The VI Text Editor

 
vi is the most useful standard text editor on your system. (vi is
short for visual editor and is pronounced "vee-eye.") Unlike emacs,
it is available in nearly identical form on almost every UNIX system,
thus providing a kind of text-editing lingua franca.[1] The same might
be said of ed and ex, but screen editors are generally much easier
to use. With a screen editor, you can scroll the page, move the
cursor, delete lines, insert characters, and more, while seeing the
results of your edits as you make them. Screen editors are very
popular, since they allow you to make changes as you read through
a file, like you would edit a printed copy, only faster.

[1] Actually, these days, GNU emacs is pretty much the universal version of emacs; the only problem is it
doesn't come standard with most commercial UNIX systems; you must retrieve and install it yourself.

To many beginners, vi looks unintuitive and cumbersome—instead
of using special control keys for word processing functions and just
letting you type normally, it uses all of the regular keyboard keys
for issuing commands. When the keyboard keys are issuing
commands, vi is said to be in command mode. You must be in a
special insert mode before you can type actual text on the screen.
In addition, there seem to be so many commands.

Once you start learning, however, you realize that vi is well
designed. You need only a few keystrokes to tell vi to do complex
tasks. As you learn vi, you learn shortcuts that transfer more and
more of the editing work to the computer—where it belongs.

vi (like any text editor) is not a "what you see is what you get" word
processor. If you want to produce formatted documents, you must
type in codes that are used by another formatting program to
control the appearance of the printed copy. If you want to indent
several paragraphs, for instance, you put a code where the indent
begins and ends. Formatting codes allow you to experiment with or
 



change the appearance of your printed files, and in many ways,
give you much more control over the appearance of your
documents than a word processor. UNIX supports the troff
formatting package.[2] The and formatters are popular, commonly
available alternatives.

[2]    troff is for laser printers and typesetters. Its "twin brother" is nroff, for line printers and terminals. Both
accept the same input language. Following common UNIX convention, we refer to both with the name troff.

(vi does support some simple formatting mechanisms. For example,
you can tell it to automatically wrap when you come to the end of a
line, or to automatically indent new lines.)

As with any skill, the more editing you do, the easier the basics
become, and the more you can accomplish. Once you are used to all
the powers you have while editing with vi, you may never want to
return to any "simpler" editor.

What are the components of editing? First, you want to insert text
(a forgotten word or a missing sentence), and you want to delete
text (a stray character or an entire paragraph). You also need to
change letters and words (to correct misspellings or to reflect a
change of mind about a term). You might want to move text from
one place to another part of your file. And, on occasion, you want to
copy text to duplicate it in another part of your file.

Unlike many word processors, vi's command mode is the initial or
"default" mode. Complex, interactive edits can be performed with
only a few keystrokes. (And to insert raw text, you simply give any
of the several "insert" commands and then type away.)

One or two characters are used for the basic commands. For
example:

i

insert

cw

change word

Using letters as commands, you can edit a file with great speed.
You don't have to memorize banks of function keys or stretch your
fingers to reach awkward combinations of keys. Most of the
commands can be remembered by the letter that performs them,
and nearly all commands follow similar patterns and are related to
each other.
 



In general, vi commands:

•    Are case-sensitive (uppercase and lowercase keystrokes mean
different things; I is different from i).
•    Are not shown (or "echoed") on the screen when you type
them. 
•    Do not require a RETURN after the command.

There is also a group of commands that echo on the bottom line of
the screen. Bottom-line commands are preceded by different
symbols. The slash (/) and the question mark (?) begin search
commands, and are discussed in Chapter 3. A colon (:) begins all
ex commands. ex commands are those that are used by the ex line
editor. The ex editor is available to you when you use vi, because
ex is the underlying editor, and vi is really just its "visual" mode. ex
commands and concepts are discussed fully in Chapter 5, but this
chapter introduces you to the ex commands to quit a file without
saving edits. 

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