Deletion and Killing
====================

Most commands that erase text from the buffer save it. You can get the text back if you change your mind, or you can move or copy it to other parts of the buffer.  Commands which erase text and save it in the kill ring are known as kill commands.  Some other commands erase text but do not save it; they are known as delete commands.  (This distinction is made only for erasing text in the buffer.)

The commands' names and individual descriptions use the words kill and delete to indicate what they do.  If you perform a kill or delete command by mistake, use the C-x u (undo) command to undo it (see Undo). The delete commands include C-d (delete-char) and DEL (delete-backward-char), which delete only one character at a time, and those commands that delete only spaces or newlines.  Commands that can destroy significant amounts of nontrivial data usually kill.

Deletion
--------

C-d
     Delete next character (delete-char).

DEL
     Delete previous character (delete-backward-char).

M-\
     Delete spaces and tabs around point (delete-horizontal-space).

M-SPC
     Delete spaces and tabs around point, leaving one space (just-one-space).

C-x C-o
     Delete blank lines around the current line (delete-blank-lines).

M-^
     Join two lines by deleting the intervening newline, and any indentation following it (delete-indentation).

The most basic delete commands are C-d (delete-char) and DEL (delete-backward-char).  C-d deletes the character after point, the one the cursor is ``on top of''.  Point doesn't move.  DEL deletes the character before the cursor, and moves point back.  You can delete newlines like any other characters in the buffer; deleting a newline joins two lines.  Actually, C-d and DEL aren't always delete commands; if you give them an argument, they kill instead, since they can erase more than one character this way.

The other delete commands delete only formatting characters: spaces, tabs and newlines.  M-\ (delete-horizontal-space) deletes all spaces and tab characters before and after point. M-SPC (just-one-space) does the same but leaves a single space after point, regardless of the number of spaces that existed previously (even zero).

C-x C-o (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 as leaving one blank line, the current line.  M-^ (delete-indentation) joins the current line and the previous line, or, if given an argument, joins the current line and the next line by deleting a newline and all surrounding spaces, possibly leaving a single space.  See M-^.

Killing by Lines
----------------

C-k
     Kill rest of line or one or more lines (kill-line).

The simplest kill command is C-k.  If given at the beginning of a line, it kills all the text on the line, leaving the line blank.  If given on a blank line, the blank line disappears.  As a consequence, a line disappears completely if you go to the front of a non-blank line and type C-k twice.

More generally, C-k kills from point up to the end of the line, unless it is at the end of a line.  In that case, it kills the newline following the line, thus merging the next line into the current one. Emacs ignores invisible spaces and tabs at the end of the line when deciding which case applies: if point appears to be at the end of the line, you can be sure the newline will be killed.

If you give C-k a positive argument, it kills that many lines and the newlines that follow them (however, text on the current line before point is not killed).  With a negative argument, C-k kills back to a number of line beginnings.  An argument of -2 means kill back to the second line beginning.  If point is at the beginning of a line, that line beginning doesn't count, so C-u - 2 C-k with point at the front of a line kills the two previous lines.

C-k with an argument of zero kills all the text before point on the current line.

Other Kill Commands
-------------------

C-w
     Kill region (from point to the mark) (kill-region). See Words.

M-d
     Kill word (kill-word).

M-DEL
     Kill word backwards (backward-kill-word).

C-x DEL
     Kill back to beginning of sentence (backward-kill-sentence). See Sentences.

M-k
     Kill to end of sentence (kill-sentence).

C-M-k
     Kill sexp (kill-sexp).  See Lists.

M-z CHAR
     Kill up to next occurrence of CHAR (zap-to-char).

C-w (kill-region) is a very general kill command; it kills everything between point and the mark. You can use this command to kill any contiguous sequence of characters by first setting the mark at one end of a sequence of characters, then going to the other end and typing C-w.

A convenient way of killing is combined with searching: M-z (zap-to-char) reads a character and kills from point up to (but not including) the next occurrence of that character in the buffer.  If there is no next occurrence, killing goes to the end of the buffer.  A numeric argument acts as a repeat count.  A negative argument means to search backward and kill text before point.

