emacs/doc/emacs/killing.texi

@c This is part of the Emacs manual.
@c Copyright (C) 1985--1987, 1993--1995, 1997, 2000--2024 Free Software
@c Foundation, Inc.
@c See file emacs.texi for copying conditions.

@node Killing
@chapter Killing and Moving Text

  In Emacs, @dfn{killing} means erasing text and copying it into the
@dfn{kill ring}.  @dfn{Yanking} means bringing text from the kill ring
back into the buffer.  (Some applications use the terms ``cutting''
and ``pasting'' for similar operations.)  The kill ring is so-named
because it can be visualized as a set of blocks of text arranged in a
ring, which you can access in cyclic order.  @xref{Kill Ring}.

  Killing and yanking are the most common way to move or copy text
within Emacs.  It is very versatile, because there are commands for
killing many different types of syntactic units.

@menu
* Deletion and Killing:: Commands that remove text.
* Yanking::              Commands that insert text.
* Cut and Paste::        Clipboard and selections on graphical displays.
* Accumulating Text::    Other methods to add text to the buffer.
* Rectangles::           Operating on text in rectangular areas.
* CUA Bindings::         Using @kbd{C-x}/@kbd{C-c}/@kbd{C-v} to kill and yank.
@end menu

@node Deletion and Killing
@section Deletion and Killing

@cindex killing text
@cindex cutting text
@cindex deletion
  Most commands which erase text from the buffer save it in the kill
ring (@pxref{Kill Ring}).  These are known as @dfn{kill} commands, and
their names normally contain the word @samp{kill} (e.g.,
@code{kill-line}).  The kill ring stores several recent kills, not
just the last one, so killing is a very safe operation: you don't have
to worry much about losing text that you previously killed.  The kill
ring is shared by all buffers, so text that is killed in one buffer
can be yanked into another buffer.

  When you use @kbd{C-/} (@code{undo}) to undo a kill command
(@pxref{Undo}), that brings the killed text back into the buffer, but
does not remove it from the kill ring.

  On graphical displays, killing text also copies it to the system
clipboard.  @xref{Cut and Paste}.

  Commands that erase text but do not save it in the kill ring are
known as @dfn{delete} commands; their names usually contain the word
@samp{delete}.  These include @kbd{C-d} (@code{delete-char}) and
@key{DEL} (@code{delete-backward-char}), which delete only one
character at a time, and those commands that delete only spaces or
newlines.  Commands that can erase significant amounts of nontrivial
data generally do a kill operation instead.

  You can also use the mouse to kill and yank.  @xref{Cut and Paste}.

@menu
* Deletion::            Commands for deleting small amounts of text and
                          blank areas.
* Killing by Lines::    How to kill entire lines of text at one time.
* Other Kill Commands:: Commands to kill large regions of text and
                          syntactic units such as words and sentences.
* Kill Options::        Options that affect killing.
@end menu

@node Deletion
@subsection Deletion
@findex delete-backward-char
@findex delete-char

  Deletion means erasing text and not saving it in the kill ring.  For
the most part, the Emacs commands that delete text are those that
erase just one character or only whitespace.

@table @kbd
@item @key{DEL}
@itemx @key{BACKSPACE}
Delete the previous character, or the text in the region if it is
active (@code{delete-backward-char}).

@item @key{Delete}
Delete the next character, or the text in the region if it is active
(@code{delete-forward-char}).

@item C-d
Delete the next character (@code{delete-char}).

@item M-\
Delete spaces and tabs around point (@code{delete-horizontal-space}).
@item M-x just-one-space
Delete spaces and tabs around point, leaving one space.
@item M-@key{SPC}
Delete spaces and tabs around point in flexible ways
(@code{cycle-spacing}).
@item C-x C-o
Delete blank lines around the current line (@code{delete-blank-lines}).
@item M-^
Join two lines by deleting the intervening newline, along with any
indentation following it (@code{delete-indentation}).
@end table

  We have already described the basic deletion commands @key{DEL}
(@code{delete-backward-char}), @key{delete}
(@code{delete-forward-char}), and @kbd{C-d} (@code{delete-char}).
@xref{Erasing}.  With a numeric argument, they delete the specified
number of characters.  If the numeric argument is omitted or one,
@key{DEL} and @key{delete} delete all the text in the region if it is
active (@pxref{Using Region}).

@kindex M-\
@findex delete-horizontal-space
The other delete commands are those that delete only whitespace
characters: spaces, tabs and newlines.  @kbd{M-\}
(@code{delete-horizontal-space}) deletes all the spaces and tab
characters before and after point.  With a prefix argument, this only
deletes spaces and tab characters before point.

@findex just-one-space
@kbd{M-x just-one-space} deletes tabs and spaces around point, but
leaves a single space before point, regardless of the number of spaces
that existed previously (even if there were none before).  With a
numeric argument @var{n}, it leaves @var{n} spaces before point if
@var{n} is positive; if @var{n} is negative, it deletes newlines in
addition to spaces and tabs, leaving @minus{}@var{n} spaces before
point.

@kindex M-SPC
@findex cycle-spacing
@vindex cycle-spacing-actions
The command @code{cycle-spacing} (@kbd{M-@key{SPC}}) acts like a more
flexible version of @code{just-one-space}.  It performs different
space cleanup actions defined by @code{cycle-spacing-actions}, in a
cyclic manner, if you call it repeatedly in succession.  By default,
the first invocation does the same as @code{just-one-space}, the
second deletes all whitespace characters around point like
@code{delete-horizontal-space}, and the third restores the original
whitespace characters; then it cycles.  If invoked with a prefix
argument, each action is given that value of the argument.  The user
option @code{cycle-spacing-actions} can include other members; see the
doc string of that option for the details.

