vi is a Unix/Linux text editor used for creating and modifying a range of different types of files. Use of vi can be cumbersome at first and requires knowledge of at least 15 or so special commands in order to be useful.
At linux prompt type "vimtutor" (without the quotes) to start a built in tutorial
See vi on Wikipedia for a list of commands.
Here is a link to a vi reference card that lists all the commands.
Insert Mode vs. Normal Mode
i enter insert mode <Esc> enter normal mode
In insert mode, you can type and delete text just as you would in a word processor. When you are done, press the <Esc> key to go back into normal mode.
Navigating the file:
<Arrow keys> move up, down, left, right 0 move to the beginning of a line $ move to the end of a line 1G move to the first line of the file 10G move to the 10th line of the file G move to the last line of the file <ctrl+u> move up 1/2 a page <ctrl+d> move down 1/2 a page
Search for text:
/ After pressing the '/'key, a prompt will show up on the bottom left of the screen. Type in the text you want to match and press 'Return'. Press the 'n' key to go to the next matched result (press the 'N' key to cycle through the results in reverse)
Find and replace text:
:%s/old/new/g will search through the file and replace every instance of 'old' with 'new'
Delete, copy and paste text:
dl delete a letter dw delete a word dd delete a line 5dd delete 5 lines yy copy a line of text 3yy copy 3 lines of text p paste the last text you copied of deleted
Saving and quitting
:w save the file :wq save the file and quit :q quit vi mode :q! quit without saving the changes you made to the file
Other useful things to know
u undo the last change you made . repeat the last change you made