EDLIN — portable C11 line editor

EDLIN is a small line-oriented editor inspired by the classic DOS editor: a * prompt, numbered lines, one current line, and single-letter commands such as List, Insert, Delete, Write, End, and Quit.

This repository contains a modern portable C11 implementation that builds on macOS and Linux.

The original ASM source files included for reference come from the official MS-DOS source releases published by Microsoft.

Build and Run

Requirements:

• A C11 compiler
• make
• Python 3 plus pexpect for the integration tests

Build the editor:

make

Run it on a text file:

./edlin myfile.txt

If the file does not exist, EDLIN prints New file and starts with an empty buffer.

Use binary mode when Ctrl-Z bytes should be treated as normal data:

./edlin /B binary.bin

Basic Usage

At the * prompt, type commands and press Enter:

• I inserts lines; end insert mode with . on a line by itself.
• L lists lines.
• D deletes lines.
• Stext searches for text.
• Rold;new replaces text.
• Tfile merges another file.
• E saves and exits.
• Q quits without saving after confirmation.
• H prints in-session help.

Many commands accept line numbers before the command letter, such as 1,3L to list lines 1 through 3 or #I to insert after the last line. See Tutorial.md for a guided introduction and Manual.md for the full command reference.

Testing

Install test dependencies once:

pip install -r requirements-dev.txt

Run the full test suite:

make test

Project Layout

• src/ — C source files and headers.
• tests/test_parser.c — parser unit test.
• tests/test_edlin_commands.py — integration tests that drive ./edlin.
• Manual.md — full command reference.
• Tutorial.md — beginner walkthrough.
• AGENT.md — concise implementation notes for coding agents and contributors.

License

See LICENSE.