* buffers.texi (Buffers): Correct the size limit.

[bpt/emacs.git] / doc / emacs / buffers.texi

@c This is part of the Emacs manual.
@c Copyright (C) 1985-1987, 1993-1995, 1997, 2000-2011
@c   Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Buffers, Windows, Files, Top
@chapter Using Multiple Buffers

@cindex buffers
  The text you are editing in Emacs resides in an object called a
@dfn{buffer}.  Each time you visit a file, a buffer is created to hold the
file's text.  Each time you invoke Dired, a buffer is created to hold the
directory listing.  If you send a message with @kbd{C-x m}, a buffer named
@samp{*mail*} is used to hold the text of the message.  When you ask for a
command's documentation, that appears in a buffer called @samp{*Help*}.

  Each buffer has a unique name, which can be of any length.  When a
buffer is displayed in a window, its name is shown in the mode line
(@pxref{Mode Line}).  The distinction between upper and lower case
matters in buffer names.  Most buffers are made by visiting files, and
their names are derived from the files' names; however, you can also
create an empty buffer with any name you want.  A newly started Emacs
has a buffer named @samp{*scratch*}, which is not associated with any
file and can be used for evaluating Lisp expressions in Emacs
(@pxref{Lisp Interaction}).

@cindex selected buffer
@cindex current buffer
  At any time, one and only one buffer is @dfn{current}.  This is also
called the @dfn{selected buffer}.  We often say that a command
operates on ``the buffer''; this really means that the command
operates on the current buffer (most commands do).  When there is only
one Emacs window, the buffer displayed in that window is current.
When there are multiple windows present, the buffer displayed in the
@dfn{selected window} is current.  @xref{Windows}.

  Each buffer records individually what file it is visiting (if any),
whether it is modified, and what major mode and minor modes are in
effect (@pxref{Major Modes}).  Any Emacs variable can be made
@dfn{local to} a particular buffer, meaning its value in that buffer
can be different from the value in other buffers.  @xref{Locals}.

@cindex buffer size, maximum
  A buffer's size cannot be larger than some maximum, which is defined
by the largest buffer position representable by the @dfn{Emacs
integer} data type.  This is because Emacs tracks buffer positions
using that data type.  For 64-bit machines, the maximum buffer size
enforced by the data types is @math{2^61 - 2} bytes, or about 2 EiB.
For most 32-bit machines, the maximum is @math{2^31 - 1} bytes, or about 2 GiB.
For some older machines, the maximum is @math{2^29 - 2} bytes, or
about 512 MiB.  Buffer sizes are also limited by the size of Emacs's
virtual memory.

@menu
* Select Buffer::       Creating a new buffer or reselecting an old one.
* List Buffers::        Getting a list of buffers that exist.
* Misc Buffer::         Renaming; changing read-onlyness; copying text.
* Kill Buffer::         Killing buffers you no longer need.
* Several Buffers::     How to go through the list of all buffers
                          and operate variously on several of them.
* Indirect Buffers::    An indirect buffer shares the text of another buffer.
* Buffer Convenience::  Convenience and customization features for
                          buffer handling.
@end menu

@node Select Buffer
@section Creating and Selecting Buffers
@cindex change buffers
@cindex switch buffers

@table @kbd
@item C-x b @var{buffer} @key{RET}
Select or create a buffer named @var{buffer} (@code{switch-to-buffer}).
@item C-x 4 b @var{buffer} @key{RET}
Similar, but select @var{buffer} in another window
(@code{switch-to-buffer-other-window}).
@item C-x 5 b @var{buffer} @key{RET}
Similar, but select @var{buffer} in a separate frame
(@code{switch-to-buffer-other-frame}).
@item C-x @key{LEFT}
Select the previous buffer in the list of existing buffers.
@item C-x @key{RIGHT}
Select the next buffer in the list of existing buffers.
@item C-u M-g M-g
@itemx C-u M-g g
Read a number @var{n} and move to line @var{n} in the most recently
selected buffer other than the current buffer.
@end table

@kindex C-x b
@findex switch-to-buffer
  To select the buffer named @var{bufname}, type @kbd{C-x b
@var{bufname} @key{RET}}.  This runs the command
@code{switch-to-buffer} with argument @var{bufname}.  While entering
the buffer name, you can use the usual minibuffer completion and
history commands (@pxref{Minibuffer}).  An empty argument to @kbd{C-x
b} specifies the buffer that was current most recently among those not
now displayed in any window.

