1870 The picture rectangle commands @kbd{C-c C-k}
1871 (@code{picture-clear-rectangle}) and @kbd{C-c C-w}
1872 (@code{picture-clear-rectangle-to-register}) differ from the standard
1873 rectangle commands in that they normally clear the rectangle instead of
1874 deleting it; this is analogous with the way @kbd{C-d} is changed in Picture
1877 However, deletion of rectangles can be useful in Picture mode, so
1878 these commands delete the rectangle if given a numeric argument.
1879 @kbd{C-c C-k} either with or without a numeric argument saves the
1880 rectangle for @kbd{C-c C-y}.
1882 @kindex C-c C-y @r{(Picture mode)}
1883 @kindex C-c C-x @r{(Picture mode)}
1884 @findex picture-yank-rectangle
1885 @findex picture-yank-rectangle-from-register
1886 The Picture mode commands for yanking rectangles differ from the
1887 standard ones in that they overwrite instead of inserting. This is
1888 the same way that Picture mode insertion of other text differs from
1889 other modes. @kbd{C-c C-y} (@code{picture-yank-rectangle}) inserts
1890 (by overwriting) the rectangle that was most recently killed, while
1891 @kbd{C-c C-x} (@code{picture-yank-rectangle-from-register}) does
1892 likewise for the rectangle found in a specified register.
1894 @node Advanced VC Usage
1895 @chapter Advanced VC Usage
1897 Commonly used features of Emacs' version control (VC) support are
1898 described in the main Emacs manual (@pxref{Version Control,,,emacs,
1899 the Emacs Manual}). This chapter describes more advanced VC usage.
1902 * VC Dired Mode:: Listing files managed by version control.
1903 * VC Dired Commands:: Commands to use in a VC Dired buffer.
1904 * Remote Repositories:: Efficient access to remote CVS servers.
1905 * Snapshots:: Sets of file versions treated as a unit.
1906 * Miscellaneous VC:: Various other commands and features of VC.
1907 * Customizing VC:: Variables that change VC's behavior.
1911 @section Dired under VC
1915 @cindex CVS Dired Mode
1916 The VC Dired Mode described here works with all the version control
1917 systems that VC supports. Another more powerful facility, designed
1918 specifically for CVS, is called PCL-CVS. @xref{Top, , About PCL-CVS,
1919 pcl-cvs, PCL-CVS --- The Emacs Front-End to CVS}.
1922 @findex vc-directory
1923 When you are working on a large program, it is often useful to find
1924 out which files have changed within an entire directory tree, or to view
1925 the status of all files under version control at once, and to perform
1926 version control operations on collections of files. You can use the
1927 command @kbd{C-x v d} (@code{vc-directory}) to make a directory listing
1928 that includes only files relevant for version control.
1930 @vindex vc-dired-terse-display
1931 @kbd{C-x v d} creates a buffer which uses VC Dired Mode. This looks
1932 much like an ordinary Dired buffer (@pxref{Dired,,,emacs, the
1933 Emacs Manual}); however, normally it shows only the noteworthy files
1934 (those locked or not up-to-date). This is called @dfn{terse display}.
1935 If you set the variable @code{vc-dired-terse-display} to @code{nil},
1936 then VC Dired shows all relevant files---those managed under version
1937 control, plus all subdirectories (@dfn{full display}). The command
1938 @kbd{v t} in a VC Dired buffer toggles between terse display and full
1939 display (@pxref{VC Dired Commands}).
1941 @vindex vc-dired-recurse
1942 By default, VC Dired produces a recursive listing of noteworthy or
1943 relevant files at or below the given directory. You can change this by
1944 setting the variable @code{vc-dired-recurse} to @code{nil}; then VC
1945 Dired shows only the files in the given directory.
1947 The line for an individual file shows the version control state in the
1948 place of the hard link count, owner, group, and size of the file. If
1949 the file is unmodified, in sync with the master file, the version
1950 control state shown is blank. Otherwise it consists of text in
1951 parentheses. Under RCS and SCCS, the name of the user locking the file
1952 is shown; under CVS, an abbreviated version of the @samp{cvs status}
1953 output is used. Here is an example using RCS:
1959 -rw-r--r-- (jim) Apr 2 23:39 file1
1960 -r--r--r-- Apr 5 20:21 file2
1965 The files @samp{file1} and @samp{file2} are under version control,
1966 @samp{file1} is locked by user jim, and @samp{file2} is unlocked.
1968 Here is an example using CVS:
1974 -rw-r--r-- (modified) Aug 2 1997 file1.c
1975 -rw-r--r-- Apr 4 20:09 file2.c
1976 -rw-r--r-- (merge) Sep 13 1996 file3.c
1980 Here @samp{file1.c} is modified with respect to the repository, and
1981 @samp{file2.c} is not. @samp{file3.c} is modified, but other changes
1982 have also been checked in to the repository---you need to merge them
1983 with the work file before you can check it in.
1985 @vindex vc-stay-local
1986 @vindex vc-cvs-stay-local
1987 In the above, if the repository were on a remote machine, VC would
1988 only contact it when the variable @code{vc-stay-local} (or
1989 @code{vc-cvs-stay-local}) is nil (@pxref{CVS Options}). This is
1990 because access to the repository may be slow, or you may be working
1991 offline and not have access to the repository at all. As a
1992 consequence, VC would not be able to tell you that @samp{file3.c} is
1993 in the ``merge'' state; you would learn that only when you try to
1994 check-in your modified copy of the file, or use a command such as
1997 In practice, this is not a problem because CVS handles this case
1998 consistently whenever it arises. In VC, you'll simply get prompted to
1999 merge the remote changes into your work file first. The benefits of
2000 less network communication usually outweigh the disadvantage of not
2001 seeing remote changes immediately.
2003 @vindex vc-directory-exclusion-list
2004 When VC Dired displays subdirectories (in the ``full'' display mode),
2005 it omits some that should never contain any files under version control.
2006 By default, this includes Version Control subdirectories such as
2007 @samp{RCS} and @samp{CVS}; you can customize this by setting the
2008 variable @code{vc-directory-exclusion-list}.
2010 You can fine-tune VC Dired's format by typing @kbd{C-u C-x v d}---as in
2011 ordinary Dired, that allows you to specify additional switches for the
2014 @node VC Dired Commands
2015 @section VC Dired Commands
2017 All the usual Dired commands work normally in VC Dired mode, except
2018 for @kbd{v}, which is redefined as the version control prefix. You can
2019 invoke VC commands such as @code{vc-diff} and @code{vc-print-log} by
2020 typing @kbd{v =}, or @kbd{v l}, and so on. Most of these commands apply
2021 to the file name on the current line.
2023 The command @kbd{v v} (@code{vc-next-action}) operates on all the
2024 marked files, so that you can lock or check in several files at once.
2025 If it operates on more than one file, it handles each file according to
2026 its current state; thus, it might lock one file, but check in another
2027 file. This could be confusing; it is up to you to avoid confusing
2028 behavior by marking a set of files that are in a similar state. If no
2029 files are marked, @kbd{v v} operates on the file in the current line.
2031 If any files call for check-in, @kbd{v v} reads a single log entry,
2032 then uses it for all the files being checked in. This is convenient for
2033 registering or checking in several files at once, as part of the same
2036 @findex vc-dired-toggle-terse-mode
2037 @findex vc-dired-mark-locked
2038 You can toggle between terse display (only locked files, or files not
2039 up-to-date) and full display at any time by typing @kbd{v t}
2040 (@code{vc-dired-toggle-terse-mode}). There is also a special command
2041 @kbd{* l} (@code{vc-dired-mark-locked}), which marks all files currently
2042 locked (or, with CVS, all files not up-to-date). Thus, typing @kbd{* l
2043 t k} is another way to delete from the buffer all files except those
2046 @node Remote Repositories
2047 @section Remote Repositories
2048 @cindex remote repositories (CVS)
2050 A common way of using CVS is to set up a central CVS repository on
2051 some Internet host, then have each developer check out a personal
2052 working copy of the files on his local machine. Committing changes to
2053 the repository, and picking up changes from other users into one's own
2054 working area, then works by direct interactions with the CVS server.
2056 One difficulty is that access to the CVS server is often slow, and
2057 that developers might need to work off-line as well. VC is designed
2058 to reduce the amount of network interaction necessary.
2061 * Version Backups:: Keeping local copies of repository versions.
2062 * Local Version Control:: Using another version system for local editing.
2065 @node Version Backups
2066 @subsection Version Backups
2067 @cindex version backups
2069 @cindex automatic version backups
2070 When VC sees that the CVS repository for a file is on a remote
2071 machine, it automatically makes local backups of unmodified versions
2072 of the file---@dfn{automatic version backups}. This means that you
2073 can compare the file to the repository version (@kbd{C-x v =}), or
2074 revert to that version (@kbd{C-x v u}), without any network
2077 The local copy of the unmodified file is called a @dfn{version
2078 backup} to indicate that it corresponds exactly to a version that is
2079 stored in the repository. Note that version backups are not the same
2080 as ordinary Emacs backup files (@pxref{Backup,,,emacs, the Emacs
2081 Manual}). But they follow a similar naming convention.
2083 For a file that comes from a remote CVS repository, VC makes a
2084 version backup whenever you save the first changes to the file, and
2085 removes it after you have committed your modified version to the
2086 repository. You can disable the making of automatic version backups by
2087 setting @code{vc-cvs-stay-local} to @code{nil} (@pxref{CVS Options}).
2089 @cindex manual version backups
2090 The name of the automatic version backup for version @var{version}
2091 of file @var{file} is @code{@var{file}.~@var{version}.~}. This is
2092 almost the same as the name used by @kbd{C-x v ~} (@pxref{Old
2093 Versions,,,emacs, the Emacs Manual}), the only difference being
2094 the additional dot (@samp{.}) after the version number. This
2095 similarity is intentional, because both kinds of files store the same
2096 kind of information. The file made by @kbd{C-x v ~} acts as a
2097 @dfn{manual version backup}.
2099 All the VC commands that operate on old versions of a file can use
2100 both kinds of version backups. For instance, @kbd{C-x v ~} uses
2101 either an automatic or a manual version backup, if possible, to get
2102 the contents of the version you request. Likewise, @kbd{C-x v =} and
2103 @kbd{C-x v u} use either an automatic or a manual version backup, if
2104 one of them exists, to get the contents of a version to compare or
2105 revert to. If you changed a file outside of Emacs, so that no
2106 automatic version backup was created for the previous text, you can
2107 create a manual backup of that version using @kbd{C-x v ~}, and thus
2108 obtain the benefit of the local copy for Emacs commands.
2110 The only difference in Emacs's handling of manual and automatic
2111 version backups, once they exist, is that Emacs deletes automatic
2112 version backups when you commit to the repository. By contrast,
2113 manual version backups remain until you delete them.