  @kbd{C-x C-o} (@code{delete-blank-lines}) deletes all blank lines
after the current line.  If the current line is blank, it deletes all
blank lines preceding the current line as well (leaving one blank line,
the current line).  On a solitary blank line, it deletes that line.

  @kbd{M-^} (@code{delete-indentation}) joins the current line and the
previous line, by deleting a newline and all surrounding spaces, usually
leaving a single space.  @xref{Indentation,M-^}.

@c Not really sure where to put this...
@findex delete-duplicate-lines
  The command @code{delete-duplicate-lines} searches the region for
identical lines, and removes all but one copy of each.  Normally it
keeps the first instance of each repeated line, but with a @kbd{C-u}
prefix argument it keeps the last.  With a @kbd{C-u C-u} prefix
argument, it only searches for adjacent identical lines.  This is a
more efficient mode of operation, useful when the lines have already
been sorted.  With a @kbd{C-u C-u C-u} prefix argument, it retains
repeated blank lines.

@node Killing by Lines
@subsection Killing by Lines

@table @kbd
@item C-k
Kill rest of line or one or more lines (@code{kill-line}).
@item C-S-backspace
Kill an entire line at once (@code{kill-whole-line})
@end table

@kindex C-k
@findex kill-line
  The simplest kill command is @kbd{C-k} (@code{kill-line}).  If used
at the end of a line, it kills the line-ending newline character,
merging the next line into the current one (thus, a blank line is
entirely removed).  Otherwise, @kbd{C-k} kills all the text from point
up to the end of the line; if point was originally at the beginning of
the line, this leaves the line blank.

  Spaces and tabs at the end of the line are ignored when deciding
which case applies.  As long as point is after the last non-whitespace
character in the line, you can be sure that @kbd{C-k} will kill the
newline.  To kill an entire non-blank line, go to the beginning and
type @kbd{C-k} twice.

  In this context, ``line'' means a logical text line, not a screen
line (@pxref{Continuation Lines}).

  When @kbd{C-k} is given a positive argument @var{n}, it kills
@var{n} lines and the newlines that follow them (text on the current
line before point is not killed).  With a negative argument
@minus{}@var{n}, it kills @var{n} lines preceding the current line,
together with the text on the current line before point.  @kbd{C-k}
with an argument of zero kills the text before point on the current
line.

@vindex kill-whole-line
  If the variable @code{kill-whole-line} is non-@code{nil}, @kbd{C-k} at
the very beginning of a line kills the entire line including the
following newline.  This variable is normally @code{nil}.

@kindex C-S-backspace
@findex kill-whole-line
  @kbd{C-S-backspace} (@code{kill-whole-line}) kills a whole line
including its newline, regardless of the position of point within the
line.  Note that many text terminals will prevent you from typing the
key sequence @kbd{C-S-backspace}.

@node Other Kill Commands
@subsection Other Kill Commands

@table @kbd
@item C-w
Kill the region (@code{kill-region}).
@item M-w
Copy the region into the kill ring (@code{kill-ring-save}).
@item M-d
Kill the next word (@code{kill-word}).  @xref{Words}.
@item M-@key{DEL}
Kill one word backwards (@code{backward-kill-word}).
@item C-x @key{DEL}
Kill back to beginning of sentence (@code{backward-kill-sentence}).
@xref{Sentences}.
@item M-k
Kill to the end of the sentence (@code{kill-sentence}).
@item C-M-k
Kill the following balanced expression (@code{kill-sexp}).  @xref{Expressions}.
@item M-z @var{char}
Kill through the next occurrence of @var{char} (@code{zap-to-char}).
@item M-x zap-up-to-char @var{char}
Kill up to, but not including, the next occurrence of @var{char}.
@end table

@kindex C-w
@findex kill-region
@kindex M-w
@findex kill-ring-save
  One of the commonly-used kill commands is @kbd{C-w}
(@code{kill-region}), which kills the text in the region
(@pxref{Mark}).  Similarly, @kbd{M-w} (@code{kill-ring-save}) copies
the text in the region into the kill ring without removing it from the
buffer.  If the mark is inactive when you type @kbd{C-w} or @kbd{M-w},
the command acts on the text between point and where you last set the
mark (@pxref{Using Region}).

  Emacs also provides commands to kill specific syntactic units:
words, with @kbd{M-@key{DEL}} and @kbd{M-d} (@pxref{Words}); balanced
expressions, with @kbd{C-M-k} (@pxref{Expressions}); and sentences,
with @kbd{C-x @key{DEL}} and @kbd{M-k} (@pxref{Sentences}).

@kindex M-z
@findex zap-to-char
  The command @kbd{M-z} (@code{zap-to-char}) combines killing with
searching: it reads a character and kills from point up to (and
including) the next occurrence of that character in the buffer.  A
numeric argument acts as a repeat count; a negative argument means to
search backward and kill text before point.  A history of previously
used characters is maintained and can be accessed via the
@kbd{M-p}/@kbd{M-n} keystrokes.  This is mainly useful if the
character to be used has to be entered via a complicated input method.
@findex zap-up-to-char
A similar command @code{zap-up-to-char} kills from point up to, but
not including the next occurrence of a character, with numeric
argument acting as a repeat count.