@cindex minibuffer confirmation
@cindex confirming in the minibuffer
  If you specify a buffer that does not exist, @kbd{C-x b} creates a
new, empty buffer that is not visiting any file, and selects it for
editing.  First, however, Emacs might prompt you for confirmation, in
case you entered the wrong buffer name.  Emacs asks for confirmation
only if the last key you typed, before submitting the minibuffer input
with @key{RET}, was @key{TAB} (@code{minibuffer-complete}).  This
catches a common mistake, in which one types @key{RET} before
realizing that @key{TAB} did not complete far enough to yield the
desired buffer name (@pxref{Completion}).  Emacs asks for confirmation
by putting the message @samp{[Confirm]} in the minibuffer; type
@key{RET} again to confirm and visit the buffer.

@vindex confirm-nonexistent-file-or-buffer
  The variable @code{confirm-nonexistent-file-or-buffer} controls
whether Emacs asks for confirmation before visiting a buffer that did
not previously exist.  The default value, @code{after-completion},
gives the behavior we have just described.  If the value is
@code{nil}, Emacs never asks for confirmation; for any other
non-@code{nil} value, Emacs always asks for confirmation.  This
variable also affects the @code{find-file} command (@pxref{Visiting}).

  One reason to create a new buffer is to use it for making temporary
notes.  If you try to save it, Emacs asks for the file name to use.
The default value of the variable @code{major-mode} determines the new
buffer's major mode; the default value is Fundamental mode.  @xref{Major
Modes}.

@kindex C-x @key{LEFT}
@kindex C-x @key{RIGHT}
@findex next-buffer
@findex previous-buffer
  For conveniently switching between a few buffers, use the commands
@kbd{C-x @key{LEFT}} and @kbd{C-x @key{RIGHT}}.  @kbd{C-x @key{RIGHT}}
(@code{previous-buffer}) selects the previous buffer (following the order
of most recent selection in the current frame), while @kbd{C-x @key{LEFT}}
(@code{next-buffer}) moves through buffers in the reverse direction.

@kindex C-x 4 b
@findex switch-to-buffer-other-window
@vindex even-window-heights
  To select a buffer in a window other than the current one, type
@kbd{C-x 4 b} (@code{switch-to-buffer-other-window}).  This prompts
for a buffer name using the minibuffer, displays that buffer in
another window, and selects that window.  By default, if displaying
the buffer causes two vertically adjacent windows to be displayed, the
heights of those windows are evened out; to countermand that and
preserve the window configuration, set the variable
@code{even-window-heights} to @code{nil}.

@kindex C-x 5 b
@findex switch-to-buffer-other-frame
  Similarly, @kbd{C-x 5 b} (@code{switch-to-buffer-other-frame})
prompts for a buffer name, displays that buffer in another frame, and
selects that frame.

  In addition, @kbd{C-x C-f}, and any other command for visiting a
file, can also be used to switch to an existing file-visiting buffer.
@xref{Visiting}.

@vindex display-buffer-reuse-frames
  You can control how certain buffers are handled by these commands by
customizing the variables @code{special-display-buffer-names},
@code{special-display-regexps}, @code{same-window-buffer-names}, and
@code{same-window-regexps}.  See @ref{Force Same Window}, and
@ref{Special Buffer Frames}, for more about these variables.  In
addition, if the value of @code{display-buffer-reuse-frames} is
non-@code{nil}, and the buffer you want to switch to is already
displayed in some frame, Emacs will just raise that frame.

@findex goto-line
  @kbd{C-u M-g M-g}, that is @code{goto-line} with a plain prefix
argument, reads a number @var{n} using the minibuffer, selects the
most recently selected buffer other than the current buffer in another
window, and then moves point to the beginning of line number @var{n}
in that buffer.  This is mainly useful in a buffer that refers to line
numbers in another buffer: if point is on or just after a number,
@code{goto-line} uses that number as the default for @var{n}.  Note
that prefix arguments other than just @kbd{C-u} behave differently.
@kbd{C-u 4 M-g M-g} goes to line 4 in the @emph{current} buffer,
without reading a number from the minibuffer.  (Remember that @kbd{M-g
M-g} without prefix argument reads a number @var{n} and then moves to
line number @var{n} in the current buffer.  @xref{Moving Point}.)