2115 @node Local Version Control
2116 @subsection Local Version Control
2117 @cindex local version control
2118 @cindex local back end (version control)
2120 When you make many changes to a file that comes from a remote
2121 repository, it can be convenient to have version control on your local
2122 machine as well. You can then record intermediate versions, revert to
2123 a previous state, etc., before you actually commit your changes to the
2126 VC lets you do this by putting a file under a second, local version
2127 control system, so that the file is effectively registered in two
2128 systems at the same time. For the description here, we will assume
2129 that the remote system is CVS, and you use RCS locally, although the
2130 mechanism works with any combination of version control systems
2133 To make it work with other back ends, you must make sure that the
2134 ``more local'' back end comes before the ``more remote'' back end in
2135 the setting of @code{vc-handled-backends} (@pxref{Customizing VC}). By
2136 default, this variable is set up so that you can use remote CVS and
2137 local RCS as described here.
2139 To start using local RCS for a file that comes from a remote CVS
2140 server, you must @emph{register the file in RCS}, by typing @kbd{C-u
2141 C-x v v rcs @key{RET}}. (In other words, use @code{vc-next-action} with a
2142 prefix argument, and specify RCS as the back end.)
2144 You can do this at any time; it does not matter whether you have
2145 already modified the file with respect to the version in the CVS
2146 repository. If possible, VC tries to make the RCS master start with
2147 the unmodified repository version, then checks in any local changes
2148 as a new version. This works if you have not made any changes yet, or
2149 if the unmodified repository version exists locally as a version
2150 backup (@pxref{Version Backups}). If the unmodified version is not
2151 available locally, the RCS master starts with the modified version;
2152 the only drawback to this is that you cannot compare your changes
2153 locally to what is stored in the repository.
2155 The version number of the RCS master is derived from the current CVS
2156 version, starting a branch from it. For example, if the current CVS
2157 version is 1.23, the local RCS branch will be 1.23.1. Version 1.23 in
2158 the RCS master will be identical to version 1.23 under CVS; your first
2159 changes are checked in as 1.23.1.1. (If the unmodified file is not
2160 available locally, VC will check in the modified file twice, both as
2161 1.23 and 1.23.1.1, to make the revision numbers consistent.)
2163 If you do not use locking under CVS (the default), locking is also
2164 disabled for RCS, so that editing under RCS works exactly as under
2167 When you are done with local editing, you can commit the final version
2168 back to the CVS repository by typing @kbd{C-u C-x v v cvs @key{RET}}.
2169 This initializes the log entry buffer (@pxref{Log Buffer,,,emacs, the
2170 Emacs Manual}) to contain all the log entries you have recorded in the
2171 RCS master; you can edit them as you wish, and then commit in CVS by
2172 typing @kbd{C-c C-c}. If the commit is successful, VC removes the RCS
2173 master, so that the file is once again registered under CVS only.
2174 (The RCS master is not actually deleted, just renamed by appending
2175 @samp{~} to the name, so that you can refer to it later if you wish.)
2177 While using local RCS, you can pick up recent changes from the CVS
2178 repository into your local file, or commit some of your changes back
2179 to CVS, without terminating local RCS version control. To do this,
2180 switch to the CVS back end temporarily, with the @kbd{C-x v b} command:
2184 Switch to another back end that the current file is registered
2185 under (@code{vc-switch-backend}).
2187 @item C-u C-x v b @var{backend} @key{RET}
2188 Switch to @var{backend} for the current file.
2192 @findex vc-switch-backend
2193 @kbd{C-x v b} does not change the buffer contents, or any files; it
2194 only changes VC's perspective on how to handle the file. Any
2195 subsequent VC commands for that file will operate on the back end that
2196 is currently selected.
2198 If the current file is registered in more than one back end, typing
2199 @kbd{C-x v b} ``cycles'' through all of these back ends. With a
2200 prefix argument, it asks for the back end to use in the minibuffer.
2202 Thus, if you are using local RCS, and you want to pick up some recent
2203 changes in the file from remote CVS, first visit the file, then type
2204 @kbd{C-x v b} to switch to CVS, and finally use @kbd{C-x v m
2205 @key{RET}} to merge the news (@pxref{Merging,,,emacs, the Emacs
2206 Manual}). You can then switch back to RCS by typing @kbd{C-x v b}
2207 again, and continue to edit locally.
2209 But if you do this, the revision numbers in the RCS master no longer
2210 correspond to those of CVS. Technically, this is not a problem, but
2211 it can become difficult to keep track of what is in the CVS repository
2212 and what is not. So we suggest that you return from time to time to
2213 CVS-only operation, by committing your local changes back to the
2214 repository using @kbd{C-u C-x v v cvs @key{RET}}.
2218 @cindex snapshots and version control
2220 A @dfn{snapshot} is a named set of file versions (one for each
2221 registered file) that you can treat as a unit. One important kind of
2222 snapshot is a @dfn{release}, a (theoretically) stable version of the
2223 system that is ready for distribution to users.
2226 * Making Snapshots:: The snapshot facilities.
2227 * Snapshot Caveats:: Things to be careful of when using snapshots.
2230 @node Making Snapshots
2231 @subsection Making and Using Snapshots
2233 There are two basic commands for snapshots; one makes a
2234 snapshot with a given name, the other retrieves a named snapshot.
2238 @findex vc-create-snapshot
2239 @item C-x v s @var{name} @key{RET}
2240 Define the last saved versions of every registered file in or under the
2241 current directory as a snapshot named @var{name}
2242 (@code{vc-create-snapshot}).
2245 @findex vc-retrieve-snapshot
2246 @item C-x v r @var{name} @key{RET}
2247 For all registered files at or below the current directory level, select
2248 whatever versions correspond to the snapshot @var{name}
2249 (@code{vc-retrieve-snapshot}).
2251 This command reports an error if any files are locked at or below the
2252 current directory, without changing anything; this is to avoid
2253 overwriting work in progress.
2256 A snapshot uses a very small amount of resources---just enough to record
2257 the list of file names and which version belongs to the snapshot. Thus,
2258 you need not hesitate to create snapshots whenever they are useful.
2260 You can give a snapshot name as an argument to @kbd{C-x v =} or
2261 @kbd{C-x v ~} (@pxref{Old Versions,,,emacs, the Emacs Manual}).
2262 Thus, you can use it to compare a snapshot against the current files,
2263 or two snapshots against each other, or a snapshot against a named
2266 @node Snapshot Caveats
2267 @subsection Snapshot Caveats
2269 @cindex named configurations (RCS)
2270 VC's snapshot facilities are modeled on RCS's named-configuration
2271 support. They use RCS's native facilities for this, so
2272 snapshots made using RCS through VC are visible even when you bypass VC.
2274 With CVS, Meta-CVS, and Subversion, VC also uses the native
2275 mechanism provided by that back end to make snapshots and retrieve them
2276 (@dfn{tags} for CVS and Meta-CVS, @dfn{copies} for Subversion).
2278 @c worded verbosely to avoid overfull hbox.
2279 For SCCS, VC implements snapshots itself. The files it uses contain
2280 name/file/version-number triples. These snapshots are visible only
2283 There is no support for VC snapshots using GNU Arch yet.
2285 A snapshot is a set of checked-in versions. So make sure that all the
2286 files are checked in and not locked when you make a snapshot.
2288 File renaming and deletion can create some difficulties with snapshots.
2289 This is not a VC-specific problem, but a general design issue in version
2290 control systems that no one has solved very well yet.
2292 If you rename a registered file, you need to rename its master along
2293 with it (the command @code{vc-rename-file} does this automatically). If
2294 you are using SCCS, you must also update the records of the snapshot, to
2295 mention the file by its new name (@code{vc-rename-file} does this,
2296 too). An old snapshot that refers to a master file that no longer
2297 exists under the recorded name is invalid; VC can no longer retrieve
2298 it. It would be beyond the scope of this manual to explain enough about
2299 RCS and SCCS to explain how to update the snapshots by hand.
2301 Using @code{vc-rename-file} makes the snapshot remain valid for
2302 retrieval, but it does not solve all problems. For example, some of the
2303 files in your program probably refer to others by name. At the very
2304 least, the makefile probably mentions the file that you renamed. If you
2305 retrieve an old snapshot, the renamed file is retrieved under its new
2306 name, which is not the name that the makefile expects. So the program
2307 won't really work as retrieved.
2309 @node Miscellaneous VC
2310 @section Miscellaneous Commands and Features of VC
2312 This section explains the less-frequently-used features of VC.
2315 * Change Logs and VC:: Generating a change log file from log entries.
2316 * Renaming and VC:: A command to rename both the source and master
2318 * Version Headers:: Inserting version control headers into working files.
2321 @node Change Logs and VC
2322 @subsection Change Logs and VC
2324 If you use RCS or CVS for a program and also maintain a change log
2325 file for it (@pxref{Change Log,,,emacs, the Emacs Manual}), you
2326 can generate change log entries automatically from the version control
2332 @findex vc-update-change-log
2333 Visit the current directory's change log file and, for registered files
2334 in that directory, create new entries for versions checked in since the
2335 most recent entry in the change log file.
2336 (@code{vc-update-change-log}).
2338 This command works with RCS or CVS only, not with any of the other
2342 As above, but only find entries for the current buffer's file.
2345 As above, but find entries for all the currently visited files that are
2346 maintained with version control. This works only with RCS, and it puts
2347 all entries in the log for the default directory, which may not be
2351 For example, suppose the first line of @file{ChangeLog} is dated
2352 1999-04-10, and that the only check-in since then was by Nathaniel
2353 Bowditch to @file{rcs2log} on 1999-05-22 with log text @samp{Ignore log
2354 messages that start with `#'.}. Then @kbd{C-x v a} visits
2355 @file{ChangeLog} and inserts text like this:
2362 1999-05-22 Nathaniel Bowditch <nat@@apn.org>
2364 * rcs2log: Ignore log messages that start with `#'.
2372 You can then edit the new change log entry further as you wish.
2374 Some of the new change log entries may duplicate what's already in
2375 ChangeLog. You will have to remove these duplicates by hand.
2377 Normally, the log entry for file @file{foo} is displayed as @samp{*
2378 foo: @var{text of log entry}}. The @samp{:} after @file{foo} is omitted
2379 if the text of the log entry starts with @w{@samp{(@var{functionname}):
2380 }}. For example, if the log entry for @file{vc.el} is
2381 @samp{(vc-do-command): Check call-process status.}, then the text in
2382 @file{ChangeLog} looks like this:
2389 1999-05-06 Nathaniel Bowditch <nat@@apn.org>
2391 * vc.el (vc-do-command): Check call-process status.
2398 When @kbd{C-x v a} adds several change log entries at once, it groups
2399 related log entries together if they all are checked in by the same
2400 author at nearly the same time. If the log entries for several such
2401 files all have the same text, it coalesces them into a single entry.
