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+@c -*-texinfo-*-
+@c This is part of the XEmacs Lisp Reference Manual.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+@c See the file lispref.texi for copying conditions.
+@setfilename ../../info/buffers.info
+@node Buffers, Windows, Backups and Auto-Saving, Top
+@chapter Buffers
+@cindex buffer
+A @dfn{buffer} is a Lisp object containing text to be edited.  Buffers
+are used to hold the contents of files that are being visited; there may
+also be buffers that are not visiting files.  While several buffers may
+exist at one time, exactly one buffer is designated the @dfn{current
+buffer} at any time.  Most editing commands act on the contents of the
+current buffer.  Each buffer, including the current buffer, may or may
+not be displayed in any windows.
+@menu
+* Buffer Basics::       What is a buffer?
+* Current Buffer::      Designating a buffer as current
+so primitives will access its contents.
+* Buffer Names::        Accessing and changing buffer names.
+* Buffer File Name::    The buffer file name indicates which file is visited.
+* Buffer Modification:: A buffer is @dfn{modified} if it needs to be saved.
+* Modification Time::   Determining whether the visited file was changed
+``behind XEmacs's back''.
+* Read Only Buffers::   Modifying text is not allowed in a read-only buffer.
+* The Buffer List::     How to look at all the existing buffers.
+* Creating Buffers::    Functions that create buffers.
+* Killing Buffers::     Buffers exist until explicitly killed.
+* Indirect Buffers::    An indirect buffer shares text with some other buffer.
+@end menu
+@node Buffer Basics
+@section Buffer Basics
+@ifinfo
+A @dfn{buffer} is a Lisp object containing text to be edited.  Buffers
+are used to hold the contents of files that are being visited; there may
+also be buffers that are not visiting files.  While several buffers may
+exist at one time, exactly one buffer is designated the @dfn{current
+buffer} at any time.  Most editing commands act on the contents of the
+current buffer.  Each buffer, including the current buffer, may or may
+not be displayed in any windows.
+@end ifinfo
+Buffers in Emacs editing are objects that have distinct names and hold
+text that can be edited.  Buffers appear to Lisp programs as a special
+data type.  You can think of the contents of a buffer as an extendable
+string; insertions and deletions may occur in any part of the buffer.
+@xref{Text}.
+A Lisp buffer object contains numerous pieces of information.  Some of
+this information is directly accessible to the programmer through
+variables, while other information is accessible only through
+special-purpose functions.  For example, the visited file name is
+directly accessible through a variable, while the value of point is
+accessible only through a primitive function.
+Buffer-specific information that is directly accessible is stored in
+@dfn{buffer-local} variable bindings, which are variable values that are
+effective only in a particular buffer.  This feature allows each buffer
+to override the values of certain variables.  Most major modes override
+variables such as @code{fill-column} or @code{comment-column} in this
+way.  For more information about buffer-local variables and functions
+related to them, see @ref{Buffer-Local Variables}.
+For functions and variables related to visiting files in buffers, see
+@ref{Visiting Files} and @ref{Saving Buffers}.  For functions and
+variables related to the display of buffers in windows, see
+@ref{Buffers and Windows}.
+@defun bufferp object
+This function returns @code{t} if @var{object} is a buffer,
+@code{nil} otherwise.
+@end defun
+@node Current Buffer
+@section The Current Buffer
+@cindex selecting a buffer
+@cindex changing to another buffer
+@cindex current buffer
+There are, in general, many buffers in an Emacs session.  At any time,
+one of them is designated as the @dfn{current buffer}.  This is the
+buffer in which most editing takes place, because most of the primitives
+for examining or changing text in a buffer operate implicitly on the
+current buffer (@pxref{Text}).  Normally the buffer that is displayed on
+the screen in the selected window is the current buffer, but this is not
+always so: a Lisp program can designate any buffer as current
+temporarily in order to operate on its contents, without changing what
+is displayed on the screen.
+The way to designate a current buffer in a Lisp program is by calling
+@code{set-buffer}.  The specified buffer remains current until a new one
+is designated.
+When an editing command returns to the editor command loop, the
+command loop designates the buffer displayed in the selected window as
+current, to prevent confusion: the buffer that the cursor is in when
+Emacs reads a command is the buffer that the command will apply to.
