There are a number of freely available "clones" of the vi editor. Appendix E, provides a pointer to a web site that lists all known vi clones. We have chosen to cover four of the most popular ones. They are:
Version 1.79 of Keith Bostic's nvi
Version 2.0 of Steve Kirkendall's elvis
Version 5.0 of Bram Moolenaar's vim
Version 7.4 of vile, by Kevin Buettner, Tom Dickey, and Paul Fox
The clones were written because the source code for vi is not freely available, making it impossible to either port vi to a non-UNIX environment or to study the code, and/or because UNIX vi (or another clone!) did not provide desired functionality. For example, UNIX vi often has limits on the maximum length of a line, and it cannot edit binary files. (The chapters on the various programs present more information about each one's history.)
Each program provides a large number of extensions to UNIX vi; often, several of the clones provide the same extensions, although usually not in an identical way. Instead of repeating the treatment of each common feature in each program's chapter, we have centralized the discussion here. You can think of this chapter as presenting "what the clones do," with each clone's chapter presenting "how the clone does it."
This chapter covers the following topics:
This is the ability to split the screen into multiple "windows." You can edit a different file in each window, or have several views ...