2402 For example, suppose the most recent check-ins have the following log
2406 @bullet{} For @file{vc.texinfo}: @samp{Fix expansion typos.}
2407 @bullet{} For @file{vc.el}: @samp{Don't call expand-file-name.}
2408 @bullet{} For @file{vc-hooks.el}: @samp{Don't call expand-file-name.}
2412 They appear like this in @file{ChangeLog}:
2419 1999-04-01 Nathaniel Bowditch <nat@@apn.org>
2421 * vc.texinfo: Fix expansion typos.
2423 * vc.el, vc-hooks.el: Don't call expand-file-name.
2430 Normally, @kbd{C-x v a} separates log entries by a blank line, but you
2431 can mark several related log entries to be clumped together (without an
2432 intervening blank line) by starting the text of each related log entry
2433 with a label of the form @w{@samp{@{@var{clumpname}@} }}. The label
2434 itself is not copied to @file{ChangeLog}. For example, suppose the log
2438 @bullet{} For @file{vc.texinfo}: @samp{@{expand@} Fix expansion typos.}
2439 @bullet{} For @file{vc.el}: @samp{@{expand@} Don't call expand-file-name.}
2440 @bullet{} For @file{vc-hooks.el}: @samp{@{expand@} Don't call expand-file-name.}
2444 Then the text in @file{ChangeLog} looks like this:
2451 1999-04-01 Nathaniel Bowditch <nat@@apn.org>
2453 * vc.texinfo: Fix expansion typos.
2454 * vc.el, vc-hooks.el: Don't call expand-file-name.
2461 A log entry whose text begins with @samp{#} is not copied to
2462 @file{ChangeLog}. For example, if you merely fix some misspellings in
2463 comments, you can log the change with an entry beginning with @samp{#}
2464 to avoid putting such trivia into @file{ChangeLog}.
2466 @node Renaming and VC
2467 @subsection Renaming VC Work Files and Master Files
2469 @findex vc-rename-file
2470 When you rename a registered file, you must also rename its master
2471 file correspondingly to get proper results. Use @code{vc-rename-file}
2472 to rename the source file as you specify, and rename its master file
2473 accordingly. It also updates any snapshots (@pxref{Snapshots}) that
2474 mention the file, so that they use the new name; despite this, the
2475 snapshot thus modified may not completely work (@pxref{Snapshot
2478 Some back ends do not provide an explicit rename operation to their
2479 repositories. After issuing @code{vc-rename-file}, use @kbd{C-x v v}
2480 on the original and renamed buffers and provide the necessary edit
2483 You cannot use @code{vc-rename-file} on a file that is locked by
2486 @node Version Headers
2487 @subsection Inserting Version Control Headers
2489 Sometimes it is convenient to put version identification strings
2490 directly into working files. Certain special strings called
2491 @dfn{version headers} are replaced in each successive version by the
2492 number of that version, the name of the user who created it, and other
2493 relevant information. All of the back ends that VC supports have such
2494 a mechanism, except GNU Arch.
2496 VC does not normally use the information contained in these headers.
2497 The exception is RCS---with RCS, version headers are sometimes more
2498 reliable than the master file to determine which version of the file
2499 you are editing. Note that in a multi-branch environment, version
2500 headers are necessary to make VC behave correctly (@pxref{Multi-User
2501 Branching,,,emacs, the Emacs Manual}).
2503 Searching for RCS version headers is controlled by the variable
2504 @code{vc-consult-headers}. If it is non-@code{nil} (the default),
2505 Emacs searches for headers to determine the version number you are
2506 editing. Setting it to @code{nil} disables this feature.
2508 Note that although CVS uses the same kind of version headers as RCS
2509 does, VC never searches for these headers if you are using CVS,
2510 regardless of the above setting.
2513 @findex vc-insert-headers
2514 You can use the @kbd{C-x v h} command (@code{vc-insert-headers}) to
2515 insert a suitable header string.
2519 Insert headers in a file for use with your version-control system.
2522 @vindex vc-@var{backend}-header
2523 The default header string is @samp{@w{$}Id$} for RCS and
2524 @samp{@w{%}W%} for SCCS. You can specify other headers to insert by
2525 setting the variables @code{vc-@var{backend}-header} where
2526 @var{backend} is @code{rcs} or @code{sccs}.
2528 Instead of a single string, you can specify a list of strings; then
2529 each string in the list is inserted as a separate header on a line of
2532 It may be necessary to use apparently-superfluous backslashes when
2533 writing the strings that you put in this variable. For instance, you
2534 might write @code{"$Id\$"} rather than @code{"$Id@w{$}"}. The extra
2535 backslash prevents the string constant from being interpreted as a
2536 header, if the Emacs Lisp file containing it is maintained with
2539 @vindex vc-comment-alist
2540 Each header is inserted surrounded by tabs, inside comment delimiters,
2541 on a new line at point. Normally the ordinary comment
2542 start and comment end strings of the current mode are used, but for
2543 certain modes, there are special comment delimiters for this purpose;
2544 the variable @code{vc-comment-alist} specifies them. Each element of
2545 this list has the form @code{(@var{mode} @var{starter} @var{ender})}.
2547 @vindex vc-static-header-alist
2548 The variable @code{vc-static-header-alist} specifies further strings
2549 to add based on the name of the buffer. Its value should be a list of
2550 elements of the form @code{(@var{regexp} . @var{format})}. Whenever
2551 @var{regexp} matches the buffer name, @var{format} is inserted as part
2552 of the header. A header line is inserted for each element that matches
2553 the buffer name, and for each string specified by
2554 @code{vc-@var{backend}-header}. The header line is made by processing the
2555 string from @code{vc-@var{backend}-header} with the format taken from the
2556 element. The default value for @code{vc-static-header-alist} is as follows:
2561 "\n#ifndef lint\nstatic char vcid[] = \"\%s\";\n\
2562 #endif /* lint */\n"))
2567 It specifies insertion of text of this form:
2573 static char vcid[] = "@var{string}";
2579 Note that the text above starts with a blank line.
2581 If you use more than one version header in a file, put them close
2582 together in the file. The mechanism in @code{revert-buffer} that
2583 preserves markers may not handle markers positioned between two version
2586 @node Customizing VC
2587 @section Customizing VC
2589 @vindex vc-handled-backends
2590 The variable @code{vc-handled-backends} determines which version
2591 control systems VC should handle. The default value is @code{(RCS CVS
2592 SVN SCCS Arch MCVS)}, so it contains all six version systems that are
2593 currently supported. If you want VC to ignore one or more of these
2594 systems, exclude its name from the list. To disable VC entirely, set
2595 this variable to @code{nil}.
2597 The order of systems in the list is significant: when you visit a file
2598 registered in more than one system (@pxref{Local Version Control}), VC
2599 uses the system that comes first in @code{vc-handled-backends} by
2600 default. The order is also significant when you register a file for
2601 the first time, @pxref{Registering,,,emacs, the Emacs Manual} for
2605 * General VC Options:: Options that apply to multiple back ends.
2606 * RCS and SCCS:: Options for RCS and SCCS.
2607 * CVS Options:: Options for CVS.
2610 @node General VC Options
2611 @subsection General Options
2613 @vindex vc-make-backup-files
2614 Emacs normally does not save backup files for source files that are
2615 maintained with version control. If you want to make backup files even
2616 for files that use version control, set the variable
2617 @code{vc-make-backup-files} to a non-@code{nil} value.
2619 @vindex vc-keep-workfiles
2620 Normally the work file exists all the time, whether it is locked or
2621 not. If you set @code{vc-keep-workfiles} to @code{nil}, then checking
2622 in a new version with @kbd{C-x v v} deletes the work file; but any
2623 attempt to visit the file with Emacs creates it again. (With CVS, work
2624 files are always kept.)
2626 @vindex vc-follow-symlinks
2627 Editing a version-controlled file through a symbolic link can be
2628 dangerous. It bypasses the version control system---you can edit the
2629 file without locking it, and fail to check your changes in. Also,
2630 your changes might overwrite those of another user. To protect against
2631 this, VC checks each symbolic link that you visit, to see if it points
2632 to a file under version control.
2634 The variable @code{vc-follow-symlinks} controls what to do when a
2635 symbolic link points to a version-controlled file. If it is @code{nil},
2636 VC only displays a warning message. If it is @code{t}, VC automatically
2637 follows the link, and visits the real file instead, telling you about
2638 this in the echo area. If the value is @code{ask} (the default), VC
2639 asks you each time whether to follow the link.
2641 @vindex vc-suppress-confirm
2642 If @code{vc-suppress-confirm} is non-@code{nil}, then @kbd{C-x v v}
2643 and @kbd{C-x v i} can save the current buffer without asking, and
2644 @kbd{C-x v u} also operates without asking for confirmation. (This
2645 variable does not affect @kbd{C-x v c}; that operation is so drastic
2646 that it should always ask for confirmation.)
2648 @vindex vc-command-messages
2649 VC mode does much of its work by running the shell commands for RCS,
2650 CVS and SCCS. If @code{vc-command-messages} is non-@code{nil}, VC
2651 displays messages to indicate which shell commands it runs, and
2652 additional messages when the commands finish.
2655 You can specify additional directories to search for version control
2656 programs by setting the variable @code{vc-path}. These directories
2657 are searched before the usual search path. It is rarely necessary to
2658 set this variable, because VC normally finds the proper files
2662 @subsection Options for RCS and SCCS
2664 @cindex non-strict locking (RCS)
2665 @cindex locking, non-strict (RCS)
2666 By default, RCS uses locking to coordinate the activities of several
2667 users, but there is a mode called @dfn{non-strict locking} in which
2668 you can check-in changes without locking the file first. Use
2669 @samp{rcs -U} to switch to non-strict locking for a particular file,
2670 see the @code{rcs} manual page for details.
2672 When deducing the version control state of an RCS file, VC first
2673 looks for an RCS version header string in the file (@pxref{Version
2674 Headers}). If there is no header string, VC normally looks at the
2675 file permissions of the work file; this is fast. But there might be
2676 situations when the file permissions cannot be trusted. In this case
2677 the master file has to be consulted, which is rather expensive. Also
2678 the master file can only tell you @emph{if} there's any lock on the
2679 file, but not whether your work file really contains that locked
2682 @vindex vc-consult-headers
2683 You can tell VC not to use version headers to determine the file
2684 status by setting @code{vc-consult-headers} to @code{nil}. VC then
2685 always uses the file permissions (if it is supposed to trust them), or
2686 else checks the master file.
2688 @vindex vc-mistrust-permissions
2689 You can specify the criterion for whether to trust the file
2690 permissions by setting the variable @code{vc-mistrust-permissions}.
2691 Its value can be @code{t} (always mistrust the file permissions and
2692 check the master file), @code{nil} (always trust the file
2693 permissions), or a function of one argument which makes the decision.