  Emacs uses buffer names that start with a space for internal purposes.
It treats these buffers specially in minor ways---for example, by
default they do not record undo information.  It is best to avoid using
such buffer names yourself.

@node List Buffers
@section Listing Existing Buffers

@table @kbd
@item C-x C-b
List the existing buffers (@code{list-buffers}).
@end table

@cindex listing current buffers
@kindex C-x C-b
@findex list-buffers
  To display a list of existing buffers, type @kbd{C-x C-b}.  Each
line in the list shows one buffer's name, major mode and visited file.
The buffers are listed in the order that they were current; the
buffers that were current most recently come first.

  @samp{.} in the first field of a line indicates that the buffer is
current.  @samp{%} indicates a read-only buffer.  @samp{*} indicates
that the buffer is ``modified.''  If several buffers are modified, it
may be time to save some with @kbd{C-x s} (@pxref{Save Commands}).
Here is an example of a buffer list:

@smallexample
CRM Buffer                Size  Mode              File
. * .emacs                3294  Emacs-Lisp        ~/.emacs
 %  *Help*                 101  Help
    search.c             86055  C                 ~/cvs/emacs/src/search.c
 %  src                  20959  Dired by name     ~/cvs/emacs/src/
  * *mail*                  42  Mail
 %  HELLO                 1607  Fundamental       ~/cvs/emacs/etc/HELLO
 %  NEWS                481184  Outline           ~/cvs/emacs/etc/NEWS
    *scratch*              191  Lisp Interaction
  * *Messages*            1554  Fundamental
@end smallexample

@noindent
The buffer @samp{*Help*} was made by a help request (@pxref{Help}); it
is not visiting any file.  The buffer @code{src} was made by Dired on
the directory @file{~/cvs/emacs/src/}.  You can list only buffers that
are visiting files by giving the command a prefix argument, as in
@kbd{C-u C-x C-b}.

  @code{list-buffers} omits buffers whose names begin with a space,
unless they visit files: such buffers are used internally by Emacs.

@node Misc Buffer
@section Miscellaneous Buffer Operations

@table @kbd
@item C-x C-q
Toggle read-only status of buffer (@code{toggle-read-only}).
@item M-x rename-buffer @key{RET} @var{name} @key{RET}
Change the name of the current buffer.
@item M-x rename-uniquely
Rename the current buffer by adding @samp{<@var{number}>} to the end.
@item M-x view-buffer @key{RET} @var{buffer} @key{RET}
Scroll through buffer @var{buffer}.
@end table

@kindex C-x C-q
@vindex buffer-read-only
@cindex read-only buffer
  A buffer can be @dfn{read-only}, which means that commands to change
its contents are not allowed.  The mode line indicates read-only
buffers with @samp{%%} or @samp{%*} near the left margin.  Read-only
buffers are usually made by subsystems such as Dired and Rmail that
have special commands to operate on the text; also by visiting a file
whose access control says you cannot write it.

@findex toggle-read-only
  If you wish to make changes in a read-only buffer, use the command
@kbd{C-x C-q} (@code{toggle-read-only}).  It makes a read-only buffer
writable, and makes a writable buffer read-only.  This
works by setting the variable @code{buffer-read-only}, which has a local
value in each buffer and makes the buffer read-only if its value is
non-@code{nil}.  If you have files under version control, you may find
it convenient to bind @kbd{C-x C-q} to @code{vc-toggle-read-only}
instead.  This will guard you against an operation that will confuse
most modern version-conmtrol systems. @xref{Version Control}.

@findex rename-buffer
  @kbd{M-x rename-buffer} changes the name of the current buffer.  You
specify the new name as a minibuffer argument; there is no default.
If you specify a name that is in use for some other buffer, an error
happens and no renaming is done.

