Part1 - Part2

vi editor FAQ (Frequently Asked Question List), Part 1/2

Newsgroups: comp.unix.questions,comp.editors,comp.answers,news.answers
From: ellidz@kimbark.uchicago.edu (E. Larry Lidz)
Subject: vi editor FAQ (Frequently Asked Question List), Part 1/2
Message-ID: <EEBHIA.I06@midway.uchicago.edu>
Followup-To: comp.editors
Summary: This posting contains a list of Frequently Asked
        Questions (and their answers) about the vi editor.  
Sender: news@midway.uchicago.edu (News Administrator)
Reply-To: ellidz@midway.uchicago.edu (E. Larry Lidz)
Organization: University of Chicago -- Academic Computing Services
Date: Sun, 3 Aug 1997 02:56:33 GMT
X-Last-Modified: 1997-03-21

Archive-name: editor-faq/vi/part1
Posting-Frequency: 2nd and 17th of every month
Last-modified: 1997-03-21
Version: 1.76

				vi editor FAQ 
                                -------------

0.0 - Introduction -- How do I use this FAQ?

  This document is broken into multiple sections.  First, a general
introduction and discussion of what vi is in sections 0 and 1.  Section
2 is a collection of "novice" questions, questions that someone without
much experience with vi might ask.  These include the differences
between command and insert mode, and continue ending with questions
such as "How do I cut and paste?"  Then, section 3 is geared toward the
intermediate vi user.  Starting with "How do I do a search and
replace," and continuing onward from there, until it finally ends with
a discussion of vi macros.  Also included is a vi quick reference.
This should give a canonical list of vi commands.  Next, is a list of
:set commands, all of which can be put into a .exrc file to customize
your editing environment.
  The quick reference was confirmed on a machine running SunOS with the
UCB distribution of vi.  Each command should work under System V and
UCB versions of vi other than the one shipped with SunOS, but I have
not personally confirmed this.
  Unless otherwise specified this document assumes that you are in
command mode.
  An attempt was made to retain much of the terminology used in the
original vi documentation, wherever I could remember what it was.
  Also, I will often refer to regular expressions (often called
regex's). Please look at the man page (man 5 regexp will show it on
most Unix programs) or another reference (the O'Reilly Mastering
Regular Expressions book in the bibliography, for example) for more
information on what they are and what they do. They're really useful,
and it won't be a waste of time. Trust me.

0.1 - Index

First File:

0.0 - Introduction -- How do I use this FAQ?
  0.1 - Index
  0.2 - Can I distribute this FAQ?
  0.3 - What can you do to help out with this faq?
1.0 - What is vi?
  1.1 - What is the big deal about vi?  Why does anyone use it?  More
         importantly, why should *I* use it?
  1.2 - Wow!  This sounds great!  Is there any reason not to use vi?
  1.3 - What different operating systems is vi available for?
  1.4 - Okay, you've convinced me.  I'm going to learn vi.  Where do I
         start?
  1.5 - What are some of the vi clones that are available?
2.0 - Learning vi.
  2.1 - What games will help me learn vi?
  2.2 - What is the difference between Command mode & Insert mode?
  2.3 - Wait, my keyboard doesn't have a <Esc> key!  What should I do?
  2.4 - What are all of those ~s?
  2.6 - How do I quit without saving?
  2.7 - How do I insert a file?
  2.8 - How do I search for text?
  2.9 - How do I search for a control sequence?
  2.10 - How do I reformat text?
  2.11 - How do I copy text?
  2.12 - Ahhhh!!!  I just hit dG and lost my dissertation!  What can I
          do?  (Or, I've just made a mistake, what should I do?)
  2.13 - vi appears to be frozen or acting strange, what can I do?
          (Also, I can't get rid of the colon prompt, now what?)
  2.14 - I've just written my dissertation and have been told that I 
          need to have each section in a different file, what should 
          I do?
  2.15 - What's the deal with all of these : commands?
3.0 - How do you do a search and replace?
  3.1 - My / key is broken!  How can I search and replace?
  3.2 - How do I run a program from within vi?
  3.3 - Ahhh!!  I was writing my dissertation, and the computer crashed!
  3.4 - Any tips for making vi programmer friendly?
  3.5 - Macros -- How do I write them?
  3.6 - How do I make a function key a Macro?
  3.7 - Is there anyway to abbreviate text?
  3.8 - How do I spell check the current document?
  3.9 - How do I get rid the ^M's at the end of each line of my file?
         How do I make a macro to do it?
  3.10 - I've got a hardcopy terminal, can I still use vi?
  3.11 - Oh, okay, is THAT what open mode is?  But I don't have a 
         hardcopy terminal, and it still starts in open mode!
  3.12 - How can I get the source code to vi?
4.0 - More advanced topics in vi
  4.1 - I see that sections are defined by SHNHH HU and paragraphs by
        IPLPPPQPPLIbp by default? What language is that in? What in
        the world does it mean?
  4.2 - But when I program, I've noticed that I can use ]] and [[
        to move between functions. My functions don't have .SH or 
        anything at the beginning, what gives?