2694 The argument is the directory name of the @file{RCS} subdirectory. A
2695 non-@code{nil} value from the function says to mistrust the file
2696 permissions. If you find that the file permissions of work files are
2697 changed erroneously, set @code{vc-mistrust-permissions} to @code{t}.
2698 Then VC always checks the master file to determine the file's status.
2700 VC determines the version control state of files under SCCS much as
2701 with RCS. It does not consider SCCS version headers, though. Thus,
2702 the variable @code{vc-mistrust-permissions} affects SCCS use, but
2703 @code{vc-consult-headers} does not.
2706 @subsection Options specific for CVS
2708 @cindex locking (CVS)
2709 By default, CVS does not use locking to coordinate the activities of
2710 several users; anyone can change a work file at any time. However,
2711 there are ways to restrict this, resulting in behavior that resembles
2714 @cindex CVSREAD environment variable (CVS)
2715 For one thing, you can set the @env{CVSREAD} environment variable
2716 (the value you use makes no difference). If this variable is defined,
2717 CVS makes your work files read-only by default. In Emacs, you must
2718 type @kbd{C-x v v} to make the file writable, so that editing works
2719 in fact similar as if locking was used. Note however, that no actual
2720 locking is performed, so several users can make their files writable
2721 at the same time. When setting @env{CVSREAD} for the first time, make
2722 sure to check out all your modules anew, so that the file protections
2725 @cindex cvs watch feature
2726 @cindex watching files (CVS)
2727 Another way to achieve something similar to locking is to use the
2728 @dfn{watch} feature of CVS. If a file is being watched, CVS makes it
2729 read-only by default, and you must also use @kbd{C-x v v} in Emacs to
2730 make it writable. VC calls @code{cvs edit} to make the file writable,
2731 and CVS takes care to notify other developers of the fact that you
2732 intend to change the file. See the CVS documentation for details on
2733 using the watch feature.
2735 @vindex vc-stay-local
2736 @vindex vc-cvs-stay-local
2737 @cindex remote repositories (CVS)
2738 When a file's repository is on a remote machine, VC tries to keep
2739 network interactions to a minimum. This is controlled by the variable
2740 @code{vc-cvs-stay-local}. There is another variable,
2741 @code{vc-stay-local}, which enables the feature also for other back
2742 ends that support it, including CVS. In the following, we will talk
2743 only about @code{vc-cvs-stay-local}, but everything applies to
2744 @code{vc-stay-local} as well.
2746 If @code{vc-cvs-stay-local} is @code{t} (the default), then VC uses
2747 only the entry in the local CVS subdirectory to determine the file's
2748 state (and possibly information returned by previous CVS commands).
2749 One consequence of this is that when you have modified a file, and
2750 somebody else has already checked in other changes to the file, you
2751 are not notified of it until you actually try to commit. (But you can
2752 try to pick up any recent changes from the repository first, using
2753 @kbd{C-x v m @key{RET}}, @pxref{Merging,,,emacs, the Emacs Manual}).
2755 When @code{vc-cvs-stay-local} is @code{t}, VC also makes local
2756 version backups, so that simple diff and revert operations are
2757 completely local (@pxref{Version Backups}).
2759 On the other hand, if you set @code{vc-cvs-stay-local} to @code{nil},
2760 then VC queries the remote repository @emph{before} it decides what to
2761 do in @code{vc-next-action} (@kbd{C-x v v}), just as it does for local
2762 repositories. It also does not make any version backups.
2764 You can also set @code{vc-cvs-stay-local} to a regular expression
2765 that is matched against the repository host name; VC then stays local
2766 only for repositories from hosts that match the pattern.
2768 @vindex vc-cvs-global-switches
2769 You can specify additional command line options to pass to all CVS
2770 operations in the variable @code{vc-cvs-global-switches}. These
2771 switches are inserted immediately after the @code{cvs} command, before
2772 the name of the operation to invoke.
2776 @chapter Fortran Mode
2777 @cindex Fortran mode
2778 @cindex mode, Fortran
2780 Fortran mode provides special motion commands for Fortran statements
2781 and subprograms, and indentation commands that understand Fortran
2782 conventions of nesting, line numbers and continuation statements.
2783 Fortran mode has support for Auto Fill mode that breaks long lines into
2784 proper Fortran continuation lines.
2786 Special commands for comments are provided because Fortran comments
2787 are unlike those of other languages. Built-in abbrevs optionally save
2788 typing when you insert Fortran keywords.
2790 Use @kbd{M-x fortran-mode} to switch to this major mode. This
2791 command runs the hook @code{fortran-mode-hook}. @xref{Hooks,,, emacs,
2794 @cindex Fortran77 and Fortran90
2796 @findex fortran-mode
2797 Fortran mode is meant for editing Fortran77 ``fixed format'' (and also
2798 ``tab format'') source code. For editing the modern Fortran90 or
2799 Fortran95 ``free format'' source code, use F90 mode (@code{f90-mode}).
2800 Emacs normally uses Fortran mode for files with extension @samp{.f},
2801 @samp{.F} or @samp{.for}, and F90 mode for the extension @samp{.f90} and
2802 @samp{.f95}. GNU Fortran supports both kinds of format.
2805 * Motion: Fortran Motion. Moving point by statements or subprograms.
2806 * Indent: Fortran Indent. Indentation commands for Fortran.
2807 * Comments: Fortran Comments. Inserting and aligning comments.
2808 * Autofill: Fortran Autofill. Auto fill support for Fortran.
2809 * Columns: Fortran Columns. Measuring columns for valid Fortran.
2810 * Abbrev: Fortran Abbrev. Built-in abbrevs for Fortran keywords.
2813 @node Fortran Motion
2814 @section Motion Commands
2816 In addition to the normal commands for moving by and operating on
2817 ``defuns'' (Fortran subprograms---functions and subroutines, as well as
2818 modules for F90 mode), Fortran mode provides special commands to move by
2819 statements and other program units.
2822 @kindex C-c C-n @r{(Fortran mode)}
2823 @findex fortran-next-statement
2824 @findex f90-next-statement
2826 Move to the beginning of the next statement
2827 (@code{fortran-next-statement}/@code{f90-next-statement}).
2829 @kindex C-c C-p @r{(Fortran mode)}
2830 @findex fortran-previous-statement
2831 @findex f90-previous-statement
2833 Move to the beginning of the previous statement
2834 (@code{fortran-previous-statement}/@code{f90-previous-statement}).
2835 If there is no previous statement (i.e. if called from the first
2836 statement in the buffer), move to the start of the buffer.
2838 @kindex C-c C-e @r{(F90 mode)}
2839 @findex f90-next-block
2841 Move point forward to the start of the next code block
2842 (@code{f90-next-block}). A code block is a subroutine,
2843 @code{if}--@code{endif} statement, and so forth. This command exists
2844 for F90 mode only, not Fortran mode. With a numeric argument, this
2845 moves forward that many blocks.
2847 @kindex C-c C-a @r{(F90 mode)}
2848 @findex f90-previous-block
2850 Move point backward to the previous code block
2851 (@code{f90-previous-block}). This is like @code{f90-next-block}, but
2854 @kindex C-M-n @r{(Fortran mode)}
2855 @findex fortran-end-of-block
2856 @findex f90-end-of-block
2858 Move to the end of the current code block
2859 (@code{fortran-end-of-block}/@code{f90-end-of-block}). With a numeric
2860 agument, move forward that number of blocks. The mark is set before
2861 moving point. The F90 mode version of this command checks for
2862 consistency of block types and labels (if present), but it does not
2863 check the outermost block since that may be incomplete.
2865 @kindex C-M-p @r{(Fortran mode)}
2866 @findex fortran-beginning-of-block
2867 @findex f90-beginning-of-block
2869 Move to the start of the current code block
2870 (@code{fortran-beginning-of-block}/@code{f90-beginning-of-block}). This
2871 is like @code{fortran-end-of-block}, but moves backwards.
2874 @node Fortran Indent
2875 @section Fortran Indentation
2877 Special commands and features are needed for indenting Fortran code in
2878 order to make sure various syntactic entities (line numbers, comment line
2879 indicators and continuation line flags) appear in the columns that are
2880 required for standard, fixed (or tab) format Fortran.
2883 * Commands: ForIndent Commands. Commands for indenting and filling Fortran.
2884 * Contline: ForIndent Cont. How continuation lines indent.
2885 * Numbers: ForIndent Num. How line numbers auto-indent.
2886 * Conv: ForIndent Conv. Conventions you must obey to avoid trouble.
2887 * Vars: ForIndent Vars. Variables controlling Fortran indent style.
2890 @node ForIndent Commands
2891 @subsection Fortran Indentation and Filling Commands
2895 Break the current line at point and set up a continuation line
2896 (@code{fortran-split-line}).
2898 Join this line to the previous line (@code{fortran-join-line}).
2900 Indent all the lines of the subprogram point is in
2901 (@code{fortran-indent-subprogram}).
2903 Fill a comment block or statement.
2906 @kindex C-M-q @r{(Fortran mode)}
2907 @findex fortran-indent-subprogram
2908 The key @kbd{C-M-q} runs @code{fortran-indent-subprogram}, a command
2909 to reindent all the lines of the Fortran subprogram (function or
2910 subroutine) containing point.
2912 @kindex C-M-j @r{(Fortran mode)}
2913 @findex fortran-split-line
2914 The key @kbd{C-M-j} runs @code{fortran-split-line}, which splits
2915 a line in the appropriate fashion for Fortran. In a non-comment line,
2916 the second half becomes a continuation line and is indented
2917 accordingly. In a comment line, both halves become separate comment
2920 @kindex M-^ @r{(Fortran mode)}
2921 @kindex C-c C-d @r{(Fortran mode)}
2922 @findex fortran-join-line
2923 @kbd{M-^} or @kbd{C-c C-d} runs the command @code{fortran-join-line},
2924 which joins a continuation line back to the previous line, roughly as
2925 the inverse of @code{fortran-split-line}. The point must be on a
2926 continuation line when this command is invoked.
2928 @kindex M-q @r{(Fortran mode)}
2929 @kbd{M-q} in Fortran mode fills the comment block or statement that
2930 point is in. This removes any excess statement continuations.
2932 @node ForIndent Cont
2933 @subsection Continuation Lines
2934 @cindex Fortran continuation lines
2936 @vindex fortran-continuation-string
2937 Most Fortran77 compilers allow two ways of writing continuation lines.
2938 If the first non-space character on a line is in column 5, then that
2939 line is a continuation of the previous line. We call this @dfn{fixed
2940 format}. (In GNU Emacs we always count columns from 0; but note that
2941 the Fortran standard counts from 1.) The variable
2942 @code{fortran-continuation-string} specifies what character to put in
2943 column 5. A line that starts with a tab character followed by any digit
2944 except @samp{0} is also a continuation line. We call this style of
2945 continuation @dfn{tab format}. (Fortran90 introduced ``free format'',
2946 with another style of continuation lines).