+(@xref{Command Loop}.)  Therefore, @code{set-buffer} is not the way to
+switch visibly to a different buffer so that the user can edit it.  For
+this, you must use the functions described in @ref{Displaying Buffers}.
+However, Lisp functions that change to a different current buffer
+should not depend on the command loop to set it back afterwards.
+Editing commands written in XEmacs Lisp can be called from other programs
+as well as from the command loop.  It is convenient for the caller if
+the subroutine does not change which buffer is current (unless, of
+course, that is the subroutine's purpose).  Therefore, you should
+normally use @code{set-buffer} within a @code{save-excursion} that will
+restore the current buffer when your function is done
+(@pxref{Excursions}).  Here is an example, the code for the command
+@code{append-to-buffer} (with the documentation string abridged):
+@example
+@group
+(defun append-to-buffer (buffer start end)
+"Append to specified buffer the text of the region.
+@dots{}"
+(interactive "BAppend to buffer: \nr")
+(let ((oldbuf (current-buffer)))
+(save-excursion
+(set-buffer (get-buffer-create buffer))
+(insert-buffer-substring oldbuf start end))))
+@end group
+@end example
+@noindent
+This function binds a local variable to the current buffer, and then
+@code{save-excursion} records the values of point, the mark, and the
+original buffer.  Next, @code{set-buffer} makes another buffer current.
+Finally, @code{insert-buffer-substring} copies the string from the
+original current buffer to the new current buffer.
+If the buffer appended to happens to be displayed in some window,
+the next redisplay will show how its text has changed.  Otherwise, you
+will not see the change immediately on the screen.  The buffer becomes
+current temporarily during the execution of the command, but this does
+not cause it to be displayed.
+If you make local bindings (with @code{let} or function arguments) for
+a variable that may also have buffer-local bindings, make sure that the
+same buffer is current at the beginning and at the end of the local
+binding's scope.  Otherwise you might bind it in one buffer and unbind
+it in another!  There are two ways to do this.  In simple cases, you may
+see that nothing ever changes the current buffer within the scope of the
+binding.  Otherwise, use @code{save-excursion} to make sure that the
+buffer current at the beginning is current again whenever the variable
+is unbound.
+It is not reliable to change the current buffer back with
+@code{set-buffer}, because that won't do the job if a quit happens while
+the wrong buffer is current.  Here is what @emph{not} to do:
+@example
+@group
+(let (buffer-read-only
+(obuf (current-buffer)))
+(set-buffer @dots{})
+@dots{}
+(set-buffer obuf))
+@end group
+@end example
+@noindent
+Using @code{save-excursion}, as shown below, handles quitting, errors,
+and @code{throw}, as well as ordinary evaluation.
+@example
+@group
+(let (buffer-read-only)
+(save-excursion
+(set-buffer @dots{})
+@dots{}))
+@end group
+@end example
+@defun current-buffer
+This function returns the current buffer.
+@example
+@group
+(current-buffer)
+@result{} #<buffer buffers.texi>
+@end group
+@end example
+@end defun
+@defun set-buffer buffer-or-name
+This function makes @var{buffer-or-name} the current buffer.  It does
+not display the buffer in the currently selected window or in any other
+window, so the user cannot necessarily see the buffer.  But Lisp
+programs can in any case work on it.
+This function returns the buffer identified by @var{buffer-or-name}.
+An error is signaled if @var{buffer-or-name} does not identify an
+existing buffer.
+@end defun
+@node Buffer Names
+@section Buffer Names
+@cindex buffer names
+Each buffer has a unique name, which is a string.  Many of the
+functions that work on buffers accept either a buffer or a buffer name
+as an argument.  Any argument called @var{buffer-or-name} is of this
+sort, and an error is signaled if it is neither a string nor a buffer.
+Any argument called @var{buffer} must be an actual buffer
+object, not a name.
+Buffers that are ephemeral and generally uninteresting to the user
+have names starting with a space, so that the @code{list-buffers} and
+@code{buffer-menu} commands don't mention them.  A name starting with
+space also initially disables recording undo information; see
+@ref{Undo}.
+@defun buffer-name &optional buffer
+This function returns the name of @var{buffer} as a string.  If
+@var{buffer} is not supplied, it defaults to the current buffer.
+If @code{buffer-name} returns @code{nil}, it means that @var{buffer}
+has been killed.  @xref{Killing Buffers}.
