tutorial

早期freebsd实现

You've now learned the most basic way of typing something in
Emacs and correcting errors.  You can delete by words or lines
as well.  Here is a summary of the delete operations:

	<Rubout>     delete the character just before the cursor
	C-d   	     delete the next character after the cursor

	M-<Rubout>   kill the word immediately before the cursor
	M-d	     kill the next word after the cursor

	C-k	     kill from the cursor position to end of line
	M-k	     kill to the end of the current sentence

Notice that <Rubout> and C-d vs M-<Rubout> and M-d extend the parallel
started by C-f and M-f (well, <Rubout> isn't really a control
character, but let's not worry about that).  C-k and M-k are like C-e
and M-e, sort of, in that lines are opposite sentences.

Now suppose you kill something, and then you decide that you want to
get it back?  Well, whenever you kill something bigger than a
character, Emacs saves it for you.  To yank it back, use C-y.  You
can kill text in one place, move elsewhere, and then do C-y; this is
a good way to move text around.  Note that the difference
between "Killing" and "Deleting" something is that "Killed" things
can be yanked back, and "Deleted" things cannot.  Generally, the
commands that can destroy a lot of text save it, while the ones that
attack only one character, or nothing but blank lines and spaces, do
not save.

For instance, type C-n a couple times to postion the cursor
at some line on this screen.

>> Do this now, move the cursor and kill that line with C-k.

Note that a single C-k kills the contents of the line, and a second
C-k kills the line itself, and make all the other lines move up.  If
you give C-k a repeat count, it kills that many lines AND their
contents.

The text that has just disappeared is saved so that you can
retrieve it.  To retrieve the last killed text and put it where
the cursor currently is, type C-y.

>> Try it; type C-y to yank the text back.

Think of C-y as if you were yanking something back that someone
took away from you.  Notice that if you do several C-k's in a row
the text that is killed is all saved together so that one C-y will
yank all of the lines.

>> Do this now, type C-k several times.

Now to retrieve that killed text:

>> Type C-y.  Then move the cursor down a few lines and type C-y
   again.  You now see how to copy some text.

What do you do if you have some text you want to yank back, and then
you kill something else?  C-y would yank the more recent kill.  But
the previous text is not lost.  You can get back to it using the M-y
command.  After you have done C-y to get the most recent kill, typing
M-Y replaces that yanked text with the previous kill.  Typing M-y
again and again brings in earlier and earlier kills.  When you
have reached the text you are looking for, you can just go away and
leave it there.  If you M-y enough times, you come back to the
starting point (the most recent kill).

>> Kill a line, move around, kill another line.
   Then do C-y to get back the second killed line.
   Then do M-y and it will be replaced by the first killed line.
   Do more M-y's and see what you get.  Keep doing them until
   the second kill line comes back, and then a few more.
   If you like, you can try giving M-y positive and negative
   arguments.


UNDO
----

Any time you make a change to the text and wish you had not done so,
you can undo the change (return the text to its previous state)
with the undo command, C-x u.  Normally, C-x u undoes one command's
worth of changes; if you repeat the C-x u several times in a row,
each time undoes one more command.  There are two exceptions:
commands that made no change (just moved the cursor) do not count,
and self-inserting characters are often lumped together in groups
of up to 20.  This is to reduce the number of C-x u's you have to type.

>> Kill this line with C-k, then type C-x u and it should reappear.

C-_ is another command for undoing; it is just the same as C-x u
but easier to type several times in a row.  The problem with C-_ is
that on some keyboards it is not obvious how to type it.  That is
why C-x u is provided as well.  On some DEC terminals, you can type
C-_ by typing / while holding down CTRL.  Illogical, but what can
you expect from DEC?

Giving a numeric argument to C-_ or C-x u is equivalent to repeating
it as many times as the argument says.


FILES
-----

In order to make the text you edit permanent, you must put it in a
file.  Otherwise, it will go away when your invocation of Emacs goes
away.  You put your editing in a file by "finding" the file.  What
finding means is that you see the contents of the file in your Emacs;
and, loosely speaking, what you are editing is the file itself.
However, the changes still don't become permanent until you "save" the
file.  This is so you can have control to avoid leaving a half-changed
file around when you don't want to.  Even then, Emacs leaves the
original file under a changed name in case your changes turn out
to be a mistake.

If you look near the bottom of the screen you will see a line that
begins and ends with dashes, and contains the string "Emacs: TUTORIAL".
Your copy of the Emacs tutorial is called "TUTORIAL".  Whatever
file you find, that file's name will appear in that precise
spot.

The commands for finding and saving files are unlike the other
commands you have learned in that they consist of two characters.
They both start with the character Control-x.  There is a whole series
of commands that start with Control-x; many of them have to do with
files, buffers, and related things, and all of them consist of
Control-x followed by some other character.