2948 @vindex indent-tabs-mode @r{(Fortran mode)}
2949 @vindex fortran-analyze-depth
2950 @vindex fortran-tab-mode-default
2951 Fortran mode can use either style of continuation line. When you
2952 enter Fortran mode, it tries to deduce the proper continuation style
2953 automatically from the buffer contents. It does this by scanning up to
2954 @code{fortran-analyze-depth} (default 100) lines from the start of the
2955 buffer. The first line that begins with either a tab character or six
2956 spaces determines the choice. If the scan fails (for example, if the
2957 buffer is new and therefore empty), the value of
2958 @code{fortran-tab-mode-default} (@code{nil} for fixed format, and
2959 non-@code{nil} for tab format) is used. @samp{/t} in the mode line
2960 indicates tab format is selected. Fortran mode sets the value of
2961 @code{indent-tabs-mode} accordingly.
2963 If the text on a line starts with the Fortran continuation marker
2964 @samp{$}, or if it begins with any non-whitespace character in column
2965 5, Fortran mode treats it as a continuation line. When you indent a
2966 continuation line with @key{TAB}, it converts the line to the current
2967 continuation style. When you split a Fortran statement with
2968 @kbd{C-M-j}, the continuation marker on the newline is created according
2969 to the continuation style.
2971 The setting of continuation style affects several other aspects of
2972 editing in Fortran mode. In fixed format mode, the minimum column
2973 number for the body of a statement is 6. Lines inside of Fortran
2974 blocks that are indented to larger column numbers always use only the
2975 space character for whitespace. In tab format mode, the minimum
2976 column number for the statement body is 8, and the whitespace before
2977 column 8 must always consist of one tab character.
2980 @subsection Line Numbers
2982 If a number is the first non-whitespace in the line, Fortran
2983 indentation assumes it is a line number and moves it to columns 0
2984 through 4. (Columns always count from 0 in GNU Emacs.)
2986 @vindex fortran-line-number-indent
2987 Line numbers of four digits or less are normally indented one space.
2988 The variable @code{fortran-line-number-indent} controls this; it
2989 specifies the maximum indentation a line number can have. The default
2990 value of the variable is 1. Fortran mode tries to prevent line number
2991 digits passing column 4, reducing the indentation below the specified
2992 maximum if necessary. If @code{fortran-line-number-indent} has the
2993 value 5, line numbers are right-justified to end in column 4.
2995 @vindex fortran-electric-line-number
2996 Simply inserting a line number is enough to indent it according to
2997 these rules. As each digit is inserted, the indentation is recomputed.
2998 To turn off this feature, set the variable
2999 @code{fortran-electric-line-number} to @code{nil}.
3002 @node ForIndent Conv
3003 @subsection Syntactic Conventions
3005 Fortran mode assumes that you follow certain conventions that simplify
3006 the task of understanding a Fortran program well enough to indent it
3011 Two nested @samp{do} loops never share a @samp{continue} statement.
3014 Fortran keywords such as @samp{if}, @samp{else}, @samp{then}, @samp{do}
3015 and others are written without embedded whitespace or line breaks.
3017 Fortran compilers generally ignore whitespace outside of string
3018 constants, but Fortran mode does not recognize these keywords if they
3019 are not contiguous. Constructs such as @samp{else if} or @samp{end do}
3020 are acceptable, but the second word should be on the same line as the
3021 first and not on a continuation line.
3025 If you fail to follow these conventions, the indentation commands may
3026 indent some lines unaesthetically. However, a correct Fortran program
3027 retains its meaning when reindented even if the conventions are not
3030 @node ForIndent Vars
3031 @subsection Variables for Fortran Indentation
3033 @vindex fortran-do-indent
3034 @vindex fortran-if-indent
3035 @vindex fortran-structure-indent
3036 @vindex fortran-continuation-indent
3037 @vindex fortran-check-all-num@dots{}
3038 @vindex fortran-minimum-statement-indent@dots{}
3039 Several additional variables control how Fortran indentation works:
3042 @item fortran-do-indent
3043 Extra indentation within each level of @samp{do} statement (default 3).
3045 @item fortran-if-indent
3046 Extra indentation within each level of @samp{if}, @samp{select case}, or
3047 @samp{where} statements (default 3).
3049 @item fortran-structure-indent
3050 Extra indentation within each level of @samp{structure}, @samp{union},
3051 @samp{map}, or @samp{interface} statements (default 3).
3053 @item fortran-continuation-indent
3054 Extra indentation for bodies of continuation lines (default 5).
3056 @item fortran-check-all-num-for-matching-do
3057 In Fortran77, a numbered @samp{do} statement is ended by any statement
3058 with a matching line number. It is common (but not compulsory) to use a
3059 @samp{continue} statement for this purpose. If this variable has a
3060 non-@code{nil} value, indenting any numbered statement must check for a
3061 @samp{do} that ends there. If you always end @samp{do} statements with
3062 a @samp{continue} line (or if you use the more modern @samp{enddo}),
3063 then you can speed up indentation by setting this variable to
3064 @code{nil}. The default is @code{nil}.
3066 @item fortran-blink-matching-if
3067 If this is @code{t}, indenting an @samp{endif} (or @samp{enddo}
3068 statement moves the cursor momentarily to the matching @samp{if} (or
3069 @samp{do}) statement to show where it is. The default is @code{nil}.
3071 @item fortran-minimum-statement-indent-fixed
3072 Minimum indentation for Fortran statements when using fixed format
3073 continuation line style. Statement bodies are never indented less than
3074 this much. The default is 6.
3076 @item fortran-minimum-statement-indent-tab
3077 Minimum indentation for Fortran statements for tab format continuation line
3078 style. Statement bodies are never indented less than this much. The
3082 The variables controlling the indentation of comments are described in
3083 the following section.
3085 @node Fortran Comments
3086 @section Fortran Comments
3088 The usual Emacs comment commands assume that a comment can follow a
3089 line of code. In Fortran77, the standard comment syntax requires an
3090 entire line to be just a comment. Therefore, Fortran mode replaces the
3091 standard Emacs comment commands and defines some new variables.
3093 @vindex fortran-comment-line-start
3094 Fortran mode can also handle the Fortran90 comment syntax where comments
3095 start with @samp{!} and can follow other text. Because only some Fortran77
3096 compilers accept this syntax, Fortran mode will not insert such comments
3097 unless you have said in advance to do so. To do this, set the variable
3098 @code{fortran-comment-line-start} to @samp{"!"}.
3102 Align comment or insert new comment (@code{fortran-indent-comment}).
3105 Applies to nonstandard @samp{!} comments only.
3108 Turn all lines of the region into comments, or (with argument) turn them back
3109 into real code (@code{fortran-comment-region}).
3112 @findex fortran-indent-comment
3113 @kbd{M-;} in Fortran mode is redefined as the command
3114 @code{fortran-indent-comment}. Like the usual @kbd{M-;} command, this
3115 recognizes any kind of existing comment and aligns its text appropriately;
3116 if there is no existing comment, a comment is inserted and aligned. But
3117 inserting and aligning comments are not the same in Fortran mode as in
3120 When a new comment must be inserted, if the current line is blank, a
3121 full-line comment is inserted. On a non-blank line, a nonstandard @samp{!}
3122 comment is inserted if you have said you want to use them. Otherwise a
3123 full-line comment is inserted on a new line before the current line.
3125 Nonstandard @samp{!} comments are aligned like comments in other
3126 languages, but full-line comments are different. In a standard full-line
3127 comment, the comment delimiter itself must always appear in column zero.
3128 What can be aligned is the text within the comment. You can choose from
3129 three styles of alignment by setting the variable
3130 @code{fortran-comment-indent-style} to one of these values:
3132 @vindex fortran-comment-indent-style
3133 @vindex fortran-comment-line-extra-indent
3136 Align the text at a fixed column, which is the sum of
3137 @code{fortran-comment-line-extra-indent} and the minimum statement
3138 indentation. This is the default.
3140 The minimum statement indentation is
3141 @code{fortran-minimum-statement-indent-fixed} for fixed format
3142 continuation line style and @code{fortran-minimum-statement-indent-tab}
3143 for tab format style.
3146 Align the text as if it were a line of code, but with an additional
3147 @code{fortran-comment-line-extra-indent} columns of indentation.
3150 Don't move text in full-line comments automatically.
3153 @vindex fortran-comment-indent-char
3154 In addition, you can specify the character to be used to indent within
3155 full-line comments by setting the variable
3156 @code{fortran-comment-indent-char} to the single-character string you want
3159 @vindex fortran-directive-re
3160 Compiler directive lines, or preprocessor lines, have much the same
3161 appearance as comment lines. It is important, though, that such lines
3162 never be indented at all, no matter what the value of
3163 @code{fortran-comment-indent-style}. The variable
3164 @code{fortran-directive-re} is a regular expression that specifies which
3165 lines are directives. Matching lines are never indented, and receive
3166 distinctive font-locking.
3168 The normal Emacs comment command @kbd{C-x ;} has not been redefined. If
3169 you use @samp{!} comments, this command can be used with them. Otherwise
3170 it is useless in Fortran mode.
3172 @kindex C-c ; @r{(Fortran mode)}
3173 @findex fortran-comment-region
3174 @vindex fortran-comment-region
3175 The command @kbd{C-c ;} (@code{fortran-comment-region}) turns all the
3176 lines of the region into comments by inserting the string @samp{C$$$} at
3177 the front of each one. With a numeric argument, it turns the region
3178 back into live code by deleting @samp{C$$$} from the front of each line
3179 in it. The string used for these comments can be controlled by setting
3180 the variable @code{fortran-comment-region}. Note that here we have an
3181 example of a command and a variable with the same name; these two uses
3182 of the name never conflict because in Lisp and in Emacs it is always
3183 clear from the context which one is meant.
3185 @node Fortran Autofill
3186 @section Auto Fill in Fortran Mode
3188 Fortran mode has specialized support for Auto Fill mode, which is a
3189 minor mode that automatically splits statements as you insert them
3190 when they become too wide. Splitting a statement involves making
3191 continuation lines using @code{fortran-continuation-string}
3192 (@pxref{ForIndent Cont}). This splitting happens when you type
3193 @key{SPC}, @key{RET}, or @key{TAB}, and also in the Fortran
3194 indentation commands. You activate Auto Fill in Fortran mode in the
3195 normal way. @xref{Auto Fill,,, emacs, the Emacs Manual}.
3197 @vindex fortran-break-before-delimiters
3198 Auto Fill breaks lines at spaces or delimiters when the lines get
3199 longer than the desired width (the value of @code{fill-column}). The
3200 delimiters (besides whitespace) that Auto Fill can break at are
3201 @samp{+}, @samp{-}, @samp{/}, @samp{*}, @samp{=}, @samp{<}, @samp{>},
3202 and @samp{,}. The line break comes after the delimiter if the
3203 variable @code{fortran-break-before-delimiters} is @code{nil}.
