Chapter 8. vi Clones
Feature Summary
8.1. And These Are My Brothers,
Darrell, Darrell, and Darrell
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:
- Multiwindow editing
- This is the ability to split the screen
into multiple "windows."[38]
You can edit a different file in each window, or have several views into
the same file.
This is perhaps the single most important extension over regular
vi.
- GUI interfaces
- All of the clones except nvi can be compiled to support
an X Window interface. If you have a system running X, use of the GUI
version may be preferable to splitting the screen
of an xterm (or other terminal emulator);
the GUI versions generally provide such nice features as scrollbars
and multiple fonts. The native GUIs of other operating systems may
also be supported.
- Extended regular expressions
- All of the clones make it possible to match text using regular
expressions that are similar or identical to those provided by
the UNIX egrep(1) command.
- Enhanced tags
- As described in Section 7.5.3 in
Chapter 7, you can use the ctags
program to build up a
searchable database of your files. The clones make it possible
to "stack" tags, by saving your current location when
you do a tag search. You can then return to that location.
Multiple locations can be saved in a Last In First Out (LIFO) order,
producing a stack of locations.
Several of the vi clone authors and the author of
at least one ctags clone have gotten together
to define a standard form for an enhanced version of the
ctags format. In particular, it is now easier to
use the tags functionality with programs written in
C++, which allows overloaded function names.
- Improved editing facilities
- All of the clones provide
the ability to edit the ex command line,
"infinite undo" capability,
arbitrary length lines and eight-bit data,
incremental searching,
(at least an option) to scroll the screen
left to right for long lines instead of wrapping long lines,
and
mode indicators,
as well as other features.
- Programming assistance
- Several of the editors provide features that allow you to stay
within the editor during the typical
"edit-compile-debug"
cycle of software development.
- Syntax highlighting
- In elvis, vim,
and vile, you can arrange to display different
parts of a file in
different colors and/or fonts.
This is particularly useful for editing program source code.
There is one additional feature in the clones that we have chosen
not to cover: extension languages.
As of May 1998,
nvi has preliminary support for Perl and Tcl integration,
elvis has its own C-like expression evaluator,[39]
vim has
a C-like expression evaluator, plus
support for Perl, Python, and Tcl integration,
and vile, which has always had its own built-in
extension language,
has preliminary support for Perl integration.
The extension language integration and support are very recent for
all of the programs and will undoubtedly change significantly.
For this reason, any discussion of the extension language facilities
would be obsolete almost as soon as this book goes to press.
We recommend that you check the online documentation for your
clone if you're interested in programming your editor with
an extension language.[40]
Extension languages are a feature worth watching; they promise to
bring a new dimension of power to vi users.
The use of well-known programming languages, such as Perl, Python,
and Tcl, is an additional advantage, since it is likely that
users will already know one or more of them.
 |  |  | II. Extensions and Clones |  | 8.2. Multiwindow Editing |
Copyright © 2003 O'Reilly & Associates. All rights reserved.
|
|