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H. The Mark and the RegionMany Emacs commands operate on an arbitrary contiguous part of the current buffer. To specify the text for such a command to operate on, you set the mark at one end of it, and move point to the other end. The text between point and the mark is called the region. Emacs highlights the region whenever there is one, if you enable Transient Mark mode (see section H.2 Transient Mark Mode). Certain Emacs commands set the mark; other editing commands do not affect it, so the mark remains where you set it last. Each Emacs buffer has its own mark, and setting the mark in one buffer has no effect on other buffers' marks. When you return to a buffer that was current earlier, its mark is at the same place as before. The ends of the region are always point and the mark. It doesn't matter which of them was put in its current place first, or which one comes earlier in the text--the region starts from point or the mark (whichever comes first), and ends at point or the mark (whichever comes last). Every time you move point, or set the mark in a new place, the region changes.
Many commands that insert text, such as C-y ( Aside from delimiting the region, the mark is also useful for remembering a spot that you may want to go back to. To make this feature more useful, each buffer remembers 16 previous locations of the mark in the mark ring.
H.1 Setting the MarkHere are some commands for setting the mark:
For example, suppose you wish to convert part of the buffer to
upper case, using the C-x C-u (
The most common way to set the mark is with the C-SPC command
( There are two ways to set the mark with the mouse. You can drag mouse button one across a range of text; that puts point where you release the mouse button, and sets the mark at the other end of that range. Or you can click mouse button three, which sets the mark at point (like C-SPC) and then moves point (like Mouse-1). Both of these methods copy the region into the kill ring in addition to setting the mark; that gives behavior consistent with other window-driven applications, but if you don't want to modify the kill ring, you must use keyboard commands to set the mark. See section P.1 Mouse Commands for Editing.
Ordinary terminals have only one cursor, so there is no way for Emacs
to show you where the mark is located. You have to remember. The usual
solution to this problem is to set the mark and then use it soon, before
you forget where it is. Alternatively, you can see where the mark is
with the command C-x C-x ( C-x C-x is also useful when you are satisfied with the position of point but want to move the other end of the region (where the mark is); do C-x C-x to put point at that end of the region, and then move it. Using C-x C-x a second time, if necessary, puts the mark at the new position with point back at its original position. For more facilities that allow you to go to previously set marks, see H.5 The Mark Ring.
There is no such character as C-SPC in ASCII; when you
type SPC while holding down CTRL, what you get on most
ordinary terminals is the character C-@. This key is actually
bound to
H.2 Transient Mark ModeOn a terminal that supports colors, Emacs can highlight the current region. But normally it does not. Why not? Highlighting the region whenever it exists would not be desirable in Emacs, because once you have set a mark, there is always a region (in that buffer). And highlighting the region all the time would be a nuisance. So normally Emacs highlights the region only immediately after you have selected one with the mouse. You can turn on region highlighting by enabling Transient Mark mode. This is a more rigid mode of operation in which the region "lasts" only temporarily, so you must set up a region for each command that uses one. In Transient Mark mode, most of the time there is no region; therefore, highlighting the region when it exists is useful and not annoying. To enable Transient Mark mode, type M-x transient-mark-mode. This command toggles the mode, so you can repeat the command to turn off the mode. Here are the details of Transient Mark mode:
The highlighting of the region uses the
When multiple windows show the same buffer, they can have different
regions, because they can have different values of point (though they
all share one common mark position). Ordinarily, only the selected
window highlights its region (see section O. Multiple Windows). However, if the
variable When Transient Mark mode is not enabled, every command that sets the mark also activates it, and nothing ever deactivates it.
If the variable Transient Mark mode is also sometimes known as "Zmacs mode" because the Zmacs editor on the MIT Lisp Machine handled the mark in a similar way.
H.3 Operating on the RegionOnce you have a region and the mark is active, here are some of the ways you can operate on the region:
Most commands that operate on the text in the region have the word
H.4 Commands to Mark Textual ObjectsHere are the commands for placing point and the mark around a textual object such as a word, list, paragraph or page.
M-@ (
Other commands set both point and mark, to delimit an object in the
buffer. For example, M-h (
C-M-h (
Finally, C-x h ( In Transient Mark mode, all of these commands activate the mark.
