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<chapter id="ch_emacs">
<title>Emacs</title>

<para>
While <application>vi</application> (with its clones) is without a
doubt the most ubiquitous
editor on Unix-like systems, <application>emacs</application>(1) comes
in a good second. Instead of
using different "modes", like <application>vi</application> does, it uses <keycap>CTRL</keycap> and <keycap>ALT</keycap> key
combinations to enter commands, in much the same way that you can use
<keycap>CTRL</keycap>  and <keycap>ALT</keycap> key combinations in a word processor and indeed in
many other applications to execute certain functions. (Though it should
be noted that the commands rarely correspond; so while many modern
applications use Ctrl-C/ X/ V for copying, cutting and pasting, <application>emacs</application>
uses different keys and actually a somewhat different mechanism for
this.)
</para>

<para>
Also unlike <application>vi</application>, which is an (excellent) editor and nothing more, <application>emacs</application>
is a program with near endless capabilities. <application>emacs</application> is (for the most
part) written in Lisp, which is a very powerful programming language
that has the peculiar property that every program written in it is
automatically a Lisp compiler of its own. This means that the user can
extend <application>emacs</application>, and in fact write completely new programs "in <application>emacs</application>".
</para>

<para>
As a result, <application>emacs</application> is not just an editor anymore. There are many add-on
packages for <application>emacs</application> available (many come with the program's source) that
provide all sorts of functionality. Many of these are related to text
editing, which is after all <application>emacs</application>' basic task, but it doesn't stop
there. There are for example several spreadsheet programs for <application>emacs</application>,
there are databases, games, mail and news clients (the top one being
Gnus), etc.
</para>

<para>
There are two main versions of <application>emacs</application>: GNU Emacs (which is the version
that comes with Slackware) and XEmacs. The latter is not a version for
Emacs running under X. In fact, both <application>emacs</application> and XEmacs run on the
console as well as under X. XEmacs was once started as a project to
tidy up the <application>emacs</application> code. Currently, both versions are being actively
developed, and there is in fact much interaction between the two
development teams. For the present chapter, it is immaterial whether
you use <application>emacs</application> or XEmacs, the differences between them are not relevant
to the normal user.
</para>

<section id="emacs_starting-emacs">
<title>Starting Emacs</title>

<para>
Emacs can be started from the shell by simply typing <application>emacs</application>. When you
are running X, <application>emacs</application> will (normally) come up with its own X window,
usually with a menu bar at the top, where you can find the most
important functions. On startup, <application>emacs</application> will first show a welcome
message, and then after a few seconds will drop you in the *scratch*
buffer. (See Section 17.2.)
</para>

<para>
You can also start <application>emacs</application> on an existing file by typing
</para>

<screen>
    <prompt>&#37; </prompt> <command><application>emacs</application>
    <filename>&#47;etc&#47;resolv.conf</filename>
  </command>
</screen>

<para>
This will cause <application>emacs</application> to load the specified file when it starts up,
skipping the welcome message.
</para>

<section id="emacs_command-keys">
<title>Command Keys</title>
<para>
As mentioned above, <application>emacs</application> uses <keycap>CTRL</keycap> and <keycap>ALT</keycap> combinations for
commands. The usual convention is to write these with <keycap>C</keycap>-letter and
<keycap>M</keycap>-letter, respectively. So <keycap>C</keycap>-x means <keycap>CTRL</keycap>+x, and <keycap>M</keycap>-x  means <keycap>ALT</keycap>+x.
</para>

<note>
  <para>
    The letter M is used instead of A because originally the key was not
the <keycap>ALT</keycap> key but the Meta key. The Meta key has all but disappeared from
computer keyboards, and in <application>emacs</application> the <keycap>ALT</keycap> key has taken over its
function.
  </para>
</note>

<para>
Many <application>emacs</application> commands consist of sequences of keys and key combinations.
For example, <keycap>C</keycap>-x <keycap>C</keycap>-c &#40;that is <keycap>CTRL</keycap>-x followed by <keycap>CTRL</keycap>-c&#41; quits
Emacs, <keycap>C</keycap>-x <keycap>C</keycap>-s saves the current file. Keep in mind that <keycap>C</keycap>-x <keycap>C</keycap>-b is not
the same as <keycap>C</keycap>-x b. The former means <keycap>CTRL</keycap>-x followed by <keycap>CTRL</keycap>-b,
while the latter means <keycap>CTRL</keycap>-x followed by just &#39;b&#39;.
</para>