+@example
+@group
+(buffer-name)
+@result{} "buffers.texi"
+@end group
+@group
+(setq foo (get-buffer "temp"))
+@result{} #<buffer temp>
+@end group
+@group
+(kill-buffer foo)
+@result{} nil
+@end group
+@group
+(buffer-name foo)
+@result{} nil
+@end group
+@group
+foo
+@result{} #<killed buffer>
+@end group
+@end example
+@end defun
+@deffn Command rename-buffer newname &optional unique
+This function renames the current buffer to @var{newname}.  An error
+is signaled if @var{newname} is not a string, or if there is already a
+buffer with that name.  The function returns @code{nil}.
+@c Emacs 19 feature
+Ordinarily, @code{rename-buffer} signals an error if @var{newname} is
+already in use.  However, if @var{unique} is non-@code{nil}, it modifies
+@var{newname} to make a name that is not in use.  Interactively, you can
+make @var{unique} non-@code{nil} with a numeric prefix argument.
+One application of this command is to rename the @samp{*shell*} buffer
+to some other name, thus making it possible to create a second shell
+buffer under the name @samp{*shell*}.
+@end deffn
+@defun get-buffer buffer-or-name
+This function returns the buffer specified by @var{buffer-or-name}.
+If @var{buffer-or-name} is a string and there is no buffer with that
+name, the value is @code{nil}.  If @var{buffer-or-name} is a buffer, it
+is returned as given.  (That is not very useful, so the argument is usually
+a name.)  For example:
+@example
+@group
+(setq b (get-buffer "lewis"))
+@result{} #<buffer lewis>
+@end group
+@group
+(get-buffer b)
+@result{} #<buffer lewis>
+@end group
+@group
+(get-buffer "Frazzle-nots")
+@result{} nil
+@end group
+@end example
+See also the function @code{get-buffer-create} in @ref{Creating Buffers}.
+@end defun
+@c Emacs 19 feature
+@c IGNORE is only in XEmacs
+@defun generate-new-buffer-name starting-name &optional ignore
+This function returns a name that would be unique for a new buffer---but
+does not create the buffer.  It starts with @var{starting-name}, and
+produces a name not currently in use for any buffer by appending a
+number inside of @samp{<@dots{}>}.
+If @var{ignore} is given, it specifies a name that is okay to use (if it
+is in the sequence to be tried), even if a buffer with that name exists.
+See the related function @code{generate-new-buffer} in @ref{Creating
+Buffers}.
+@end defun
+@node Buffer File Name
+@section Buffer File Name
+@cindex visited file
+@cindex buffer file name
+@cindex file name of buffer
+The @dfn{buffer file name} is the name of the file that is visited in
+that buffer.  When a buffer is not visiting a file, its buffer file name
+is @code{nil}.  Most of the time, the buffer name is the same as the
+nondirectory part of the buffer file name, but the buffer file name and
+the buffer name are distinct and can be set independently.
+@xref{Visiting Files}.
+@defun buffer-file-name &optional buffer
+This function returns the absolute file name of the file that
+@var{buffer} is visiting.  If @var{buffer} is not visiting any file,
+@code{buffer-file-name} returns @code{nil}.  If @var{buffer} is not
+supplied, it defaults to the current buffer.
+@example
+@group
+(buffer-file-name (other-buffer))
+@result{} "/usr/user/lewis/manual/files.texi"
+@end group
+@end example
+@end defun
+@defvar buffer-file-name
+This buffer-local variable contains the name of the file being visited
+in the current buffer, or @code{nil} if it is not visiting a file.  It
+is a permanent local, unaffected by @code{kill-local-variables}.
+@example
+@group
+buffer-file-name
+@result{} "/usr/user/lewis/manual/buffers.texi"
+@end group
+@end example
+It is risky to change this variable's value without doing various other
+things.  See the definition of @code{set-visited-file-name} in
+@file{files.el}; some of the things done there, such as changing the
+buffer name, are not strictly necessary, but others are essential to
+avoid confusing XEmacs.
+@end defvar
+@defvar buffer-file-truename
+This buffer-local variable holds the truename of the file visited in the
+current buffer, or @code{nil} if no file is visited.  It is a permanent
+local, unaffected by @code{kill-local-variables}.  @xref{Truenames}.