@findex rename-uniquely
  @kbd{M-x rename-uniquely} renames the current buffer to a similar
name with a numeric suffix added to make it both different and unique.
This command does not need an argument.  It is useful for creating
multiple shell buffers: if you rename the @samp{*shell*} buffer, then
do @kbd{M-x shell} again, it makes a new shell buffer named
@samp{*shell*}; meanwhile, the old shell buffer continues to exist
under its new name.  This method is also good for mail buffers,
compilation buffers, and most Emacs features that create special
buffers with particular names.  (With some of these features, such as
@kbd{M-x compile}, @kbd{M-x grep} an @kbd{M-x info}, you need to
switch to some other buffer before using the command, in order for it
to make a different buffer.)

@findex view-buffer
  @kbd{M-x view-buffer} is much like @kbd{M-x view-file} (@pxref{Misc
File Ops}) except that it examines an already existing Emacs buffer.
View mode provides commands for scrolling through the buffer
conveniently but not for changing it.  When you exit View mode with
@kbd{q}, that switches back to the buffer (and the position) which was
previously displayed in the window.  Alternatively, if you exit View
mode with @kbd{e}, the buffer and the value of point that resulted from
your perusal remain in effect.

  The commands @kbd{M-x append-to-buffer} and @kbd{M-x insert-buffer}
can be used to copy text from one buffer to another.  @xref{Accumulating
Text}.

@node Kill Buffer
@section Killing Buffers

@cindex killing buffers
  If you continue an Emacs session for a while, you may accumulate a
large number of buffers.  You may then find it convenient to @dfn{kill}
the buffers you no longer need.  On most operating systems, killing a
buffer releases its space back to the operating system so that other
programs can use it.  Here are some commands for killing buffers:

@table @kbd
@item C-x k @var{bufname} @key{RET}
Kill buffer @var{bufname} (@code{kill-buffer}).
@item M-x kill-some-buffers
Offer to kill each buffer, one by one.
@item M-x kill-matching-buffers
Offer to kill all buffers matching a regular expression.
@end table

@findex kill-buffer
@kindex C-x k
  @kbd{C-x k} (@code{kill-buffer}) kills one buffer, whose name you
specify in the minibuffer.  The default, used if you type just
@key{RET} in the minibuffer, is to kill the current buffer.  If you
kill the current buffer, another buffer becomes current: one that was
current in the recent past but is not displayed in any window now.  If
you ask to kill a file-visiting buffer that is modified, then you must
confirm with @kbd{yes} before the buffer is killed.

@findex kill-some-buffers
  The command @kbd{M-x kill-some-buffers} asks about each buffer, one
by one.  An answer of @kbd{y} means to kill the buffer, just like
@code{kill-buffer}.  This command ignores buffers whose names begin
with a space, which are used internally by Emacs.

@findex kill-matching-buffers
  The command @kbd{M-x kill-matching-buffers} prompts for a regular
expression and kills all buffers whose names match that expression.
@xref{Regexps}.  Like @code{kill-some-buffers}, it asks for
confirmation before each kill.  This command normally ignores buffers
whose names begin with a space, which are used internally by Emacs.
To kill internal buffers as well, call @code{kill-matching-buffers}
with a prefix argument.

  The buffer menu feature is also convenient for killing various
buffers.  @xref{Several Buffers}.

@vindex kill-buffer-hook
  If you want to do something special every time a buffer is killed, you
can add hook functions to the hook @code{kill-buffer-hook} (@pxref{Hooks}).

@findex clean-buffer-list
  If you run one Emacs session for a period of days, as many people do,
it can fill up with buffers that you used several days ago.  The command
@kbd{M-x clean-buffer-list} is a convenient way to purge them; it kills
all the unmodified buffers that you have not used for a long time.  An
ordinary buffer is killed if it has not been displayed for three days;
however, you can specify certain buffers that should never be killed
automatically, and others that should be killed if they have been unused
for a mere hour.

@cindex Midnight mode
@vindex midnight-mode
@vindex midnight-hook
  You can also have this buffer purging done for you, every day at
midnight, by enabling Midnight mode.  Midnight mode operates each day
at midnight; at that time, it runs @code{clean-buffer-list}, or
whichever functions you have placed in the normal hook
@code{midnight-hook} (@pxref{Hooks}).  To enable Midnight mode, use
the Customization buffer to set the variable @code{midnight-mode} to
@code{t}.  @xref{Easy Customization}.