</section>

</section>

<section id="emacs_buffers">
<title>Buffers</title>
<para>
In <application>emacs</application>, the concept of &#39;buffers&#39; is essential. Every file that you
open is loaded into its own buffer. Furthermore, <application>emacs</application> has several
special buffers, which do not contain a file but are used for other
things. Such special buffers usually have a name that starts and ends
with an asterisk. For example, the buffer that <application>emacs</application> shows when it is
first started, is the so-called &#42;scratch&#42; buffer. In the &#42;scratch&#42;
buffer, you can type text in the normal way, but text that is typed
there is not saved when <application>emacs</application> is closed.
</para>
<para>
There is one other special buffer you need to know about, and that is
the minibuffer. This buffer consists of only one line, and is always on
the screen: it is the very last line of the <application>emacs</application> window, below the
status bar for the current buffer. The minibuffer is where <application>emacs</application> shows
messages for the user, and it is also the place where commands that
require some user input are executed. For example, when you open a
file, <application>emacs</application> will ask for its name in the minibuffer.
</para>
<para>
Switching from one buffer to another can be done with the command <keycap>C</keycap>-x
b. This will prompt you for the name of a buffer (a buffer's name is
usually the name of the file you are editing in it), and it gives a
default choice, which is normally the buffer that you were in before
you switched to or created the current buffer. Just hitting Enter will
switch to that default buffer.
</para>
<para>
If you want to switch to another buffer than the default offered by
Emacs, just type its name. Note that you can use so-called
Tab-completion here: type the first few letters of the buffer's name
and hit Tab; <application>emacs</application> will then complete the name of the buffer. Tab
completion works everywhere in <application>emacs</application> where it makes sense.
</para>
<para>
You can get a list of open buffers by hitting <keycap>C</keycap>-x <keycap>C</keycap>-b. This command
will usually split the screen in two, displaying the buffer you were
working in in the top half, and a new buffer called &#42;Buffer List&#42; in
the bottom half. This buffer contains a list of all the buffers, their
sizes and modes, and the files, if any, that those buffers are visiting
(as it is called in <application>emacs</application>). You can get rid of this split screen by
typing <keycap>C</keycap>-x 1.
</para>
</section>

<section id="emacs_modes">
<title>Modes</title>
<para>
Every buffer in <application>emacs</application> has an associated mode. This mode is very
different from the idea of modes in <application>vi</application>: a mode tells you what kind of
buffer you are in. For example, there is text-mode for normal text
files, but there are also modes such as c-mode for editing C programs,
sh-mode for editing shell scripts, latex-mode for editing LaTeX files,
mail-mode for editing email and news messages, etc. A mode provides
special customizations and functionality that is useful for the kind of
file you are editing. It is even possible for a mode to redefine keys
and key commands. For example, in Text mode, the <keycap>Tab</keycap> key simply jumps
to the next tab stop, but in many programming language modes, the <keycap>Tab</keycap>
key indents the current line according to the depth of the block that
line is in.
</para>

<para>
The modes mentioned above are called <emphasis>major modes</emphasis>. Each buffer has
exactly one major mode. Additionally, a buffer can have one or more
minor modes. A <emphasis>minor mode</emphasis> provides additional features that may be
useful for certain editing tasks. For example, if you hit the <keycap>INSERT</keycap>
key, you invoke overwrite-mode, which does what you&#39;d expect. There is
also an auto-fill-mode, which is handy in combination with text-mode or
latex-mode: it causes each line that you type to be automatically
wrapped once the line reaches a certain number of characters. Without
auto-fill-mode, you have to type <keycap>M</keycap>-q to fill out a paragraph. &#40;Which
you can also use to reformat a paragraph after you&#39;ve edited some text
in it and it is no longer nicely filled out.&#41;
</para>

<section id="emacs_opening-files">
<title>Opening Files</title>

<para>
To open a file in <application>emacs</application>, type <keycap>C</keycap>-x <keycap>C</keycap>-f
</para>

<para>
<application>Emacs</application> will ask you for the name of the file, filling in some default
path for you &#40;which is usually &#126;&#47; &#41;. After you type the filename &#40;you
can use <keycap>Tab</keycap> completion&#41; and hit <keycap>ENTER</keycap>, <application>emacs</application> will open the file in a
new buffer and display that buffer on the screen.
</para>