+@end defvar
+@defvar buffer-file-number
+This buffer-local variable holds the file number and directory device
+number of the file visited in the current buffer, or @code{nil} if no
+file or a nonexistent file is visited.  It is a permanent local,
+unaffected by @code{kill-local-variables}.  @xref{Truenames}.
+The value is normally a list of the form @code{(@var{filenum}
+@var{devnum})}.  This pair of numbers uniquely identifies the file among
+all files accessible on the system.  See the function
+@code{file-attributes}, in @ref{File Attributes}, for more information
+about them.
+@end defvar
+@defun get-file-buffer filename
+This function returns the buffer visiting file @var{filename}.  If
+there is no such buffer, it returns @code{nil}.  The argument
+@var{filename}, which must be a string, is expanded (@pxref{File Name
+Expansion}), then compared against the visited file names of all live
+buffers.
+@example
+@group
+(get-file-buffer "buffers.texi")
+@result{} #<buffer buffers.texi>
+@end group
+@end example
+In unusual circumstances, there can be more than one buffer visiting
+the same file name.  In such cases, this function returns the first
+such buffer in the buffer list.
+@end defun
+@deffn Command set-visited-file-name filename
+If @var{filename} is a non-empty string, this function changes the
+name of the file visited in current buffer to @var{filename}.  (If the
+buffer had no visited file, this gives it one.)  The @emph{next time}
+the buffer is saved it will go in the newly-specified file.  This
+command marks the buffer as modified, since it does not (as far as XEmacs
+knows) match the contents of @var{filename}, even if it matched the
+former visited file.
+If @var{filename} is @code{nil} or the empty string, that stands for
+``no visited file''.  In this case, @code{set-visited-file-name} marks
+the buffer as having no visited file.
+@c Wordy to avoid overfull hbox.  --rjc 16mar92
+When the function @code{set-visited-file-name} is called interactively, it
+prompts for @var{filename} in the minibuffer.
+See also @code{clear-visited-file-modtime} and
+@code{verify-visited-file-modtime} in @ref{Buffer Modification}.
+@end deffn
+@defvar list-buffers-directory
+This buffer-local variable records a string to display in a buffer
+listing in place of the visited file name, for buffers that don't have a
+visited file name.  Dired buffers use this variable.
+@end defvar
+@node Buffer Modification
+@section Buffer Modification
+@cindex buffer modification
+@cindex modification flag (of buffer)
+XEmacs keeps a flag called the @dfn{modified flag} for each buffer, to
+record whether you have changed the text of the buffer.  This flag is
+set to @code{t} whenever you alter the contents of the buffer, and
+cleared to @code{nil} when you save it.  Thus, the flag shows whether
+there are unsaved changes.  The flag value is normally shown in the
+modeline (@pxref{Modeline Variables}), and controls saving
+(@pxref{Saving Buffers}) and auto-saving (@pxref{Auto-Saving}).
+Some Lisp programs set the flag explicitly.  For example, the function
+@code{set-visited-file-name} sets the flag to @code{t}, because the text
+does not match the newly-visited file, even if it is unchanged from the
+file formerly visited.
+The functions that modify the contents of buffers are described in
+@ref{Text}.
+@defun buffer-modified-p &optional buffer
+This function returns @code{t} if the buffer @var{buffer} has been modified
+since it was last read in from a file or saved, or @code{nil}
+otherwise.  If @var{buffer} is not supplied, the current buffer
+is tested.
+@end defun
+@defun set-buffer-modified-p flag
+This function marks the current buffer as modified if @var{flag} is
+non-@code{nil}, or as unmodified if the flag is @code{nil}.
+Another effect of calling this function is to cause unconditional
+redisplay of the modeline for the current buffer.  In fact, the
+function @code{redraw-modeline} works by doing this:
+@example
+@group
+(set-buffer-modified-p (buffer-modified-p))
+@end group
+@end example
+@end defun
+@c ARG is only in XEmacs
+@deffn Command not-modified &optional arg
+This command marks the current buffer as unmodified, and not needing
+to be saved. (If @var{arg} is non-@code{nil}, the buffer is instead
+marked as modified.) Don't use this function in programs, since it
+prints a message in the echo area; use @code{set-buffer-modified-p}
+(above) instead.
