Icod.DiffUtils

Icod.DiffUtils is a managed .NET implementation of GNU Diffutils 3.12, providing the familiar cmp, diff, diff3, and sdiff command-line tools in C#.

The project targets .NET 10 and C# 13 and is designed for Windows, Linux, and macOS, with best-effort support for BSD-family systems. Shared comparison and merge behavior is factored into the reusable Icod.DiffUtils.Shared library, while general command-line and platform infrastructure is supplied by Icod.CommandFramework.

The goal is practical GNU Diffutils compatibility without shelling out to the host operating system's native Diffutils installation.

Included commands

Command	Purpose
cmp	Compare two files byte by byte.
diff	Compare files or directories line by line and emit GNU-style difference formats.
diff3	Compare three files and report, script, or merge three-way changes.
sdiff	Display side-by-side differences and optionally perform an interactive merge.

Each executable directory contains a dedicated man-page-style README.md describing its implemented command-line profile, exit statuses, platform behavior, and relevant compatibility notes.

Icod.DiffUtils.Shared

Icod.DiffUtils.Shared is the suite-specific class library used by the Diffutils commands.

It contains behavior genuinely shared by two or more tools, including:

• comparison inputs and result status;
• byte-preserving UTF-8 comparison documents;
• incomplete-line tracking;
• line-normalization policies;
• Myers edit scripts;
• contiguous difference blocks;
• context-expanded hunks;
• GNU-compatible three-way alignment and overlap classification; and
• side-by-side layout and display-column mechanics.

Command-specific concerns such as command-line policy, directory traversal, labels, binary reporting, output syntax, editor invocation, and interactive behavior remain in the individual command projects.

General-purpose command-line, filesystem, stream, text, locale, process, and platform mechanics come from the published Icod.CommandFramework package rather than being duplicated in this repository.

Compatibility philosophy

GNU Diffutils 3.12 is the behavioral reference for this project.

The implementation aims to preserve familiar GNU command syntax, output formats, and exit-status behavior while remaining a managed, cross-platform .NET codebase. The commands do not invoke an external diff, cmp, diff3, or sdiff executable to perform their core work.

Platform-neutral comparison and merge behavior lives in managed code. Where a feature necessarily interacts with the host filesystem, process environment, or terminal, the implementation uses the abstractions supplied by .NET and Icod.CommandFramework.

Highlights

cmp

cmp performs binary, byte-for-byte comparison and supports GNU-style initial offsets, comparison limits, quiet operation, visible-byte output, and verbose difference reporting.

diff

diff supports file and directory comparison, recursive operation, normal, context, unified, ed, forward-ed, RCS, side-by-side, brief, and conditional merged output, together with GNU-style whitespace and matching controls.

diff3

diff3 performs three-way comparison and can produce human-readable reports, ed scripts, conflict-marked output, or a directly merged result using the in-process three-way merge engine.

sdiff

sdiff provides side-by-side comparison and interactive merge operation, including selection and editing of differing regions.

See each command's own README for its exact implemented option set.

Building

The repository requires a .NET 10 SDK.

On Windows:

build.cmd

On Unix-like hosts:

./build.sh

Or build the solution directly:

dotnet restore Icod.DiffUtils.sln
dotnet build Icod.DiffUtils.sln -c Debug --no-restore
dotnet test Icod.DiffUtils.sln -c Debug --no-build --no-restore

The solution defines Debug, Staging, and Release configurations.

Continuous integration

Pull requests are restored, built, and tested with .NET 10 on:

• windows-latest
• ubuntu-latest
• macos-latest

Pushes to main are built and tested in the repository's Release configuration on the same three operating systems. Release builds treat compiler warnings as errors except for documentation warning CS1591.

Project layout

Icod.DiffUtils/
├── Icod.DiffUtils.Shared/    shared Diffutils comparison and merge library
├── cmp/                      byte-by-byte comparison
├── diff/                     two-way file and directory comparison
├── diff3/                    three-way comparison and merge
├── sdiff/                    side-by-side comparison and interactive merge
├── tests/                    command and shared-library tests
├── Icod.DiffUtils.sln
├── build.cmd
└── build.sh

Documentation

Every executable has a dedicated README.md intended to function much like a manual page.

For the reusable comparison and merge architecture, see Icod.DiffUtils.Shared/README.md.

Licensing

The executable tools in this repository use the repository LICENSE, with command-specific licensing notices included alongside the individual tools.

Icod.DiffUtils.Shared has its own licensing terms and declares LGPL-3.0-or-later; see Icod.DiffUtils.Shared/LICENSE for the complete license applicable to the reusable library.

Upstream inspiration and authorship

These programs are migrated from and modeled on GNU Diffutils 3.12.

The upstream GNU command authors credited by Diffutils are:

• cmp — Torbjörn Granlund and David MacKenzie
• diff — Paul Eggert, Mike Haertel, David Hayes, Richard Stallman, and Len Tower
• diff3 — Randy Smith
• sdiff — Thomas Lord

Individual tool READMEs retain the corresponding upstream authorship attribution.

Migrated to .Net by Timothy J. Bruce uniblab@hotmail.com.

Copyright

Copyright (c) 2026 Timothy J. Bruce