3204 Otherwise (and by default), the break comes before the delimiter.
3206 To enable Auto Fill in all Fortran buffers, add
3207 @code{turn-on-auto-fill} to @code{fortran-mode-hook}. @xref{Hooks,,,
3208 emacs, the Emacs Manual}.
3210 @node Fortran Columns
3211 @section Checking Columns in Fortran
3215 Display a ``column ruler'' momentarily above the current line
3216 (@code{fortran-column-ruler}).
3218 Split the current window horizontally temporarily so that it is 72
3219 columns wide (@code{fortran-window-create-momentarily}). This may
3220 help you avoid making lines longer than the 72-character limit that
3221 some Fortran compilers impose.
3223 Split the current window horizontally so that it is 72 columns wide
3224 (@code{fortran-window-create}). You can then continue editing.
3225 @item M-x fortran-strip-sequence-nos
3226 Delete all text in column 72 and beyond.
3229 @kindex C-c C-r @r{(Fortran mode)}
3230 @findex fortran-column-ruler
3231 The command @kbd{C-c C-r} (@code{fortran-column-ruler}) shows a column
3232 ruler momentarily above the current line. The comment ruler is two lines
3233 of text that show you the locations of columns with special significance in
3234 Fortran programs. Square brackets show the limits of the columns for line
3235 numbers, and curly brackets show the limits of the columns for the
3236 statement body. Column numbers appear above them.
3238 Note that the column numbers count from zero, as always in GNU Emacs.
3239 As a result, the numbers may be one less than those you are familiar
3240 with; but the positions they indicate in the line are standard for
3243 @vindex fortran-column-ruler-fixed
3244 @vindex fortran-column-ruler-tabs
3245 The text used to display the column ruler depends on the value of the
3246 variable @code{indent-tabs-mode}. If @code{indent-tabs-mode} is
3247 @code{nil}, then the value of the variable
3248 @code{fortran-column-ruler-fixed} is used as the column ruler.
3249 Otherwise, the value of the variable @code{fortran-column-ruler-tab} is
3250 displayed. By changing these variables, you can change the column ruler
3253 @kindex C-c C-w @r{(Fortran mode)}
3254 @findex fortran-window-create-momentarily
3255 @kbd{C-c C-w} (@code{fortran-window-create-momentarily}) temporarily
3256 splits the current window horizontally, making a window 72 columns
3257 wide, so you can see any lines that are too long. Type a space to
3258 restore the normal width.
3260 @kindex C-u C-c C-w @r{(Fortran mode)}
3261 @findex fortran-window-create
3262 You can also split the window horizontally and continue editing with
3263 the split in place. To do this, use @kbd{C-u C-c C-w} (@code{M-x
3264 fortran-window-create}). By editing in this window you can
3265 immediately see when you make a line too wide to be correct Fortran.
3267 @findex fortran-strip-sequence-nos
3268 The command @kbd{M-x fortran-strip-sequence-nos} deletes all text in
3269 column 72 and beyond, on all lines in the current buffer. This is the
3270 easiest way to get rid of old sequence numbers.
3272 @node Fortran Abbrev
3273 @section Fortran Keyword Abbrevs
3275 Fortran mode provides many built-in abbrevs for common keywords and
3276 declarations. These are the same sort of abbrev that you can define
3277 yourself. To use them, you must turn on Abbrev mode.
3278 @xref{Abbrevs,,, emacs, the Emacs Manual}.
3280 The built-in abbrevs are unusual in one way: they all start with a
3281 semicolon. You cannot normally use semicolon in an abbrev, but Fortran
3282 mode makes this possible by changing the syntax of semicolon to ``word
3285 For example, one built-in Fortran abbrev is @samp{;c} for
3286 @samp{continue}. If you insert @samp{;c} and then insert a punctuation
3287 character such as a space or a newline, the @samp{;c} expands automatically
3288 to @samp{continue}, provided Abbrev mode is enabled.@refill
3290 Type @samp{;?} or @samp{;C-h} to display a list of all the built-in
3291 Fortran abbrevs and what they stand for.
3295 @chapter Emacs and MS-DOS
3297 @cindex MS-DOS peculiarities
3299 This section briefly describes the peculiarities of using Emacs on
3300 the MS-DOS ``operating system'' (also known as ``MS-DOG'').
3301 Information about Emacs and Microsoft's current operating system
3302 Windows (also known as ``Losedows) is in the main Emacs manual
3303 (@pxref{Emacs and Microsoft Systems,,, emacs, the Emacs Manual}).
3305 If you build Emacs for MS-DOS, the binary will also run on Windows
3306 3.X, Windows NT, Windows 9X/ME, Windows 2000, or OS/2 as a DOS
3307 application; all of this chapter applies for all of those systems, if
3308 you use an Emacs that was built for MS-DOS.
3310 @xref{Text and Binary,,,emacs, the Emacs Manual}, for information
3311 about Emacs' special handling of text files under MS-DOS (and
3315 * Keyboard: MS-DOS Keyboard. Keyboard conventions on MS-DOS.
3316 * Mouse: MS-DOS Mouse. Mouse conventions on MS-DOS.
3317 * Display: MS-DOS Display. Fonts, frames and display size on MS-DOS.
3318 * Files: MS-DOS File Names. File name conventions on MS-DOS.
3319 * Printing: MS-DOS Printing. Printing specifics on MS-DOS.
3320 * I18N: MS-DOS and MULE. Support for internationalization on MS-DOS.
3321 * Processes: MS-DOS Processes. Running subprocesses on MS-DOS.
3324 @node MS-DOS Keyboard
3325 @section Keyboard Usage on MS-DOS
3327 @kindex DEL @r{(MS-DOS)}
3328 @kindex BS @r{(MS-DOS)}
3329 The key that is called @key{DEL} in Emacs (because that's how it is
3330 designated on most workstations) is known as @key{BS} (backspace) on a
3331 PC. That is why the PC-specific terminal initialization remaps the
3332 @key{BS} key to act as @key{DEL}; the @key{DELETE} key is remapped to act
3333 as @kbd{C-d} for the same reasons.
3335 @kindex C-g @r{(MS-DOS)}
3336 @kindex C-BREAK @r{(MS-DOS)}
3337 @cindex quitting on MS-DOS
3338 Emacs built for MS-DOS recognizes @kbd{C-@key{BREAK}} as a quit
3339 character, just like @kbd{C-g}. This is because Emacs cannot detect
3340 that you have typed @kbd{C-g} until it is ready for more input. As a
3341 consequence, you cannot use @kbd{C-g} to stop a running command
3342 (@pxref{Quitting,,,emacs, the Emacs Manual}). By contrast,
3343 @kbd{C-@key{BREAK}} @emph{is} detected as soon as you type it (as
3344 @kbd{C-g} is on other systems), so it can be used to stop a running
3345 command and for emergency escape (@pxref{Emergency Escape,,,emacs, the
3348 @cindex Meta (under MS-DOS)
3349 @cindex Hyper (under MS-DOS)
3350 @cindex Super (under MS-DOS)
3351 @vindex dos-super-key
3352 @vindex dos-hyper-key
3353 The PC keyboard maps use the left @key{ALT} key as the @key{META} key.
3354 You have two choices for emulating the @key{SUPER} and @key{HYPER} keys:
3355 choose either the right @key{CTRL} key or the right @key{ALT} key by
3356 setting the variables @code{dos-hyper-key} and @code{dos-super-key} to 1
3357 or 2 respectively. If neither @code{dos-super-key} nor
3358 @code{dos-hyper-key} is 1, then by default the right @key{ALT} key is
3359 also mapped to the @key{META} key. However, if the MS-DOS international
3360 keyboard support program @file{KEYB.COM} is installed, Emacs will
3361 @emph{not} map the right @key{ALT} to @key{META}, since it is used for
3362 accessing characters like @kbd{~} and @kbd{@@} on non-US keyboard
3363 layouts; in this case, you may only use the left @key{ALT} as @key{META}
3366 @kindex C-j @r{(MS-DOS)}
3367 @vindex dos-keypad-mode
3368 The variable @code{dos-keypad-mode} is a flag variable that controls
3369 what key codes are returned by keys in the numeric keypad. You can also
3370 define the keypad @key{ENTER} key to act like @kbd{C-j}, by putting the
3371 following line into your @file{_emacs} file:
3374 ;; @r{Make the @key{ENTER} key from the numeric keypad act as @kbd{C-j}.}
3375 (define-key function-key-map [kp-enter] [?\C-j])
3379 @section Mouse Usage on MS-DOS
3381 @cindex mouse support under MS-DOS
3382 Emacs on MS-DOS supports a mouse (on the default terminal only).
3383 The mouse commands work as documented, including those that use menus
3384 and the menu bar (@pxref{Menu Bar,,,emacs, the Emacs Manual}). Scroll
3385 bars don't work in MS-DOS Emacs. PC mice usually have only two
3386 buttons; these act as @kbd{Mouse-1} and @kbd{Mouse-2}, but if you
3387 press both of them together, that has the effect of @kbd{Mouse-3}. If
3388 the mouse does have 3 buttons, Emacs detects that at startup, and all
3389 the 3 buttons function normally, as on X.
3391 Help strings for menu-bar and pop-up menus are displayed in the echo
3392 area when the mouse pointer moves across the menu items. Highlighting
3393 of mouse-sensitive text (@pxref{Mouse References,,,emacs, the Emacs
3394 Manual}) is also supported.
3396 @cindex mouse, set number of buttons
3397 @findex msdos-set-mouse-buttons
3398 Some versions of mouse drivers don't report the number of mouse
3399 buttons correctly. For example, mice with a wheel report that they
3400 have 3 buttons, but only 2 of them are passed to Emacs; the clicks on
3401 the wheel, which serves as the middle button, are not passed. In
3402 these cases, you can use the @kbd{M-x msdos-set-mouse-buttons} command
3403 to tell Emacs how many mouse buttons to expect. You could make such a
3404 setting permanent by adding this fragment to your @file{_emacs} init
3408 ;; @r{Treat the mouse like a 2-button mouse.}
3409 (msdos-set-mouse-buttons 2)
3412 @cindex Windows clipboard support
3413 Emacs built for MS-DOS supports clipboard operations when it runs on
3414 Windows. Commands that put text on the kill ring, or yank text from
3415 the ring, check the Windows clipboard first, just as Emacs does on the
3416 X Window System (@pxref{Mouse Commands,,,emacs, the Emacs Manual}).
3417 Only the primary selection and the cut buffer are supported by MS-DOS
3418 Emacs on Windows; the secondary selection always appears as empty.
3420 Due to the way clipboard access is implemented by Windows, the
3421 length of text you can put into the clipboard is limited by the amount
3422 of free DOS memory that is available to Emacs. Usually, up to 620KB of
3423 text can be put into the clipboard, but this limit depends on the system
3424 configuration and is lower if you run Emacs as a subprocess of
3425 another program. If the killed text does not fit, Emacs outputs a
3426 message saying so, and does not put the text into the clipboard.