Other syntactic units can be killed: words, with M-DEL and M-d (see Words); sexps, with C-M-k (see Lists); and sentences, with C-x DEL and M-k (see Sentences).

Yanking
=======

Yanking means getting back text which was killed. Some systems call this ``pasting''.  The usual way to move or copy text is to kill it and then yank it one or more times.

C-y
     Yank last killed text (yank).

M-y
     Replace re-inserted killed text with the previously killed text (yank-pop).

M-w
     Save region as last killed text without actually killing it (copy-region-as-kill).

C-M-w
     Append next kill to last batch of killed text (append-next-kill).

The Kill Ring
-------------

All killed text is recorded in the kill ring, a list of blocks of text that have been killed.  There is only one kill ring, used in 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 file to another. (see Accumulating Text, for some other ways.)

If you have two separate Emacs processes, you cannot use the kill ring to move text. If you are using XEmacs under X, however, you can use the X selection mechanism to move text from one to another.

If you are using XEmacs under X and have one Emacs process with multiple frames, they do share the same kill ring.  You can kill or copy text in one Emacs frame, then yank it in the other frame belonging to the same process.

The command C-y (yank) reinserts the text of the most recent kill.  It leaves the cursor at the end of the text and sets the mark at the beginning of the text.  See Mark.

C-u C-y yanks the text, leaves the cursor in front of the text, and sets the mark after it, if the argument is with just a C-u. Any other argument, including C-u and digits, has different results, described below, under ``Yanking Earlier Kills''.

To copy a block of text, you can also use M-w (copy-region-as-kill), which copies the region into the kill ring without removing it from the buffer. M-w is similar to C-w followed by C-y but does not mark the buffer as ``modified'' and does not actually cut anything.

Appending Kills
---------------

Normally, each kill command pushes a new block onto the kill ring. However, two or more kill commands in a row combine their text into a single entry, so that a single C-y yanks it all back. This means you don't have to kill all the text you want to yank in one command; you can kill line after line, or word after word, until you have killed what you want, then get it all back at once using C-y. (Thus we join television in leading people to kill thoughtlessly.)

Commands that kill forward from point add onto the end of the previous killed text.  Commands that kill backward from point add 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 is the first
     line of sample text
     and here is the third.

with point at the beginning of the second line.  If you type C-k C-u 2 M-DEL C-k, the first C-k kills the text line of sample text, C-u 2 M-DEL kills the first with the newline that followed it, and the second C-k kills the newline after the second line.  The result is that the buffer contains This is and here is the third. and a single kill entry contains the firstRETline of sample textRET---all the killed text, in its original order.

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.  To force a kill command to append, first type the command C-M-w (append-next-kill). C-M-w tells the following command, if it is a kill command, to append the text it kills to the last killed text, instead of starting a new entry.  With C-M-w, you can kill several separated pieces of text and accumulate them to be yanked back in one place.

Yanking Earlier Kills
---------------------

To recover killed text that is no longer the most recent kill, you need the Meta-y (yank-pop) command.  You can use M-y only after a C-y or another M-y.  It takes the text previously yanked and replaces it with the text from an earlier kill.  To recover the text of the next-to-the-last kill, first use C-y to recover the last kill, then M-y to replace it with the previous kill.

You can think in terms of a ``last yank'' pointer which points at an item in the kill ring.  Each time you kill, the ``last yank'' pointer moves to the new item at the front of the ring.  C-y yanks the item which the ``last yank'' pointer points to.  M-y moves the ``last yank'' pointer to a different item, and the text in the buffer changes to match.  Enough M-y commands can move the pointer to any item in the ring, so you can get any item into the buffer.  Eventually the pointer reaches the end of the ring; the next M-y moves it to the first item again.

Yanking moves the ``last yank'' pointer around the ring, but 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.

Use M-y with a numeric argument to advance the ``last yank'' pointer by the specified number of items.  A negative argument moves the pointer toward the front of the ring; from the front of the ring, it moves to the last entry and starts moving forward from there.

Once the text you are looking for is brought into the buffer, you can stop doing M-y commands and the text will stay there. Since the text is just a copy of the kill ring item, editing it in the buffer does not change what's in the ring.  As long you don't kill additional text, the ``last yank'' pointer remains at the same place in the kill ring: repeating C-y will yank another copy of the same old kill.