Another thing about the command for finding a file is that you have
to say what file name you want.  We say the command "reads an argument
from the terminal" (in this case, the argument is the name of the
file).  After you type the command

	C-x C-f   Find a file

Emacs asks you to type the file name.  It echoes on the bottom
line of the screen.  You are using the minibuffer now!  this is
what the minibuffer is for.  When you type <Return> to end the
file name, the minibuffer is no longer needed, so it disappears.

>> Type C-x C-f, then type C-g.  This cancels the minibuffer,
   and also cancels the C-x C-f command that was using the
   minibuffer.  So you do not find any file.

In a little while the file contents appear on the screen.  You can
edit the contents.  When you wish to make the changes permanent,
issue the command

	C-x C-s   Save the file

The contents of Emacs are written into the file.  The first time you
do this, the original file is renamed to a new name so that it
is not lost.  The new name is made by appending "~" to the end
of the original file's name.

When saving is finished, Emacs prints the name of the file written.
You should save fairly often, so that you will not lose very much
work if the system should crash.

>> Type C-x C-s, saving your copy of the tutorial.
   This should print "Wrote .../TUTORIAL" at the bottom of the screen.
   On VMS it will print "Wrote ...[...]TUTORIAL."

To make a new file, just find it "as if" it already existed.  Then
start typing in the text.  When you ask to "save" the file, Emacs
will really create the file with the text that you have inserted.
From then on, you can consider yourself to be editing an already
existing file.


BUFFERS
-------

If you find a second file with C-x C-f, the first file remains
inside Emacs.  You can switch back to it by finding it again with
C-x C-f.  This way you can get quite a number of files inside Emacs.

The object inside Emacs which holds the text read from one file
is called a "buffer."  Finding a file makes a new buffer inside Emacs.
To see a list of the buffers that exist in Emacs, type

	C-x C-b   List buffers

>> Try C-x C-b now.

See how each buffer has a name, and it may also have a file name
for the file whose contents it holds.  Some buffers do not correspond
to files.  For example, the buffer named "*Buffer List*" does
not have any file.  It is the buffer which contains the buffer
list that was made by C-x C-b.  ANY text you see in an Emacs window
has to be in some buffer.

>> Type C-x 1 to get rid of the buffer list.

If you make changes to the text of one file, then find another file,
this does not save the first file.  Its changes remain inside Emacs,
in that file's buffer.  The creation or editing of the second file's
buffer has no effect on the first file's buffer.  This is very useful,
but it also means that you need a convenient way to save the first
file's buffer.  It would be a nuisance to have to switch back to
it with C-x C-f in order to save it with C-x C-s.  So we have

	C-x s     Save some buffers

C-x s goes through the list of all the buffers you have
and finds the ones that contain files you have changed.
For each such buffer, C-x s asks you whether to save it.


EXTENDING THE COMMAND SET
-------------------------

There are many, many more Emacs commands than could possibly be put
on all the control and meta characters.  Emacs gets around this with
the X (eXtend) command.  This comes in two flavors:

	C-x	Character eXtend.  Followed by one character.
	M-x	Named command eXtend.  Followed by a long name.

These are commands that are generally useful but used less than the
commands you have already learned about.  You have already seen two
of them: the file commands C-x C-f to Find and C-x C-s to Save.
Another example is the command to tell Emacs that you'd like to stop
editing and get rid of Emacs.  The command to do this is C-x C-c.
(Don't worry; it offers to save each changed file before it kills the
Emacs.)

C-z is the usual way to exit Emacs, because it is always better not to
kill the Emacs if you are going to do any more editing.  On systems
which allow it, C-z exits from Emacs to the shell but does not destroy
the Emacs; if you use the C shell, you can resume Emacs with the `fg'
command (or, more generally, with `%emacs', which works even if your
most recent job was some other).  On systems where suspending is not
possible, C-z creates a subshell running under Emacs to give you the
chance to run other programs and return to Emacs afterward, but it
does not truly "exit" from Emacs.  In this case, the shell command
`exit' is the usual way to get back to Emacs from the subshell.

You would use C-x C-c if you were about to log out.  You would
also use it to exit an Emacs invoked under mail handling programs
and other random utilities, since they may not believe you have
really finished using the Emacs if it continues to exist.

There are many C-x commands.  The ones you know are:

	C-x C-f		Find file.
	C-x C-s		Save file.
	C-x C-b		List buffers.
	C-x C-c		Quit Emacs.
	C-x u		Undo.

Named eXtended commands are commands which are used even less
frequently, or commands which are used only in certain modes.  These
commands are usually called "functions".  An example is the function
replace-string, which globally replaces one string with another.  When
you type M-x, Emacs prompts you at the bottom of the screen with
M-x and you should type the name of the function you wish to call; in
this case, "replace-string".  Just type "repl s<TAB>" and Emacs will
complete the name.  End the command name with <Return>.
Then type the two "arguments"--the string to be replaced, and the string
to replace it with--each one ended with a Return.

>> Move the cursor to the blank line two lines below this one.
   Then type M-x repl s<Return>changed<Return>altered<Return>.

   Notice how this line has changed: you've replaced
   the word c-h-a-n-g-e-d with "altered" wherever it occured
   after the cursor.