@node Several Buffers
@section Operating on Several Buffers
@cindex buffer menu

@table @kbd
@item M-x buffer-menu
Begin editing a buffer listing all Emacs buffers.
@item M-x buffer-menu-other-window.
Similar, but do it in another window.
@end table

  The @dfn{buffer menu} opened by @kbd{C-x C-b} (@pxref{List Buffers})
does not merely list buffers.  It also allows you to perform various
operations on buffers, through an interface similar to Dired
(@pxref{Dired}).  You can save buffers, kill them (here called
@dfn{deleting} them, for consistency with Dired), or display them.

@findex buffer-menu
@findex buffer-menu-other-window
  To use the buffer menu, type @kbd{C-x C-b} and switch to the window
displaying the @samp{*Buffer List*} buffer.  You can also type
@kbd{M-x buffer-menu} to open the buffer menu in the selected window.
Alternatively, the command @kbd{M-x buffer-menu-other-window} opens
the buffer menu in another window, and selects that window.

  The buffer menu is a read-only buffer, and can be changed only
through the special commands described in this section.  The usual
Emacs cursor motion commands can be used in this buffer.  The
following commands apply to the buffer described on the current line:

@table @kbd
@item d
Request to delete (kill) the buffer, then move down.  The request
shows as a @samp{D} on the line, before the buffer name.  Requested
deletions take place when you type the @kbd{x} command.
@item C-d
Like @kbd{d} but move up afterwards instead of down.
@item s
Request to save the buffer.  The request shows as an @samp{S} on the
line.  Requested saves take place when you type the @kbd{x} command.
You may request both saving and deletion for the same buffer.
@item x
Perform previously requested deletions and saves.
@item u
Remove any request made for the current line, and move down.
@item @key{DEL}
Move to previous line and remove any request made for that line.
@end table

  The @kbd{d}, @kbd{C-d}, @kbd{s} and @kbd{u} commands to add or remove
flags also move down (or up) one line.  They accept a numeric argument
as a repeat count.

  These commands operate immediately on the buffer listed on the current
line:

@table @kbd
@item ~
Mark the buffer ``unmodified.''  The command @kbd{~} does this
immediately when you type it.
@item %
Toggle the buffer's read-only flag.  The command @kbd{%} does
this immediately when you type it.
@item t
Visit the buffer as a tags table.  @xref{Select Tags Table}.
@end table

  There are also commands to select another buffer or buffers:

@table @kbd
@item q
Quit the buffer menu---immediately display the most recent formerly
visible buffer in its place.
@item @key{RET}
@itemx f
Immediately select this line's buffer in place of the @samp{*Buffer
List*} buffer.
@item o
Immediately select this line's buffer in another window as if by
@kbd{C-x 4 b}, leaving @samp{*Buffer List*} visible.
@item C-o
Immediately display this line's buffer in another window, but don't
select the window.
@item 1
Immediately select this line's buffer in a full-screen window.
@item 2
Immediately set up two windows, with this line's buffer selected in
one, and the previously current buffer (aside from the buffer
@samp{*Buffer List*}) displayed in the other.
@item b
Bury the buffer listed on this line.
@item m
Mark this line's buffer to be displayed in another window if you exit
with the @kbd{v} command.  The request shows as a @samp{>} at the
beginning of the line.  (A single buffer may not have both a delete
request and a display request.)
@item v
Immediately select this line's buffer, and also display in other windows
any buffers previously marked with the @kbd{m} command.  If you have not
marked any buffers, this command is equivalent to @kbd{1}.
@end table

  There is also a command that affects the entire buffer list:

@table @kbd
@item T
Delete, or reinsert, lines for non-file buffers.  This command toggles
the inclusion of such buffers in the buffer list.
@end table

  What @code{buffer-menu} actually does is create and switch to a
suitable buffer, and turn on Buffer Menu mode in it.  Everything else
described above is implemented by the special commands provided in
Buffer Menu mode.  One consequence of this is that you can switch from
the @samp{*Buffer List*} buffer to another Emacs buffer, and edit
there.  You can reselect the @samp{*Buffer List*} buffer later, to
perform the operations already requested, or you can kill it, or pay
no further attention to it.