@node Kill Options
@subsection Options for Killing

@vindex kill-read-only-ok
@cindex read-only text, killing
  Some specialized buffers contain @dfn{read-only text}, which cannot
be modified and therefore cannot be killed.  The kill commands work
specially in a read-only buffer: they move over text and copy it to
the kill ring, without actually deleting it from the buffer.
Normally, they also beep and display an error message when this
happens.  But if you set the variable @code{kill-read-only-ok} to a
non-@code{nil} value, they just print a message in the echo area to
explain why the text has not been erased.

@vindex kill-transform-function
  Before saving the kill to the kill ring, you can transform the
string using @code{kill-transform-function}.  It's called with the
string to be killed, and it should return the string you want to be
saved.  It can also return @code{nil}, in which case the string won't
be saved to the kill ring.  For instance, if you never want to save
a pure white space string to the kill ring, you can say:

@lisp
(setq kill-transform-function
      (lambda (string)
        (and (not (string-blank-p string))
             string)))
@end lisp

@vindex kill-do-not-save-duplicates
  If you change the variable @code{kill-do-not-save-duplicates} to a
non-@code{nil} value, identical subsequent kills yield a single
kill-ring entry, without duplication.

@node Yanking
@section Yanking
@cindex moving text
@cindex copying text
@cindex kill ring
@cindex yanking
@cindex pasting

  @dfn{Yanking} means reinserting text previously killed.  The usual
way to move or copy text is to kill it and then yank it elsewhere.

@table @kbd
@item C-y
Yank the last kill into the buffer, at point (@code{yank}).
@item M-y
Either replace the text just yanked with an earlier batch of killed
text (@code{yank-pop}), or allow selecting from the list of
previously-killed batches of text.  @xref{Earlier Kills}.
@item C-M-w
Cause the following command, if it is a kill command, to append to the
previous kill (@code{append-next-kill}).  @xref{Appending Kills}.
@end table

@kindex C-y
@findex yank
  The basic yanking command is @kbd{C-y} (@code{yank}).  It inserts
the most recent kill, leaving the cursor at the end of the inserted
text.  It also sets the mark at the beginning of the inserted text,
without activating the mark; this lets you jump easily to that
position, if you wish, with @kbd{C-u C-@key{SPC}} (@pxref{Mark Ring}).

  With a plain prefix argument (@kbd{C-u C-y}), the command instead
leaves the cursor in front of the inserted text, and sets the mark at
the end.  Using any other prefix argument specifies an earlier kill;
e.g., @kbd{C-u 4 C-y} reinserts the fourth most recent kill.
@xref{Earlier Kills}.

  On graphical displays and on capable text-mode displays, @kbd{C-y}
first checks if another application has placed any text in the system
clipboard more recently than the last Emacs kill.  If so, it inserts
the clipboard's text instead.  Thus, Emacs effectively treats ``cut''
or ``copy'' clipboard operations performed in other applications like
Emacs kills, except that they are not recorded in the kill ring.
@xref{Cut and Paste}, for details.

@menu
* Kill Ring::           Where killed text is stored.
* Earlier Kills::       Yanking something killed some time ago.
* Appending Kills::     Several kills in a row all yank together.
@end menu

@node Kill Ring
@subsection The Kill Ring

  The @dfn{kill ring} is a list of blocks of text that were previously
killed.  There is only one kill ring, shared by all buffers, so you
can kill text in one buffer and yank it in another buffer.  This is
the usual way to move text from one buffer to another.  (There are
several other methods: for instance, you could store the text in a
register; see @ref{Registers}.  @xref{Accumulating Text}, for some
other ways to move text around.)

@vindex kill-ring-max
  The maximum number of entries in the kill ring is controlled by the
variable @code{kill-ring-max}.  The default is 120.  If you make a new
kill when this limit has been reached, Emacs makes room by deleting
the oldest entry in the kill ring.

@vindex kill-ring
  The actual contents of the kill ring are stored in a variable named
@code{kill-ring}; you can view the entire contents of the kill ring
with @kbd{C-h v kill-ring}.

@node Earlier Kills
@subsection Yanking Earlier Kills
@cindex yanking previous kills

  As explained in @ref{Yanking}, you can use a numeric argument to
@kbd{C-y} to yank text that is no longer the most recent kill.  This
is useful if you remember which kill ring entry you want.  If you
don't, you can use the @kbd{M-y} (@code{yank-pop}) command to cycle
through the possibilities or to select one of the earlier kills.

@kindex M-y
@findex yank-pop
  If the previous command was a yank command, @kbd{M-y} takes the text
that was yanked and replaces it with the text from an earlier kill.
So, to recover the text of the next-to-the-last kill, first use
@kbd{C-y} to yank the last kill, and then use @kbd{M-y} to replace it
with the previous kill.  This works only after a @kbd{C-y}
or another @kbd{M-y}.  (If @kbd{M-y} is invoked after some other
command, it works differently, see below.)

  You can understand this operation mode of @kbd{M-y} in terms of a
last-yank pointer which points at an entry in the kill ring.  Each
time you kill, the last-yank pointer moves to the newly made entry at
the front of the ring.  @kbd{C-y} yanks the entry which the last-yank
pointer points to.  @kbd{M-y} after a @kbd{C-y} or another @kbd{M-y}
moves the last-yank pointer to the previous entry, and the text in the
buffer changes to match.  Enough @kbd{M-y} commands one after another
can move the pointer to any entry in the ring, so you can get any
entry into the buffer.  Eventually the pointer reaches the end of the
ring; the next @kbd{M-y} loops back around to the first entry again.

