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+ − 1
+ − 2 @node Buffers, Windows, Files, Top
+ − 3 @chapter Using Multiple Buffers
+ − 4
+ − 5 @cindex buffers
+ − 6 Text you are editing in Emacs resides in an object called a
+ − 7 @dfn{buffer}. Each time you visit a file, Emacs creates a buffer to
+ − 8 hold the file's text. Each time you invoke Dired, Emacs creates a buffer
+ − 9 to hold the directory listing. If you send a message with @kbd{C-x m},
+ − 10 a buffer named @samp{*mail*} is used to hold the text of the message.
+ − 11 When you ask for a command's documentation, it appears in a buffer
+ − 12 called @samp{*Help*}.
+ − 13
+ − 14 @cindex selected buffer
+ − 15 @cindex current buffer
+ − 16 At any time, one and only one buffer is @dfn{selected}. It is also
+ − 17 called the @dfn{current buffer}. Saying a command operates on ``the
+ − 18 buffer'' really means that the command operates on the selected
+ − 19 buffer, as most commands do.
+ − 20
+ − 21 When Emacs creates multiple windows, each window has a chosen buffer which
+ − 22 is displayed there, but at any time only one of the windows is selected and
+ − 23 its chosen buffer is the selected buffer. Each window's mode line displays
+ − 24 the name of the buffer the window is displaying (@pxref{Windows}).
+ − 25
+ − 26 Each buffer has a name which can be of any length but is
+ − 27 case-sensitive. You can select a buffer using its name. Most
+ − 28 buffers are created when you visit files; their names are derived from
+ − 29 the files' names. You can also create an empty buffer with any name you
+ − 30 want. A newly started Emacs has a buffer named @samp{*scratch*} which
+ − 31 you can use for evaluating Lisp expressions in Emacs.
+ − 32
+ − 33 Each buffer records what file it is visiting, whether it is
+ − 34 modified, and what major mode and minor modes are in effect in it
+ − 35 (@pxref{Major Modes}). Any Emacs variable can be made @dfn{local to} a
+ − 36 particular buffer, meaning its value in that buffer can be different from
+ − 37 the value in other buffers. @xref{Locals}.
+ − 38
+ − 39 @menu
+ − 40 * Select Buffer:: Creating a new buffer or reselecting an old one.
+ − 41 * List Buffers:: Getting a list of buffers that exist.
+ − 42 * Misc Buffer:: Renaming; changing read-onliness; copying text.
+ − 43 * Kill Buffer:: Killing buffers you no longer need.
+ − 44 * Several Buffers:: How to go through the list of all buffers
+ − 45 and operate variously on several of them.
+ − 46 @end menu
+ − 47
+ − 48 @node Select Buffer, List Buffers, Buffers, Buffers
+ − 49 @section Creating and Selecting Buffers
+ − 50 @cindex changing buffers
+ − 51 @cindex switching buffers
+ − 52
+ − 53 @table @kbd
+ − 54 @item C-x b @var{buffer} @key{RET}
+ − 55 Select or create a buffer named @var{buffer} (@code{switch-to-buffer}).
+ − 56 @item C-x 4 b @var{buffer} @key{RET}
+ − 57 Similar, but select a buffer named @var{buffer} in another window
+ − 58 (@code{switch-to-buffer-other-window}).
+ − 59 @item M-x switch-to-other-buffer @var{n}
+ − 60 Switch to the previous buffer.
+ − 61 @end table
+ − 62
+ − 63 @kindex C-x 4 b
+ − 64 @kindex C-x 5 b
+ − 65 @findex switch-to-buffer-other-window
+ − 66 @kindex C-x b
+ − 67 @findex switch-to-buffer
+ − 68 @findex switch-to-buffer-other-frame
+ − 69 To select a buffer named @var{bufname}, type @kbd{C-x b @var{bufname}
+ − 70 @key{RET}}. This is the command @code{switch-to-buffer} with argument
+ − 71 @var{bufname}. You can use completion on an abbreviation for the buffer
+ − 72 name you want (@pxref{Completion}). An empty argument to @kbd{C-x b}
+ − 73 specifies the most recently selected buffer that is not displayed in any
+ − 74 window.@refill
+ − 75
+ − 76 Most buffers are created when you visit files, or use Emacs commands
+ − 77 that display text. You can also create a buffer explicitly by typing
+ − 78 @kbd{C-x b @var{bufname} @key{RET}}, which creates a new, empty buffer
+ − 79 that is not visiting any file, and selects it for editing. The new
+ − 80 buffer's major mode is determined by the value of
+ − 81 @code{default-major-mode} (@pxref{Major Modes}). Buffers not visiting
+ − 82 files are usually used for making notes to yourself. If you try to save
+ − 83 one, you are asked for the file name to use.
