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1 @c This is part of the Emacs manual.
2 @c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2000, 2001,
3 @c 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
4 @c See file emacs.texi for copying conditions.
5 @node Buffers, Windows, Files, Top
6 @chapter Using Multiple Buffers
7
8 @cindex buffers
9 The text you are editing in Emacs resides in an object called a
10 @dfn{buffer}. Each time you visit a file, a buffer is created to hold the
11 file's text. Each time you invoke Dired, a buffer is created to hold the
12 directory listing. If you send a message with @kbd{C-x m}, a buffer named
13 @samp{*mail*} is used to hold the text of the message. When you ask for a
14 command's documentation, that appears in a buffer called @samp{*Help*}.
15
16 Each buffer has a unique name, which can be of any length. When a
17 buffer is displayed in a window, its name is shown in the mode line
18 (@pxref{Mode Line}). The distinction between upper and lower case
19 matters in buffer names. Most buffers are made by visiting files, and
20 their names are derived from the files' names; however, you can also
21 create an empty buffer with any name you want. A newly started Emacs
22 has a buffer named @samp{*scratch*}, which is not associated with any
23 file and can be used for evaluating Lisp expressions in Emacs
24 (@pxref{Lisp Interaction}).
25
26 @cindex selected buffer
27 @cindex current buffer
28 At any time, one and only one buffer is @dfn{current}. This is also
29 called the @dfn{selected buffer}. We often say that a command
30 operates on ``the buffer''; this really means that the command
31 operates on the current buffer (most commands do). When there is only
32 one Emacs window, the buffer displayed in that window is current.
33 When there are multiple windows present, the buffer displayed in the
34 @dfn{selected window} is current. @xref{Windows}.
35
36 Each buffer records individually what file it is visiting (if any),
37 whether it is modified, and what major mode and minor modes are in
38 effect (@pxref{Major Modes}). Any Emacs variable can be made
39 @dfn{local to} a particular buffer, meaning its value in that buffer
40 can be different from the value in other buffers. @xref{Locals}.
41
42 @cindex buffer size, maximum
43 A buffer's size cannot be larger than some maximum, which is defined
44 by the largest buffer position representable by the @dfn{Emacs integer}
45 data type. This is because Emacs tracks buffer positions using that
46 data type. For 32-bit machines, the largest buffer size is 256
47 megabytes.
48
49 @menu
50 * Select Buffer:: Creating a new buffer or reselecting an old one.
51 * List Buffers:: Getting a list of buffers that exist.
52 * Misc Buffer:: Renaming; changing read-onlyness; copying text.
53 * Kill Buffer:: Killing buffers you no longer need.
54 * Several Buffers:: How to go through the list of all buffers
55 and operate variously on several of them.
56 * Indirect Buffers:: An indirect buffer shares the text of another buffer.
57 * Buffer Convenience:: Convenience and customization features for
58 buffer handling.
59 @end menu
60
61 @node Select Buffer
62 @section Creating and Selecting Buffers
63 @cindex change buffers
64 @cindex switch buffers
65
66 @table @kbd
67 @item C-x b @var{buffer} @key{RET}
68 Select or create a buffer named @var{buffer} (@code{switch-to-buffer}).
69 @item C-x 4 b @var{buffer} @key{RET}
70 Similar, but select @var{buffer} in another window
71 (@code{switch-to-buffer-other-window}).
72 @item C-x 5 b @var{buffer} @key{RET}
73 Similar, but select @var{buffer} in a separate frame
74 (@code{switch-to-buffer-other-frame}).
75 @item C-x @key{LEFT}
76 Select the previous buffer in the list of existing buffers.
77 @item C-x @key{RIGHT}
78 Select the next buffer in the list of existing buffers.
79 @item C-u M-g M-g
80 @itemx C-u M-g g
81 Read a number @var{n} and move to line @var{n} in the most recently
82 selected buffer other than the current buffer.
83 @end table
84
85 @kindex C-x b
86 @findex switch-to-buffer
87 To select the buffer named @var{bufname}, type @kbd{C-x b
88 @var{bufname} @key{RET}}. This runs the command
89 @code{switch-to-buffer} with argument @var{bufname}. While entering
90 the buffer name, you can use the usual minibuffer completion and
91 history commands (@pxref{Minibuffer}). An empty argument to @kbd{C-x
92 b} specifies the buffer that was current most recently among those not
93 now displayed in any window.