If you know how many M-y commands it would take to find the text you want, you can yank that text in one step using C-y with a numeric argument.  C-y with an argument greater than one restores the text the specified number of entries back in the kill ring.  Thus, C-u 2 C-y gets the next to the last block of killed text.  It is equivalent to C-y M-y.  C-y with a numeric argument starts counting from the ``last yank'' pointer, and sets the ``last yank'' pointer to the entry that it yanks.

The variable kill-ring-max controls the length of the kill ring; no more than that many blocks of killed text are saved.

Using X Selections
==================

In the X window system, mouse selections provide a simple mechanism for text transfer between different applications.  In a typical X application, you can select text by pressing the left mouse button and dragging the cursor over the text you want to copy.  The text becomes the primary X selection and is highlighted.  The highlighted region is also the Emacs selected region.

  * Since the region is the primary X selection, you can go to a different X application and click the middle mouse button: the text that you selected in the previous application is pasted into the current application.

  * Since the region is the Emacs selected region, you can use all region commands (C-w, M-w etc.) as well as the options of the Edit menu to manipulate the selected text.

The Clipboard Selection
-----------------------

There are other kinds of X selections besides the Primary selection; one common one is the Clipboard selection.  Some applications prefer to transfer data using this selection in preference to the Primary. One can transfer text from the Primary selection to the  Clipboard selection with the Copy command under the Edit menu in the menubar.

Usually, the clipboard selection is not visible.  However, if you run the xclipboard application, the text most recently copied to the clipboard (with the Copy command) is displayed in a window.  Any time new text is thus copied, the xclipboard application makes a copy of it and displays it in its window.  The value of the clipboard can survive the lifetime of the running Emacs process.  The xclipboard man page provides more details.

Warning: If you use the xclipboard application, remember that it maintains a list of all things that have been pasted to the clipboard (that is, copied with the Copy command).  If you don't manually delete elements from this list by clicking on the Delete button in the xclipboard window, the clipboard will eventually consume a lot of memory.

In summary, some X applications (such as xterm) allow one to paste text in them from XEmacs in the following way:

  * Drag out a region of text in Emacs with the left mouse button, making that text be the Primary selection.

  * Click the middle button in the other application, pasting the Primary selection.

With some other applications (notably, the OpenWindows and Motif tools) you must use this method instead:

  * Drag out a region of text in Emacs with the left mouse button, making that text be the Primary selection.

  * Copy the selected text to the Clipboard selection by selecting the Copy menu item from the Edit menu, or by hitting the Copy key on your keyboard.

  * Paste the text in the other application by selecting Paste from its menu, or by hitting the Paste key on your keyboard.

Miscellaneous X Selection Commands
----------------------------------

M-x x-copy-primary-selection
     Copy the primary selection to both the kill ring and the Clipboard.

M-x x-insert-selection
     Insert the current selection into the buffer at point.

M-x x-delete-primary-selection
     Deletes the text in the primary selection without copying it to the kill ring or the Clipboard.

M-x x-kill-primary-selection
     Deletes the text in the primary selection and copies it to both the kill ring and the Clipboard.

M-x x-mouse-kill
     Kill the text between point and the mouse and copy it to the clipboard and to the cut buffer.

M-x x-own-secondary-selection
     Make a secondary X selection of the given argument.

M-x x-own-selection
     Make a primary X selection of the given argument.

M-x x-set-point-and-insert-selection
     Set point where clicked and insert the primary selection or the cut buffer.

X Cut Buffers
-------------

X cut buffers are a different, older way of transferring text between applications.  XEmacs supports cut buffers for compatibility with older programs, even though selections are now the preferred way of transferring text.

X has a concept of applications "owning" selections.  When you select text by clicking and dragging inside an application, the application tells the X server that it owns the selection.  When another application asks the X server for the value of the selection, the X server requests the information from the owner. When you use selections, the selection data is not actually transferred unless someone wants it; the act of making a selection doesn't transfer data. Cut buffers are different: when you "own" a cut buffer, the data is actually transferred to the X server immediately, and survives the lifetime of the application.

