path: root/chapter_12.xml

<?xml version="1.0"?>
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "/usr/share/xml/docbook/xml-dtd-4.5/docbookx.dtd">

<chapter>
<title><application>vi</application></title>

<section>
<title>What is <application>vi</application>?</title>

<para>
Scattered all around your computer are thousands of text files. To a
new user, this may seem inconsequential, but almost everything in
Slackware Linux uses a plain-text file for configuration. This allows
users to make changes to the system quickly, easily, and intuitively.
In chapter 5, we looked at a few commands such as
<application>cat</application> and <application>less</application> that
can be used to read these files, but what if we want to make changes to
them? For that, we need a text editor, and
<application>vi</application> is up to the task.
</para>

<para>
In short, <application>vi</application> is one of the oldest and most
powerful text editors still used today. It's beloved by system
administrators, programmers, hobbiests, and others the world over. In
fact, nearly this entire book was written using
<application>vi</application>; only the next chapter on
<application>emacs</application> was written with that editor.
</para>

<para>
A little further explanation is needed to learn exactly what
<application>vi</application> is today though, as Slackware Linux
technically doesn't include <application>vi</application>. Rather,
Slackware includes two vi "clones", <application>elvis</application>(1)
and <application>vim</application>(1). These clones add many additional
features to vi such as syntax highlighting, binary editing modes, and
network support. We won't go too deeply into all these details. By
default, if you execute <application>vi</application> on Slackware
Linux, you'll be using <application>elvis</application>, so all
examples in this chapter will assume that is what you are using. If
you've used another Linux distribution before, you may be more familiar
with <application>vim</application>. If so, you might wish to change
the symlink for <filename>/usr/bin/vi</filename> to point to
<filename>/usr/bin/vim</filename>, or add an alias to your shell's
startup scripts. <application>vim</application> is generally considered
to be more feature-rich than <application>elvis</application>, but
<application>elvis</application> is a much smaller program and contains
more features than most users will ever need.
</para>

<para>
<application>vi</application> is very powerful, but also somewhat
cumbersome and challening for a new user to learn. However, mastering 
<application>vi</application> is an important skill for any
self-respecting system administrator to learn, as 
<application>vi</application> is included on nearly every Linux
distribution, every BSD system, and every UNIX system in existance. 
It's even included in Mac OS X.
Once you've learned <application>vi</application>, you'll not have to
learn another text editor to work on any of these systems. In fact,
<application>vi</application> clones have even been ported to Microsoft Windows
systems, so you can use it there too.
</para>

</section>

<section>
<title>The Different Modes of <application>vi</application></title>

<para>
New users are often frustrated when using <application>vi</application>
for the first time. When invoked without any arguments, 
<application>vi</application> will display a screen something like
this.
</para>

<screen>
~
~
~
~
~
~
~
~
~
~
~
                                     Command
</screen>

<para>
At this point, the user will being typing and expect the keys he
presses to appear in the document. Instead, something really strange
happens. The reason for this is simple. <application>vi</application>
has different operation "modes". There is a command mode and an insert
mode. Command mode is the default; in this mode, each keystroke
performs a particular action such as moving the cursor around, deleting
text, yanking (copying) text, searching, etc.
</para>


</section>

<section>
<title>Opening, Saving, and Quitting</title>

<para>
Ok, so you've decided that you want to learn how to use 
<application>vi</application>. The first thing to do is learn how to
open and save files. Opening files is actually pretty easy. Simply type
the filename as an argument on the command-line and 
<application>vi</application> will happily load it for you. For
example, <userinput>vi chapter_11.xml</userinput> will open the file
<filename>chapter_11.xml</filename> and load its content onto the
screen, simple enough. But what if we've finished with one document and
wish to save it? We can do that in command mode using the <arg>:w</arg>
command. When in command mode, pressing the <keycap>:</keycap> key
temporarily positions the cursor on the very bottom line of the window
and allows you to enter special commands. (This is technically known as
ex-mode after the venerable <application>ex</application> application
which we will not document here.) The command to save your current work
is <arg>:w</arg>. Once this is done, <application>vi</application> will
write your changes to the buffer back into the file. If you wish to
open another document, simply use the <arg>:e other_document</arg>
command and <application>vi</application> will happily open it for you.
If you've made changes to the buffer but haven't saved it yet,
<arg>:e</arg> will fail and print a warning message on the bottom line.
You can bypass this with the <arg>:e!</arg> command. Most ex-mode
commands in <application>vi</application> can be "forced" by adding
<keycap>!</keycap> to them. This tells <application>vi</application>
that you want to abandon any changes you've made to the buffer and open
the other document immediately.
</para>

<para>
But what if I don't like my changes and want to quit or start over?
That's easily done as well. Executing the <arg>:e!</arg> command
without any arguments will re-open the current document from the
beginning. Quitting <application>vi</application> is as simple as
running the <arg>:q</arg> command if you haven't made any changes to
the buffer, or <arg>:q!</arg> if you'd like to quit and abandon those
changes.
</para>

