Basics of the vi editor

Opening a file
vi filename

               Creating text
Edit modes: These keys enter editing modes and type in the text
of your document.

i     Insert before current cursor position
I     Insert at beginning of current line
a     Insert (append) after current cursor position
A     Append to end of line
r     Replace 1 character
R     Replace mode
 Terminate insertion or overwrite mode

                Deletion of text

x     Delete single character
dd    Delete current line and put in buffer
ndd   Delete n lines (n is a number) and put them in buffer
J     Attaches the next line to the end of the current line (deletes carriage return).

                Oops

u     Undo last command

                cut and paste
yy    Yank current line into buffer
nyy   Yank n lines into buffer
p     Put the contents of the buffer after the current line
P     Put the contents of the buffer before the current line

               cursor positioning
^d    Page down
^u    Page up
:n    Position cursor at line n
:$    Position cursor at end of file
^g    Display current line number
h,j,k,l Left,Down,Up, and Right respectivly. Your arrow keys should also work if
     if your keyboard mappings are anywhere near sane.

              string substitution

:n1,n2:s/string1/string2/[g]       Substitute string2 for string1 on lines
                                  n1 to n2. If g is included (meaning global), 
                                  all instances of string1 on each line
                                  are substituted. If g is not included,
                                  only the first instance per matching line is
                                  substituted.

   ^ matches start of line
   . matches any single character
   $ matches end of line

These and other "special characters" (like the forward slash) can be "escaped" with \
i.e to match the string "/usr/STRIM100/SOFT" say "\/usr\/STRIM100\/SOFT"

Examples:

:1,$:s/dog/cat/g                   Substitute 'cat' for 'dog', every instance
                                  for the entire file - lines 1 to $ (end of file)

:23,25:/frog/bird/                 Substitute 'bird' for 'frog' on lines
                                  23 through 25. Only the first instance
                                  on each line is substituted.


             Saving and quitting and other "ex" commands

These commands are all prefixed by pressing colon (:) and then entered in the lower
left corner of the window. They are called "ex" commands because they are commands
of the ex text editor - the precursor line editor to the screen editor
vi.   You cannot enter an "ex" command when you are in an edit mode (typing text onto the screen)
Press  to exit from an editing mode.

:w                Write the current file.
:w new.file       Write the file to the name 'new.file'.
:w! existing.file Overwrite an existing file with the file currently being edited.
:wq               Write the file and quit.
:q                Quit.
:q!               Quit with no changes.

:e filename       Open the file 'filename' for editing.

:set number       Turns on line numbering
:set nonumber     Turns off line numbering