Second File:

5.0 - What's online at the vi archives?
6.0 - Silly vi tricks, and silly macros
  6.1 - Silly vi tricks
  6.2 - Silly macros
7.0 - Alphabetical vi quick reference
  7.1 - Command mode input options ( : commands)
  7.2 - set options
8.0 - Setting up .exrc file
  8.1 - Sample .exrc file
9.0 - Bugs in vi
10.0 - Glossary of terms
11.0 - Bibliography of Books that cover vi

0.2 - Can I distribute this FAQ?

  Yes, as long as you do not alter it in any fashion, or charge any
money for it.  If you plan on including it in a book, CDRom, or other
such publication, please contact me first.

0.3 - What can you do to help out with this faq?

  First, send me any errors that you may find.  Also, any suggestions
that you might have are also appreciated.  Better yet, anything that
you think is unclear.  My email address is:
            ellidz@midway.uchicago.edu
  Also, use vi!  Spread the word!  I'm sorry I can't list everyone who
has contributed to this faq, as many, many people have given me advice
and helped out, but I fear if I were to, the list of contributers would
become as long as the document itself.

1.0 - What is vi?

  vi is a Visual Editor (hence the name -- vi for VIsual).  What is a
visual editor (as opposed to a non-visual one)?  Visual editors are
ones that let you see the document that you are editing as you edit
it.  This seems pretty common in most editors today, so the idea of a
non-visual editor is a little strange.  Examples of non-visual editors
are sed, ex, ed, and edlin (the last one being the editor shipped with
DOS until relatively recently.)
  vi was written by William Joy as part of the bsd distribution of
Unix.  It was later used by AT&T, and has been standard Unix since.

1.1 - What is the big deal about vi?  Why does anyone use it?  More
importantly, why should *I* use it?

  vi is default visual editor under Unix, and is therefore shipped with
all recent version of Unix.  (Recent being defined as post 1984 or
so.)  This means that whenever you run across a machine that is running
a Unix of some sort, you will know that you have a powerful editor at
your finger tips.  Why else? vi is a powerful editor.  Also, once you
know vi, you can edit files really quickly, as it is extremely
economical with the keystrokes.  Due to its different modes for
inserting and issuing commands, it is much faster than most non-mode
based editors.  It is also a very small editor.  (The version on my
machine is 200k) Also, it can do almost anything, as long as you know
how to get it to do what you want.

1.2 - Wow!  This sounds great!  Is there any reason not to use vi?

  Yes.  There is a very good reason.  It can be somewhat hard to learn,
and until you do so, it will be slow and painful.  Once you learn it,
it will be faster, but the process of learning it is slow.  I've been
asked if vi was an easy editor to learn, whether it was intuitive or
not.  My general response to this question is:  "Yes, some of us think
so.  But most people think that we are crazy."

1.3 - What different operating systems is vi available for?

 Unix.  That's it.  However, there are many, many clones of vi that are
available for different operating systems.  I personally have used vi
clones under:  Unix, Dos, OS/2, Mac System 7.  (See below for a list of
specifics.)

1.4 - Okay, you've convinced me.  I'm going to learn vi.  Where do I
start?

  Well...  That's a tricky one.  There are many good books out there
that cover vi; most books on Unix have at least one chapter devoted to
it.  There are also many books devoted specifically to vi.  I don't
have any preference, so your best bet might be to ask your local vi
guru where they learned.  Also, play around.  Fire up vi with a
non-important document (your dissertation is NOT a good document to
learn vi with...) and play around.  I can't imagine anyone learning vi
without playing around with it quite a bit.  Remember, if you get
confused, just hit the Escape key a couple of times, and you'll be in
command mode again.
  I should mention at some point, and I guess here is as good a place
as any, that people who think they might want to do Unix system
administration, or any type of configuration of unix machines will
probably also want to learn ed or ex, as some versions of Unix do not
put vi in the root partition, and one might be stranded without it at
some point.  Ed is a good choice.