  @kbd{M-y} moves the last-yank pointer around the ring, but it does
not change the order of the entries in the ring, which always runs from
the most recent kill at the front to the oldest one still remembered.

  When used after @kbd{C-y} or @kbd{M-y}, @kbd{M-y} can take a numeric
argument, which tells it how many entries to advance the last-yank
pointer by.  A negative argument moves the pointer toward the front of
the ring; from the front of the ring, it moves around to the last
entry and continues forward from there.

  Once the text you are looking for is brought into the buffer, you
can stop doing @kbd{M-y} commands and the last yanked text will stay
there.  It's just a copy of the kill ring entry, so editing it in the
buffer does not change what's in the ring.  As long as no new killing
is done, the last-yank pointer remains at the same place in the kill
ring, so repeating @kbd{C-y} will yank another copy of the same
previous kill.

  When you call @kbd{C-y} with a numeric argument, that also sets the
last-yank pointer to the entry that it yanks.

  You can also invoke @kbd{M-y} after a command that is not a yank
command.  In that case, @kbd{M-y} prompts you in the minibuffer for
one of the previous kills.  You can use the minibuffer history
commands (@pxref{Minibuffer History}) to navigate or search through
the entries in the kill ring until you find the one you want to
reinsert.  Or you can use completion commands (@pxref{Completion
Commands}) to complete on an entry from the list of entries in the
kill ring or pop up the @file{*Completions*} buffer with the candidate
entries from which you can choose.  After selecting the kill-ring
entry, you can optionally edit it in the minibuffer.  Finally, type
@kbd{RET} to exit the minibuffer and insert the text of the selected
kill-ring entry.  Like in case of @kbd{M-y} after another yank
command, the last-yank pointer is left pointing at the text you just
yanked, whether it is one of the previous kills or an entry from the
kill-ring that you edited before inserting it.  (In the latter case,
the edited entry is added to the front of the kill-ring.)  So here,
too, typing @kbd{C-y} will yank another copy of the text just
inserted.

  When invoked with a plain prefix argument (@kbd{C-u M-y}) after a
command that is not a yank command, @kbd{M-y} leaves the cursor in
front of the inserted text, and sets the mark at the end, like
@kbd{C-y} does.

@node Appending Kills
@subsection Appending Kills

@cindex appending kills in the ring
  Normally, each kill command pushes a new entry onto the kill ring.
However, two or more kill commands in a row combine their text into a
single entry, so that a single @kbd{C-y} yanks all the text as a unit,
just as it was before it was killed.

  Thus, if you want to yank text as a unit, you need not kill all of it
with one command; you can keep killing line after line, or word after
word, until you have killed it all, and you can still get it all back at
once.

  Commands that kill forward from point add onto the end of the previous
killed text.  Commands that kill backward from point add text onto the
beginning.  This way, any sequence of mixed forward and backward kill
commands puts all the killed text into one entry without rearrangement.
Numeric arguments do not break the sequence of appending kills.  For
example, suppose the buffer contains this text:

@example
This is a line @point{}of sample text.
@end example

@noindent
with point shown by @point{}.  If you type @kbd{M-d M-@key{DEL} M-d
M-@key{DEL}}, killing alternately forward and backward, you end up with
@samp{a line of sample} as one entry in the kill ring, and
@w{@samp{This is@ @ text.}} in the buffer.  (Note the double space
between @samp{is} and @samp{text}, which you can clean up with
@kbd{M-@key{SPC}} or @kbd{M-q}.)

  Another way to kill the same text is to move back two words with
@kbd{M-b M-b}, then kill all four words forward with @kbd{C-u M-d}.
This produces exactly the same results in the buffer and in the kill
ring.  @kbd{M-f M-f C-u M-@key{DEL}} kills the same text, all going
backward; once again, the result is the same.  The text in the kill ring
entry always has the same order that it had in the buffer before you
killed it.

@kindex C-M-w
@findex append-next-kill
  If a kill command is separated from the last kill command by other
commands (not just numeric arguments), it starts a new entry on the
kill ring.  But you can force it to combine with the last killed text,
by typing @kbd{C-M-w} (@code{append-next-kill}) right beforehand.  The
@kbd{C-M-w} tells its following command, if it is a kill command, to
treat the kill as part of the sequence of previous kills.  As usual,
the kill is appended to the previous killed text if the command kills
forward, and prepended if the command kills backward.  In this way,
you can kill several separated pieces of text and accumulate them to
be yanked back in one place.

  A kill command following @kbd{M-w} (@code{kill-ring-save}) does not
append to the text that @kbd{M-w} copied into the kill ring.

@node Cut and Paste
@section ``Cut and Paste'' Operations on Graphical Displays
@cindex cut
@cindex copy
@cindex paste

  In most graphical desktop environments, you can transfer data
(usually text) between different applications using a system facility
called the @dfn{clipboard}.  On X, two other similar facilities are
available: the primary selection and the secondary selection.  When
Emacs is run on a graphical display, its kill and yank commands
integrate with these facilities, so that you can easily transfer text
between Emacs and other graphical applications.