94
95 If you specify a buffer that does not exist, @kbd{C-x b} creates a
96 new, empty buffer that is not visiting any file, and selects it for
97 editing. You can use such a buffer for making temporary notes. If
98 you try to save it, you are asked for the file name to use. The new
99 buffer's major mode is determined by the variable
100 @code{default-major-mode}; the default value is Fundamental mode.
101 @xref{Major Modes}.
102
103 @kindex C-x @key{LEFT}
104 @kindex C-x @key{RIGHT}
105 @findex next-buffer
106 @findex previous-buffer
107 For conveniently switching between a few buffers, use the commands
108 @kbd{C-x @key{LEFT}} and @kbd{C-x @key{RIGHT}}. @kbd{C-x @key{RIGHT}}
109 (@code{previous-buffer}) selects the previous buffer (following the order
110 of most recent selection in the current frame), while @kbd{C-x @key{LEFT}}
111 (@code{next-buffer}) moves through buffers in the reverse direction.
112
113 @kindex C-x 4 b
114 @findex switch-to-buffer-other-window
115 @vindex even-window-heights
116 To select a buffer in a window other than the current one, type
117 @kbd{C-x 4 b} (@code{switch-to-buffer-other-window}). This prompts
118 for a buffer name using the minibuffer, displays that buffer in
119 another window, and selects that window. By default, if displaying
120 the buffer causes two vertically adjacent windows to be displayed, the
121 heights of those windows are evened out; to countermand that and
122 preserve the window configuration, set the variable
123 @code{even-window-heights} to @code{nil}.
124
125 @kindex C-x 5 b
126 @findex switch-to-buffer-other-frame
127 Similarly, @kbd{C-x 5 b} (@code{switch-to-buffer-other-frame})
128 prompts for a buffer name, displays that buffer in another frame, and
129 selects that frame.
130
131 In addition, @kbd{C-x C-f}, and any other command for visiting a
132 file, can also be used to switch to an existing file-visiting buffer.
133 @xref{Visiting}.
134
135 @vindex display-buffer-reuse-frames
136 You can control how certain buffers are handled by these commands by
137 customizing the variables @code{special-display-buffer-names},
138 @code{special-display-regexps}, @code{same-window-buffer-names}, and
139 @code{same-window-regexps}. See @ref{Force Same Window}, and
140 @ref{Special Buffer Frames}, for more about these variables. In
141 addition, if the value of @code{display-buffer-reuse-frames} is
142 non-@code{nil}, and the buffer you want to switch to is already
143 displayed in some frame, Emacs will just raise that frame.
144
145 @kbd{C-u M-g M-g}, that is @code{goto-line} with a plain prefix
146 argument, reads a number @var{n} using the minibuffer, selects the
147 most recently selected buffer other than the current buffer in another
148 window, and then moves point to the beginning of line number @var{n}
149 in that buffer. This is mainly useful in a buffer that refers to line
150 numbers in another buffer: if point is on or just after a number,
151 @code{goto-line} uses that number as the default for @var{n}. Note
152 that prefix arguments other than just @kbd{C-u} behave differently.
153 @kbd{C-u 4 M-g M-g} goes to line 4 in the @emph{current} buffer,
154 without reading a number from the minibuffer. (Remember that @kbd{M-g
155 M-g} without prefix argument reads a number @var{n} and then moves to
156 line number @var{n} in the current buffer. @xref{Moving Point}.)
157
158 Emacs uses buffer names that start with a space for internal purposes.
159 It treats these buffers specially in minor ways---for example, by
160 default they do not record undo information. It is best to avoid using
161 such buffer names yourself.
162
163 @node List Buffers
164 @section Listing Existing Buffers
165
166 @table @kbd
167 @item C-x C-b
168 List the existing buffers (@code{list-buffers}).
169 @end table
170
171 @cindex listing current buffers
172 @kindex C-x C-b
173 @findex list-buffers
174 To display a list of existing buffers, type @kbd{C-x C-b}. Each
175 line in the list shows one buffer's name, major mode and visited file.
176 The buffers are listed in the order that they were current; the
177 buffers that were current most recently come first.
178
179 @samp{.} in the first field of a line indicates that the buffer is
180 current. @samp{%} indicates a read-only buffer. @samp{*} indicates
181 that the buffer is ``modified.'' If several buffers are modified, it
182 may be time to save some with @kbd{C-x s} (@pxref{Save Commands}).
