Vi Command in Unix.

A)Entering vi
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vi filename - The filename can be the name of an existing file or the name of the file you want to create.

view filename - Starts vi in "read only" mode. Allows you to look at a file without the risk of altering its contents.

B)Exiting vi
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:q - quit - if you have made any changes, vi will warn you of this, and you'll need to use one of the other quits.
:w - write edit buffer to disk
:w filename - write edit buffer to disk as filename
:wq - write edit buffer to disk and quit
ZZ - write edit buffer to disk and quit
:q! - quit without writing edit buffer to disk

C)Positioning within text
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By character
left arrow - left one character
right arrow - right one character
backspace - left one character
space - right one character
h - left one character
l - right one character

By word
w - beginning of next word
nw - beginning of nth next word
b - back to previous word
nb - back to nth previous word
e - end of next word
ne - end of nth next word

By line
down arrow - down one line
up arrow - up one line
j - down one line
k - up one line
+ - beginning of next line down
- - beginning of previous line up
0 - first column of current line (zero)
^ - first character of current line
$ - last character of current line

By block
( - beginning of sentence
) - end of sentence
{ - beginning of paragraph
} - end of paragraph

By screen
CTRL-f - forward 1 screen
CTRL-b - backward 1 screen
CTRL-d - down 1/2 screen
CTRL-u - up 1/2 screen
H - top line on screen
M - mid-screen
L - last line on screen

Within file
nG - line n within file
1G - first line in file
G - last line in file

D)Inserting text
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a - append text after cursor *
A - append text at end of line *
i - insert text before cursor *
I - insert text at beginning of line *
o - open a blank line after the current line for text input *
O - open a blank line before the current line for text input *

* Note: hit ESC (escape) key when finished inserting!

E)Deleting text
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x - delete character at cursor
dh - delete character before cursor
nx - delete n characters at cursor
dw - delete next word
db - delete previous word
dnw - delete n words from cursor
dnb - delete n words before cursor
d0 - delete to beginning of line
d$ - delete to end of line
D - delete to end of line
dd - delete current line
d( - delete to beginning of sentence
d) - delete to end of sentence
d{ - delete to beginning of paragraph
d} - delete to end of paragraph
ndd - delete n lines (start at current line)

F)Changing text
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cw - replace word with text *
cc - replace line with text *
c0 - change to beginning of line *
c$ - change to end of line *
C - change to end of line *
c( - change to beginning of sentence *
c) - change to end of sentence *
c{ - change to beginning of paragraph *
c} - change to end of paragraph *
r - overtype only 1 character
R - overtype text until ESC is hit *
J - join two lines

* Note: hit ESC (escape) key when finished changing!

G)Copying lines
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yy - "yank": copy 1 line into buffer
nyy - "yank": copy n lines into buffer
p - put contents of buffer after current line
P - put contents of buffer before current line

H)Moving lines (cutting and pasting)
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ndd - delete n lines (placed in buffer)
p - put contents of buffer after current line
P - put contents of buffer before current line

I)Searching / Substituting
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/str - search forward for str
?str - search backward for str
n - find next occurrence of current string
N - repeat previous search in reverse direction

The substitution command requires a line range specification. If it is omitted, the default is the current line only. The examples below show how to specify line ranges.

:s/old/new - substitute new for first occurrence of old in current line
:s/old/new/g - substitute new for all occurrences of old in current line
:1,10s/old/new - substitute new for first occurrence of old in lines 1 - 10
:.,$s/old/new - substitute new for first occurrence of old in remainder of file
:.,+5s/old/new - substitute new for first occurrence of old in current line and next 5 lines
:.,-5s/old/new - substitute new for first occurrence of old in current line and previous 5 lines
:%s/old/new/g - substitute new for all occurrences of old in the entire file
:%s/old/new/gc - interactively substitute new for all occurrences of old - will prompt for y/n response for each substitution.

J)Miscellaneous commands
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u - undo the last command (including undo)
. - repeat last command
xp - swap two adjacent characters
m[a-z] - set a marker (a - z)
'[a-z] - go to a previously set marker (a - z)
:!command - execute specified UNIX command
:r filename - read/insert contents of filename after current line.
:1,100!fmt - reformat the first 100 lines
:!fmt - reformat the entire file