+ − 84
+ − 85 The function @code{switch-to-buffer-other-frame} is similar to
+ − 86 @code{switch-to-buffer} except that it creates a new frame in which to
+ − 87 display the selected buffer.
+ − 88
+ − 89 @findex switch-to-other-buffer
+ − 90 Use @kbd{M-x switch-to-other-buffer} to visit the previous buffer. If
+ − 91 you supply a positive integer @var{n}, the @var{n}th most recent buffer
+ − 92 is displayed. If you supply an argument of 0, the current buffer is
+ − 93 moved to the bottom of the buffer stack.
+ − 94
+ − 95 Note that you can also use @kbd{C-x C-f} and any other command for
+ − 96 visiting a file to switch buffers. @xref{Visiting}.
+ − 97
+ − 98 @node List Buffers, Misc Buffer, Select Buffer, Buffers
+ − 99 @section Listing Existing Buffers
+ − 100
+ − 101 @table @kbd
+ − 102 @item C-x C-b
+ − 103 List the existing buffers (@code{list-buffers}).
+ − 104 @end table
+ − 105
+ − 106 @kindex C-x C-b
+ − 107 @findex list-buffers
+ − 108 To print a list of all existing buffers, type @kbd{C-x C-b}. Each
+ − 109 line in the list shows one buffer's name, major mode, and visited file.
+ − 110 A @samp{*} at the beginning of a line indicates the buffer has been
+ − 111 ``modified''. If several buffers are modified, it may be time to save
+ − 112 some with @kbd{C-x s} (@pxref{Saving}). A @samp{%} indicates a read-only
+ − 113 buffer. A @samp{.} marks the selected buffer. Here is an example of a
+ − 114 buffer list:@refill
+ − 115
+ − 116 @smallexample
+ − 117 MR Buffer Size Mode File
+ − 118 -- ------ ---- ---- ----
+ − 119 .* emacs.tex 383402 Texinfo /u2/emacs/man/emacs.tex
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+ − 120 *Help* 1287 Fundamental
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+ − 121 files.el 23076 Emacs-Lisp /u2/emacs/lisp/files.el
+ − 122 % RMAIL 64042 RMAIL /u/rms/RMAIL
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+ − 123 *% man 747 Dired /u2/emacs/man/
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+ − 124 net.emacs 343885 Fundamental /u/rms/net.emacs
+ − 125 fileio.c 27691 C /u2/emacs/src/fileio.c
+ − 126 NEWS 67340 Text /u2/emacs/etc/NEWS
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+ − 127 *scratch* 0 Lisp Interaction
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+ − 128 @end smallexample
+ − 129
+ − 130 @noindent
+ − 131 Note that the buffer @samp{*Help*} was made by a help request; it is not
+ − 132 visiting any file. The buffer @code{man} was made by Dired on the
+ − 133 directory @file{/u2/emacs/man/}.
+ − 134
+ − 135 As you move the mouse over the @samp{*Buffer List*} buffer, the lines
+ − 136 are highlighted. This visual cue indicates that clicking the right
+ − 137 mouse button (@code{button3}) will pop up a menu of commands on the
+ − 138 buffer represented by this line. This menu duplicates most of those
+ − 139 commands which are bound to keys in the @samp{*Buffer List*} buffer.
+ − 140
+ − 141 @node Misc Buffer, Kill Buffer, List Buffers, Buffers
+ − 142 @section Miscellaneous Buffer Operations
+ − 143
+ − 144 @table @kbd
+ − 145 @item C-x C-q
+ − 146 Toggle read-only status of buffer (@code{toggle-read-only}).
+ − 147 @item M-x rename-buffer
+ − 148 Change the name of the current buffer.
+ − 149 @item M-x view-buffer
+ − 150 Scroll through a buffer.