183 Here is an example of a buffer list:
184
185 @smallexample
186 CRM Buffer Size Mode File
187 . * .emacs 3294 Emacs-Lisp ~/.emacs
188 % *Help* 101 Help
189 search.c 86055 C ~/cvs/emacs/src/search.c
190 % src 20959 Dired by name ~/cvs/emacs/src/
191 * *mail* 42 Mail
192 % HELLO 1607 Fundamental ~/cvs/emacs/etc/HELLO
193 % NEWS 481184 Outline ~/cvs/emacs/etc/NEWS
194 *scratch* 191 Lisp Interaction
195 * *Messages* 1554 Fundamental
196 @end smallexample
197
198 @noindent
199 The buffer @samp{*Help*} was made by a help request (@pxref{Help}); it
200 is not visiting any file. The buffer @code{src} was made by Dired on
201 the directory @file{~/cvs/emacs/src/}. You can list only buffers that
202 are visiting files by giving the command a prefix argument, as in
203 @kbd{C-u C-x C-b}.
204
205 @code{list-buffers} omits buffers whose names begin with a space,
206 unless they visit files: such buffers are used internally by Emacs.
207
208 @node Misc Buffer
209 @section Miscellaneous Buffer Operations
210
211 @table @kbd
212 @item C-x C-q
213 Toggle read-only status of buffer (@code{toggle-read-only}).
214 @item M-x rename-buffer @key{RET} @var{name} @key{RET}
215 Change the name of the current buffer.
216 @item M-x rename-uniquely
217 Rename the current buffer by adding @samp{<@var{number}>} to the end.
218 @item M-x view-buffer @key{RET} @var{buffer} @key{RET}
219 Scroll through buffer @var{buffer}.
220 @end table
221
222 @kindex C-x C-q
223 @vindex buffer-read-only
224 @cindex read-only buffer
225 A buffer can be @dfn{read-only}, which means that commands to change
226 its contents are not allowed. The mode line indicates read-only
227 buffers with @samp{%%} or @samp{%*} near the left margin. Read-only
228 buffers are usually made by subsystems such as Dired and Rmail that
229 have special commands to operate on the text; also by visiting a file
230 whose access control says you cannot write it.
231
232 @findex toggle-read-only
233 If you wish to make changes in a read-only buffer, use the command
234 @kbd{C-x C-q} (@code{toggle-read-only}). It makes a read-only buffer
235 writable, and makes a writable buffer read-only. This
236 works by setting the variable @code{buffer-read-only}, which has a local
237 value in each buffer and makes the buffer read-only if its value is
238 non-@code{nil}. If you have files under version control, you may find
239 it convenient to bind @kbd{C-x C-q} to @code{vc-toggle-read-only}
240 instead. This will guard you against an operation that will confuse
241 most modern version-conmtrol systems. @xref{Version Control}.
242
243 @findex rename-buffer
244 @kbd{M-x rename-buffer} changes the name of the current buffer. You
245 specify the new name as a minibuffer argument; there is no default.
246 If you specify a name that is in use for some other buffer, an error
247 happens and no renaming is done.
248
249 @findex rename-uniquely
250 @kbd{M-x rename-uniquely} renames the current buffer to a similar
251 name with a numeric suffix added to make it both different and unique.
252 This command does not need an argument. It is useful for creating
253 multiple shell buffers: if you rename the @samp{*shell*} buffer, then
254 do @kbd{M-x shell} again, it makes a new shell buffer named
255 @samp{*shell*}; meanwhile, the old shell buffer continues to exist
256 under its new name. This method is also good for mail buffers,
257 compilation buffers, and most Emacs features that create special
258 buffers with particular names. (With some of these features, such as
259 @kbd{M-x compile}, @kbd{M-x grep} an @kbd{M-x info}, you need to
260 switch to some other buffer before using the command, in order for it
261 to make a different buffer.)
262
263 @findex view-buffer
264 @kbd{M-x view-buffer} is much like @kbd{M-x view-file} (@pxref{Misc
265 File Ops}) except that it examines an already existing Emacs buffer.
266 View mode provides commands for scrolling through the buffer
267 conveniently but not for changing it. When you exit View mode with
268 @kbd{q}, that switches back to the buffer (and the position) which was
269 previously displayed in the window. Alternatively, if you exit View
270 mode with @kbd{e}, the buffer and the value of point that resulted from
271 your perusal remain in effect.