  Normally, the buffer @samp{*Buffer List*} is not updated
automatically when buffers are created and killed; its contents are
just text.  If you have created, deleted or renamed buffers, the way
to update @samp{*Buffer List*} to show what you have done is to type
@kbd{g} (@code{revert-buffer}).  You can make this happen regularly
every @code{auto-revert-interval} seconds if you enable Auto Revert
mode in this buffer, as long as it is not marked modified.  Global
Auto Revert mode applies to the @samp{*Buffer List*} buffer only if
@code{global-auto-revert-non-file-buffers} is non-@code{nil}.
@iftex
@inforef{Autorevert,, emacs-xtra}, for details.
@end iftex
@ifnottex
@xref{Autorevert, global-auto-revert-non-file-buffers}, for details.
@end ifnottex

@node Indirect Buffers
@section Indirect Buffers
@cindex indirect buffer
@cindex base buffer

  An @dfn{indirect buffer} shares the text of some other buffer, which
is called the @dfn{base buffer} of the indirect buffer.  In some ways it
is the analogue, for buffers, of a symbolic link between files.

@table @kbd
@findex make-indirect-buffer
@item M-x make-indirect-buffer @key{RET} @var{base-buffer} @key{RET} @var{indirect-name} @key{RET}
Create an indirect buffer named @var{indirect-name} whose base buffer
is @var{base-buffer}.
@findex clone-indirect-buffer
@item M-x clone-indirect-buffer @key{RET}
Create an indirect buffer that is a twin copy of the current buffer.
@item C-x 4 c
@kindex C-x 4 c
@findex clone-indirect-buffer-other-window
Create an indirect buffer that is a twin copy of the current buffer, and
select it in another window (@code{clone-indirect-buffer-other-window}).
@end table

  The text of the indirect buffer is always identical to the text of its
base buffer; changes made by editing either one are visible immediately
in the other.  But in all other respects, the indirect buffer and its
base buffer are completely separate.  They can have different names,
different values of point, different narrowing, different markers,
different major modes, and different local variables.

  An indirect buffer cannot visit a file, but its base buffer can.  If
you try to save the indirect buffer, that actually works by saving the
base buffer.  Killing the base buffer effectively kills the indirect
buffer, but killing an indirect buffer has no effect on its base buffer.

  One way to use indirect buffers is to display multiple views of an
outline.  @xref{Outline Views}.

@vindex clone-indirect-buffer-hook
  A quick and handy way to make an indirect buffer is with the command
@kbd{M-x clone-indirect-buffer}.  It creates and selects an indirect
buffer whose base buffer is the current buffer.  With a numeric
argument, it prompts for the name of the indirect buffer; otherwise it
uses the name of the current buffer, with a @samp{<@var{n}>} suffix
added.  @kbd{C-x 4 c} (@code{clone-indirect-buffer-other-window})
works like @kbd{M-x clone-indirect-buffer}, but it selects the new
buffer in another window.  These functions run the hook
@code{clone-indirect-buffer-hook} after creating the indirect buffer.

  The more general way to make an indirect buffer is with the command
@kbd{M-x make-indirect-buffer}.  It creates an indirect buffer from
buffer @var{base-buffer}, under the name @var{indirect-name}.  It
prompts for both @var{base-buffer} and @var{indirect-name} using the
minibuffer.

@node Buffer Convenience
@section Convenience Features and Customization of Buffer Handling

   This section describes several modes and features that make it more
convenient to switch between buffers.

@menu
* Uniquify::               Making buffer names unique with directory parts.
* Iswitchb::               Switching between buffers with substrings.
* Buffer Menus::           Configurable buffer menu.
@end menu

@node Uniquify
@subsection Making Buffer Names Unique

@cindex unique buffer names
@cindex directories in buffer names
  When several buffers visit identically-named files, Emacs must give
the buffers distinct names.  The usual method for making buffer names
unique adds @samp{<2>}, @samp{<3>}, etc. to the end of the buffer
names (all but one of them).

