vi is the classic screen-editing program for Unix. A number of enhanced versions exist, including nvi, vim, vile, and elvis. On GNU/Linux systems, the vi command is usually one of these programs (either a copy or a link). The Emacs editor, covered in Chapter 8, has several vi modes that allow you to use many of the same commands covered in this chapter.
The vi editor operates in two modes: command mode and insert mode. The dual modes make vi an attractive editor for users who separate text entry from editing. For users who edit as they type, the modeless editing of Emacs can be more comfortable. However, vim supports both ways of editing, through the insertmode option.
vi is based on an older line editor called ex. (ex, in turn, was developed by Bill Joy at the University of California, Berkeley, from the primordial Unix line editor, ed.) A user can invoke powerful editing capabilities within vi by typing a colon (:), entering an ex command, and pressing the Enter key. Furthermore, you can place ex commands in a startup file called ˜/.exrc, which vi reads at the beginning of your editing session. Because ex commands are such an important part of vi, they are also described in this chapter.
One of the most common versions of vi found on Linux systems is Bram Moolenaar’s Vi IMproved, or vim. On some Linux distributions, vim is the default version of vi and runs when you invoke vi. vim offers many extra features, and optionally changes some of the basic features of ...
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