Any time a region of text becomes the primary selection in Emacs, Emacs also copies that text to the cut buffer.  This makes it possible to copy text from an XEmacs buffer and paste it into an older, non-selection-based application (such as Emacs 18).

Note: Older versions of Emacs could not access the X selections, only the X cut buffers.

Active Regions
--------------

By default, both the text you select in an Emacs buffer using the click-and-drag mechanism and text you select by setting point and the mark is highlighted. You can use Emacs region commands as well as the Cut and Copy commands on the highlighted region you selected with the mouse.

If you prefer, you can make a distinction between text selected with the mouse and text selected with point and the mark by setting the variable zmacs-regions to nil.  In that case:

  * The text selected with the mouse becomes both the X selection and the Emacs selected region. You can use menu-bar commands as well as Emacs region commands on it.

  * The text selected with point and the mark is not highlighted. You can only use Emacs region commands on it, not the menu-bar items.

Active regions originally come from Zmacs, the Lisp Machine editor. The idea behind them is that commands can only operate on a region when the region is in an "active" state.  Put simply, you can only operate on a region that is highlighted.

The variable zmacs-regions checks whether LISPM-style active regions should be used.  This means that commands that operate on the region (the area between point and the mark) only work while the region is in the active state, which is indicated by highlighting. Most commands causes the region to not be in the active state; for example, C-w only works immediately after activating the region.

More specifically:

  * Commands that operate on the region only work if the region is active.

  * Only a very small set of commands causes the region to become active--- those commands whose semantics are to mark an area, such as mark-defun.

  * The region is deactivated after each command that is executed, except that motion commands do not change whether the region is active or not.

set-mark-command (C-SPC) pushes a mark and activates the region.  Moving the cursor with normal motion commands (C-n, C-p, etc.) will cause the region between point and the recently-pushed mark to be highlighted.  It will remain highlighted until some non-motion command is executed.

exchange-point-and-mark (C-x C-x) activates the region. So if you mark a region and execute a command that operates on it, you can reactivate the same region with C-x C-x (or perhaps C-x C-x C-x C-x) to operate on it again.

Generally, commands that push marks as a means of navigation, such as beginning-of-buffer (M-<) and end-of-buffer (M->), do not activate the region.  However, commands that push marks as a means of marking an area of text, such as mark-defun (M-C-h), mark-word (M-@), and mark-whole-buffer (C-x h), do activate the region.

When zmacs-regions is t, there is no distinction between the primary X selection and the active region selected by point and the mark.  To see this, set the mark (C-SPC) and move the cursor with any cursor-motion command: the region between point and mark is highlighted, and you can watch it grow and shrink as you move the cursor.

Any other commands besides cursor-motion commands (such as inserting or deleting text) will cause the region to no longer be active; it will no longer be highlighted, and will no longer be the primary selection. Errors also remove highlighting from a region.

Commands that require a region (such as C-w) signal an error if the region is not active.  Certain commands cause the region to be in its active state.  The most common ones are push-mark (C-SPC) and exchange-point-and-mark (C-x C-x).

When zmacs-regions is t, programs can be non-intrusive on the state of the region by setting the variable zmacs-region-stays to a non-nil value.  If you are writing a new Emacs command that is conceptually a ``motion'' command and should not interfere with the current highlightedness of the region, then you may set this variable. It is reset to nil after each user command is executed.

When zmacs-regions is t, programs can make the region between point and mark go into the active (highlighted) state by using the function zmacs-activate-region. Only a small number of commands should ever do this.

When zmacs-regions is t, programs can deactivate the region between point and the mark by using zmacs-deactivate-region. Note: you should not have to call this function; the command loop calls it when appropriate.

Accumulating Text
=================

Usually you copy or move text by killing it and yanking it, but there are other ways that are useful for copying one block of text in many places, or for copying many scattered blocks of text into one place.

If you like, you can accumulate blocks of text from scattered locations either into a buffer or into a file.  The relevant commands are described here.  You can also use Emacs registers for storing and accumulating text.  See Registers.

M-x append-to-buffer
     Append region to contents of specified buffer (append-to-buffer).

M-x prepend-to-buffer
     Prepend region to contents of specified buffer.

M-x copy-to-buffer
     Copy region into specified buffer, deleting that buffer's old contents.