<note>
  <para>
    <application>Emacs</application> will automatically create a new
    buffer, it will not load the file into the current buffer.
  </para>
</note>

  <para>
    In order to create a new file in <application>emacs</application>,
    you cannot just go typing right away. You first have to create a
    buffer for it, and come up with a filename. You do this by typing
    <keycap>C</keycap>-x <keycap>C</keycap>-f and typing a filename,
    just as if you were opening an existing
    file. <application>Emacs</application> will notice that the file
    you typed doesn&#39;t exist, and will create a new buffer and report
    &#34;&#40;New file&#41;&#34; in the minibuffer.
  </para>

  <para>
When you type <keycap>C</keycap>-x <keycap>C</keycap>-f and then enter a directory name instead of a
filename, <application>emacs</application> will create a new buffer in which you will find a list
of all the files in that directory. You can move the cursor to the file
that you are looking for and type , and
<application>emacs</application> will open it.
  </para>

<note>
  <para>
    There are in fact a lot more actions you can perform here, such as
    deleting, renaming and moving files,
    and so on. This is the dired-mode of <application>emacs</application>, which
    is basically a simple file manager.
  </para>
</note>

<para>
When you have typed <keycap>C</keycap>-x <keycap>C</keycap>-f and suddenly change your mind, you can type
<keycap>C</keycap>-g to cancel the action. <keycap>C</keycap>-g works almost everywhere where you want to
cancel an action or command that you've started but don&#39;t want to
finish.
</para>
</section> <!-- closing OPENING FILES section --> 

</section> <!-- closing MODES section --> 

<section id="emacs_basic-editing">
<title>Basic Editing</title>

<para>
When you have opened a file, you can of course move around in it with
the cursor. The cursor keys and <keycap>PgUp</keycap>, <keycap>PgDn</keycap> do what you&#39;d expect. <keycap>Home</keycap>
and <keycap>End</keycap> jump to the beginning and end of the line. &#40;In older versions,
they would actually jump to the beginning and end of the buffer.&#41;
However, there are also <keycap>CTRL</keycap> and Meta &#40;<keycap>ALT</keycap>&#41; key combos that move the
cursor around. Because you do not need to move your hands to another
part of the keyboard for these, they are much quicker once you get used
to them.
</para>

<table>
<title>Basic <application>emacs</application> Editing Commands</title>
<tgroup cols="2">
  <thead>
    <row>
      <entry>Command</entry>
      <entry>Result</entry>
    </row>
  </thead>
  <tbody>
    <row>
      <entry><keycap>C</keycap>-b</entry>
      <entry>go one character back</entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-f</entry>
      <entry>go one character forward</entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-n</entry>
      <entry>go one line down</entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-p</entry>
      <entry>go one line up</entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-a</entry>
      <entry>go to the beginning of the line</entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-e</entry>
      <entry>go to the end of the line</entry>
    </row>
    <row>
      <entry><keycap>M</keycap>-b</entry>
      <entry>go one word back</entry>
    </row>
    <row>
      <entry><keycap>M</keycap>-f</entry>
      <entry>go one word forward</entry>
    </row>
    <row>
      <entry><keycap>M</keycap>-&#125;</entry>
      <entry>go one paragraph forward</entry>
    </row>
    <row>
      <entry><keycap>M</keycap>-&#123;</entry>
      <entry>go one paragraph backward</entry>
    </row>
    <row>
      <entry><keycap>M</keycap>-a</entry>
      <entry>go one sentence backward</entry>
    </row>
    <row>
      <entry><keycap>M</keycap>-e</entry>
      <entry>go one sentence forward</entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-d</entry>
      <entry>delete the character under the cursor</entry>
    </row>
    <row>
      <entry><keycap>M</keycap>-d</entry>
      <entry>delete until the end of the current word</entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-v</entry>
      <entry>go down one screen &#40;i.e.,
      <keycap>PgDn</keycap>&#41;</entry>
    </row>
    <row>
      <entry><keycap>M</keycap>-v</entry>
      <entry>go up one screen &#40;i.e.,
      <keycap>PgUp</keycap>&#41;</entry>
    </row>
    <row>
      <entry><keycap>M</keycap>-&lt;</entry>
      <entry>go to the beginning of the buffer</entry>
    </row>
    <row>
      <entry><keycap>M</keycap>-&gt;</entry>
      <entry>go to the end of the buffer</entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-&#95;</entry>
      <entry>undo the last change &#40;can be repeated&#41;&#59; note
      that you actually have to type
      <keycap>SHIFT</keycap>+<keycap>CTRL</keycap>+hyphen for this.
      </entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-k</entry>
      <entry>delete to end of line</entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-s</entry>
	<entry>forward search</entry>
    </row>
    <row>
      <entry><keycap>C</keycap>-r</entry>
      <entry>reverse search</entry>
    </row>
  </tbody>
</tgroup>
</table>

