Introduction Vi(Visual Editor) in Linux Operating System

 Vi(Visual Editor)

Entering Input Mode

vi starts up in command mode. To enter text, you need to switch to input mode. vi provides several ways to do this. For example, the command a puts vi in input mode and begins appending typed text into the buffer immediately after the position of the cursor. (Note that it appends text after the character pointed to by the cursor, not after the line pointed to, as in ed.) The command i puts vi in input mode and begins inserting typed text immediately before the position of the cursor. The command A puts vi in input mode and appends material at the end of the current line. The command I puts vi in input mode and inserts material at the beginning of the current line. The command O (uppercase O) Opens up a line above the current line, places the cursor there, and puts vi in input mode. The command o (lowercase o) opens up a line below the current line, places the cursor there, and puts vi in input mode.

All further typing that you do is entered into the buffer. Whenever you are in input mode, existing text moves as new text is entered. The new text you type in does not overwrite the old.

 

Leaving Input Mode

Because vi is a two-mode editor, the most important commands for a beginner to remember are the ones that are needed to change modes. The commands a and A, i and I, and o and O place you in input mode.

When you are done creating text, you can leave input mode and go into command mode by pressing ESC (the escape key is usually at the upper-left of the keyboard). Anytime you press ESC, even in the middle of a line, you will be put back in command mode. The only way to stop appending or inserting text and return to command mode is to press ESC. This gets vi out of input mode and back into command mode.

To automatically keep track of where you are (command or input mode), it is a good idea to press ESC as soon as you are done entering a portion of text. This puts you back into command mode.

 

Exiting vi

When you have finished typing in your text, you need to exit the editor. Remember, if you make serious errors, you can always exit and start again. First get out of input mode by hitting ESC. Typing : (colon) puts you in a mode in which ed commands work. The cursor drops to the bottom of the screen, prints a : (colon), and waits. The command : w will write the contents of the editing buffer into the file. It is at this point that the original file is replaced with the new, edited version. The combined commands : wq will write and quit. Since : wq is a common command sequence in every editing session, the abbreviation ZZ, which represents “last command,” is equivalent to : wq. The command : x stands for exit and is also equivalent to : wq. If you have made some changes you regret, you can cancel all the changes you’ve made by quitting the editor without writing the buffer to a file. To do this, use the : q! command. This means “quit, and I really mean it.”

Moving Within a Window

The main benefit of a screen editor is that you can see a portion of your file and use context to move around and decide on changes. In vi’s command mode, you have several ways to move around a window. One set of commands enables you to move around by lines or characters

l or SPACEBAR or →	Moves right one character
h or CTRL-H or BACKSPACE or ←	Moves left one character
j or CTRL-J or CTRL-N or ↓	Moves down one line
k or CTRL-P or ↑	Moves up one line
0	Moves to the beginning of the line
$	Moves to the end of the current line
+ or ENTER	Moves to the beginning of the next line
−	Moves to the beginning of the previous line

You don’t need to think only in terms of characters and lines; vi also lets you move in other units. In normal text entry, a word is a sequence of letters delimited by spaces or by punctuation; and a sentence ends with a period (.), question mark (?), or exclamation point (!) and is separated from the previous sentence by two spaces, or by a ENTER. With these definitions, the commands shown in below

Command	What It Does
w	Moves to the next word or punctuation mark
W	Moves to the next word
e	Moves to the end of this word or punctuation mark
E	Moves to the next end of word
b	Moves back to the beginning of word or punctuation
B	Moves back to the beginning of the word
)	Moves to the start of the next sentence
(	Moves back to the start of the sentence
}	Moves to the start of the next paragraph
{	Moves back to the last start of paragraph
]]	Moves to the start of the next section
[[	Moves back to the last start of section

Moving the Window in the Buffer

vi shows you the text file, one window at a time. Normally, you edit by moving the cursor around on the screen, making changes and additions, and by displaying different portions of the text on the screen. The commands in the previous section showed you how to move the cursor in the text. You can also move the window that displays the text with the following five commands

CTRL-F (Forward)	Moves forward one full screen
CTRL-D (Down)	Moves forward one half screen

CTRL-B (Back)	Moves back one full screen
CTRL-U (Up)	Moves back one half screen
G (Go)	Moves to end of file

These commands also take numeric prefixes to move further ahead in the file. The command 3CTRL- F (hitting the number 3 key, then the CTRL and F keys simultaneously) will move ahead three full screens, whereas the command 4CTRL-B will move back four screens. The G command goes to a specific line number or goes to the end if no line number is specified. Therefore, the command 23G positions the cursor at line 23; the command 1G (number 1 and letter G) positions it at the first line in the file, whereas the command G goes to the last line.

 

Modifying Text

vi provides simple commands for changing and deleting parts of your text. The command rn means replace the current character (where the cursor is located) with the character n. You can also replace multiple characters; for example, the command 3rn replaces three characters with n.

The command RstringESC replaces the current characters with the string you type in. Characters are overwritten until you press ESC (the escape key, usually in the upper left-hand of the keyboard).

The c (change) command enables you to make larger-scale modifications to words or lines. For example, the command cwstringESC changes the current word by replacing it (that is, overwriting it) with whatever string you type. The change continues until you press ESC. When you make such a change, vi puts a $ over the last character of the word to be changed. The $ disappears when you press ESC.

The command c$stringESC will change everything from the current cursor position to the end of the line ($) by replacing the text with the string you type in. ESC takes you out of input mode.

The change commands also can take numerical arguments, so the command 4cw will change the next four words, and the command 3c$ will change the next three lines.

 

DeletingText

vi provides two delete commands that let you delete small or large chunks of text. To delete single letters, use the command x. x deletes the current character. As with other vi commands, x takes a numerical argument. This means that the command 7x deletes seven characters-the character under the cursor and the six to the right of it. The d (delete) command works on larger units of text.

Command	What It Does
dw	Deletes from the cursor to the end of the word
3dw	Deletes three words
d$	Deletes to the end of the line
D	Deletes to the end of the line (a synonym for d$)
3d$	Deletes to the end of the third line ahead
d)	Deletes to the beginning of the next line
d}	Deletes to the beginning of the next paragraph
d]]	Deletes to the beginning of the next section
dd	Deletes the current line
2dd	Deletes two lines