  By default, Emacs uses UTF-8 as the coding system for inter-program
text transfers.  If you find that the pasted text is not what you
expected, you can specify another coding system by typing @kbd{C-x
@key{RET} x} or @kbd{C-x @key{RET} X}.  You can also request a
different data type by customizing @code{x-select-request-type}.
@xref{Communication Coding}.

@menu
* Clipboard::           How Emacs uses the system clipboard.
* Primary Selection::   The temporarily selected text selection.
* Secondary Selection:: Cutting without altering point and mark.
@end menu

@node Clipboard
@subsection Using the Clipboard
@cindex clipboard

  The @dfn{clipboard} is the facility that most graphical applications
use for ``cutting and pasting''.  When the clipboard exists, the kill
and yank commands in Emacs make use of it.

  When you kill some text with a command such as @kbd{C-w}
(@code{kill-region}), or copy it to the kill ring with a command such
as @kbd{M-w} (@code{kill-ring-save}), that text is also put in the
clipboard.

@vindex save-interprogram-paste-before-kill
  When an Emacs kill command puts text in the clipboard, the existing
clipboard contents are normally lost.  Optionally, Emacs can save the
existing clipboard contents to the kill ring, preventing you from
losing the old clipboard data.  If
@code{save-interprogram-paste-before-kill} has been set to a number,
then the data is copied over if it's smaller (in characters) than
this number.  If this variable is any other non-@code{nil} value, the
data is always copied over---at the risk of high memory consumption if
that data turns out to be large.

  Yank commands, such as @kbd{C-y} (@code{yank}), also use the
clipboard.  If another application ``owns'' the clipboard---i.e., if
you cut or copied text there more recently than your last kill command
in Emacs---then Emacs yanks from the clipboard instead of the kill
ring.

@vindex yank-pop-change-selection
  Normally, rotating the kill ring with @kbd{M-y} (@code{yank-pop})
does not alter the clipboard.  However, if you change
@code{yank-pop-change-selection} to @code{t}, then @kbd{M-y} saves the
new yank to the clipboard.

@vindex select-enable-clipboard
  To prevent kill and yank commands from accessing the clipboard,
change the variable @code{select-enable-clipboard} to @code{nil}.

@findex yank-media
  Programs can put other things than plain text on the clipboard.  For
instance, a web browser will usually let you choose ``Copy Image'' on
images, and this image will be put on the clipboard.  On capable
platforms, Emacs can yank these objects with the @code{yank-media}
command---but only in modes that have support for it (@pxref{Yanking
Media,,, elisp, The Emacs Lisp Reference Manual}).

@cindex clipboard manager
@vindex x-select-enable-clipboard-manager
  Many X desktop environments support a feature called the
@dfn{clipboard manager}.  If you exit Emacs while it is the current
``owner'' of the clipboard data, and there is a clipboard manager
running, Emacs transfers the clipboard data to the clipboard manager
so that it is not lost.  In some circumstances, this may cause a delay
when exiting Emacs; if you wish to prevent Emacs from transferring
data to the clipboard manager, change the variable
@code{x-select-enable-clipboard-manager} to @code{nil}.

  Since strings containing NUL bytes are usually truncated when passed
through the clipboard, Emacs replaces such characters with ``\0''
before transferring them to the system's clipboard.

@vindex select-enable-primary
@findex clipboard-kill-region
@findex clipboard-kill-ring-save
@findex clipboard-yank
  Prior to Emacs 24, the kill and yank commands used the primary
selection (@pxref{Primary Selection}), not the clipboard.  If you
prefer this behavior, change @code{select-enable-clipboard} to
@code{nil}, @code{select-enable-primary} to @code{t}, and
@code{mouse-drag-copy-region} to @code{t}.  In this case, you can use
the following commands to act explicitly on the clipboard:
@code{clipboard-kill-region} kills the region and saves it to the
clipboard; @code{clipboard-kill-ring-save} copies the region to the
kill ring and saves it to the clipboard; and @code{clipboard-yank}
yanks the contents of the clipboard at point.

@node Primary Selection
@subsection Cut and Paste with Other Window Applications
@cindex X cutting and pasting
@cindex X selection
@cindex primary selection
@cindex selection, primary

  Under the X Window System, PGTK and Haiku, there exists a
@dfn{primary selection} containing the last stretch of text selected
in an X application (usually by dragging the mouse).  Typically, this
text can be inserted into other X applications by @kbd{mouse-2}
clicks.  The primary selection is separate from the clipboard.  Its
contents are more fragile; they are overwritten each time you select
text with the mouse, whereas the clipboard is only overwritten by
explicit cut or copy commands.

  Under X, whenever the region is active (@pxref{Mark}), the text in
the region is saved in the primary selection.  This applies regardless
of whether the region was made by dragging or clicking the mouse
(@pxref{Mouse Commands}), or by keyboard commands (e.g., by typing
@kbd{C-@key{SPC}} and moving point; @pxref{Setting Mark}).

@vindex select-active-regions
  If you change the variable @code{select-active-regions} to
@code{only}, Emacs saves only temporarily active regions to the
primary selection, i.e., those made with the mouse or with shift
selection (@pxref{Shift Selection}).  If you change
@code{select-active-regions} to @code{nil}, Emacs avoids saving active
regions to the primary selection entirely.

  To insert the primary selection into an Emacs buffer, click
@kbd{mouse-2} (@code{mouse-yank-primary}) where you want to insert it.
@xref{Mouse Commands}.  You can also use the normal Emacs yank command
(@kbd{C-y}) to insert this text if @code{select-enable-primary} is set
(@pxref{Clipboard}).

