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Go to the previous, next chapter. 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 Transient Mark Mode). You can move point or the mark to adjust the boundaries of the region. It doesn't matter which one is set first chronologically, or which one comes earlier in the text. Once the mark has been set, it remains where you put it until you set it again at another place. Each Emacs buffer has its own mark, so that when you return to a buffer that had been selected previously, it has the same mark it had before. 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.
Setting the MarkHere are some commands for setting the mark:
For example, suppose you wish to convert part of the buffer to all 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 them 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 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 mark; do C-x C-x to put point at that end of the region, and then move it. A second use of C-x C-x, if necessary, puts the mark at the new position with point back at its original position. 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 Transient Mark ModeEmacs can highlight the current region, using X Windows. But normally it does not. Why not? Highlighting the region doesn't work well ordinarily 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. 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 convenient. 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:
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. When multiple windows show the same buffer, they can have different regions, because they can have different values of point (though they all share common one mark position). In Transient Mark mode, each window highlights its own region. The part that is highlighted in the selected window is the region that editing commands use. See section Multiple Windows. When Transient Mark mode is not enabled, every command that sets the mark also activates it, and nothing ever deactivates it. 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 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. The Mark RingAside 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 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
( Deletion and KillingMost 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 ( The delete commands include C-d (
Deletion
The most basic delete commands are C-d ( The other delete commands are those which delete only whitespace characters: spaces,
tabs and newlines. M-\ ( C-x C-o ( M-^ ( 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 spared). 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 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 Words); sexps, with C-M-k (see section Lists and Sexps); and sentences, with C-x DEL and M-k (see section 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. 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.
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 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 Yanking Earlier Kills). To copy a block of text,
you can use M-w ( 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: This is a line *of sample 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, 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. Yanking Earlier KillsTo 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 moves it 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 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 length of the kill ring is controlled by the variable The actual contents of the kill ring are stored in a variable named 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 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, them 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 M-x insert-buffer; this too takes buffername as an argument. It inserts a copy of the text in buffer buffername into the selected buffer. You can alternatively select the other buffer for editing, then optionally move text from it by killing. See section 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 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 about the same way 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 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 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 Saving Rectangles in Registers. There are two commands for making with blank rectangles: M-x
clear-rectangle
to blank out existing text,
and C-x r o ( The command M-x string-rectangle is similar to C-x r o, but it inserts a specified string instead of blanks. You specify the string with the minibuffer. Since the length of the string specifies how many columns to insert, the width of the region-rectangle does not matter for this command. What does matter is the position of the left edge (which specifies the column position for the insertion in each line) and the range of lines that the rectangle occupies. The previous contents of the text beyond the insertion column are pushed rightward. To return to the Ready-to-Run Software Super ReadyPak Table of Contents please press here. |
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