vi.beginner

早期freebsd实现

Section 13:
Up until this point, the tutorial has always tried to make sure that the first
line of each screen has on it the section number and a list of the commands
covered in that section.  This will no longer be strictly maintained.  If you
want the section line at the top of the screen, you now know enough commands to
do it easily: do {^M} or {-} until the cursor is on the section line and
then {z^M}.  Also, from this point on, it may not be the case that a {^F} will
put you at the beginning of the next section.  Therefore, be aware of where you
are in the file as we look at other commands.  You may have to find your way
back to a particular section without any help from the tutorial.  If you do not
feel comfortable with this, then it is suggested that you practice moving from
section 1 to section 13, back and forth, using {^M}, {-}, {^F}, and {^B}
commands for a while.

Also make liberal use of the mark command {m}: if, for example, you make a
habit of using {mz} to mark your current location in the file, then you will
always be able to return to that location with {'z} if the editor does
something strange and you have no idea where you are or what happened.

And finally, the proscription against experimentation is hereby lifted: play
with the editor.  Feel free to try out variations on the commands and move
around in the file.  By this time you should be able to recover from any gross
errors.

Section 14: {^E} {^Y} {^D} {^U}
Let us now look at a few other commands for moving around in the file, and
moving the file around on the screen.  Note that the commands we have already
looked at are sufficient: you really don't need any more commands for looking
in a file.  The following commands are not absolutely necessary.  However,
they can make editing more convenient, and you should take note of their
existence.  But it would be perfectly valid to decide to ignore them on this
first pass: you can learn them later when you see a need for them, if you ever
do.

First, let's clear up some potentially confusing language.  In at least one
place in the official document ('An Introduction to Display Editing with Vi'
by William Joy, and Mark Horton, September 1980), the expression "to scroll
down text" means that the cursor is moved down in your file.  However, note
that this may result in the text on the screen moving UP.  This use of the
word 'scroll' refers to the action of the cursor within the file.  However,
another legitimate use of the word refers to the action of the text on the
screen.  That is, if the lines on your screen move up toward the top of the
screen, this would be 'scrolling the screen up'.  If the lines move down
toward the bottom of the screen, this would be refered to as scrolling down.

I have tried to maintain the following jargon: 'scrolling' refers to what the
text does on the screen, not to what the cursor does within the file.  For the
latter I will refer to the cursor 'moving', or to 'moving the cursor'.  I
realize that this is not necessarily consistent with Joy and Horton, but they
were wrong.

{^E} scrolls the whole screen up one line, keeping the cursor on the same line,
if possible.  However, if the cursor line is the first line on the screen, then
the cursor is moved to the next line in the file.  Try typing {^E}.

{^Y} scrolls the screen down one line, keeping the cursor on the same line, if
possible.  However, if the cursor line is the last line on the screen, then the
cursor is moved to the previous line in the file.  Try it.

{^D} moves the cursor down into the file, scrolling the screen up.

{^U} moves the cursor up into the file, also scrolling the screen if the
terminal you are on has the reverse scroll capability.  Otherwise the
screen is repainted.

Note that {^E} and {^Y} move the cursor on the screen while trying to keep the
cursor at the same place in the file (if possible: however, the cursor can
never move off screen), while {^D} and {^U} keep the cursor at the same place
on the screen while moving the cursor within the file.

Section 15: {/ .. /^M}

Another way to position yourself in the file is by giving the editor a string
to search for.  Type the following: {/Here 1/^M} and the cursor should end up
right ...........................here ^.  Now type {/Section 15:/^M} and the
cursor will end up over/on .....................here ^.  Now type {//^M} and
observe that the cursor is now over the capital S five lines above this line.
Typing {//^M} several more times will bounce the cursor back and forth between
the two occurrences of the string.  In other words, when you type a string
between the two slashes, it is searched for.  Typing the slashes with nothing
between them acts as if you had typed the previous string again.

Observe that the string you type between the two slashes is entered on the
bottom line of the screen.  Now type {/Search for x /^M} except replace the 'x'
in the string with some other character, say 'b'.  The message "Pattern not
found" should appear on the bottom of the screen.  If you hadn't replaced the
'x', then you would have found the string.  Try it.

Section 16: {? .. ?^M} {n} (search strings: ^ $)

When you surround the sought-for string with slashes as in {/Search/}, the
file is searched beginning from your current position in the file.  If the
string is not found by the end of the file, searching is restarted at the
beginning of the file.  However, if you do want the search to find the
PREVIOUS rather than the NEXT occurrence of the string, surround the string
with question marks instead of slash marks.

Below are several occurrences of the same string.  
Here 2            Here 2 Here 2
 Here 2             Here 2.
Observe the effect of the following search commands (try them in the
sequence shown):
{/Here 2/^M}  {//^M}  {??^M}
{/^Here 2/^M}  {//^M}  {??^M}
{/Here 2$/^M}  {//^M}  {??^M}

The first command looks for the next occurrence of the string 'Here 2'.
However the second line of commands looks for an occurrence of 'Here 2' that
is at the beginning of the line.  When the up-arrow is the first character of
a search string it stands for the beginning of the line.  When the dollar-sign
is the last character of the search string it stands for the end of the line.
Therefore, the third line of commands searches for the string only when it is
at the end of the line.  Since there is only one place the string begins a
line, and only one place the string ends the line, subsequent {//^M} and
{??^M} will find those same strings over and over.

The {n} command will find the next occurrence of the / or ? search
string.  Try {/Here 2/^M} followed by several {n} and observe the
effect.  Then try {??^M} followed by several {n}.  The {n} command
remembers the direction of the last search.  It is just a way to save a
few keystrokes.