+ − 151 @end table
+ − 152
+ − 153 @cindex read-only buffer
+ − 154 @kindex C-x C-q
+ − 155 @findex toggle-read-only
+ − 156 @vindex buffer-read-only
+ − 157 A buffer can be @dfn{read-only}, which means that commands to change
+ − 158 its text are not allowed. Normally, read-only buffers are created by
+ − 159 subsystems such as Dired and Rmail that have special commands to operate
+ − 160 on the text. Emacs also creates a read-only buffer if you
+ − 161 visit a file that is protected. To make changes in a read-only buffer,
+ − 162 use the command @kbd{C-x C-q} (@code{toggle-read-only}). It makes a
+ − 163 read-only buffer writable, and makes a writable buffer read-only. This
+ − 164 works by setting the variable @code{buffer-read-only}, which has a local
+ − 165 value in each buffer and makes a buffer read-only if its value is
+ − 166 non-@code{nil}.
+ − 167
+ − 168 @findex rename-buffer
+ − 169 @kbd{M-x rename-buffer} changes the name of the current buffer,
+ − 170 prompting for the new name in the minibuffer. There is no default. If you
+ − 171 specify a name that is used by a different buffer, an error is signalled and
+ − 172 renaming is not done.
+ − 173
+ − 174 @findex view-buffer
+ − 175 @kbd{M-x view-buffer} is similar to @kbd{M-x view-file} (@pxref{Misc
+ − 176 File Ops}), but it examines an already existing Emacs buffer. View mode
+ − 177 provides convenient commands for scrolling through the buffer but not
+ − 178 for changing it. When you exit View mode, the resulting value of point
+ − 179 remains in effect.
+ − 180
+ − 181 To copy text from one buffer to another, use the commands @kbd{M-x
+ − 182 append-to-buffer} and @kbd{M-x insert-buffer}. @xref{Accumulating
+ − 183 Text}.@refill
+ − 184
+ − 185 @node Kill Buffer, Several Buffers, Misc Buffer, Buffers
+ − 186 @section Killing Buffers
+ − 187
+ − 188 After using Emacs for a while, you may accumulate a large number of
+ − 189 buffers and may want to eliminate the ones you no
+ − 190 longer need. There are several commands for doing this.
+ − 191
+ − 192 @c WideCommands
+ − 193 @table @kbd
+ − 194 @item C-x k
+ − 195 Kill a buffer, specified by name (@code{kill-buffer}).
+ − 196 @item M-x kill-some-buffers
+ − 197 Offer to kill each buffer, one by one.
+ − 198 @end table
+ − 199
+ − 200 @findex kill-buffer
+ − 201 @findex kill-some-buffers
+ − 202 @kindex C-x k
+ − 203
+ − 204 @kbd{C-x k} (@code{kill-buffer}) kills one buffer, whose name you
+ − 205 specify in the minibuffer. If you type just @key{RET} in the
+ − 206 minibuffer, the default, killing the current buffer, is used. If the
+ − 207 current buffer is killed, the buffer that has been selected recently but
+ − 208 does not appear in any window now is selected. If the buffer being
+ − 209 killed contains unsaved changes, you are asked to confirm with @kbd{yes}
+ − 210 before the buffer is killed.
+ − 211
+ − 212 The command @kbd{M-x kill-some-buffers} asks about each buffer, one by
+ − 213 one. An answer of @kbd{y} means to kill the buffer. Killing the current
+ − 214 buffer or a buffer containing unsaved changes selects a new buffer or asks
+ − 215 for confirmation just like @code{kill-buffer}.
+ − 216
+ − 217 @node Several Buffers,, Kill Buffer, Buffers
+ − 218 @section Operating on Several Buffers
+ − 219 @cindex buffer menu
+ − 220
+ − 221 The @dfn{buffer-menu} facility is like a ``Dired for buffers''; it allows
+ − 222 you to request operations on various Emacs buffers by editing a
+ − 223 buffer containing a list of them. You can save buffers, kill them
+ − 224 (here called @dfn{deleting} them, for consistency with Dired), or display
+ − 225 them.
+ − 226
+ − 227 @table @kbd
+ − 228 @item M-x buffer-menu
+ − 229 Begin editing a buffer listing all Emacs buffers.
