The “other” interactive editor that’s commonly used is Emacs. Emacs actually refers to a family of editors; versions of Emacs run under most operating systems available. However, the most important (and most commonly used) version of Emacs is “GNU Emacs,” developed by the Free Software Foundation.
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GNU Emacs is popular because it’s the most powerful editor in the Emacs family; it is also freely available under the terms of the FSF’s General Public License. Although there are certainly strong differences of opinion between Emacs and vi users, most people agree that Emacs provides a much more powerful and richer working environment.
What’s so good about Emacs, aside from the fact that it’s free? There are any number of individual features that I could mention. (I’ll give a list of favorite features in Section 19.2.) Emacs’ best feature is the extent to which it interacts with other Unix features. For example, it has a built-in email system so you can send and receive mail without leaving the editor. It has tools for “editing” (deleting, copying, renaming) files, for running a Unix shell within Emacs, and so on. The C shell has a rather awkward command-history mechanism; the Korn shell has something more elaborate. But imagine being able to recall and edit your commands as ...