272
273 The commands @kbd{M-x append-to-buffer} and @kbd{M-x insert-buffer}
274 can be used to copy text from one buffer to another. @xref{Accumulating
275 Text}.
276
277 @node Kill Buffer
278 @section Killing Buffers
279
280 @cindex killing buffers
281 If you continue an Emacs session for a while, you may accumulate a
282 large number of buffers. You may then find it convenient to @dfn{kill}
283 the buffers you no longer need. On most operating systems, killing a
284 buffer releases its space back to the operating system so that other
285 programs can use it. Here are some commands for killing buffers:
286
287 @table @kbd
288 @item C-x k @var{bufname} @key{RET}
289 Kill buffer @var{bufname} (@code{kill-buffer}).
290 @item M-x kill-some-buffers
291 Offer to kill each buffer, one by one.
292 @item M-x kill-matching-buffers
293 Offer to kill all buffers matching a regular expression.
294 @end table
295
296 @findex kill-buffer
297 @kindex C-x k
298 @kbd{C-x k} (@code{kill-buffer}) kills one buffer, whose name you
299 specify in the minibuffer. The default, used if you type just
300 @key{RET} in the minibuffer, is to kill the current buffer. If you
301 kill the current buffer, another buffer becomes current: one that was
302 current in the recent past but is not displayed in any window now. If
303 you ask to kill a file-visiting buffer that is modified, then you must
304 confirm with @kbd{yes} before the buffer is killed.
305
306 @findex kill-some-buffers
307 The command @kbd{M-x kill-some-buffers} asks about each buffer, one
308 by one. An answer of @kbd{y} means to kill the buffer, just like
309 @code{kill-buffer}. This command ignores buffers whose names begin
310 with a space, which are used internally by Emacs.
311
312 @findex kill-matching-buffers
313 The command @kbd{M-x kill-matching-buffers} prompts for a regular
314 expression and kills all buffers whose names match that expression.
315 @xref{Regexps}. Like @code{kill-some-buffers}, it asks for
316 confirmation before each kill. This command normally ignores buffers
317 whose names begin with a space, which are used internally by Emacs.
318 To kill internal buffers as well, call @code{kill-matching-buffers}
319 with a prefix argument.
320
321 The buffer menu feature is also convenient for killing various
322 buffers. @xref{Several Buffers}.
323
324 @vindex kill-buffer-hook
325 If you want to do something special every time a buffer is killed, you
326 can add hook functions to the hook @code{kill-buffer-hook} (@pxref{Hooks}).
327
328 @findex clean-buffer-list
329 If you run one Emacs session for a period of days, as many people do,
330 it can fill up with buffers that you used several days ago. The command
331 @kbd{M-x clean-buffer-list} is a convenient way to purge them; it kills
332 all the unmodified buffers that you have not used for a long time. An
333 ordinary buffer is killed if it has not been displayed for three days;
334 however, you can specify certain buffers that should never be killed
335 automatically, and others that should be killed if they have been unused
336 for a mere hour.
337
338 @cindex Midnight mode
339 @vindex midnight-mode
340 @vindex midnight-hook
341 You can also have this buffer purging done for you, every day at
342 midnight, by enabling Midnight mode. Midnight mode operates each day
343 at midnight; at that time, it runs @code{clean-buffer-list}, or
344 whichever functions you have placed in the normal hook
345 @code{midnight-hook} (@pxref{Hooks}). To enable Midnight mode, use
346 the Customization buffer to set the variable @code{midnight-mode} to
347 @code{t}. @xref{Easy Customization}.
348
349 @node Several Buffers
350 @section Operating on Several Buffers
351 @cindex buffer menu
352
353 @table @kbd
354 @item M-x buffer-menu
355 Begin editing a buffer listing all Emacs buffers.
356 @item M-x buffer-menu-other-window.
357 Similar, but do it in another window.
358 @end table
359
360 The @dfn{buffer menu} opened by @kbd{C-x C-b} (@pxref{List Buffers})
361 does not merely list buffers. It also allows you to perform various
362 operations on buffers, through an interface similar to Dired
363 (@pxref{Dired}). You can save buffers, kill them (here called
364 @dfn{deleting} them, for consistency with Dired), or display them.
