Intro

I was looking for a tiny editor which can be easily adapted and embedded into a (Forth) system. The vi EMACS war is over but others have won. However for me vi is better suited for restricted (embedded) systems. I have not used vi for a very long time, but to see a screen full with ~ at the beginning of the lines makes me feel like coming home. I never thought I would ever take the book Learning the vi Editor, by Linda Lamb, 5th edition 1990 off the bookshelf again for reading. I kept the book only for sentimental reasons.

My editor history:

• CP/M Turbo Pascal Editor (Wordstar) OKI if800, Z80 Assembler, Pascal, 1984
• UNIX Rand Editor, Perkin Elmer, 1985
• VMS EDT MicroVAX, Pascal, Oracle DB, 1987
• vi (MKS Toolkit) IBM PC DOS cross-assembler for NEC's 75X 4-bit MCUs, Coherent OS, Linux, 1988
• UNIX EMACS as system administrator for DEC Tru64 UNIX, SUN Solaris, and Linux servers, 1996
• IDE (Eclipse, NetBeans, EWARM), 2010

Features

This vi has its origin in BusyBox tiny vi. But there are some differences:

• The program is resident. The text buffer and other buffers too. You can leave the program without saving, do some work on the command line and go back to vi and continue the edit task.
• The text buffer is restricted to 40 KiB. Large files have to be split up.
• 8-bit characters are allowed e.g. UTF8
• Mecrisp Forth uses DOS/Windows style line endings carriage return and line feed ("\r\n"). Unix (and vi) uses just line feed ("\n"). Files are saved as Unix text files. https://vim.fandom.com/wiki/File_format
• The command v evaluates a line. The command V evaluates a line and inserts the results into the text buffer.
• :!<line> evaluates the line and put the result to the status line

Don't forget: you can't use any special keys (e.g. cursor movement keys) in the insert/replace mode.

Documentation, Manual

There are plenty of documents about vi:

• Busybox vi tutorial https://k.japko.eu/busybox-vi-tutorial.html
• Learning the vi Editor/BusyBox vi https://en.wikibooks.org/wiki/Learning_the_vi_Editor/BusyBox_vi
• Unix/Linux - The vi Editor Tutorial https://www.tutorialspoint.com/unix/unix-vi-editor.htm
• vi Editor "Cheat Sheet" http://www.atmos.albany.edu/daes/atmclasses/atm350/vi_cheat_sheet.pdf
• The Vi Lovers Home Page ... this makes a great starting point. https://thomer.com/vi/vi.html
• Learning the vi Editor, by Linda Lamb

BusyBox and ToyBox

• https://git.busybox.net/busybox/plain/editors/vi.c
• Toybox
• https://github.com/landley/toybox/blob/master/toys/pending/vi.c

Usage

vi [-R] [-h] [-c <COLUMNS>] [-r <ROWS>] [FILE..]
   -h show features
   -R Read-only mode. You can still edit the buffer, but will be prevented from overwriting a file.
   -e erase the text buffer
   -c <COLUMNS> screen columns, range 40..128 default 80
   -r <ROWS> screen rows, range 16..30 default 24

vi ( "line<EOL>" -- )  a (Forth) programmer's text editor