H.5 The Mark Ring
Aside from delimiting the region, the mark is also useful for
remembering a spot that you may want to go back to. To make this
feature more useful, each buffer remembers 16 previous locations of the
mark, in the mark ring. Commands that set the mark also push the
old mark onto this ring. To return to a marked location, use C-u
C-SPC (or C-u C-@); this is the command
Each buffer has its own mark ring. All editing commands use the current buffer's mark ring. In particular, C-u C-SPC always stays in the same buffer.
Many commands that can move long distances, such as M-<
( If you want to move back to the same place over and over, the mark ring may not be convenient enough. If so, you can record the position in a register for later retrieval (see section Saving Positions in Registers).
The variable
The variable
H.6 The Global Mark RingIn addition to the ordinary mark ring that belongs to each buffer, Emacs has a single global mark ring. It records a sequence of buffers in which you have recently set the mark, so you can go back to those buffers. Setting the mark always makes an entry on the current buffer's mark ring. If you have switched buffers since the previous mark setting, the new mark position makes an entry on the global mark ring also. The result is that the global mark ring records a sequence of buffers that you have been in, and, for each buffer, a place where you set the mark.
The command C-x C-SPC (
H.7 Deletion and Killing
Most commands which erase text from the buffer save it in the kill
ring so that you can move or copy it to other parts of the buffer.
These commands are known as kill commands. The rest of the
commands that erase text do not save it in the kill ring; they are known
as delete commands. (This distinction is made only for erasure of
text in the buffer.) If you do a kill or delete command by mistake, you
can use the C-x u (
You cannot kill read-only text, since such text does not allow any
kind of modification. But some users like to use the kill commands to
copy read-only text into the kill ring, without actually changing it.
If you set the variable
The delete commands include C-d ( Many window systems follow the convention that insertion while text is selected deletes the selected text. You can make Emacs behave this way by enabling Delete Selection mode, with M-x delete-selection-mode, or using Custom. Another effect of this mode is that DEL, C-d and some other keys, when a selection exists, will kill the whole selection. It also enables Transient Mark mode (see section H.2 Transient Mark Mode).
H.7.1 DeletionDeletion 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.
The most basic delete commands are C-d ( Every keyboard has a large key, labeled DEL, BACKSPACE, BS or DELETE, which is a short distance above the RET or ENTER key and is normally used for erasing what you have typed. Regardless of the actual name on the key, in Emacs it is equivalent to DEL---or it should be. Many keyboards (including standard PC keyboards) have a BACKSPACE key a short ways above RET or ENTER, and a DELETE key elsewhere. In that case, the BACKSPACE key is DEL, and the DELETE key is equivalent to C-d---or it should be. Why do we say "or it should be"? When Emacs starts up using a window system, it determines automatically which key or keys should be equivalent to DEL. As a result, BACKSPACE and/or DELETE keys normally do the right things. But in some unusual cases Emacs gets the wrong information from the system. If these keys don't do what they ought to do, you need to tell Emacs which key to use for DEL. See section AD.9.1 If DEL Fails to Delete, for how to do this. On most text-only terminals, Emacs cannot tell which keys the keyboard really has, so it follows a uniform plan which may or may not fit your keyboard. The uniform plan is that the ASCII DEL character deletes, and the ASCII BS (backspace) character asks for help (it is the same as C-h). If this is not right for your keyboard, such as if you find that the key which ought to delete backwards enters Help instead, see AD.9.1 If DEL Fails to Delete.
The other delete commands are those which delete only whitespace
characters: spaces, tabs and newlines. M-\
(
C-x C-o (
M-^ (
H.7.2 Killing by Lines
The simplest kill command is C-k. If given at the beginning of a line, it kills all the text on the line, leaving it blank. When used on a blank line, it kills the whole line including its newline. To kill an entire non-blank line, go to the beginning 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 point, thus merging the next line into the current one. Spaces and tabs that you can't see at the end of the line are ignored when deciding which case applies, so if point appears to be at the end of the line, you can be sure C-k will kill the newline. When C-k is given 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 -n, it kills n lines preceding the current line (together with the text on the current line before point). Thus, C-u - 2 C-k at the front of a line kills the two previous lines. C-k with an argument of zero kills the text before point on the current line.
