Edj (pronounced like the English word "edge") is the skeleton of a simple line editor patterned after Unix ed(1). sedj is the stream editor - a tiny subset of Unix sed(1). vedj is - wait for it - the visual edj. The names all rhyme.

It was not created to be a useful editor - you cannot yet save your work! - but to provide a platform for some demonstrations of Design Patterns and related issues, particularly in the Java language, including the "undo" command. If someone (or even me) tries to turn it into a useful line editor, you’ll know that CLI fans have regained the upper hand in geekdom. Or not.

It was also written to show that you can, in fact, do something small and (possibly) useful in Java without dragging in 47 different add-on JAR files. This project has zero external run-time dependencies and only one test-time dependency (JUnit).

Note that the BufferPrims code has changed slightly from the version shown in Part 1 of the article, appearing in the July/August issue of Java Magazine, due to the need to support a screen editor as well. If you want that exact version, use git checkout edj_article.

• Compile and package:

• Copy the edj and vedj scripts to a directory on your path (for MS-DOS-derived systems, somebody needs to write DOS bat files to do the same thing).

• Copy the JAR file from target/ to someplace like $HOME/lib/

• Hack the scripts script to find the jar file there.

Invoke with a filename argument, or, start with an 'r' (read file) command.

Commands are single lower-case letters (or '.' or '=') Command lines are of the form start,endCOMMANDoperands

The line range start,end is optional; if omitted altogether the current line (most recently added or modified, or clicked on in vedj) is meant. If only one line is intended, omit the comma and the second number. A command line that consists only of a line number will move the current line to that number.

The original ed's special line number '$' (dollar sign) meaning 'last line' is not yet implemented. Line numbers beginning with '+' or '-' are not implemented. The special filename syntax beginning with '!' ('bang' or exclamation mark) will not be implemented.

The following commands are implemented so far:

The following are not implemented:

When computers were very young, there were no graphics systems for them, no touchscreens, no mice, only "terminals" that read from a keyboard and printed on paper. It was in this era that line editors were the dominant way of editing text for program source code, emails, instant messages, and so on.

An ed command that is recognizably the origin of this family of tools appeared in Version 1 of AT&T Bell Labs Research UNIX around 1970.

Versions of ed have been in every flavor of Unix (including *BSD and Mac OS X), and in every Unix-like system (Linux etc.), since then. Berkeley Unix mutated ed into ex, and then added visual editing mode, which became the vi editor, in the late 1970’s. Vi still has ex (and hence ed) line mode editing built in.

So this project is a months-young implementation of a fifty-year-old specification.