365
366 @findex buffer-menu
367 @findex buffer-menu-other-window
368 To use the buffer menu, type @kbd{C-x C-b} and switch to the window
369 displaying the @samp{*Buffer List*} buffer. You can also type
370 @kbd{M-x buffer-menu} to open the buffer menu in the selected window.
371 Alternatively, the command @kbd{M-x buffer-menu-other-window} opens
372 the buffer menu in another window, and selects that window.
373
374 The buffer menu is a read-only buffer, and can be changed only
375 through the special commands described in this section. The usual
376 Emacs cursor motion commands can be used in this buffer. The
377 following commands apply to the buffer described on the current line:
378
379 @table @kbd
380 @item d
381 Request to delete (kill) the buffer, then move down. The request
382 shows as a @samp{D} on the line, before the buffer name. Requested
383 deletions take place when you type the @kbd{x} command.
384 @item C-d
385 Like @kbd{d} but move up afterwards instead of down.
386 @item s
387 Request to save the buffer. The request shows as an @samp{S} on the
388 line. Requested saves take place when you type the @kbd{x} command.
389 You may request both saving and deletion for the same buffer.
390 @item x
391 Perform previously requested deletions and saves.
392 @item u
393 Remove any request made for the current line, and move down.
394 @item @key{DEL}
395 Move to previous line and remove any request made for that line.
396 @end table
397
398 The @kbd{d}, @kbd{C-d}, @kbd{s} and @kbd{u} commands to add or remove
399 flags also move down (or up) one line. They accept a numeric argument
400 as a repeat count.
401
402 These commands operate immediately on the buffer listed on the current
403 line:
404
405 @table @kbd
406 @item ~
407 Mark the buffer ``unmodified.'' The command @kbd{~} does this
408 immediately when you type it.
409 @item %
410 Toggle the buffer's read-only flag. The command @kbd{%} does
411 this immediately when you type it.
412 @item t
413 Visit the buffer as a tags table. @xref{Select Tags Table}.
414 @end table
415
416 There are also commands to select another buffer or buffers:
417
418 @table @kbd
419 @item q
420 Quit the buffer menu---immediately display the most recent formerly
421 visible buffer in its place.
422 @item @key{RET}
423 @itemx f
424 Immediately select this line's buffer in place of the @samp{*Buffer
425 List*} buffer.
426 @item o
427 Immediately select this line's buffer in another window as if by
428 @kbd{C-x 4 b}, leaving @samp{*Buffer List*} visible.
429 @item C-o
430 Immediately display this line's buffer in another window, but don't
431 select the window.
432 @item 1
433 Immediately select this line's buffer in a full-screen window.
434 @item 2
435 Immediately set up two windows, with this line's buffer selected in
436 one, and the previously current buffer (aside from the buffer
437 @samp{*Buffer List*}) displayed in the other.
438 @item b
439 Bury the buffer listed on this line.
440 @item m
441 Mark this line's buffer to be displayed in another window if you exit
442 with the @kbd{v} command. The request shows as a @samp{>} at the
443 beginning of the line. (A single buffer may not have both a delete
444 request and a display request.)
445 @item v
446 Immediately select this line's buffer, and also display in other windows
447 any buffers previously marked with the @kbd{m} command. If you have not
448 marked any buffers, this command is equivalent to @kbd{1}.
449 @end table
450
451 There is also a command that affects the entire buffer list:
452
453 @table @kbd
454 @item T
455 Delete, or reinsert, lines for non-file buffers. This command toggles
456 the inclusion of such buffers in the buffer list.
457 @end table
458
459 What @code{buffer-menu} actually does is create and switch to a
460 suitable buffer, and turn on Buffer Menu mode in it. Everything else
461 described above is implemented by the special commands provided in
462 Buffer Menu mode. One consequence of this is that you can switch from
463 the @samp{*Buffer List*} buffer to another Emacs buffer, and edit
464 there. You can reselect the @samp{*Buffer List*} buffer later, to
465 perform the operations already requested, or you can kill it, or pay
466 no further attention to it.
467
468 Normally, the buffer @samp{*Buffer List*} is not updated
469 automatically when buffers are created and killed; its contents are
470 just text. If you have created, deleted or renamed buffers, the way
471 to update @samp{*Buffer List*} to show what you have done is to type
472 @kbd{g} (@code{revert-buffer}). You can make this happen regularly
473 every @code{auto-revert-interval} seconds if you enable Auto Revert
474 mode in this buffer, as long as it is not marked modified. Global
475 Auto Revert mode applies to the @samp{*Buffer List*} buffer only if
476 @code{global-auto-revert-non-file-buffers} is non-@code{nil}.
