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Go to the previous, next chapter. Basic Editing CommandsWe now give the basics of how to enter text, make corrections, and save
the text in a file. If this
material is new to you, you might learn it more easily by running
the Emacs learn-by-doing tutorial. To use the tutorial, run Emacs
and type Control-h t ( To clear the screen and redisplay,
type C-l (
Inserting TextTo insert printing characters into the text you are editing, just type them. This inserts the characters you type into the buffer at the cursor (that is, at point; see section Point). The cursor moves forward, and any text after the cursor moves forward too. If the text in the buffer is FOOBAR, with the cursor before the B, then if you type XX, you get FOOXXBAR, with the cursor still before the B. To delete text you have just inserted, use DEL. DEL deletes the character before the cursor (not the one that the cursor is on top of or under; that is the character after the cursor). The cursor and all characters after it move backwards. Therefore, if you type a printing character and then type DEL, they cancel out. To end a line and start typing a new one, type RET. This inserts a newline character in the buffer. If point is in the middle of a line, RET splits the line. Typing DEL when the cursor is at the beginning of a line deletes the preceding newline, thus joining the line with the preceding line. Emacs can split lines automatically when they become too long, if you turn on a special minor mode called Auto Fill mode. See section Filling Text, for how to use Auto Fill mode. If you prefer to have text characters replace (overwrite) existing text rather than shove it to the right, you can enable Overwrite mode, a minor mode. See section Minor Modes. Direct insertion works for
printing characters and SPC, but other characters act
as editing commands and do not insert themselves. If you need to
insert a control character or
a character whose code is
above 200 octal, you must quote it by typing the character Control-q (
A numeric argument to C-q specifies how many copies of the quoted character should be inserted (see section Numeric Arguments). Customization information: DEL
in most modes runs the command Changing the Location of PointTo do more than insert characters, you have to know how to move point (see section Point). The simplest way to do this is with arrow keys, or by clicking the left mouse button where you want to move to. There are also control and meta characters for cursor motion. Some are equivalent to the arrow keys (these date back to the days before terminals had arrow keys, and are usable on terminals which don't have them). Others do more sophisticated things.
If you set the variable Normally, C-n on the last line of a buffer appends a newline to it. If the variable Erasing Text
You already know about the DEL key which deletes the character before point (that is, before the cursor). Another key, Control-d (C-d for short), deletes the character after point (that is, the character that the cursor is on). This shifts the rest of the text on the line to the left. If you type C-d at the end of a line, it joins together that line and the next line. To erase a larger amount of text, use the C-k key, which kills a line at a time. If you type C-k at the beginning or middle of a line, it kills all the text up to the end of the line. If you type C-k at the end of a line, it joins that line and the next line. See section Deletion and Killing, for more flexible ways of killing text. Undoing ChangesYou can undo all the recent changes in the buffer text, up to a certain point. Each buffer records changes
individually, and the undo command
always applies to the current buffer.
Usually each editing command
makes a separate entry in the undo records, but some commands
such as
The command C-x u or C-_ is how you undo. The first time you give this command, it undoes the last change. Point moves back to where it was before the command that made the change. Consecutive repetitions of C-_ or C-x u undo earlier and earlier changes, back to the limit of the undo information available. If all recorded changes have already been undone, the undo command prints an error message and does nothing. Any command other than an undo command breaks the sequence of undo commands. Starting from that moment, the previous undo commands become ordinary changes that you can undo. Thus, to redo changes you have undone, type C-f or any other command that will harmlessly break the sequence of undoing, then type more undo commands. If you notice that a buffer has been modified accidentally, the easiest way to recover is to type C-_ repeatedly until the stars disappear from the front of the mode line. At this time, all the modifications you made have been canceled. Whenever an undo command makes the stars disappear from the mode line, it means that the buffer contents are the same as they were when the file was last read in or saved. If you do not remember whether you changed the buffer deliberately, type C-_ once. When you see the last change you made undone, you will see whether it was an intentional change. If it was an accident, leave it undone. If it was deliberate, redo the change as described above. Not all buffers record undo information. Buffers whose names start with spaces don't; these buffers are used internally by Emacs and its extensions to hold text that users don't normally look at or edit. You cannot undo mere cursor motion; only changes in the buffer contents save undo information. However, some cursor motion commands set the mark, so if you use these commands from time to time, you can move back to the neighborhoods you have moved through by popping the mark ring (see section The Mark Ring). When the undo information for a buffer
becomes too large, Emacs discards the oldest undo information
from time to time (during garbage collection). You can specify
how much undo information to keep by setting two variables: The variable Regardless of the values of those variables, the most recent change is never discarded, so there is no danger that garbage collection occurring right after an unintentional large change might prevent you from undoing it. The reason the FilesThe commands described above are sufficient for creating and altering text in an Emacs buffer; the more advanced Emacs commands just make things easier. But to keep any text permanently you must put it in a file. Files are named units of text which are stored by the operating system for you to retrieve later by name. To look at or use the contents of a file in any way, including editing the file with Emacs, you must specify the file name. Consider a file named /usr/rms/foo.c. In Emacs, to begin editing this file, type C-x C-f /usr/rms/foo.c RET Here the file name is given as an argument to the command C-x C-f ( Emacs obeys the command by visiting the file:
creating a buffer, copying the
contents of the file into the buffer,
and then displaying the buffer
for you to edit. If you alter the text,
you can save the new text
in the file by typing C-x C-s ( To create a file, just visit the file with C-x C-f as if it already existed. This creates an empty buffer in which you can insert the text you want to put in the file. The file is actually created when you save this buffer with C-x C-s. Of course, there is a lot more to learn about using files. See section File Handling. HelpIf you forget what a key does, you can find out with the Help character, which is C-h
(or F1, which is an alias for C-h). Type C-h
k followed by the key you want to know about; for example, C-h
k C-n tells you all about what C-n does. C-h
is a prefix key; C-h k is just one of its subcommands
(the command Blank LinesHere are special commands and techniques for putting in and taking out blank lines.