Section 17: \ and magic-characters in search strings

Now type {/Here 3$/^M}.  You might expect the cursor to end up
right......^ here.  However, you will get "Pattern not found" at the bottom of
the screen.  Remember that the dollar-sign stands for the end of the line.
Somehow, you must tell vi that you do not want the end of the line, but a
dollar-sign.  In other words, you must take away the special meaning that the
dollar-sign has for the search mechanism.  You do this (for any special
character, including the up-arrow ^) by putting a back-slash ('\', not '/') in
front of the character.

Now try {/Here 3\$/^M} and you should end up nine lines above this one.  Try
{//^M} and note that it returns you to the same place, and not to the first
line of this paragraph: the back-slash character is not part of the search
string and will not be found.  To find the string in the first line of this
paragraph, type {/Here 3\\\$/^M}.  There are three back-slashes: the first takes
away the special meaning from the second, and the third takes away the special
meaning from the dollar-sign.

Following is a list of the characters that have special meanings in search
strings.  If you wish to find a string containing one of these characters, you
will have to be precede the character with a backslash.  These characters are
called magic characters because of the fun and games you can have with them
and they can have with you, if you aren't aware of what they do.  

  ^ - (up-arrow)       beginning of a line
  $ - (dollar-sign)    end of a line
  . - (period)         matches any character
  \ - (backslant)      the escape character itself
  [ - (square bracket) for finding patterns (see section #SEARCH)
  ] - (square bracket) ditto
  * - (asterisk)       ditto

Without trying to explain it here, note that {:set nomagic^M} turns off the
special meanings of all but the ^ up-arrow, $ dollar-sign, and backslash
characters.

Section 18: {: (colon commands)} {ZZ}

In this section we will discuss getting into and out of the editor in more
detail.  If you are editing a file and wish to save the results the command
sequence {:w^M} writes the current contents of the file out to disk, using the
file name you used when you invoked the editor.  That is, if you are at the
command level in Unix, and you invoke vi with {vi foo} where foo is the name
of the file you wish to edit, then foo is the name of the file used by the
{:w^M} command.

If you are done, the write and quit commands can be combined into a single
command {:wq^M}.  An even simpler way is the command {ZZ} (two capital Z's).

If, for some reason, you wish to exit without saving any changes you have made,
{:q!^M} does the trick.  If you have not made any changes, the exclamation
point is not necessary: {:q^M}.  Vi is pretty good about not letting you
get out without warning you that you haven't saved your file.

We have mentioned before that you are currently in the vi editor, editing a
file.  If you wish to start the tutorial over from the very beginning, you
could {ZZ}, and then type {vi.tut beginner} in response to the Unix prompt.
This will create a fresh copy of this file for you, which might be necessary 
if you accidentally destroyed the copy you were working with.  Just do a 
search for the last section you were in: e.g.  {/Section 18:/^Mz^M}.

Section 19: {H} {M} {L}

Here are a few more commands that will move you around on the screen.  Again,
they are not absolutely necessary, but they can make screen positioning easier:

{H} - puts the cursor at the top of the screen (the 'home' position)

{M} - puts the cursor in the middle of the screen

{L} - puts the cursor at the bottom of the screen.

Try typing {HML} and watch the cursor.

Try typing {5HM5L} and note that 5H puts you five lines from the top of the
screen, and 5L puts you five lines from the bottom of the screen.

Section 20: {w} {b} {0} {W} {B} {e} {E} {'} {`}

Up to this point we have concentrated on positioning in the file, and
positioning on the screen.  Now let's look at positioning in a line.  Put the
cursor at the beginning of the following line and type {z^M}:

This is a test line: your cursor should initially be at its beginning.

The test line should now be at the top of your screen. Type {w} several times.
Note that it moves you forward to the beginning of the next word.  Now type
{b} (back to the beginning of the word) several times till you are at the
beginning of the line.  (If you accidentally type too many {b}, type {w} until
you are on the beginning of the line again.) Type {wwwww} (five w's) and note
that the cursor is now on the colon in the sentence.  The lower-case w command
moves you forward one word, paying attention to certain characters such as
colon and period as delimiters and counting them as words themselves.  Now
type {0} (zero, not o 'oh'): this moves you to the beginning of the current
line.  Now type {5w} and notice that this has the effect of repeating {w} five
times and that you are now back on the colon.  Type {0} (zero) again.  To
ignore the delimiters and to move to the beginning of the next word using only
blanks, tabs and carriage-returns (these are called white-space characters) to
delimit the words, use the {W} command: upper-case W.  {B} takes you back a
word using white-space characters as word delimiters.

Note that the commands {wbWB} do not stop at the beginning or end of a line:
they will continue to the next word on the next line in the direction specified
(a blank line counts as a word).

If you are interested in the END of the word, and not the BEGINNING, then use
the {e} and {E} commands.  These commands only move forward and there are no
corresponding 'reverse search' commands for the end of a word.

Also, we have been using the {'} command to move the cursor to a position that
we have previously marked with the {m} command.  However, position the cursor
in the middle of a line (any line, just pick one) and type {mk}, marking that
position with the letter k.  Now type a few returns {^M} and type {'k}.
Observe that the cursor is now at the beginning of the line that you marked.
Now try {`k}: note that this is the reverse apostrophe, or back-quote, or grave
accent, or whatever you want to call it.  Also note that it moves you to the
character that was marked, not just to the line that was marked.

In addition, the {``} command works just like the {''} command except that you
are taken to the exact character, not just to the line.  (I'm still not
sure which exact character, just as I'm still not sure which line.)