477 @iftex
478 @inforef{Autorevert,, emacs-xtra}, for details.
479 @end iftex
480 @ifnottex
481 @xref{Autorevert, global-auto-revert-non-file-buffers}, for details.
482 @end ifnottex
483
484 @node Indirect Buffers
485 @section Indirect Buffers
486 @cindex indirect buffer
487 @cindex base buffer
488
489 An @dfn{indirect buffer} shares the text of some other buffer, which
490 is called the @dfn{base buffer} of the indirect buffer. In some ways it
491 is the analogue, for buffers, of a symbolic link between files.
492
493 @table @kbd
494 @findex make-indirect-buffer
495 @item M-x make-indirect-buffer @key{RET} @var{base-buffer} @key{RET} @var{indirect-name} @key{RET}
496 Create an indirect buffer named @var{indirect-name} whose base buffer
497 is @var{base-buffer}.
498 @findex clone-indirect-buffer
499 @item M-x clone-indirect-buffer @key{RET}
500 Create an indirect buffer that is a twin copy of the current buffer.
501 @item C-x 4 c
502 @kindex C-x 4 c
503 @findex clone-indirect-buffer-other-window
504 Create an indirect buffer that is a twin copy of the current buffer, and
505 select it in another window (@code{clone-indirect-buffer-other-window}).
506 @end table
507
508 The text of the indirect buffer is always identical to the text of its
509 base buffer; changes made by editing either one are visible immediately
510 in the other. But in all other respects, the indirect buffer and its
511 base buffer are completely separate. They can have different names,
512 different values of point, different narrowing, different markers,
513 different major modes, and different local variables.
514
515 An indirect buffer cannot visit a file, but its base buffer can. If
516 you try to save the indirect buffer, that actually works by saving the
517 base buffer. Killing the base buffer effectively kills the indirect
518 buffer, but killing an indirect buffer has no effect on its base buffer.
519
520 One way to use indirect buffers is to display multiple views of an
521 outline. @xref{Outline Views}.
522
523 @vindex clone-indirect-buffer-hook
524 A quick and handy way to make an indirect buffer is with the command
525 @kbd{M-x clone-indirect-buffer}. It creates and selects an indirect
526 buffer whose base buffer is the current buffer. With a numeric
527 argument, it prompts for the name of the indirect buffer; otherwise it
528 uses the name of the current buffer, with a @samp{<@var{n}>} suffix
529 added. @kbd{C-x 4 c} (@code{clone-indirect-buffer-other-window})
530 works like @kbd{M-x clone-indirect-buffer}, but it selects the new
531 buffer in another window. These functions run the hook
532 @code{clone-indirect-buffer-hook} after creating the indirect buffer.
533
534 The more general way to make an indirect buffer is with the command
535 @kbd{M-x make-indirect-buffer}. It creates an indirect buffer from
536 buffer @var{base-buffer}, under the name @var{indirect-name}. It
537 prompts for both @var{base-buffer} and @var{indirect-name} using the
538 minibuffer.
539
540 @node Buffer Convenience
541 @section Convenience Features and Customization of Buffer Handling
542
543 This section describes several modes and features that make it more
544 convenient to switch between buffers.
545
546 @menu
547 * Uniquify:: Making buffer names unique with directory parts.
548 * Iswitchb:: Switching between buffers with substrings.
549 * Buffer Menus:: Configurable buffer menu.
550 @end menu
551
552 @node Uniquify
553 @subsection Making Buffer Names Unique
554
555 @cindex unique buffer names
556 @cindex directories in buffer names
557 When several buffers visit identically-named files, Emacs must give
558 the buffers distinct names. The usual method for making buffer names
559 unique adds @samp{<2>}, @samp{<3>}, etc. to the end of the buffer
560 names (all but one of them).
561
562 @vindex uniquify-buffer-name-style
563 Other methods work by adding parts of each file's directory to the
564 buffer name. To select one, customize the variable
565 @code{uniquify-buffer-name-style} (@pxref{Easy Customization}).
