Fedora Linux

Basic Text Editing Using vi

Fedora Core, like most other Linux and Unix systems, stores most of its configuration information in text files. These files can be edited using various system administration tools, but they can also be edited by hand using any standard text editor.

vi is one such text editor. Some people love it, and some people hate it, but it has one advantage over just about every other editor available: it’s universal. If you know how to use vi, you can confidently walk up to just about any Linux or Unix computer in the world and edit text files, so it’s a valuable skill. The other nice fact about Vi is that it’s not very demanding; you can use it in character mode or graphic mode, over a congested remote connection or with a foreign keyboard, and still get the job done. You can get by with less than a dozen commands to start, and then learn more when you need them.

Tip

vi is pronounced “vee-eye,” not “vye” or “six.”

How Do I Do That?

To start up the vi editor, simply type its name at a shell prompt, optionally providing the name of a file you wish to edit as an argument:

$ vi 
               
                  filename
               

The screen will clear, and the specified file will be displayed, as shown in Figure 4-4.

Figure 4-4. Initial vi display

Notice that unused lines are marked with a tilde (~) character.

vi modes

vi uses two distinct modes:

• Normal mode, where the text keys issue editing commands. This is sometimes called command mode.

• Insert mode, where text keys insert text into the document.

The lower-left corner of the display shows the current mode: if it says -- INSERT --, then you’re in insert mode; otherwise, you’re in normal mode.

Moving around

You can move the cursor around using the arrow keys. If your arrow keys don’t work (which may be the case if you’re using a remote connection from a bad terminal program), you can use the h, j, k, and l keys, as shown in Table 4-7.

Table 4-7. Basic vi movement commands

Command	Description
Left, h, or Backspace	Move left one character.
Down or j	Move down one line.
Up or k	Move up one line.
Right, l, or Space	Move right one character.
Enter	Move to the start of the next line.
Home, ^, |, or 0 (Zero)	Move to the start of the line.
End, $	Move to the end of the line.
:number Enter	Move to line number.
:0 Enter	Move to the start of the file.
:$	Move to the end of the file.
w	Move forward one word.

You can put a number in front of any command to repeat the command. For example, typing 10j will move down 10 lines.

Inserting text

There are several commands for inserting text, as shown in Table 4-8.

Table 4-8. Commands to enter insert mode

Command	Description
i	Insert before the cursor.
I	Insert at the start of the line.
a	Append after the cursor.
A	Append at the end of the line.
o	Open a line after the current line and insert text.
O	Open a line before the current line and insert text.

All of these commands place the editor into insert mode; the only difference is where the cursor is positioned for the inserted text. The word -- INSERT -- will appear in the lower-left corner of the display.

To exit from insert mode and return to normal mode, press Esc. The -- INSERT -- indicator in the lower-left corner of the display will disappear.

Deleting, yanking, and putting: vi’s version of cutting, copying, and pasting

vi offers three basic commands for deleting or yanking, as shown in Figure 4-9. Deleting is roughly equivalent to cutting in a GUI-based editor, and yanking is similar to copying.

Table 4-9. Basic delete and yank commands

Command	Description	Examples
x	Delete one character to the right of the cursor.	x deletes one character to the right of the cursor; 25x deletes the character at the cursor position and 24 characters to the right.
X	Delete one character to the left of the cursor.	X deletes one character to the left of the cursor; 19X deletes 19 characters to the left.
d, followed by a cursor movement	Delete from the cursor position to the indicated position.	dj deletes the current line and the line below; dw deletes one word.
dd	Deletes a line.	dd deletes the current line; 15dd deletes 15 lines.
y, followed by a cursor movement	Yank from the cursor position to the indicated position.	yj yanks the current line and the line below; yw yanks one word.
yy	Yanks a line.	yy yanks the current line; 15yy yanks 15 lines.
p	Puts yanked or deleted text after the cursor. If the text contains any partial lines, it is inserted directly after the cursor; otherwise, it is inserted starting on the next line.	p puts one copy of the yanked text into the document after the cursor; 20p puts 20 copies of the yanked text after the cursor.
P	Puts yanked or deleted text before the cursor. If the text contains any partial lines, it is inserted directly before the cursor; otherwise, it is inserted on the previous line.	P puts one copy of the yanked text into the document before the cursor; 20P puts 20 copies of the yanked text before the cursor.

Searching

Typing / followed by some text (actually, a regular expression) and pressing Enter will search forward in the document. Typing n will repeat the previous search in the forward direction. Typing ? instead of / will search backward instead of forward; N will repeat a search backward.

Searching can be combined with deleting and yanking; for example, d/hello will delete from the cursor position up to the start of the word hello.

Undoing, redoing, and repeating

Pressing u will undo the last operation performed; pressing Ctrl-R will redo it. Typing a dot (.) will repeat the last operation.

Saving and exiting

There are a number of commands available for saving the document and exiting vi, as shown in Table 4-10; you must press Enter after these commands.

Table 4-10. Saving text and exiting vi

Command	Description
:w	Write (save) using the current filename.
:w newfilename	Write to the file newfilename (subsequent :w commands will still write to the original filename).
:w!	Force-write (write even if in read-only mode).
:q	Quit (succeeds only if the document is saved).
:q!	Force quit even if the document isn’t saved (abort!).
:wq or :x or ZZ	Write and quit (exit with save).

How Does It Work?

vi is one of a group of programs that uses a terminal-control system called curses. curses enables an application to manage a character-mode display by positioning the cursor and interpreting keystrokes using a database of information about each terminal—i.e., which codes to send to produce different effects and which codes can be received from the terminal. Fedora’s terminfo database has entries for about 2,500 different hardware terminals and terminal programs that have been produced through the years.

curses keeps two buffers—areas of memory arranged in the same size and layout as the screen—to store the current terminal screen contents and the desired display. When vi needs to update the screen, it updates the display buffer; curses compares the two buffers to determine the minimum number of commands it can send to the terminal to produce the desired display. It then sends the appropriate codes from the terminal database (terminfo/termcap) to update the terminal, copies the display buffer to the terminal buffer, and repeats the process.

The version of vi used by Fedora Core is Vim (Vi iMproved), which adds many, many features to the traditional vi capabilities; the commands covered in this chapter outline only the basics. Vim offers syntax highlighting, macro recording, support for multiple character sets, accents, right-to-left text, and many other features, making it a useful text editor for programming, scripting, and editing system files.

Vim can be configured by creating a .vimrc file; for details, type :help vimrc-intro within Vim.

What About...

...using vi with a GUI?

If you execute gvim instead of vi, a window will appear with a full graphical user interface—including pull-down menus and a toolbar—as shown in Figure 4-5. Using the File→Save menu option, clicking on the Save toolbar icon, or typing the vi save command ( :w) will perform the same operation.

Figure 4-5. gvim: vi with a GUI

...using other text editors?

In addition to vi, Fedora ships with a plethora of other text editors, including:

• nano (an improved clone of the easy-to-use editor Pico)

• mcedit

• joe (the commands jstar, jmacs, or jpico will start joe configured to emulate WordStar, emacs, or Pico).

• emacs and emacs-x

• kedit and gedit

All of these text editors are capable of editing just about any text file. Each has its advantages and disadvantages.

Since the choice of editor is very personal, take some time to experiment with each of the editors to see which one you prefer. In any case, I’d recommend knowing the basics of vi so that you can always fall back to it if you encounter a situation where your favorite editor is unavailable.

Where Can I Learn More?

• The Vim web site: http://www.vim.org/

• The vi help file and online tutorial: start vi, then type :help and press Enter