+ − 230 @end table
+ − 231
+ − 232 @findex buffer-menu
+ − 233 The command @code{buffer-menu} writes a list of all Emacs buffers into
+ − 234 the buffer @samp{*Buffer List*}, and selects that buffer in Buffer Menu
+ − 235 mode. The buffer is read-only. You can only change it using the special
+ − 236 commands described in this section. Most of the commands are graphic
+ − 237 characters. You can use Emacs cursor motion commands in the
+ − 238 @samp{*Buffer List*} buffer. If the cursor is on a line describing a
+ − 239 buffer, the following special commands apply to that buffer:
+ − 240
+ − 241 @table @kbd
+ − 242 @item d
+ − 243 Request to delete (kill) the buffer, then move down. A @samp{D} before
+ − 244 the buffer name on a line indicates a deletion request. Requested
+ − 245 deletions actually take place when you use the @kbd{x} command.
+ − 246 @item k
+ − 247 Synonym for @kbd{d}.
+ − 248 @item C-d
+ − 249 Like @kbd{d} but move up afterwards instead of down.
+ − 250 @item s
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+ − 251 Request to save the buffer. An @samp{S} before the buffer name on a line
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+ − 252 indicates the request. Requested saves actually take place when you use
+ − 253 the @kbd{x} command. You can request both saving and deletion for the
+ − 254 same buffer.
+ − 255 @item ~
+ − 256 Mark buffer ``unmodified''. The command @kbd{~} does this
+ − 257 immediately when typed.
+ − 258 @item x
+ − 259 Perform previously requested deletions and saves.
+ − 260 @item u
+ − 261 Remove any request made for the current line, and move down.
+ − 262 @item @key{DEL}
+ − 263 Move to previous line and remove any request made for that line.
+ − 264 @end table
+ − 265
+ − 266 All commands that add or remove flags to request later operations
+ − 267 also move down a line. They accept a numeric argument as a repeat count,
+ − 268 unless otherwise specified.
+ − 269
+ − 270 There are also special commands to use the buffer list to select another
+ − 271 buffer, and to specify one or more other buffers for display in additional
+ − 272 windows.
+ − 273
+ − 274 @table @kbd
+ − 275 @item 1
+ − 276 Select the buffer in a full-frame window. This command takes effect
+ − 277 immediately.
+ − 278 @item 2
+ − 279 Immediately set up two windows, with this buffer in one and the
+ − 280 buffer selected before @samp{*Buffer List*} in the other.
+ − 281 @item f
+ − 282 Immediately select the buffer in place of the @samp{*Buffer List*} buffer.
+ − 283 @item o
+ − 284 Immediately select the buffer in another window as if by @kbd{C-x 4 b},
+ − 285 leaving @samp{*Buffer List*} visible.
+ − 286 @item q
+ − 287 Immediately select this buffer, and display any buffers previously
+ − 288 flagged with the @kbd{m} command in other windows. If there are no
+ − 289 buffers flagged with @kbd{m}, this command is equivalent to @kbd{1}.
+ − 290 @item m
+ − 291 Flag this buffer to be displayed in another window if the @kbd{q}
+ − 292 command is used. The request shows as a @samp{>} at the beginning of
+ − 293 the line. The same buffer may not have both a delete request and a
+ − 294 display request.
+ − 295 @end table
+ − 296
+ − 297 Going back between a @code{buffer-menu} buffer and other Emacs buffers is
+ − 298 easy. You can, for example, switch from the @samp{*Buffer List*}
+ − 299 buffer to another Emacs buffer, and edit there. You can then reselect the
+ − 300 @code{buffer-menu} buffer and perform operations already
+ − 301 requested, or you can kill that buffer or pay no further attention to it.
+ − 302 All that @code{buffer-menu} does directly is create and select a
+ − 303 suitable buffer, and turn on Buffer Menu mode. All the other
+ − 304 capabilities of the buffer menu are implemented by special commands
+ − 305 provided in Buffer Menu mode.
+ − 306
+ − 307 The only difference between @code{buffer-menu} and @code{list-buffers} is
+ − 308 that @code{buffer-menu} selects the @samp{*Buffer List*} buffer and
+ − 309 @code{list-buffers} does not. If you run @code{list-buffers} (that is,
+ − 310 type @kbd{C-x C-b}) and select the buffer list manually, you can use all
+ − 311 the commands described here.