When you want to insert a new line of text before an existing line,
you can do it by typing the new line of text, followed by RET.
However, it may be easier to see what you are doing if you first
make a blank line and then insert the desired text into it. This is easy to do
using the key C-o ( You can make several blank lines by typing C-o several times, or by giving it a numeric argument to tell it how many blank lines to make. See section Numeric Arguments, for how. If you have a fill prefix, then C-o command inserts the fill prefix on the new line, when you use it at the beginning of a line. See section The Fill Prefix. The easy way to get rid of extra blank lines is with the command C-x C-o ( Continuation LinesIf you add too many characters to one line without breaking it with RET, the line will grow to occupy two (or more) lines on the screen, with a \ at the extreme right margin of all but the last of them. The \ says that the following screen line is not really a distinct line in the text, but just the continuation of a line too long to fit the screen. Continuation is also called line wrapping. Sometimes it is nice to have Emacs insert newlines automatically when a line gets too long. Continuation on the screen does not do that. Use Auto Fill mode (see section Filling Text) if that's what you want. As an alternative to continuation, Emacs can display long lines by truncation. This means that all the characters that do not fit in the width of the screen or window do not appear at all. They remain in the buffer, temporarily invisible. $ is used in the last column instead of \ to inform you that truncation is in effect. Truncation instead of
continuation happens whenever horizontal scrolling is in use, and
optionally in all side-by-side windows (see section Multiple Windows). You can enable truncation for a particular buffer by setting the variable See section Variables Controlling Display, for additional variables that affect how text is displayed. Cursor Position InformationHere are commands to get information about the size and position of parts of the buffer, and to count lines.
There are two commands for working with line numbers. M-x what-line computes the current line number and displays it in the echo area. To go to a given line by number, use M-x goto-line; it prompts you for the number. These line numbers count from one at the beginning of the buffer. M-x line-number-mode enables display of the current line number in the mode line; once you turn this on, the number updates as you move point, so it remains valid all the time. See section The Mode Line. If you narrow the buffer, only the accessible portion counts for this feature. By contrast, M-x what-page counts pages from the beginning of the file, and counts lines within the page, printing both numbers. See section Pages. While on this subject, we might as well mention M-=
( The command C-x =
( Char: x (0170) point=65986 of 563027(12%) x=44 (In fact, this is the output produced when point is before the x=44 in the example.) The two values after Char: describe the character that follows point, first by showing it and second by giving its octal character code. point= is followed by the position of point expressed as a character count. The front of the buffer counts as position 1, one character later as 2, and so on. The next, larger number is the total number of characters in the buffer. Afterward in parentheses comes the position expressed as a percentage of the total size. x= is followed by the horizontal position of point, in columns from the left edge of the window. If the buffer has been narrowed, making some of the text at the beginning and the end temporarily inaccessible, C-x = prints additional text describing the currently accessible range. For example, it might display this: Char: x (0170) point=65986 of 563025(12%) x=44 where the two extra numbers give the smallest and largest character position that point is allowed to assume. The characters between those two positions are the accessible ones. See section Narrowing. If point is at the end of the buffer (or the end of the accessible part), C-x = omits any description of the character after point. The output looks like this: point=563026 of 563025(100%) x=0 Numeric ArgumentsAny Emacs command can be given a numeric argument (also called a prefix argument). Some commands interpret the argument as a repetition count. For example, C-f with an argument of ten moves forward ten characters instead of one. With these commands, no argument is equivalent to an argument of one. Negative arguments tell most such commands to move or act in the opposite direction. If your terminal keyboard has a META key, the easiest way to specify a numeric argument is to type digits and/or a minus sign while holding down the the META key. For example, M-5 C-n would move down five lines. The characters Meta-1, Meta-2, and
so on, as well as Meta--,
do this because they are keys bound to commands ( Another way of specifying an argument is to use the C-u
( C-u followed by a character which is neither a digit nor a minus sign has the special meaning of ``multiply by four''. It multiplies the argument for the next command by four. C-u twice multiplies it by sixteen. Thus, C-u C-u C-f moves forward sixteen characters. This is a good way to move forward ``fast'', since it moves about 1/5 of a line in the usual size screen. Other useful combinations are C-u C-n, C-u C-u C-n (move down a good fraction of a screen), C-u C-u C-o (make ``a lot'' of blank lines), and C-u C-k (kill four lines). Some commands care only about whether there is an argument,
and not about its value. For example, the command M-q ( Some commands use the value of the argument as a repeat count,
but do something peculiar when there is no argument. For example,
the command C-k ( A few commands treat a plain C-u differently from an ordinary argument. A few others may treat an argument of just a minus sign differently from an argument of -1. These unusual cases are described when they come up; they are always for reasons of convenience of use of the individual command. You can use a numeric argument to insert multiple copies of a character. This is straightforward unless the character is a digit; for example, C-u 6 4 a inserts 64 copies of the character a. But this does not work for inserting digits; C-u 6 4 1 specifies an argument of 641, rather than inserting anything. To separate the digit to insert from the argument, type another C-u; for example, C-u 6 4 C-u 1 does insert 64 copies of the character 1. We use the term ``prefix argument'' as well as ``numeric argument'' to emphasize that you type the argument before the command, and to distinguish these arguments from minibuffer arguments that come after the command. To return to the Ready-to-Run Software Super ReadyPak Table of Contents please press here. |
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