3428 Null characters also cannot be put into the Windows clipboard. If the
3429 killed text includes null characters, Emacs does not put such text into
3430 the clipboard, and displays in the echo area a message to that effect.
3432 @vindex dos-display-scancodes
3433 The variable @code{dos-display-scancodes}, when non-@code{nil},
3434 directs Emacs to display the @acronym{ASCII} value and the keyboard scan code of
3435 each keystroke; this feature serves as a complement to the
3436 @code{view-lossage} command, for debugging.
3438 @node MS-DOS Display
3439 @section Display on MS-DOS
3440 @cindex faces under MS-DOS
3441 @cindex fonts, emulating under MS-DOS
3443 Display on MS-DOS cannot use font variants, like bold or italic, but
3444 it does support multiple faces, each of which can specify a foreground
3445 and a background color. Therefore, you can get the full functionality
3446 of Emacs packages that use fonts (such as @code{font-lock}, Enriched
3447 Text mode, and others) by defining the relevant faces to use different
3448 colors. Use the @code{list-colors-display} command (@pxref{Frame
3449 Parameters,,,emacs, the Emacs Manual}) and the
3450 @code{list-faces-display} command (@pxref{Faces,,,emacs, the Emacs
3451 Manual}) to see what colors and faces are available and what they look
3454 @xref{MS-DOS and MULE}, later in this chapter, for information on
3455 how Emacs displays glyphs and characters that aren't supported by the
3456 native font built into the DOS display.
3458 @cindex cursor shape on MS-DOS
3459 When Emacs starts, it changes the cursor shape to a solid box. This
3460 is for compatibility with other systems, where the box cursor is the
3461 default in Emacs. This default shape can be changed to a bar by
3462 specifying the @code{cursor-type} parameter in the variable
3463 @code{default-frame-alist} (@pxref{Creating Frames,,,emacs, the Emacs
3464 Manual}). The MS-DOS terminal doesn't support a vertical-bar cursor,
3465 so the bar cursor is horizontal, and the @code{@var{width}} parameter,
3466 if specified by the frame parameters, actually determines its height.
3467 For this reason, the @code{bar} and @code{hbar} cursor types produce
3468 the same effect on MS-DOS. As an extension, the bar cursor
3469 specification can include the starting scan line of the cursor as well
3470 as its width, like this:
3473 '(cursor-type bar @var{width} . @var{start})
3477 In addition, if the @var{width} parameter is negative, the cursor bar
3478 begins at the top of the character cell.
3480 @cindex frames on MS-DOS
3481 The MS-DOS terminal can only display a single frame at a time. The
3482 Emacs frame facilities work on MS-DOS much as they do on text-only
3483 terminals (@pxref{Frames,,,emacs, the Emacs Manual}). When you run
3484 Emacs from a DOS window on MS-Windows, you can make the visible frame
3485 smaller than the full screen, but Emacs still cannot display more than
3486 a single frame at a time.
3488 @cindex frame size under MS-DOS
3491 The @code{mode4350} command switches the display to 43 or 50
3492 lines, depending on your hardware; the @code{mode25} command switches
3493 to the default 80x25 screen size.
3495 By default, Emacs only knows how to set screen sizes of 80 columns by
3496 25, 28, 35, 40, 43 or 50 rows. However, if your video adapter has
3497 special video modes that will switch the display to other sizes, you can
3498 have Emacs support those too. When you ask Emacs to switch the frame to
3499 @var{n} rows by @var{m} columns dimensions, it checks if there is a
3500 variable called @code{screen-dimensions-@var{n}x@var{m}}, and if so,
3501 uses its value (which must be an integer) as the video mode to switch
3502 to. (Emacs switches to that video mode by calling the BIOS @code{Set
3503 Video Mode} function with the value of
3504 @code{screen-dimensions-@var{n}x@var{m}} in the @code{AL} register.)
3505 For example, suppose your adapter will switch to 66x80 dimensions when
3506 put into video mode 85. Then you can make Emacs support this screen
3507 size by putting the following into your @file{_emacs} file:
3510 (setq screen-dimensions-66x80 85)
3513 Since Emacs on MS-DOS can only set the frame size to specific
3514 supported dimensions, it cannot honor every possible frame resizing
3515 request. When an unsupported size is requested, Emacs chooses the next
3516 larger supported size beyond the specified size. For example, if you
3517 ask for 36x80 frame, you will get 40x80 instead.
3519 The variables @code{screen-dimensions-@var{n}x@var{m}} are used only
3520 when they exactly match the specified size; the search for the next
3521 larger supported size ignores them. In the above example, even if your
3522 VGA supports 38x80 dimensions and you define a variable
3523 @code{screen-dimensions-38x80} with a suitable value, you will still get
3524 40x80 screen when you ask for a 36x80 frame. If you want to get the
3525 38x80 size in this case, you can do it by setting the variable named
3526 @code{screen-dimensions-36x80} with the same video mode value as
3527 @code{screen-dimensions-38x80}.
3529 Changing frame dimensions on MS-DOS has the effect of changing all the
3530 other frames to the new dimensions.
3532 @node MS-DOS File Names
3533 @section File Names on MS-DOS
3534 @cindex file names under MS-DOS
3535 @cindex init file, default name under MS-DOS
3537 On MS-DOS, file names are case-insensitive and limited to eight
3538 characters, plus optionally a period and three more characters. Emacs
3539 knows enough about these limitations to handle file names that were
3540 meant for other operating systems. For instance, leading dots
3541 @samp{.} in file names are invalid in MS-DOS, so Emacs transparently
3542 converts them to underscores @samp{_}; thus your default init file
3543 (@pxref{Init File,,,emacs, the Emacs Manual}) is called @file{_emacs}
3544 on MS-DOS. Excess characters before or after the period are generally
3545 ignored by MS-DOS itself; thus, if you visit the file
3546 @file{LongFileName.EvenLongerExtension}, you will silently get
3547 @file{longfile.eve}, but Emacs will still display the long file name
3548 on the mode line. Other than that, it's up to you to specify file
3549 names which are valid under MS-DOS; the transparent conversion as
3550 described above only works on file names built into Emacs.
3552 @cindex backup file names on MS-DOS
3553 The above restrictions on the file names on MS-DOS make it almost
3554 impossible to construct the name of a backup file (@pxref{Backup
3555 Names,,,emacs, the Emacs Manual}) without losing some of the original
3556 file name characters. For example, the name of a backup file for
3557 @file{docs.txt} is @file{docs.tx~} even if single backup is used.
3559 @cindex file names under Windows 95/NT
3560 @cindex long file names in DOS box under Windows 95/NT
3561 If you run Emacs as a DOS application under Windows 9X, Windows ME, or
3562 Windows 2000, you can turn on support for long file names. If you do
3563 that, Emacs doesn't truncate file names or convert them to lower case;
3564 instead, it uses the file names that you specify, verbatim. To enable
3565 long file name support, set the environment variable @env{LFN} to
3566 @samp{y} before starting Emacs. Unfortunately, Windows NT doesn't allow
3567 DOS programs to access long file names, so Emacs built for MS-DOS will
3568 only see their short 8+3 aliases.
3570 @cindex @env{HOME} directory under MS-DOS
3571 MS-DOS has no notion of home directory, so Emacs on MS-DOS pretends
3572 that the directory where it is installed is the value of the @env{HOME}
3573 environment variable. That is, if your Emacs binary,
3574 @file{emacs.exe}, is in the directory @file{c:/utils/emacs/bin}, then
3575 Emacs acts as if @env{HOME} were set to @samp{c:/utils/emacs}. In
3576 particular, that is where Emacs looks for the init file @file{_emacs}.
3577 With this in mind, you can use @samp{~} in file names as an alias for
3578 the home directory, as you would on GNU or Unix. You can also set
3579 @env{HOME} variable in the environment before starting Emacs; its
3580 value will then override the above default behavior.
3582 Emacs on MS-DOS handles the directory name @file{/dev} specially,
3583 because of a feature in the emulator libraries of DJGPP that pretends
3584 I/O devices have names in that directory. We recommend that you avoid
3585 using an actual directory named @file{/dev} on any disk.
3587 @node MS-DOS Printing
3588 @section Printing and MS-DOS
3590 Printing commands, such as @code{lpr-buffer}
3591 (@pxref{Printing,,,emacs, the Emacs Manual}) and
3592 @code{ps-print-buffer} (@pxref{PostScript,,,emacs, the Emacs Manual})
3593 can work on MS-DOS by sending the output to one of the printer ports,
3594 if a Posix-style @code{lpr} program is unavailable. The same Emacs
3595 variables control printing on all systems, but in some cases they have
3596 different default values on MS-DOS.
3598 @xref{MS-Windows Printing,,,emacs, the Emacs Manual}, for details.
3600 Some printers expect DOS codepage encoding of non-@acronym{ASCII} text, even
3601 though they are connected to a Windows machine which uses a different
3602 encoding for the same locale. For example, in the Latin-1 locale, DOS
3603 uses codepage 850 whereas Windows uses codepage 1252. @xref{MS-DOS and
3604 MULE}. When you print to such printers from Windows, you can use the
3605 @kbd{C-x RET c} (@code{universal-coding-system-argument}) command before
3606 @kbd{M-x lpr-buffer}; Emacs will then convert the text to the DOS
3607 codepage that you specify. For example, @kbd{C-x RET c cp850-dos RET
3608 M-x lpr-region RET} will print the region while converting it to the
3609 codepage 850 encoding. You may need to create the @code{cp@var{nnn}}
3610 coding system with @kbd{M-x codepage-setup}.
3613 @vindex dos-ps-printer
3614 For backwards compatibility, the value of @code{dos-printer}
3615 (@code{dos-ps-printer}), if it has a value, overrides the value of
3616 @code{printer-name} (@code{ps-printer-name}), on MS-DOS.
3619 @node MS-DOS and MULE
3620 @section International Support on MS-DOS
3621 @cindex international support @r{(MS-DOS)}
3623 Emacs on MS-DOS supports the same international character sets as it
3624 does on GNU, Unix and other platforms (@pxref{International,,,emacs,
3625 the Emacs Manual}), including coding systems for converting between
3626 the different character sets. However, due to incompatibilities
3627 between MS-DOS/MS-Windows and other systems, there are several
3628 DOS-specific aspects of this support that you should be aware of.
3629 This section describes these aspects.
3631 The description below is largely specific to the MS-DOS port of
3632 Emacs, especially where it talks about practical implications for
3633 Emacs users. For other operating systems, see the @file{code-pages.el}
3634 package, which implements support for MS-DOS- and MS-Windows-specific
3635 encodings for all platforms other than MS-DOS.