1.5 - What are some of the vi clones that are available?

  Just to list a few:  STvi (STevie), elvis, vile, vim, and nvi, xvi.

elvis is available for: Amiga, DOS, OS/2, Unix, VMS, Atari, 
Psion3a Handheld.  
STevie is available for:  Atari ST, DOS, Unix, Mac System 7.  
  Mac System 7 is available at any info-mac mirror in /info-mac/text
    (Such as ftp://ftp.hawaii.edu/info-mac/text)
nvi is the vi that ships with BSD 4.4. 
vim is available for: Amiga, DOS, Mac System 7, Win 95, and Unix.
  Amiga, DOS, and the source are available at:
    ftp://ftp.fu-berlin.de/misc/editors/vim 
    The Vim Pages are available at:
    http://www.math.fu-berlin.de/~guckes/vim/
  Mac System 7 is available at any info-mac mirror in /info-mac/text
    (Such as ftp://ftp.hawaii.edu/info-mac/text)
vile is available for: DOS, OS/2, Unix, VMS, Window95, 
  WindowsNT (console mode only).  
  The source is available at: ftp://ftp.clark.net:/pub/dickey/vile
xvile, a X-windows aware version of vile exists, as well.
xvi is available for: DOS, Unix.
viper is available for GNU Emacs.
  ftp://ftp.cs.sunysb.edu/pub/TechReports/kifer/viper.tar.Z

Mortice Kern Systems (support@mks.com), who I have absolutely no
affiliation with, offers a commercial version of vi for DOS/Windows,
OS/2, and WindowsNT.

  There are some differences between the different vi clones.  Many
offer improvements, but most still allow the commands that are listed
in this document, but there may be some differences.  Refer to the
documentation that comes with the clone for details.

2.0 - Learning vi.

  These are some basic hints for the novice vi user.  First, keep a
command summary with you at all times.  A quick reference guide/command
summary is included later on.  Second, get a good book that covers vi.
This document is not the best way to learn it (at least not yet.)  I'm
not sure if this document should teach people to to use vi from
scratch, as there are many good books on it already.  However, there
are hints here.  As for choosing a book, the standard rules apply:
look at it before buying it.  See if any of it makes sense to you.
Make sure that it has exercises that you can practice with.  Compare it
with other books -- after all, vi can be very confusing, and you want
to make sure that it is the book that is confusing, and not just that
you underestimated the difficulty of learning vi.
  Also, seek out vilearn or vitutor, programs designed to teach you the
basics of vi.
  
2.1 - What games will help me learn vi?

  This may seem a bit silly, but there are many games on Unix systems
that can help you learn to use vi.  These help particularly with the
basics.  Although I don't know of any games that help with every vi
command, I do know of a few that will help you learn to use hjkl to
move the cursor around.  NetHack, a rogue-like game, is particularly
good for this, as it is a large game and can be entertaining for quite
some time.  Not to make the other games sound worse, but some other
ones are:  rogue, moria, omega, worm, and snake.

2.2 - What is the difference between Command mode & Insert mode?

  Often cited as one of the main problems with vi, and equally often
cited as being one of its best strengths, vi differentiates between a
"Command mode" and an "Insert mode."  Understanding this difference is
VITAL to learning vi.  When one starts vi it starts in command mode.
In this mode, one can move around the file, and issue commands to
change certain areas of the text, cut, copy and paste sections of the
text and do much more.  Insert mode is where one can actually insert
text.  In other words, command mode is used to move around the
document, and insert mode is used to type text into the document.
  Commands such as:  a, i, c, C, O, o and others will switch one from
command mode to insert mode.
  <Esc> or <ctrl-c> will take one out of insert mode and return one to
command mode.
  Get used to this distinction.  It is one of the things that makes vi
different from most other editors.  It also allows one to do a lot of
things without taking one's hands from the standard keyboard position.
  For novices it is often nice to know what mode you are in.  If you
type: "echo set showmode >> $HOME/.exrc" at the Unix command line, it
will make is so that each time vi is started it will default to showing
the mode on the bottom right of the screen.  (To understand what this
is doing, see the sections on "setting up a .exrc" and the "set
options.")  If it does not show anything in the bottom right, it means
that you are in command mode.  I call a few different modes (append,
open and insert) "insert mode" in this document.

2.3 - Wait, my keyboard doesn't have a <Esc> key!  What should I do?

