Chris Tyler - Fedora Linux

 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.

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

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

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

Table 4-8. Commands to enter insert mode

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.

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

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 .

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

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

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 terminali.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 screento 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.