+@end deffn
+@c Emacs 19 feature
+@defun buffer-modified-tick &optional buffer
+This function returns @var{buffer}`s modification-count.  This is a
+counter that increments every time the buffer is modified.  If
+@var{buffer} is @code{nil} (or omitted), the current buffer is used.
+@end defun
+@node Modification Time
+@section Comparison of Modification Time
+@cindex comparison of modification time
+@cindex modification time, comparison of
+Suppose that you visit a file and make changes in its buffer, and
+meanwhile the file itself is changed on disk.  At this point, saving the
+buffer would overwrite the changes in the file.  Occasionally this may
+be what you want, but usually it would lose valuable information.  XEmacs
+therefore checks the file's modification time using the functions
+described below before saving the file.
+@defun verify-visited-file-modtime buffer
+This function compares what @var{buffer} has recorded for the
+modification time of its visited file against the actual modification
+time of the file as recorded by the operating system.  The two should be
+the same unless some other process has written the file since XEmacs
+visited or saved it.
+The function returns @code{t} if the last actual modification time and
+XEmacs's recorded modification time are the same, @code{nil} otherwise.
+@end defun
+@defun clear-visited-file-modtime
+This function clears out the record of the last modification time of
+the file being visited by the current buffer.  As a result, the next
+attempt to save this buffer will not complain of a discrepancy in
+file modification times.
+This function is called in @code{set-visited-file-name} and other
+exceptional places where the usual test to avoid overwriting a changed
+file should not be done.
+@end defun
+@c Emacs 19 feature
+@defun visited-file-modtime
+This function returns the buffer's recorded last file modification time,
+as a list of the form @code{(@var{high} . @var{low})}.  (This is the
+same format that @code{file-attributes} uses to return time values; see
+@ref{File Attributes}.)
+@end defun
+@c Emacs 19 feature
+@defun set-visited-file-modtime &optional time
+This function updates the buffer's record of the last modification time
+of the visited file, to the value specified by @var{time} if @var{time}
+is not @code{nil}, and otherwise to the last modification time of the
+visited file.
+If @var{time} is not @code{nil}, it should have the form
+@code{(@var{high} . @var{low})} or @code{(@var{high} @var{low})}, in
+either case containing two integers, each of which holds 16 bits of the
+time.
+This function is useful if the buffer was not read from the file
+normally, or if the file itself has been changed for some known benign
+reason.
+@end defun
+@defun ask-user-about-supersession-threat filename
+@cindex obsolete buffer
+This function is used to ask a user how to proceed after an attempt to
+modify an obsolete buffer visiting file @var{filename}.  An
+@dfn{obsolete buffer} is an unmodified buffer for which the associated
+file on disk is newer than the last save-time of the buffer.  This means
+some other program has probably altered the file.
+@kindex file-supersession
+Depending on the user's answer, the function may return normally, in
+which case the modification of the buffer proceeds, or it may signal a
+@code{file-supersession} error with data @code{(@var{filename})}, in which
+case the proposed buffer modification is not allowed.
+This function is called automatically by XEmacs on the proper
+occasions.  It exists so you can customize XEmacs by redefining it.
+See the file @file{userlock.el} for the standard definition.
+See also the file locking mechanism in @ref{File Locks}.
+@end defun
+@node Read Only Buffers
+@section Read-Only Buffers
+@cindex read-only buffer
+@cindex buffer, read-only
+If a buffer is @dfn{read-only}, then you cannot change its contents,
+although you may change your view of the contents by scrolling and
+narrowing.
+Read-only buffers are used in two kinds of situations:
+@itemize @bullet
+@item
+A buffer visiting a write-protected file is normally read-only.
+Here, the purpose is to show the user that editing the buffer with the
+aim of saving it in the file may be futile or undesirable.  The user who
+wants to change the buffer text despite this can do so after clearing
+the read-only flag with @kbd{C-x C-q}.
+@item
+Modes such as Dired and Rmail make buffers read-only when altering the
+contents with the usual editing commands is probably a mistake.
+The special commands of these modes bind @code{buffer-read-only} to
+@code{nil} (with @code{let}) or bind @code{inhibit-read-only} to
+@code{t} around the places where they change the text.
+@end itemize
+@defvar buffer-read-only
+This buffer-local variable specifies whether the buffer is read-only.