  Try hitting <ctrl-[> instead.  If your keyboard has a <Meta> key, try
that.  If neither of these work, try <ctrl-3>.  Some DEC terminals use the
F11 key as escape. 

2.4 - What are all of those ~s?

  They're just there to let you know where the bottom of your file is,
they are not actually in your document, and you do not need to worry
about them.

2.5 - I can't get used to using hjkl, do you have any suggestions?

  First, if your terminal is set properly and you have a good
connection, you should be able to use the arrow keys.  However, if you
think that you will be using vi a lot, then it makes sense to learn
hjkl, as they are faster to type.  Also, there are occasions where you
may have a bad connection and the ESC sequences may get lost.
  Here is a simple mnemonic to help remember this: j extends below the
line, and k above the line when written by hand.

2.6 - How do I quit without saving?

  :q! will do it.

2.7 - How do I insert a file?

  :r <filename>

  For example, to insert the file /etc/motd, type:  :r /etc/motd

  This will insert the file at the current location in the file you are
working on.  If you specify a number before the r, it will insert it at
that location in the file.

2.8 - How do I search for text?

  /<text> will search forward.  ?<text> will search backwards.  ?? or
// will repeat the last search.  It is worth noting that these are
pretty much standard in Unix.  In addition, in vi, n will find the next
occurrence.  N will repeat the last search, reversing the direction.
Regular Expressions may be used within searches.

2.9 - How do I search for a control sequence?

  /<ctrl-v><ctrl-<seq>>

 <ctrl-v> will tell vi to take the next character literally, and not to take
it as a command.

2.10 - How do I reformat text?

  If your computer has the program fmt on it, all you need to do is
type !}fmt from command mode (without a : before it).  This will
reformat the text from the current location until the end of the
paragraph.  If your machine does not have fmt, you need to find a
similar program.  (I gather there are many such programs available from
the public domain, but I do not know much about them.)

2.11 - How do I copy text?

  Okay, this might be a bit complicated.  Take from this section what
you can, and reread it a few times.  Also, experiment.
  "<letter>yy will copy one line of text into register <letter>.  (A
register is vi-lingo for a place to store data that was cut or copied.)
<letter> must be between a and z.  "<letter>dd will delete one line and
place it in register <letter>.  You may use a number before the yy or
dd to specify the number of lines.  Using an uppercase <letter> will
append the text into the register leaving what was there before.
"<letter>p will put the text after the cursor.  "<letter>P will put it
before the cursor.  If the register contains the beginning or end of a
line, the line will be placed on another line as appropriate.  Y may be
used as a short cut for yy.  In addition, y$, yH, yM, etc. are valid,
as are the equivalent d commands.  For quick cuts and pastes, no
register need be specified.  In this case, no appending is allowed, and
the register will be removed if another delete command is given.
(Including x).
  For example, to move the previous paragraph, one would go to the top
of the paragraph, type "a13dd, move to the position in which one wishes
to put the paragraph, and then type "ap to put it below the current
line.
  Now, presumably you want to be able to cut and paste into areas that
are not just the end of the line.  In order to do this, use m<letter>
to mark an area.  This letter may be the same as a cut/copy register,
they are stored in different area of memory.  Then, type "<register>[y
or d]`<letter>.  Where <register> is the register to put the text into,
<letter> is the letter used to make, and yy or dd as appropriate.

2.12 - Ahhhh!!!  I just hit dG and lost my dissertation!  What can I
do?  (Or, I've just made a mistake, what should I do?)

  u will undo the last command.  U will undo changes to the current
line.  (Granted, a one line dissertation would not be much.) :e! will
reload the current document without saving any changes.  In addition,
deleted text gets stored in the registers numbered from 1 to 9.  "<n>p
will put the last nth deletion.  You can quickly search the registers
by trying one, hitting u, and trying the next.  (In order to expedite
this, vi uses . slightly differently than normal.  Instead of repeating
the last command, it will try the next register, so all you need to do
is: "1p u . u ., etc. until you undo the delete you want to undo.)

2.13 - vi appears to be frozen or acting strange, what can I do?
(Also, I can't get rid of the colon prompt, now what?)

  If vi appears to have frozen, make sure that you haven't hit <ctrl-S>
by mistake.  In order to undo a <ctrl-s>, hit <ctrl-q>.  
  If there is a colon and you can't get rid of it, you've entered ex by
accident.  Generally this happens by hitting "Q" from command mode.
Just type vi to get back into vi.