@cindex lost-selection-mode
  By default, Emacs keeps the region active even after text is
selected in another program; this is contrary to typical X behavior.
To make Emacs deactivate the region after another program places data
in the primary selection, enable the global minor mode
@code{lost-selection-mode}.

@cindex MS-Windows, and primary selection
  MS-Windows provides no primary selection, but Emacs emulates it
within a single Emacs session by storing the selected text internally.
Therefore, all the features and commands related to the primary
selection work on Windows as they do on X, for cutting and pasting
within the same session, but not across Emacs sessions or with other
applications.

@node Secondary Selection
@subsection Secondary Selection
@cindex secondary selection

  In addition to the primary selection, the X Window System provides a
second similar facility known as the @dfn{secondary selection}.
Nowadays, few X applications make use of the secondary selection, but
you can access it using the following Emacs commands:

@table @kbd
@findex mouse-set-secondary
@kindex M-Drag-mouse-1
@cindex @code{secondary-selection} face
@item M-Drag-mouse-1
Set the secondary selection, with one end at the place where you press
down the button, and the other end at the place where you release it
(@code{mouse-set-secondary}).  The selected text is highlighted, using
the @code{secondary-selection} face, as you drag.  The window scrolls
automatically if you drag the mouse off the top or bottom of the
window, just like @code{mouse-set-region} (@pxref{Mouse Commands}).

This command does not alter the kill ring.

@findex mouse-start-secondary
@kindex M-mouse-1
@item M-mouse-1
Set one endpoint for the @dfn{secondary selection}
(@code{mouse-start-secondary}); use @kbd{M-mouse-3} to set the other
end and complete the selection.  This command cancels any existing
secondary selection, when it starts a new one.

@findex mouse-secondary-save-then-kill
@kindex M-mouse-3
@item M-mouse-3
Set the secondary selection (@code{mouse-secondary-save-then-kill}),
with one end at the position you click @kbd{M-mouse-3}, and the other
at the position specified previously with @kbd{M-mouse-1}.  This also
puts the selected text in the kill ring.  A second @kbd{M-mouse-3} at
the same place kills the text selected by the secondary selection just
made.

@findex mouse-yank-secondary
@kindex M-mouse-2
@item M-mouse-2
Insert the secondary selection where you click, placing point at the
end of the yanked text (@code{mouse-yank-secondary}).
@end table

Double or triple clicking of @kbd{M-mouse-1} operates on words and
lines, much like @kbd{mouse-1}.

If @code{mouse-yank-at-point} is non-@code{nil}, @kbd{M-mouse-2} yanks
at point.  Then it does not matter precisely where you click, or even
which of the frame's windows you click on.  @xref{Mouse Commands}.
This user option also effects interactive search: if it is
non-@code{nil}, yanking with the mouse anywhere in the frame will add
the text to the search string.

@node Accumulating Text
@section Accumulating Text
@findex append-to-buffer
@findex prepend-to-buffer
@findex copy-to-buffer
@findex append-to-file

@cindex accumulating scattered text
  Usually we copy or move text by killing it and yanking it, but there
are other convenient methods for copying one block of text in many
places, or for copying many scattered blocks of text into one place.
Here we describe the commands to accumulate scattered pieces of text
into a buffer or into a file.

@table @kbd
@item M-x append-to-buffer
Append region to the contents of a specified buffer.
@item M-x prepend-to-buffer
Prepend region to the contents of a specified buffer.
@item M-x copy-to-buffer
Copy region into a specified buffer, deleting that buffer's old contents.
@item M-x insert-buffer
Insert the contents of a specified buffer into current buffer at point.
@item M-x append-to-file
Append region to the contents of a specified file, at the end.
@end table

  To accumulate text into a buffer, use @kbd{M-x append-to-buffer}.
This reads a buffer name, then inserts a copy of the region into the
buffer specified.  If you specify a nonexistent buffer,
@code{append-to-buffer} creates the buffer.  The text is inserted
wherever point is in that buffer.  If you have been using the buffer for
editing, the copied text goes into the middle of the text of the buffer,
starting from wherever point happens to be at that moment.

  Point in that buffer is left at the end of the copied text, so
successive uses of @code{append-to-buffer} accumulate the text in the
specified buffer in the same order as they were copied.  Strictly
speaking, @code{append-to-buffer} does not always append to the text
already in the buffer---it appends only if point in that buffer is at
the end.  However, if @code{append-to-buffer} is the only command you
use to alter a buffer, then point is always at the end.

  @kbd{M-x prepend-to-buffer} is just like @code{append-to-buffer}
except that point in the other buffer is left before the copied text, so
successive uses of this command add text in reverse order.  @kbd{M-x
copy-to-buffer} is similar, except that any existing text in the other
buffer is deleted, so the buffer is left containing just the text newly
copied into it.

  The command @kbd{C-x x i} (@code{insert-buffer}) can be used to
retrieve the accumulated text from another buffer.  This prompts for
the name of a buffer, and inserts a copy of all the text in that
buffer into the current buffer at point, leaving point at the
beginning of the inserted text.  It also adds the position of the end
of the inserted text to the mark ring, without activating the mark.
@xref{Buffers}, for background information on buffers.

  Instead of accumulating text in a buffer, you can append text
directly into a file with @kbd{M-x append-to-file}.  This prompts for
a filename, and adds the text of the region to the end of the
specified file.  The file is changed immediately on disk.