+The buffer is read-only if this variable is non-@code{nil}.
+@end defvar
+@defvar inhibit-read-only
+If this variable is non-@code{nil}, then read-only buffers and read-only
+characters may be modified.  Read-only characters in a buffer are those
+that have non-@code{nil} @code{read-only} properties (either text
+properties or extent properties).  @xref{Extent Properties}, for more
+information about text properties and extent properties.
+If @code{inhibit-read-only} is @code{t}, all @code{read-only} character
+properties have no effect.  If @code{inhibit-read-only} is a list, then
+@code{read-only} character properties have no effect if they are members
+of the list (comparison is done with @code{eq}).
+@end defvar
+@deffn Command toggle-read-only
+This command changes whether the current buffer is read-only.  It is
+intended for interactive use; don't use it in programs.  At any given
+point in a program, you should know whether you want the read-only flag
+on or off; so you can set @code{buffer-read-only} explicitly to the
+proper value, @code{t} or @code{nil}.
+@end deffn
+@defun barf-if-buffer-read-only
+This function signals a @code{buffer-read-only} error if the current
+buffer is read-only.  @xref{Interactive Call}, for another way to
+signal an error if the current buffer is read-only.
+@end defun
+@node The Buffer List
+@section The Buffer List
+@cindex buffer list
+The @dfn{buffer list} is a list of all live buffers.  Creating a
+buffer adds it to this list, and killing a buffer deletes it.  The order
+of the buffers in the list is based primarily on how recently each
+buffer has been displayed in the selected window.  Buffers move to the
+front of the list when they are selected and to the end when they are
+buried.  Several functions, notably @code{other-buffer}, use this
+ordering.  A buffer list displayed for the user also follows this order.
+@c XEmacs feature
+Every frame has its own order for the buffer list.  Switching to a
+new buffer inside of a particular frame changes the buffer list order
+for that frame, but does not affect the buffer list order of any other
+frames.  In addition, there is a global, non-frame buffer list order
+that is independent of the buffer list orders for any particular frame.
+Note that the different buffer lists all contain the same elements.  It
+is only the order of those elements that is different.
+@defun buffer-list &optional frame
+This function returns a list of all buffers, including those whose
+names begin with a space.  The elements are actual buffers, not their
+names.  The order of the list is specific to @var{frame}, which
+defaults to the current frame.  If @var{frame} is @code{t}, the
+global, non-frame ordering is returned instead.
+@example
+@group
+(buffer-list)
+@result{} (#<buffer buffers.texi>
+#<buffer  *Minibuf-1*> #<buffer buffer.c>
+#<buffer *Help*> #<buffer TAGS>)
+@end group
+@group
+;; @r{Note that the name of the minibuffer}
+;;   @r{begins with a space!}
+(mapcar (function buffer-name) (buffer-list))
+@result{} ("buffers.texi" " *Minibuf-1*"
+"buffer.c" "*Help*" "TAGS")
+@end group
+@end example
+Buffers appear earlier in the list if they were current more recently.
+This list is a copy of a list used inside XEmacs; modifying it has no
+effect on the buffers.
+@end defun
+@defun other-buffer &optional buffer-or-name frame visible-ok
+This function returns the first buffer in the buffer list other than
+@var{buffer-or-name}, in @var{frame}'s ordering for the buffer list.
+(@var{frame} defaults to the current frame.  If @var{frame} is
+@code{t}, then the global, non-frame ordering is used.) Usually this is
+the buffer most recently shown in the selected window, aside from
+@var{buffer-or-name}.  Buffers are moved to the front of the list when
+they are selected and to the end when they are buried.  Buffers whose
+names start with a space are not considered.
+If @var{buffer-or-name} is not supplied (or if it is not a buffer),
+then @code{other-buffer} returns the first buffer on the buffer list
+that is not visible in any window in a visible frame.
+If the selected frame has a non-@code{nil} @code{buffer-predicate}
+parameter, then @code{other-buffer} uses that predicate to decide which
+buffers to consider.  It calls the predicate once for each buffer, and
+if the value is @code{nil}, that buffer is ignored.  @xref{X Frame
+Parameters}.
+@c Emacs 19 feature
+If @var{visible-ok} is @code{nil}, @code{other-buffer} avoids returning
+a buffer visible in any window on any visible frame, except as a last
+resort.   If @var{visible-ok} is non-@code{nil}, then it does not matter
+whether a buffer is displayed somewhere or not.