2.14 - I've just written my dissertation and have been told that I need
to have each section in a different file, what should I do?

 :[m],[n]w <filename> will save between lines m and n to <filename>.
This line numbering method works for almost every : command.  If you
use :[m],[n]w >> <filename> it will append it to the file.

2.15 - What's the deal with all of these : commands?

  The commands that follow a : are commands from the ex editor.  These
allow a lot of flexibility and power.  For example, there are many
different ways to search and replace, all of with have some
similarities (in fact, they are in some ways the same...)

3.0 - How do you do a search and replace?

  Well, there are a few methods.  The simplest is:

    :s/old/new/g 
  But, this only does it on the current line...  So:
    :%s/old/new/g 
  In general: 
    :[range]s/old/new/[cgi] 

  Where [range] is any line range, including line numbers, $ (end of
file), . (current location), % (current file), or just two numbers with
a dash between them.  (Or even: .,+5 to mean the next five lines).

  [cgi] is either c, g, i, or nothing.  c tells vi to prompt you before
the changes, g to change all of the occurrences on a line.  (type yes
to tell vi to change it.)  i tells vi to be case insensitive on the
search.  The g after the last slash tells it to replace more than just
the first occurrence on each line.

  Another method is:
    :g/foobar/s/bar/baz/g This searches for foobar, and changes it to
foobaz.  It will leave jailbars alone, which the other method will not.
Unfortunately, if jailbars appears on the same line as foobar, it will
change, too.

  Of course you can also use regular expression search patterns, and a
few other commands in the replacement part of the text.  If you use \(
and \) in the pattern to escape a sequence (and use \1, \2, etc., you
can do lots of nifty things.

  For example:
    :g/foo/s/^\([^ ]*\) \([^ ]*\)/\2 \1/
  will swap the first and second words on every line containing "foo".

  Special sequences allowed are:
    &        everything which was matched by the search 
    \[1-9]   The contents of the 1st-9th \(\) pair 
    \u       The next character will be made uppercase 
    \U       The characters until \e or \E will be made uppercase 
    \l       The next character will be made lowercase
    \L       The characters until \e or \E will be made lowercase
    \[eE]    end the selection for making upper or lowercase


3.1 - My / key is broken!  How can I search and replace?

  Well, okay, it doesn't really need to be a /.  Lots of things will
work fine.  (letters, numbers and a few other things won't...)

3.2 - How do I run a program from within vi?

  :!cmd will run the program cmd.  :sh will run an interactive shell.
Within this shell, you may, if you want, run vi again.  This is
particularly useful when you are editing makefiles and config files for
programs in an attempt to get a program to compile.  The advantage over
:e is that you do not need to save the file, and it will be in its old
place when you exit the shell.  (I advise saving the file anyway...)

3.3 - Ahhh!!  I was writing my dissertation, and the computer crashed!

  Well, you should get mail about this, but you should be able to
recover the file by typing vi -r <filename> where <filename> is the
name of the file that you were editing at the time of the crash.  vi -r
will give you a list of files that can be recovered.

3.4 - Any tips for making vi programmer friendly?

  :set ai will make it auto-indent for you.  
  :set sw=# where # is a number will set the shiftwidth (tabwidth).  
You can then use <<, >> to shift a line left or right.  Plus, you 
can use <% to shift a {, ( or [ set left or right (with >%).  
You must be on top of the specific {, }, (, ), [ or ] of the pair 
to shift them.  
  :set sm will show the matching {, ( or [ when you type the closing
one.  
  :set lisp will make some changes that are useful for lisp
programming.  () will move back and forth over s-expressions, and {}
will move without stopping at atoms.

3.5 - Macros -- How do I write them?

  :map <lhs> <rhs> where <lhs> is up to ten characters and <rhs> is up
to 100.  This will make it so that whenever you type <lhs> it will
replace it with <rhs>.  All macros should start in command mode (except
those defined with map!), but may end in any mode you desire.  Remember
to use <ctrl-v> before any control characters that you may use.
  If you are using an Ex command, such as |, it needs to be escaped
while vi is scanning the line.  You should map it as :map foo
<ctrl-v><ctrl-v>|.
  :unmap <lhs> will remove the macro.  :map! <lhs> <rhs> will make
<lhs> insert <rhs> into the text of the document.  map! macros may have
lhs's that are much longer.

3.6 - How do I make a function key a Macro?

  If <lhs> is #n where n is 0-9, it will be mapped to the appropriate
function key.