M-x insert-buffer
     Insert contents of specified buffer into current buffer at point.

M-x append-to-file
     Append region to the end of the contents of specified file.

To accumulate text into a buffer, use the command M-x append-to-buffer, which inserts a copy of the region into the buffer BUFFERNAME, at the location of point in that buffer.  If there is no buffer with the given name, one is created.

If you append text to a buffer that has been used for editing, the copied text goes to the place where point is.  Point in that buffer is left at the end of the copied text, so successive uses of append-to-buffer accumulate the text in the specified buffer in the same order as they were copied.  Strictly speaking, this command does not always append to the text already in the buffer; but if this command is the only command used to alter a buffer, it does always append to the existing text because point is always at the end.

M-x prepend-to-buffer is similar to append-to-buffer, but point in the other buffer is left before the copied text, so successive prependings add text in reverse order.  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.

You can retrieve the accumulated text from that buffer with M-x insert-buffer, which takes BUFFERNAME as an argument.  It inserts a copy of the text in buffer BUFFERNAME into the selected buffer. You could alternatively select the other buffer for editing, perhaps moving text from it by killing or with append-to-buffer.  See Buffers, for background information on buffers.

Instead of accumulating text within Emacs in a buffer, you can append text directly into a file with M-x append-to-file, which takes FILE-NAME as an argument.  It adds the text of the region to the end of the specified file.  The file is changed immediately on disk. This command is normally used with files that are not being visited in Emacs.  Using it on a file that Emacs is visiting can produce confusing results, because the file's text inside Emacs does not change while the file itself changes.

Rectangles
==========

The rectangle commands affect rectangular areas of text: all characters between a certain pair of columns, in a certain range of lines. Commands are provided to kill rectangles, yank killed rectangles, clear them out, or delete them.  Rectangle commands are useful with text in multicolumnar formats, like code with comments at the right, or for changing text into or out of such formats.

To specify the rectangle a command should work on, put the mark at one corner and point at the opposite corner.  The specified rectangle is called the region-rectangle because it is controlled about the same way the region is controlled.  Remember that a given combination of point and mark values can be interpreted either as specifying a region or as specifying a rectangle; it is up to the command that uses them to choose the interpretation.

M-x delete-rectangle
     Delete the text of the region-rectangle, moving any following text on each line leftward to the left edge of the region-rectangle.

M-x kill-rectangle
     Similar, but also save the contents of the region-rectangle as the ``last killed rectangle''.

M-x yank-rectangle
     Yank the last killed rectangle with its upper left corner at point.

M-x open-rectangle
     Insert blank space to fill the space of the region-rectangle. The previous contents of the region-rectangle are pushed rightward.

M-x clear-rectangle
     Clear the region-rectangle by replacing its contents with spaces.

The rectangle operations fall into two classes: commands deleting and moving rectangles, and commands for blank rectangles.

There are two ways to get rid of the text in a rectangle: you can discard the text (delete it) or save it as the ``last killed'' rectangle.  The commands for these two ways are M-x delete-rectangle and M-x kill-rectangle.  In either case, the portion of each line that falls inside the rectangle's boundaries is deleted, causing following text (if any) on the line to move left.

Note that ``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 recently killed rectangle (that is, does not append to a killed rectangle).  Different yank commands have to be used and only one rectangle is stored, because yanking a rectangle is quite different from yanking linear text and yank-popping commands are difficult to make sense of.

Inserting a rectangle is the opposite of deleting one.  You specify where to put the upper left corner by putting point there.  The rectangle's first line is inserted at point, the rectangle's second line is inserted at a point one line vertically down, and so on.  The number of lines affected is determined by the height of the saved rectangle.

To insert the last killed rectangle, type M-x yank-rectangle. This can be used to convert single-column lists into double-column lists; kill the second half of the list as a rectangle and then yank it beside the first line of the list.

There are two commands for working with blank rectangles: M-x clear-rectangle erases existing text, and M-x open-rectangle inserts a blank rectangle.  Clearing a rectangle is equivalent to deleting it and then inserting a blank rectangle of the same size.

Rectangles can also be copied into and out of registers. See Rectangle Registers.