+If no suitable buffer exists, the buffer @samp{*scratch*} is returned
+(and created, if necessary).
+Note that in FSF Emacs 19, there is no @var{frame} argument, and
+@var{visible-ok} is the second argument instead of the third.
+FSF Emacs 19.
+@end defun
+@deffn Command list-buffers &optional files-only
+This function displays a listing of the names of existing buffers.  It
+clears the buffer @samp{*Buffer List*}, then inserts the listing into
+that buffer and displays it in a window.  @code{list-buffers} is
+intended for interactive use, and is described fully in @cite{The XEmacs
+Reference Manual}.  It returns @code{nil}.
+@end deffn
+@deffn Command bury-buffer &optional buffer-or-name
+This function puts @var{buffer-or-name} at the end of the buffer list
+without changing the order of any of the other buffers on the list.
+This buffer therefore becomes the least desirable candidate for
+@code{other-buffer} to return.
+If @var{buffer-or-name} is @code{nil} or omitted, this means to bury the
+current buffer.  In addition, if the buffer is displayed in the selected
+window, this switches to some other buffer (obtained using
+@code{other-buffer}) in the selected window.  But if the buffer is
+displayed in some other window, it remains displayed there.
+If you wish to replace a buffer in all the windows that display it, use
+@code{replace-buffer-in-windows}.  @xref{Buffers and Windows}.
+@end deffn
+@node Creating Buffers
+@section Creating Buffers
+@cindex creating buffers
+@cindex buffers, creating
+This section describes the two primitives for creating buffers.
+@code{get-buffer-create} creates a buffer if it finds no existing buffer
+with the specified name; @code{generate-new-buffer} always creates a new
+buffer and gives it a unique name.
+Other functions you can use to create buffers include
+@code{with-output-to-temp-buffer} (@pxref{Temporary Displays}) and
+@code{create-file-buffer} (@pxref{Visiting Files}).  Starting a
+subprocess can also create a buffer (@pxref{Processes}).
+@defun get-buffer-create name
+This function returns a buffer named @var{name}.  It returns an existing
+buffer with that name, if one exists; otherwise, it creates a new
+buffer.  The buffer does not become the current buffer---this function
+does not change which buffer is current.
+An error is signaled if @var{name} is not a string.
+@example
+@group
+(get-buffer-create "foo")
+@result{} #<buffer foo>
+@end group
+@end example
+The major mode for the new buffer is set to Fundamental mode.  The
+variable @code{default-major-mode} is handled at a higher level.
+@xref{Auto Major Mode}.
+@end defun
+@defun generate-new-buffer name
+This function returns a newly created, empty buffer, but does not make
+it current.  If there is no buffer named @var{name}, then that is the
+name of the new buffer.  If that name is in use, this function adds
+suffixes of the form @samp{<@var{n}>} to @var{name}, where @var{n} is an
+integer.  It tries successive integers starting with 2 until it finds an
+available name.
+An error is signaled if @var{name} is not a string.
+@example
+@group
+(generate-new-buffer "bar")
+@result{} #<buffer bar>
+@end group
+@group
+(generate-new-buffer "bar")
+@result{} #<buffer bar<2>>
+@end group
+@group
+(generate-new-buffer "bar")
+@result{} #<buffer bar<3>>
+@end group
+@end example
+The major mode for the new buffer is set to Fundamental mode.  The
+variable @code{default-major-mode} is handled at a higher level.
+@xref{Auto Major Mode}.
+See the related function @code{generate-new-buffer-name} in @ref{Buffer
+Names}.
+@end defun
+@node Killing Buffers
+@section Killing Buffers
+@cindex killing buffers
+@cindex buffers, killing
+@dfn{Killing a buffer} makes its name unknown to XEmacs and makes its
+text space available for other use.
+The buffer object for the buffer that has been killed remains in
+existence as long as anything refers to it, but it is specially marked
+so that you cannot make it current or display it.  Killed buffers retain
+their identity, however; two distinct buffers, when killed, remain
+distinct according to @code{eq}.
+If you kill a buffer that is current or displayed in a window, XEmacs
+automatically selects or displays some other buffer instead.  This means
+that killing a buffer can in general change the current buffer.