  You should use @code{append-to-file} only with files that are
@emph{not} being visited in Emacs.  Using it on a file that you are
editing in Emacs would change the file behind Emacs's back, which
can lead to losing some of your editing.

  Another way to move text around is to store it in a register.
@xref{Registers}.

@node Rectangles
@section Rectangles
@cindex rectangle
@cindex columns (and rectangles)
@cindex killing rectangular areas of text

  @dfn{Rectangle} commands operate on rectangular areas of the text:
all the characters between a certain pair of columns, in a certain
range of lines.  Emacs has commands to kill rectangles, yank killed
rectangles, clear them out, fill them with blanks or text, or delete
them.  Rectangle commands are useful with text in multicolumn formats,
and for changing text into or out of such formats.

@cindex mark rectangle
@cindex region-rectangle
@cindex rectangular region
  To specify a rectangle for a command to work on, set the mark at one
corner and point at the opposite corner.  The rectangle thus specified
is called the @dfn{region-rectangle}.  If point and the mark are in
the same column, the region-rectangle is empty.  If they are in the
same line, the region-rectangle is one line high.

  The region-rectangle is controlled in much the same way as the
region is controlled.  But remember that a given combination of point
and mark values can be interpreted either as a region or as a
rectangle, depending on the command that uses them.

  A rectangular region can also be marked using the mouse: click and drag
@kbd{C-M-mouse-1} from one corner of the rectangle to the opposite.

@table @kbd
@item C-x r k
Kill the text of the region-rectangle, saving its contents as the
last killed rectangle (@code{kill-rectangle}).
@item C-x r M-w
Save the text of the region-rectangle as the last killed rectangle
(@code{copy-rectangle-as-kill}).
@item C-x r d
Delete the text of the region-rectangle (@code{delete-rectangle}).
@item C-x r y
Yank the last killed rectangle with its upper left corner at point
(@code{yank-rectangle}).
@item C-x r o
Insert blank space to fill the space of the region-rectangle
(@code{open-rectangle}).  This pushes the previous contents of the
region-rectangle to the right.
@item C-x r N
Insert line numbers along the left edge of the region-rectangle
(@code{rectangle-number-lines}).  This pushes the previous contents of
the region-rectangle to the right.
@item C-x r c
Clear the region-rectangle by replacing all of its contents with spaces
(@code{clear-rectangle}).
@item M-x delete-whitespace-rectangle
Delete whitespace in each of the lines on the specified rectangle,
starting from the left edge column of the rectangle.
@item C-x r t @var{string} @key{RET}
Replace rectangle contents with @var{string} on each line
(@code{string-rectangle}).
@item M-x string-insert-rectangle @key{RET} @var{string} @key{RET}
Insert @var{string} on each line of the rectangle.
@item C-x @key{SPC}
Toggle Rectangle Mark mode (@code{rectangle-mark-mode}).
When this mode is active, the region-rectangle is highlighted and can
be shrunk/grown, and the standard kill and yank commands operate on it.
@end table

  The rectangle operations fall into two classes: commands to erase or
insert rectangles, and commands to make blank rectangles.

@kindex C-x r k
@kindex C-x r d
@findex kill-rectangle
@findex delete-rectangle
  There are two ways to erase the text in a rectangle: @kbd{C-x r d}
(@code{delete-rectangle}) to delete the text outright, or @kbd{C-x r
k} (@code{kill-rectangle}) to remove the text and save it as the
@dfn{last killed rectangle}.  In both cases, erasing the
region-rectangle is like erasing the specified text on each line of
the rectangle; if there is any following text on the line, it moves
backwards to fill the gap.

  Killing a rectangle is not killing in the usual sense; the
rectangle is not stored in the kill ring, but in a special place that
only records the most recent rectangle killed.  This is because
yanking a rectangle is so different from yanking linear text that
different yank commands have to be used.  Yank-popping is not defined
for rectangles.

@kindex C-x r M-w
@findex copy-rectangle-as-kill
  @kbd{C-x r M-w} (@code{copy-rectangle-as-kill}) is the equivalent of
@kbd{M-w} for rectangles: it records the rectangle as the last
killed rectangle, without deleting the text from the buffer.

@kindex C-x r y
@findex yank-rectangle
  To yank the last killed rectangle, type @kbd{C-x r y}
(@code{yank-rectangle}).  The rectangle's first line is inserted at
point, the rectangle's second line is inserted at the same horizontal
position one line vertically below, and so on.  The number of lines
affected is determined by the height of the saved rectangle.

  For example, you can convert two single-column lists into a
double-column list by killing one of the single-column lists as a
rectangle, and then yanking it beside the other list.

  You can also copy rectangles into and out of registers with @kbd{C-x r
r @var{r}} and @kbd{C-x r i @var{r}}.  @xref{Rectangle Registers}.

@kindex C-x r o
@findex open-rectangle
@kindex C-x r c
@findex clear-rectangle
  There are two commands you can use for making blank rectangles:
@kbd{C-x r c} (@code{clear-rectangle}) blanks out existing text in the
region-rectangle, and @kbd{C-x r o} (@code{open-rectangle}) inserts a
blank rectangle.

@findex delete-whitespace-rectangle
  @kbd{M-x delete-whitespace-rectangle} deletes horizontal whitespace
starting from a particular column.  This applies to each of the lines
in the rectangle, and the column is specified by the left edge of the
rectangle.  The right edge of the rectangle does not make any
difference to this command.