</section>

<section>
<title>Moving Around</title>

<para>
Moving around in <application>vi</application> is perhaps the hardest
thing for a new user to learn. <application>vi</application> does not
traditionally use the directional arrow keys for cursor movement,
although in Slackware Linux that is an option. Rather, movement is
simply another command issued in command-mode. The reason for this is
rather simple. <application>vi</application> actually predates the
inclusion of directional arrow keys on keyboards. Thus,
movement of the cursor had to be accomplished by using the few
keys available, so the right-hand "home row" keys of
<keycap>h</keycap>, <keycap>j</keycap>, <keycap>k</keycap>, and
<keycap>l</keycap> were chosen. These keys will move the cursor about
whenever <application>vi</application> is in command mode. Here's a
short table to help you remember how they work.
</para>

<table pgwide="0">
<title>vi cursor movement</title>
<tgroup cols="2">
  <thead>
    <row>
      <entry>Command</entry>
      <entry>Result</entry>
    </row>
  </thead>
  <tbody>
    <row>
      <entry>h</entry>
      <entry>Move the cursor one character left.</entry>
    </row>
    <row>
      <entry>j</entry>
      <entry>Move the cursor one line down</entry>
    </row>
    <row>
      <entry>k</entry>
      <entry>Move the cursor one line up</entry>
    </row>
    <row>
      <entry>l</entry>
      <entry>Move the cursor one character right</entry>
    </row>
  </tbody>
</tgroup>
</table>

<para>
Moving around is a little more powerful than that though. Like many
command keys, these movement keys accept numerical arguments. For
example, <keycap>10j</keycap> will move the cursor down 10 lines. You
can also move to the end or beginning of the current line with
<keycap>$</keycap> and <keycap>^</keycap>, respectively.
</para>

</section>

<section>
<title>Editing A Document</title>

<para>
Now that we're able to open and save documents, as well as move around
in them, it's time to learn how to edit them. The primary means of
editing is to enter insert mode using either the <keycap>i</keycap> or
<keycap>a</keycap> command keys.  These either insert text at the
cursor's current location, or append it after the cursor's current
location. Once into insert mode, you can type any text normally and it
will be placed into your document.  You can return to command mode in
order to save your changes by pressing the <keycap>ESC</keycap> key.
</para>

</section>

<section>
<title><application>vi</application> Cheat Sheet</title>

<para>
Since <application>vi</application> can be difficult to learn, I've
prepared a short cheat sheat that should help you with the basics until
you begin to feel comfortable.
</para>

<table pgwide="0">
<title>vi Cheat Sheet</title>
<tgroup cols="2" title="Movement">
  <thead>
    <row>
      <entry>Command</entry>
      <entry>Result</entry>
    </row>
  </thead>
  <tbody>
    <row>
      <entry>h</entry>
      <entry>Move the cursor one character left.</entry>
    </row>
    <row>
      <entry>j</entry>
      <entry>Move the cursor one line down</entry>
    </row>
    <row>
      <entry>k</entry>
      <entry>Move the cursor one line up</entry>
    </row>
    <row>
      <entry>l</entry>
      <entry>Move the cursor one character right</entry>
    </row>
    <row>
      <entry>10j</entry>
      <entry>Move the cursor ten lines down</entry>
    </row>
    <row>
      <entry>G</entry>
      <entry>Move to the end of the file</entry>
    </row>
    <row>
      <entry>^</entry>
      <entry>Move to the beginning of the line</entry>
    </row>
    <row>
      <entry>$</entry>
      <entry>Move to the end of the line</entry>
    </row>
    <row>
      <entry>dd</entry>
      <entry>Remove a line</entry>
    </row>
    <row>
      <entry>5dd</entry>
      <entry>Remove 5 lines</entry>
    </row>
    <row>
      <entry>r</entry>
      <entry>Replace a single character</entry>
    </row>
    <row>
      <entry>R</entry>
      <entry>Replace multiple characters</entry>
    </row>
    <row>
      <entry>x</entry>
      <entry>Delete a character</entry>
    </row>
    <row>
      <entry>X</entry>
      <entry>Delete the previous character</entry>
    </row>
    <row>
      <entry>u</entry>
      <entry>Undo the last action</entry>
    </row>
    <row>
      <entry>:s'old'new'g</entry>
      <entry>Replace all occurances of 'old' with 'new'</entry>
    </row>
    <row>
      <entry>/asdf</entry>
      <entry>Locate next occurance of asdf</entry>
    </row>
    <row>
      <entry>:q</entry>
      <entry>Quit (without saving)</entry>
    </row>
    <row>
      <entry>:w</entry>
      <entry>Save the current document</entry>
    </row>
    <row>
      <entry>:w file</entry>
      <entry>Save the current document as 'file'</entry>
    </row>
    <row>
      <entry>:x</entry>
      <entry>Save and quit</entry>
    </row>
  </tbody>
</tgroup>
</table>

</section>

</chapter>