3638 @item M-x dos-codepage-setup
3639 Set up Emacs display and coding systems as appropriate for the current
3642 @item M-x codepage-setup
3643 Create a coding system for a certain DOS codepage.
3646 @cindex codepage, MS-DOS
3647 @cindex DOS codepages
3648 MS-DOS is designed to support one character set of 256 characters at
3649 any given time, but gives you a variety of character sets to choose
3650 from. The alternative character sets are known as @dfn{DOS codepages}.
3651 Each codepage includes all 128 @acronym{ASCII} characters, but the other 128
3652 characters (codes 128 through 255) vary from one codepage to another.
3653 Each DOS codepage is identified by a 3-digit number, such as 850, 862,
3656 In contrast to X, which lets you use several fonts at the same time,
3657 MS-DOS normally doesn't allow use of several codepages in a single
3658 session. MS-DOS was designed to load a single codepage at system
3659 startup, and require you to reboot in order to change
3660 it@footnote{Normally, one particular codepage is burnt into the
3661 display memory, while other codepages can be installed by modifying
3662 system configuration files, such as @file{CONFIG.SYS}, and rebooting.
3663 While there is third-party software that allows changing the codepage
3664 without rebooting, we describe here how a stock MS-DOS system
3665 behaves.}. Much the same limitation applies when you run DOS
3666 executables on other systems such as MS-Windows.
3668 @cindex unibyte operation @r{(MS-DOS)}
3669 If you invoke Emacs on MS-DOS with the @samp{--unibyte} option
3670 (@pxref{Initial Options,,,emacs, the Emacs Manual}), Emacs does not
3671 perform any conversion of non-@acronym{ASCII} characters. Instead, it
3672 reads and writes any non-@acronym{ASCII} characters verbatim, and
3673 sends their 8-bit codes to the display verbatim. Thus, unibyte Emacs
3674 on MS-DOS supports the current codepage, whatever it may be, but
3675 cannot even represent any other characters.
3677 @vindex dos-codepage
3678 For multibyte operation on MS-DOS, Emacs needs to know which
3679 characters the chosen DOS codepage can display. So it queries the
3680 system shortly after startup to get the chosen codepage number, and
3681 stores the number in the variable @code{dos-codepage}. Some systems
3682 return the default value 437 for the current codepage, even though the
3683 actual codepage is different. (This typically happens when you use the
3684 codepage built into the display hardware.) You can specify a different
3685 codepage for Emacs to use by setting the variable @code{dos-codepage} in
3688 @cindex language environment, automatic selection on @r{MS-DOS}
3689 Multibyte Emacs supports only certain DOS codepages: those which can
3690 display Far-Eastern scripts, like the Japanese codepage 932, and those
3691 that encode a single ISO 8859 character set.
3693 The Far-Eastern codepages can directly display one of the MULE
3694 character sets for these countries, so Emacs simply sets up to use the
3695 appropriate terminal coding system that is supported by the codepage.
3696 The special features described in the rest of this section mostly
3697 pertain to codepages that encode ISO 8859 character sets.
3699 For the codepages which correspond to one of the ISO character sets,
3700 Emacs knows the character set name based on the codepage number. Emacs
3701 automatically creates a coding system to support reading and writing
3702 files that use the current codepage, and uses this coding system by
3703 default. The name of this coding system is @code{cp@var{nnn}}, where
3704 @var{nnn} is the codepage number.@footnote{The standard Emacs coding
3705 systems for ISO 8859 are not quite right for the purpose, because
3706 typically the DOS codepage does not match the standard ISO character
3707 codes. For example, the letter @samp{@,{c}} (@samp{c} with cedilla) has
3708 code 231 in the standard Latin-1 character set, but the corresponding
3709 DOS codepage 850 uses code 135 for this glyph.}
3711 @cindex mode line @r{(MS-DOS)}
3712 All the @code{cp@var{nnn}} coding systems use the letter @samp{D}
3713 (for ``DOS'') as their mode-line mnemonic. Since both the terminal
3714 coding system and the default coding system for file I/O are set to
3715 the proper @code{cp@var{nnn}} coding system at startup, it is normal
3716 for the mode line on MS-DOS to begin with @samp{-DD\-}. @xref{Mode
3717 Line,,,emacs, the Emacs Manual}. Far-Eastern DOS terminals do not use
3718 the @code{cp@var{nnn}} coding systems, and thus their initial mode
3719 line looks like the Emacs default.
3721 Since the codepage number also indicates which script you are using,
3722 Emacs automatically runs @code{set-language-environment} to select the
3723 language environment for that script (@pxref{Language
3724 Environments,,,emacs, the Emacs Manual}).
3726 If a buffer contains a character belonging to some other ISO 8859
3727 character set, not the one that the chosen DOS codepage supports, Emacs
3728 displays it using a sequence of @acronym{ASCII} characters. For example, if the
3729 current codepage doesn't have a glyph for the letter @samp{@`o} (small
3730 @samp{o} with a grave accent), it is displayed as @samp{@{`o@}}, where
3731 the braces serve as a visual indication that this is a single character.
3732 (This may look awkward for some non-Latin characters, such as those from
3733 Greek or Hebrew alphabets, but it is still readable by a person who
3734 knows the language.) Even though the character may occupy several
3735 columns on the screen, it is really still just a single character, and
3736 all Emacs commands treat it as one.
3738 @cindex IBM graphics characters (MS-DOS)
3739 @cindex box-drawing characters (MS-DOS)
3740 @cindex line-drawing characters (MS-DOS)
3741 Not all characters in DOS codepages correspond to ISO 8859
3742 characters---some are used for other purposes, such as box-drawing
3743 characters and other graphics. Emacs maps these characters to two
3744 special character sets called @code{eight-bit-control} and
3745 @code{eight-bit-graphic}, and displays them as their IBM glyphs.
3746 However, you should be aware that other systems might display these
3747 characters differently, so you should avoid them in text that might be
3748 copied to a different operating system, or even to another DOS machine
3749 that uses a different codepage.
3751 @vindex dos-unsupported-character-glyph
3752 Emacs supports many other characters sets aside from ISO 8859, but it
3753 cannot display them on MS-DOS. So if one of these multibyte characters
3754 appears in a buffer, Emacs on MS-DOS displays them as specified by the
3755 @code{dos-unsupported-character-glyph} variable; by default, this glyph
3756 is an empty triangle. Use the @kbd{C-u C-x =} command to display the
3757 actual code and character set of such characters. @xref{Position
3758 Info,,,emacs, the Emacs Manual}.
3760 @findex codepage-setup
3761 By default, Emacs defines a coding system to support the current
3762 codepage. To define a coding system for some other codepage (e.g., to
3763 visit a file written on a DOS machine in another country), use the
3764 @kbd{M-x codepage-setup} command. It prompts for the 3-digit code of
3765 the codepage, with completion, then creates the coding system for the
3766 specified codepage. You can then use the new coding system to read and
3767 write files, but you must specify it explicitly for the file command
3768 when you want to use it (@pxref{Text Coding,,,emacs, the Emacs Manual}).
3770 These coding systems are also useful for visiting a file encoded using
3771 a DOS codepage, using Emacs running on some other operating system.
3773 @cindex MS-Windows codepages
3774 MS-Windows provides its own codepages, which are different from the
3775 DOS codepages for the same locale. For example, DOS codepage 850
3776 supports the same character set as Windows codepage 1252; DOS codepage
3777 855 supports the same character set as Windows codepage 1251, etc.
3778 The MS-Windows version of Emacs uses the current codepage for display
3779 when invoked with the @samp{-nw} option. Support for codepages in the
3780 Windows port of Emacs is part of the @file{code-pages.el} package.
3782 @node MS-DOS Processes
3783 @section Subprocesses on MS-DOS
3785 @cindex compilation under MS-DOS
3786 @cindex inferior processes under MS-DOS
3787 @findex compile @r{(MS-DOS)}
3788 @findex grep @r{(MS-DOS)}
3789 Because MS-DOS is a single-process ``operating system,''
3790 asynchronous subprocesses are not available. In particular, Shell
3791 mode and its variants do not work. Most Emacs features that use
3792 asynchronous subprocesses also don't work on MS-DOS, including
3793 Shell mode and GUD. When in doubt, try and see; commands that
3794 don't work output an error message saying that asynchronous processes
3797 Compilation under Emacs with @kbd{M-x compile}, searching files with
3798 @kbd{M-x grep} and displaying differences between files with @kbd{M-x
3799 diff} do work, by running the inferior processes synchronously. This
3800 means you cannot do any more editing until the inferior process
3803 Spell checking also works, by means of special support for synchronous
3804 invocation of the @code{ispell} program. This is slower than the
3805 asynchronous invocation on other platforms
3807 Instead of the Shell mode, which doesn't work on MS-DOS, you can use
3808 the @kbd{M-x eshell} command. This invokes the Eshell package that
3809 implements a Posix-like shell entirely in Emacs Lisp.
3811 By contrast, Emacs compiled as a native Windows application
3812 @strong{does} support asynchronous subprocesses. @xref{Windows
3813 Processes,,,emacs, the Emacs Manual}.
3815 @cindex printing under MS-DOS
3816 Printing commands, such as @code{lpr-buffer}
3817 (@pxref{Printing,,,emacs, the Emacs Manual}) and
3818 @code{ps-print-buffer} (@pxref{PostScript,,,emacs, the Emacs Manual}),
3819 work in MS-DOS by sending the output to one of the printer ports.
3820 @xref{MS-DOS Printing,,,emacs, the Emacs Manual}.
3822 When you run a subprocess synchronously on MS-DOS, make sure the
3823 program terminates and does not try to read keyboard input. If the
3824 program does not terminate on its own, you will be unable to terminate
3825 it, because MS-DOS provides no general way to terminate a process.
3826 Pressing @kbd{C-c} or @kbd{C-@key{BREAK}} might sometimes help in these
3829 Accessing files on other machines is not supported on MS-DOS. Other
3830 network-oriented commands such as sending mail, Web browsing, remote
3831 login, etc., don't work either, unless network access is built into
3832 MS-DOS with some network redirector.
3834 @cindex directory listing on MS-DOS
3835 @vindex dired-listing-switches @r{(MS-DOS)}
3836 Dired on MS-DOS uses the @code{ls-lisp} package where other
3837 platforms use the system @code{ls} command. Therefore, Dired on
3838 MS-DOS supports only some of the possible options you can mention in
3839 the @code{dired-listing-switches} variable. The options that work are
3840 @samp{-A}, @samp{-a}, @samp{-c}, @samp{-i}, @samp{-r}, @samp{-S},
3841 @samp{-s}, @samp{-t}, and @samp{-u}.
3852 arch-tag: 75c33f13-32c6-41b6-9537-847a312e2e49