Getting Started with vi

The vi/vim editor is not very difficult to learn (vim stands for "vi
improved").  The first thing to learn about is the difference between
insert mode and command mode, described below, and then a basic set
of simple commands.

The most confusing thing about vi for most people is that there are two
modes (really three, but the third doesn't create any confusion).  If you
are in insert mode, then everything you type gets inserted into your
text. If you type a "w" then a w gets inserted wherever the cursor is.
Insert mode is usually not confusing, because it's what most people are
used to.

When you first vi a file, though, you're not in insert mode yet.  You're
in command mode.  In command mode, every character is a command.  For
example, if you type a "w", then the cursor will jump forward to the
beginning of the next word.  Try it: vi any file (this one, for example)
and type the letter "w" (without the quotation marks) a number of times.

Now here are two good questions:  how do you get from command mode into
insert mode (and vice versa), and what if you forget and don't remember
which mode you're in?

The easiest way to get into insert mode from command mode is to type "i".
This will put you in insert mode, inserting text just before the cursor.
When you're done inserting text, hit the ESCAPE key to go back to
command mode.  There is an optional setting called "showmode" which
indicates when you are in insert mode.  If you have this setting
turned on, you will see an "INSERT" or "OPEN" indication appear and
disappear at the bottom of the screen as you go between modes.  If
you don't have showmode turned on and you forget which mode you are
in, you can always just hit the ESCAPE key, at which point you are
definitely in command mode.  To turn on showmode, type
    :set showmode
and then hit the Enter or Return key.  Then type an "i" and the ESCAPE
key to see the insert mode indicator come and go.
[Notice that from the time you hit the ":" character until you hit
the Enter/Return key, the cursor jumped down to the bottom of the
screen.  That is the third, very obvious, mode.]

While you're in insert mode, you can use the DELETE or BACKSPACE key
(depending on your machine) to undo characters you have inserted.

You can stick to "i" to insert text almost all the time, unless you
happen to want to append some text at the end of the line.  If you
move the cursor to the end of the line and hit "i" you will be
inserting text BEFORE the last character in the line, not after it.
So, you need to know the "a" command, which appends after the cursor.
(You can use "a" to append after the cursor anywhere in the line,
not just at the end.)

Moving the cursor is the next basic step.  Most modern versions
of vi and vim allow you to use the arrow keys in command mode, and
many even support the arrow keys in insert mode.  Vim even allows
you to use the mouse.  If you are a fast touch typist and prefer
to use keys immediately under your fingers on the home row, you can
also use the following four commands:
        h       move left
        j       move down
        k       move up
        l       move right
Notice that h is the left-most and l is the right-most of the four,
so those two are easy.  The only two that might take some thinking
before it becomes second nature are the j and k.  (Believe it or
not, before mice were commonplace these keys were used a lot for
moving around in game software for people who didn't have joysticks.)

How about deleting text?  The simplest way is just to "x" it out.  In
command mode, the "x" will delete the character under the cursor.  If
you want to delete a whole line, type "dd".

What if, by accident, you just made a change you didn't mean to make?
The undo command is "u".  What if you also want to undo the change
before that?  In this case, the answer depends on what version of vi/vim
you are using.  The older vi behavior is to only know about the latest
change; if you undo again immediately, it undoes the last undo, i.e., it
redoes it.  Although this is handy -- you can toggle back and forth
several times deciding whether you like a change or not -- you can't
undo a previous change.  In vim, on the other hand, you can undo
multiple changes by typing "u" repeatedly.  If you undo something
and then change your mind and want to redo it, type control-R.

The last of the most basic tasks is getting out of vi.  The easiest
thing to do is to type "ZZ".  (Remember to be in command mode first,
or you'll see "ZZ" in your file.)  This writes the file to disk and
quits (e.g., Save and Quit).  If you want to do an intermediate
save without leaving vi, type ":w".  (Remember, that colon introduces
the third mode at the bottom of the screen.)  If you realize you
just made lots of changes to the wrong file, or made lots of stupid
changes because it's been too long since you ate or slept, then
":q!" means "quit without saving any of my changes, and I really
mean it!"

There are lots of other vi commands that let you move the cursor
faster (like "w" which moves the cursor a word at a time), scroll,
cut and paste, etc., etc.  Some of these are really useful and you
want to learn them pretty soon or you will go out of your mind with
frustration.  But you can get started with just the few mentioned
so far:
        vi filename     start up vi (if the file doesn't exist it creates it)
        i               insert text before the cursor (go into insert mode)
        a               append text after the cursor (go into insert mode)
        backspace       "un-type" the last character in insert mode
        ESC             go back to command mode
        arrow keys      cursor movement (or h/j/k/l)
        x               delete character under cursor
        dd              delete entire line cursor is on
        u               undo the last change (another u or Control-r to
                            remake the change, depending on version)
        ZZ              write and quit  (also :wq)
        :w              intermediate write (does not quit vi)
        :q              quit (but only works if there are no unsaved changes)
        :q!             quit, throw away any changes since the last save
        
        
Tip: Do you find showmode useful, but you're tired of typing ":set showmode"
every time you enter vi?  See if you have a .exrc file (if using vi) or
.vimrc file (if using vim) in your home directory; if not, you can
create one.  Put "set showmode" in the file.  Some other useful settings
are:
        set autoindent          new lines are automatically indented to
                                match the previous line
        set wrapmargin=8        (if you don't like automatic wrapping,
                                 set it to 0)
If you are writing code, "set showmatch" can also be very useful; it
shows matching left and right parentheses, braces, and brackets
with highlighting or a quick cursor jump in insert mode.