@vindex uniquify-buffer-name-style
  Other methods work by adding parts of each file's directory to the
buffer name.  To select one, load the library @file{uniquify} (e.g.
using @code{(require 'uniquify)}), and customize the variable
@code{uniquify-buffer-name-style} (@pxref{Easy Customization}).

  To begin with, the @code{forward} naming method includes part of the
file's directory name at the beginning of the buffer name; using this
method, buffers visiting the files @file{/u/rms/tmp/Makefile} and
@file{/usr/projects/zaphod/Makefile} would be named
@samp{tmp/Makefile} and @samp{zaphod/Makefile}, respectively (instead
of @samp{Makefile} and @samp{Makefile<2>}).

  In contrast, the @code{post-forward} naming method would call the
buffers @samp{Makefile|tmp} and @samp{Makefile|zaphod}, and the
@code{reverse} naming method would call them @samp{Makefile\tmp} and
@samp{Makefile\zaphod}.  The nontrivial difference between
@code{post-forward} and @code{reverse} occurs when just one directory
name is not enough to distinguish two files; then @code{reverse} puts
the directory names in reverse order, so that @file{/top/middle/file}
becomes @samp{file\middle\top}, while @code{post-forward} puts them in
forward order after the file name, as in @samp{file|top/middle}.

  Which rule to follow for putting the directory names in the buffer
name is not very important if you are going to @emph{look} at the
buffer names before you type one.  But as an experienced user, if you
know the rule, you won't have to look.  And then you may find that one
rule or another is easier for you to remember and apply quickly.

@node Iswitchb
@subsection Switching Between Buffers using Substrings

@findex iswitchb-mode
@cindex Iswitchb mode
@cindex mode, Iswitchb
@kindex C-x b @r{(Iswitchb mode)}
@kindex C-x 4 b @r{(Iswitchb mode)}
@kindex C-x 5 b @r{(Iswitchb mode)}
@kindex C-x 4 C-o @r{(Iswitchb mode)}

  Iswitchb global minor mode provides convenient switching between
buffers using substrings of their names.  It replaces the normal
definitions of @kbd{C-x b}, @kbd{C-x 4 b}, @kbd{C-x 5 b}, and @kbd{C-x
4 C-o} with alternative commands that are somewhat ``smarter.''

  When one of these commands prompts you for a buffer name, you can
type in just a substring of the name you want to choose.  As you enter
the substring, Iswitchb mode continuously displays a list of buffers
that match the substring you have typed.

  At any time, you can type @key{RET} to select the first buffer in
the list.  So the way to select a particular buffer is to make it the
first in the list.  There are two ways to do this.  You can type more
of the buffer name and thus narrow down the list, excluding unwanted
buffers above the desired one.  Alternatively, you can use @kbd{C-s}
and @kbd{C-r} to rotate the list until the desired buffer is first.

  @key{TAB} while entering the buffer name performs completion on the
string you have entered, based on the displayed list of buffers.

  To enable Iswitchb mode, type @kbd{M-x iswitchb-mode}, or customize
the variable @code{iswitchb-mode} to @code{t} (@pxref{Easy
Customization}).

@node Buffer Menus
@subsection Customizing Buffer Menus

@findex bs-show
@cindex buffer list, customizable
@table @kbd
@item M-x bs-show
Make a list of buffers similarly to @kbd{M-x list-buffers} but
customizable.
@end table

  @kbd{M-x bs-show} pops up a buffer list similar to the one normally
displayed by @kbd{C-x C-b} but which you can customize.  If you prefer
this to the usual buffer list, you can bind this command to @kbd{C-x
C-b}.  To customize this buffer list, use the @code{bs} Custom group
(@pxref{Easy Customization}).

@findex msb-mode
@cindex mode, MSB
@cindex MSB mode
@cindex buffer menu
@findex mouse-buffer-menu
@kindex C-Down-Mouse-1
  MSB global minor mode (``MSB'' stands for ``mouse select buffer'')
provides a different and customizable mouse buffer menu which you may
prefer.  It replaces the bindings of @code{mouse-buffer-menu},
normally on @kbd{C-Down-Mouse-1}, and the menu bar buffer menu.  You
can customize the menu in the @code{msb} Custom group.