566
567 To begin with, the @code{forward} naming method includes part of the
568 file's directory name at the beginning of the buffer name; using this
569 method, buffers visiting the files @file{/u/rms/tmp/Makefile} and
570 @file{/usr/projects/zaphod/Makefile} would be named
571 @samp{tmp/Makefile} and @samp{zaphod/Makefile}, respectively (instead
572 of @samp{Makefile} and @samp{Makefile<2>}).
573
574 In contrast, the @code{post-forward} naming method would call the
575 buffers @samp{Makefile|tmp} and @samp{Makefile|zaphod}, and the
576 @code{reverse} naming method would call them @samp{Makefile\tmp} and
577 @samp{Makefile\zaphod}. The nontrivial difference between
578 @code{post-forward} and @code{reverse} occurs when just one directory
579 name is not enough to distinguish two files; then @code{reverse} puts
580 the directory names in reverse order, so that @file{/top/middle/file}
581 becomes @samp{file\middle\top}, while @code{post-forward} puts them in
582 forward order after the file name, as in @samp{file|top/middle}.
583
584 Which rule to follow for putting the directory names in the buffer
585 name is not very important if you are going to @emph{look} at the
586 buffer names before you type one. But as an experienced user, if you
587 know the rule, you won't have to look. And then you may find that one
588 rule or another is easier for you to remember and apply quickly.
589
590 @node Iswitchb
591 @subsection Switching Between Buffers using Substrings
592
593 @findex iswitchb-mode
594 @cindex Iswitchb mode
595 @cindex mode, Iswitchb
596 @kindex C-x b @r{(Iswitchb mode)}
597 @kindex C-x 4 b @r{(Iswitchb mode)}
598 @kindex C-x 5 b @r{(Iswitchb mode)}
599 @kindex C-x 4 C-o @r{(Iswitchb mode)}
600
601 Iswitchb global minor mode provides convenient switching between
602 buffers using substrings of their names. It replaces the normal
603 definitions of @kbd{C-x b}, @kbd{C-x 4 b}, @kbd{C-x 5 b}, and @kbd{C-x
604 4 C-o} with alternative commands that are somewhat ``smarter.''
605
606 When one of these commands prompts you for a buffer name, you can
607 type in just a substring of the name you want to choose. As you enter
608 the substring, Iswitchb mode continuously displays a list of buffers
609 that match the substring you have typed.
610
611 At any time, you can type @key{RET} to select the first buffer in
612 the list. So the way to select a particular buffer is to make it the
613 first in the list. There are two ways to do this. You can type more
614 of the buffer name and thus narrow down the list, excluding unwanted
615 buffers above the desired one. Alternatively, you can use @kbd{C-s}
616 and @kbd{C-r} to rotate the list until the desired buffer is first.
617
618 @key{TAB} while entering the buffer name performs completion on the
619 string you have entered, based on the displayed list of buffers.
620
621 To enable Iswitchb mode, type @kbd{M-x iswitchb-mode}, or customize
622 the variable @code{iswitchb-mode} to @code{t} (@pxref{Easy
623 Customization}).
624
625 @node Buffer Menus
626 @subsection Customizing Buffer Menus
627
628 @findex bs-show
629 @cindex buffer list, customizable
630 @table @kbd
631 @item M-x bs-show
632 Make a list of buffers similarly to @kbd{M-x list-buffers} but
633 customizable.
634 @end table
635
636 @kbd{M-x bs-show} pops up a buffer list similar to the one normally
637 displayed by @kbd{C-x C-b} but which you can customize. If you prefer
638 this to the usual buffer list, you can bind this command to @kbd{C-x
639 C-b}. To customize this buffer list, use the @code{bs} Custom group
640 (@pxref{Easy Customization}).
641
642 @findex msb-mode
643 @cindex mode, MSB
644 @cindex MSB mode
645 @cindex buffer menu
646 @findex mouse-buffer-menu
647 @kindex C-Down-Mouse-1
648 MSB global minor mode (``MSB'' stands for ``mouse select buffer'')
649 provides a different and customizable mouse buffer menu which you may
650 prefer. It replaces the bindings of @code{mouse-buffer-menu},
651 normally on @kbd{C-Down-Mouse-1}, and the menu bar buffer menu. You
652 can customize the menu in the @code{msb} Custom group.
653
654 @ignore
655 arch-tag: 08c43460-f4f4-4b43-9cb5-1ea9ad991695
656 @end ignore