If the variable
H.7.3 Other Kill Commands
A kill command which is very general is C-w
(
A convenient way of killing is combined with searching: M-z
( Other syntactic units can be killed: words, with M-DEL and M-d (see section T.1 Words); balanced expressions, with C-M-k (see section U.4.1 Expressions with Balanced Parentheses); and sentences, with C-x DEL and M-k (see section T.2 Sentences). You can use kill commands in read-only buffers. They don't actually change the buffer, and they beep to warn you of that, but they do copy the text you tried to kill into the kill ring, so you can yank it into other buffers. Most of the kill commands move point across the text they copy in this way, so that successive kill commands build up a single kill ring entry as usual.
H.8 YankingYanking means reinserting text previously killed. This is what some systems call "pasting." The usual way to move or copy text is to kill it and then yank it elsewhere one or more times.
H.8.1 The Kill RingAll killed text is recorded in the kill ring, a list of blocks of text that have been 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 file to another. (See section H.9 Accumulating Text, for some other ways.)
The command C-y ( C-u C-y leaves the cursor in front of the text, and sets the mark after it. This happens only if the argument is specified with just a C-u, precisely. Any other sort of argument, including C-u and digits, specifies an earlier kill to yank (see section H.8.3 Yanking Earlier Kills).
To copy a block of text, you can use M-w
(
H.8.2 Appending KillsNormally, 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 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:
with point shown by -!-. If you type M-d M-DEL M-d M-DEL, killing alternately forward and backward, you end up with `a line of sample' as one entry in the kill ring, and `This is text.' in the buffer. (Note the double space between `is' and `text', which you can clean up with M-SPC or M-q.) Another way to kill the same text is to move back two words with M-b M-b, then kill all four words forward with C-u M-d. This produces exactly the same results in the buffer and in the kill ring. M-f M-f C-u M-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.
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 append by first typing the command
C-M-w ( A kill command following M-w does not append to the text that M-w copied into the kill ring.
H.8.3 Yanking Earlier Kills
To recover killed text that is no longer the most recent kill, use the
M-y command ( You can understand 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. C-y yanks the entry which the "last yank" pointer points to. M-y moves the "last yank" pointer to a different entry, and the text in the buffer changes to match. Enough M-y commands 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 M-y loops back around to the first entry again. 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. 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 M-y commands and it 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 C-y will yank another copy of the same previous 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 restores the text from the specified kill ring entry, counting back from the most recent as 1. 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 length of the kill ring is controlled by the variable
The actual contents of the kill ring are stored in a variable named
H.9 Accumulating TextUsually we copy or move text by killing it and yanking it, but there are other methods convenient for copying one block of text in many places, or for copying many scattered blocks of text into one place. To copy one block to many places, store it in a register (see section I. Registers). Here we describe the commands to accumulate scattered pieces of text into a buffer or into a file.
To accumulate text into a buffer, use 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,
Point in that buffer is left at the end of the copied text, so
successive uses of
M-x prepend-to-buffer is just like To retrieve the accumulated text from another buffer, use the command M-x insert-buffer; this too takes buffername as an argument. It inserts a copy of the whole text in buffer buffername into the current buffer at point, and sets the mark after the inserted text. Alternatively, you can select the other buffer for editing, then copy text from it by killing. See section N. Using Multiple 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 filename as an argument. It adds the text of the region to the end of the specified file. The file is changed immediately on disk.
You should use
H.10 RectanglesThe rectangle commands operate on rectangular areas of the text: all the 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, 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. When you must specify a rectangle for a command to work on, you do it by putting the mark at one corner and point at the opposite corner. The rectangle thus specified is called the region-rectangle because you control it 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. If point and the mark are in the same column, the rectangle they delimit is empty. If they are in the same line, the rectangle is one line high. This asymmetry between lines and columns comes about because point (and likewise the mark) is between two columns, but within a line.
The rectangle operations fall into two classes: commands for deleting and inserting 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 C-x r d
( 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 can only record 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 and yank-popping is hard to make sense of.
To yank the last killed rectangle, type C-x r y
( You can convert single-column lists into double-column lists using rectangle killing and yanking; kill the second half of the list as a rectangle and then yank it beside the first line of the list. See section AC.23 Two-Column Editing, for another way to edit multi-column text. You can also copy rectangles into and out of registers with C-x r r r and C-x r i r. See section Rectangle Registers.
There are two commands you can use for making blank rectangles:
M-x clear-rectangle which blanks out existing text, and C-x r
o ( The command 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.
The command C-x r t (
The command M-x string-insert-rectangle is similar to
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