<para>
Note that many Meta commands are parallel to the <keycap>CTRL</keycap> commands
except that they operate on larger units: while <keycap>C</keycap>-f goes forward one
character, <keycap>M</keycap>-f goes forward an entire word, etc.
</para>

<para>
Also note that <keycap>M</keycap>-&lt; and <keycap>M</keycap>-&gt; require you to type <keycap>SHIFT</keycap>+<keycap>ALT</keycap>+comma and
<keycap>SHIFT</keycap>+<keycap>ALT</keycap>+dot respectively, since
&lt; and &gt; are on <keycap>SHIFT</keycap>+comma and
<keycap>SHIFT</keycap>+dot. &#40;Unless of course you have a different keyboard layout from
the standard US layout.&#41;
</para>

<para>
Note that <keycap>C</keycap>-k deletes &#40;kills, as it is commonly called&#41; all the text
after the cursor to the end of the line, but doesn't delete the line
itself &#40;i.e., it doesn't delete the final newline&#41;. It only deletes the
line if there was no text after the cursor. In other words, in order to
delete a complete line, you have to put the cursor at the beginning of
the line, and then hit <keycap>C</keycap>-k twice: once to delete the text on the line,
and once to delete the line itself.
</para>

</section> <!-- closing EDITING section -->

<section id="emacs_saving-files">
<title>Saving Files</title>

<para>
In order to save a file, you type <keycap>C</keycap>-x <keycap>C</keycap>-s
</para>

<para>
<application>Emacs</application> will not ask you for a filename, the buffer will just be saved to
the file it was loaded from. If you want to save your text to another
file, type

<keycap>C</keycap>-x <keycap>C</keycap>-w
</para>

<para>
When you save the file for the first time in this session, <application>emacs</application> will
normally save the old version of your file to a backup file, which has
the same name appended with a tilde: so if you&#39;re editing a file
<filename>cars.txt</filename>, <application>emacs</application> will create a backup <filename>cars.txt~</filename>.
</para>

<para>
This backup file is a copy of the file that you opened. While you are
working, <application>emacs</application> will also regularly create an auto-save copy of the work
you are doing, to a file named with hash signs: &#35;cars.txt&#35;. This backup
is deleted when you save the file with <keycap>C</keycap>-x <keycap>C</keycap>-s.
</para>

<para>
When you are done editing a file, you can kill the buffer that holds it
by typing <keycap>C</keycap>-x k
</para>

<para>
<application>Emacs</application> will then ask you which buffer you want to kill, with the current
buffer as default, which you can select by hitting <keycap>ENTER</keycap>. If you
haven&#39;t saved your file yet, <application>emacs</application> will ask you if you really want to
kill the buffer.
</para>

<para>
  If you&#39;d prefer to save the file with a new name so that you
  don&#39;t overwrite the original version, use <keycap>C</keycap>-x
  <keycap>C</keycap>-w instead. You may then give a new name for the
  file, and the buffer will be updated to reflect the contents of this
  new file, leaving the old file unchanged.
</para>

</section>

<section id="emacs_quitting-emacs">
<title>Quitting Emacs</title>

<para>
When you are done with <application>emacs</application> altogether,
you can type <keycap>C</keycap>-x <keycap>C</keycap>-c
</para>

<para>
This quits <application>emacs</application>. If you have any unsaved files, <application>emacs</application> will tell you
so, and ask if you want to save them each in turn. If you answer no to
any of these, <application>emacs</application> will ask for one final confirmation and then quit.
</para>

</section> <!-- closing QUIT section -->

</chapter>