3.7 - Is there anyway to abbreviate text?

  Yep, of course.  This is vi, it can do anything.  :ab email
ellidz@midway.uchicago.edu will make it so that whenever you type
email as a specific word, it will extend it to the entire
unabbreviated word.  :una email will unabbreviate it.

3.8 - How do I spell check the current document?

  Here is a macro to do it.  These should be put in your .exrc file.
(More on .exrc files later on.) It is a pretty simple macro, it just
calls ispell on the current file.  Of course, to use this you need
ispell on your system.  To use it, just hit V with vi.  (V is not used
by vi, so it makes a good key.)

  map V :w<enter>:!ispell % <enter>:e!<enter><enter>

The second <enter> makes it so that one does not need to hit return
after it is done checking the spelling.

3.9 - How do I get rid the ^M's at the end of each line of my file?
How do I make a macro to do it?

  These generally appear from DOS files that get converted to Unix.
They're easy to get rid of.
  :%s/<ctrl-v><enter>//g will do it.  

  The macro bit is a bit trickier.  Not something that most people can
guess on their own.  Here it is:
  map v :%s/<ctrl-v><ctrl-v><ctrl-v><ctrl-v><ctrl-v><enter>//g

  Yes, that's right.  5 of them.  The last one is to escape the enter.
Two of the other four are to escape the other two <ctrl-v>'s.  Since the
macro gets read on the ex line, you need to have two <ctrl-v>'s (since you
are searching for <ctrl-v> <enter> to replace it with nothing...)

 In general, if you are having trouble with macro that uses the ex line,
you need to escape things a lot.  Sometimes it is quicker to just keep
throwing <ctrl-v>'s in until it works.  

3.10 - I've got a hardcopy terminal, can I still use vi?

  Okay, okay, so I don't expect anyone to actually ask this...  But, I
thought it was bizarre enough to throw in anyway.  (And, it actually
answers a very common question...)
  vi will start up in a specific mode, called "open mode" in this
situation.  Things work more or less the same.  Deleted characters will
appear on your print out as \'s.  vi will act as if the size of the
window is only one line.  ^r will retype the current line.  z redraws
the window around the current line.

3.11 - Oh, okay, is THAT what open mode is?  But I don't have a
hardcopy terminal, and it still starts in open mode!

  Well, what is happening here is that vi doesn't know what type of
terminal you have.  It decides that in this situation the best thing to
do is to assume that you have the worst terminal possible.  This might
not seem useful, as not very many people need open mode, but it also is
the mode that needs to know the least information about your terminal.
  Now, how to deal with it.  It is possible to change it for the
specific session, but in general, this is not useful.  If you know
your terminal type, you can set it from the Unix prompt (setenv TERM
<termtype> under csh and it's variants, and:  TERM=<termtype> ; export
TERM under sh and its variants.).
  Better yet would to be to edit your .profile or .cshrc to include
this so it is automatically done for you when you login.  (Of course,
you need to either know ed or be able to set it at the unix prompt
before you'll be able to edit the file...)
  If you do not know your terminal type, try vt100.  Most modern
terminals and terminal emulators can emulate vt100.  If this does not
work, find someone to help you.

3.12 - How can I get the source code to vi?

  Unfortunately, the source code to vi is owned by AT&T.  If you happen
to have a source license to a version of Unix that has vi, you should
have the source code.  Otherwise, you're out of luck.  You may want to
look at the source for some vi clones, however, as most of them are
publicly available.

4.0 - More advanced topics in vi.

4.1 - I see that sections are defined by SHNHH HU and paragraphs by
IPLPPPQPPLIbp by default? What language is that in? What in the world
does it mean?

  Man pages are written in a language called nroff/troff. Nroff is a
general purpose text formatting language, similar to TeX. What does
this have to do with vi and the sections? Use the UNIX more command to
look at a man page (say, /usr/man/man1/vi.1 or something). You'll see
parts of the page split into sections, like .SH Name. The .SH is
defining a section of the man page. Notice that SH is the first two
characters of the section set option. 
  The section and paragraph sections are defined by a listing of pairs
of macros for nroff/troff. The next section will start with a period
and then any of the pairs of letters that the section is defined as.
Paragraphs work the same way -- except that a blank line is also
considered a paragraph break.

4.2 - But when I program, I've noticed that I can use ]] and [[ to move
between functions. My functions don't have .SH or anything at the
beginning, what gives?

  Luckily for many C programmers, an open curly brace at the beginning
of a line is also defined as a section break.