@kindex C-x r N
@findex rectangle
  The command @kbd{C-x r N} (@code{rectangle-number-lines}) inserts
line numbers along the left edge of the region-rectangle.  Normally,
the numbering begins from 1 (for the first line of the rectangle).
With a prefix argument, the command prompts for a number to begin
from, and for a format string with which to print the numbers
(@pxref{Formatting Strings,,, elisp, The Emacs Lisp Reference
Manual}).

@kindex C-x r t
@findex string-rectangle
  The command @kbd{C-x r t} (@code{string-rectangle}) replaces the
contents of a region-rectangle with a string on each line.  The
string's width need not be the same as the width of the rectangle.  If
the string's width is less, the text after the rectangle shifts left;
if the string is wider than the rectangle, the text after the
rectangle shifts right.

@findex string-insert-rectangle
  The command @kbd{M-x string-insert-rectangle} is similar to
@code{string-rectangle}, but inserts the string on each line,
shifting the original text to the right.

@findex rectangle-mark-mode
  The command @kbd{C-x @key{SPC}} (@code{rectangle-mark-mode}) toggles
whether the region-rectangle or the standard region is highlighted
(first activating the region if necessary).  When this mode is enabled,
commands that resize the region (@kbd{C-f}, @kbd{C-n} etc.)@: do
so in a rectangular fashion, and killing and yanking operate on the
rectangle.  @xref{Killing}.  The mode persists only as long as the
region is active.

The region-rectangle works only when the mark is active.  In
particular, when Transient Mark mode is off (@pxref{Disabled Transient
Mark}), in addition to typing @kbd{C-x @key{SPC}} you will need to
activate the mark.

Unlike the standard region, the region-rectangle can have its corners
extended past the end of buffer, or inside stretches of white space
that point normally cannot enter, like in the middle of a TAB
character.

@findex rectangle-exchange-point-and-mark
@findex exchange-point-and-mark@r{, in rectangle-mark-mode}
@kindex C-x C-x@r{, in rectangle-mark-mode}
When the region is active (@pxref{Mark}) and in rectangle-mark-mode,
@kbd{C-x C-x} runs the command
@code{rectangle-exchange-point-and-mark}, which cycles between the
four corners of the region-rectangle.  This comes in handy if you want
to modify the dimensions of the region-rectangle before invoking an
operation on the marked text.

@node CUA Bindings
@section CUA Bindings
@findex cua-mode
@vindex cua-mode
@cindex CUA key bindings
@vindex cua-enable-cua-keys
  The command @kbd{M-x cua-mode} sets up key bindings that are
compatible with the Common User Access (CUA) system used in many other
applications.

  When CUA mode is enabled, the keys @kbd{C-x}, @kbd{C-c}, @kbd{C-v},
and @kbd{C-z} invoke commands that cut (kill), copy, paste (yank), and
undo respectively.  The @kbd{C-x} and @kbd{C-c} keys perform cut and
copy only if the region is active.  Otherwise, they still act as
prefix keys, so that standard Emacs commands like @kbd{C-x C-c} still
work.  Note that this means the variable @code{mark-even-if-inactive}
has no effect for @kbd{C-x} and @kbd{C-c} (@pxref{Using Region}).

  To enter an Emacs command like @kbd{C-x C-f} while the mark is
active, use one of the following methods: either hold @kbd{Shift}
together with the prefix key, e.g., @kbd{S-C-x C-f}, or quickly type
the prefix key twice, e.g., @kbd{C-x C-x C-f}.

  To disable the overriding of standard Emacs binding by CUA mode,
while retaining the other features of CUA mode described below, set
the variable @code{cua-enable-cua-keys} to @code{nil}.

  CUA mode by default activates Delete-Selection mode (@pxref{Mouse Commands})
so that typed text replaces the active region.  To use CUA without this
behavior, set the variable @code{cua-delete-selection} to @code{nil}.

@cindex rectangle highlighting
  CUA mode provides enhanced rectangle support with visible
rectangle highlighting.  Use @kbd{C-@key{RET}} to start a rectangle,
extend it using the movement commands, and cut or copy it using
@kbd{C-x} or @kbd{C-c}.  @key{RET} moves the cursor to the next
(clockwise) corner of the rectangle, so you can easily expand it in
any direction.  Normal text you type is inserted to the left or right
of each line in the rectangle (on the same side as the cursor).

  You can use this rectangle support without activating CUA by calling the
@code{cua-rectangle-mark-mode} command.  There's also the standard command
@code{rectangle-mark-mode}, see @ref{Rectangles}.

  With CUA you can easily copy text and rectangles into and out of
registers by providing a one-digit numeric prefix to the kill, copy,
and yank commands, e.g., @kbd{C-1 C-c} copies the region into register
@code{1}, and @kbd{C-2 C-v} yanks the contents of register @code{2}.

@cindex global mark
  CUA mode also has a global mark feature which allows easy moving and
copying of text between buffers.  Use @kbd{C-S-@key{SPC}} to toggle the
global mark on and off.  When the global mark is on, all text that you
kill or copy is automatically inserted at the global mark, and text
you type is inserted at the global mark rather than at the current
position.

  For example, to copy words from various buffers into a word list in
a given buffer, set the global mark in the target buffer, then
navigate to each of the words you want in the list, mark it (e.g., with
@kbd{S-M-f}), copy it to the list with @kbd{C-c} or @kbd{M-w}, and
insert a newline after the word in the target list by pressing
@key{RET}.