+Therefore, when you kill a buffer, you should also take the precautions
+associated with changing the current buffer (unless you happen to know
+that the buffer being killed isn't current).  @xref{Current Buffer}.
+If you kill a buffer that is the base buffer of one or more indirect
+buffers, the indirect buffers are automatically killed as well.
+The @code{buffer-name} of a killed buffer is @code{nil}.  To test
+whether a buffer has been killed, you can either use this feature
+or the function @code{buffer-live-p}.
+@defun buffer-live-p buffer
+This function returns @code{nil} if @var{buffer} is deleted, and
+@code{t} otherwise.
+@end defun
+@deffn Command kill-buffer buffer-or-name
+This function kills the buffer @var{buffer-or-name}, freeing all its
+memory for use as space for other buffers.  (Emacs version 18 and older
+was unable to return the memory to the operating system.)  It returns
+@code{nil}.
+Any processes that have this buffer as the @code{process-buffer} are
+sent the @code{SIGHUP} signal, which normally causes them to terminate.
+(The basic meaning of @code{SIGHUP} is that a dialup line has been
+disconnected.)  @xref{Deleting Processes}.
+If the buffer is visiting a file and contains unsaved changes,
+@code{kill-buffer} asks the user to confirm before the buffer is killed.
+It does this even if not called interactively.  To prevent the request
+for confirmation, clear the modified flag before calling
+@code{kill-buffer}.  @xref{Buffer Modification}.
+Killing a buffer that is already dead has no effect.
+@smallexample
+(kill-buffer "foo.unchanged")
+@result{} nil
+(kill-buffer "foo.changed")
+---------- Buffer: Minibuffer ----------
+Buffer foo.changed modified; kill anyway? (yes or no) @kbd{yes}
+---------- Buffer: Minibuffer ----------
+@result{} nil
+@end smallexample
+@end deffn
+@defvar kill-buffer-query-functions
+After confirming unsaved changes, @code{kill-buffer} calls the functions
+in the list @code{kill-buffer-query-functions}, in order of appearance,
+with no arguments.  The buffer being killed is the current buffer when
+they are called.  The idea is that these functions ask for confirmation
+from the user for various nonstandard reasons.  If any of them returns
+@code{nil}, @code{kill-buffer} spares the buffer's life.
+@end defvar
+@defvar kill-buffer-hook
+This is a normal hook run by @code{kill-buffer} after asking all the
+questions it is going to ask, just before actually killing the buffer.
+The buffer to be killed is current when the hook functions run.
+@xref{Hooks}.
+@end defvar
+@defvar buffer-offer-save
+This variable, if non-@code{nil} in a particular buffer, tells
+@code{save-buffers-kill-emacs} and @code{save-some-buffers} to offer to
+save that buffer, just as they offer to save file-visiting buffers.  The
+variable @code{buffer-offer-save} automatically becomes buffer-local
+when set for any reason.  @xref{Buffer-Local Variables}.
+@end defvar
+@node Indirect Buffers
+@section Indirect Buffers
+@cindex indirect buffers
+@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 among files.  The base
+buffer may not itself be an indirect buffer.
+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.  This includes the text properties as well as the characters
+themselves.
+But in all other respects, the indirect buffer and its base buffer are
+completely separate.  They have different names, different values of
+point, different narrowing, different markers and overlays (though
+inserting or deleting text in either buffer relocates the markers and
+overlays for both), 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 an indirect buffer has no effect on its base buffer.  Killing
+the base buffer effectively kills the indirect buffer in that it cannot
+ever again be the current buffer.
+@deffn Command make-indirect-buffer base-buffer name
+This creates an indirect buffer named @var{name} whose base buffer
+is @var{base-buffer}.  The argument @var{base-buffer} may be a buffer
+or a string.
+If @var{base-buffer} is an indirect buffer, its base buffer is used as
+the base for the new buffer.
+@end deffn
+@defun buffer-base-buffer buffer
+This function returns the base buffer of @var{buffer}.  If @var{buffer}
+is not indirect, the value is @code{nil}.  Otherwise, the value is
+another buffer, which is never an indirect buffer.
+@end defun

Mercurial > hg > xemacs-beta

comparison man/lispref/buffers.texi @ 0:376386a54a3c r19-14