Unix Platform

"vi is a visual editor (default) in Unix. Because of this we will be able to see the document we are editing. We can edit files really quickly on vi editor, 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." (ref:roxanne.org). So, vi editor is basically used to create a new file or edit the existing file.

To open a vi editor, first we have to go to the Unix shell (black screen).

Commands:
vi filename (press enter) - to open the vi editor with the given filename - we can see the filename at the bottom of the vi editor screen. At first, when we open a new file we can observe that blank lines started with tilda sign (~).
At the botoom of the screen; type :q! (press enter) - to quit and come out of the vi editor
Before typing in vi editor, we should know that there are 2 modes in vi, i.e. Insert Mode and Command Mode. In the Insert Mode, typed input is recognized only as text and goes into the file ie opened. In the command mode, whateve we typed is interpreted as command.
When we first open the file, it will be in command mode. To go back to insert mode we have to type 'i' or 'a'; and to go to command mode we have to hit 'Esc'.
To save (:w) anything we typed, we have to go back to the command mode (type 'Esc') to execute it. To save and exit at a time, type ':wq' and enter.
To go to the next line - type 'o', and it will take your cursor to the beginning of the 2nd line in order to ADD a NEW LINE. Uppercase 'O' will add a new line before our existing line, the line where the cursor is blinking.
To navigate between lines - to go up type 'j' to go down, 'k' to go up, 'l' to go right, 'h' to go left
'Shift ^' will take your cursor to the beginning of the line. [We Should Be in the Command Mode]
d - will delete the letter [We Should Be in the Command Mode]
dw - will delete the entire word (or, Shift + d) [We Should Be in the Command Mode]
dd - will delter the entire line [We Should Be in the Command Mode]
u - will undo the things [We Should Be in the Command Mode]
2 d - will delete 2 lines [We Should Be in the Command Mode]
In unix, yanking is kind of cut and paste. To do so, we have to be in command mode. To copy a line and paste it, we have put the cursor at the end of the line and type # (how many lines we want to paste) e.g. if we want to copy 3 lines from the line where the cursor is we have to type 3yy and go to the line where we want to paste it and type 'p'.

To insert a file - :r (filename)
To search forward - / e.g. if we have a number of word 'box' in the file and want to search 'box'; at the bottom of the screen we do forward slash /box
To search backward - ? e.g. ?box
To repeat the last search - ?? or //
To find the next occurance - n or next
To repeat the last search - N
To undo the changes in last command - u
To undo the changes in current line - U
To reload the current document without saving any changes - :e!
To put back the last nth deletion - "p
To go to the end of the file (say when we are at the beginning of the file) - just type press colon : and $
To go to the end of the line - just type $
To get back to the beginning of line - just type caret '^'
To replace any word in the line with another word - e.g. say the word 'budda' which is in 3rd line of the file has to be replaced by the word 'budhi'; then type => :3s/budda/budhi and ENTER (colon, s-substitute, / is forward slash for the word ahead of us substituted with the word budhi). If we want to do the same thing not for the particular line, then we have to use % instead of 3 (line#) and also need to add /g at the end to mention that it has to be acted globally. So, the command would be like :%s/budda/budhi/g and ENTER