Files

SKILL.mdagentsreferencesscripts

Install

Install the containing plugin

/plugin install shared-skills@llm-skills

Invoke this skill after installation

/shared-skills:diff

Download diff-skill.zip

This skill is bundled inside shared-skills. Install the plugin once, then Claude Code can use any of its included skills. Browse the full plugin repository at github.com/alisonaquinas/llm-shared-skills.

SKILL.md

name: diff description: Compare files and directories line-by-line with diff for detecting changes, generating patches, and reviewing modifications. Use when the agent needs to show differences between versions, generate unified diffs for version control, or verify file identity.

diff

Compare files and directories line-by-line to detect changes and generate patches.

Quick Start

Verify diff is available: diff --version or man diff
Establish the command surface: man diff or diff --help
Start with a read-only comparison: diff file1.txt file2.txt

Intent Router

Load only the reference file needed for the active request.

references/install-and-setup.md — Installing diff (GNU, BSD) on macOS, Linux, Windows
references/cheatsheet.md — Common flags, unified diffs, context diffs, side-by-side output, patch generation
references/advanced-usage.md — Recursive directory comparison, ignore patterns, patch application, three-way merge, performance
references/troubleshooting.md — Binary file detection, line ending differences (CRLF vs LF), encoding issues, exit codes

Core Workflow

Verify diff variant (GNU or BSD): diff --version or man diff
Choose comparison format: unified (-u), context (-c), or normal output
Run read-only comparison first: diff file1 file2 to see changes
For patches, use unified format: diff -u original modified > changes.patch
Verify patch applies cleanly before merging: patch --dry-run < changes.patch

Quick Command Reference

diff --version                         # Check version (GNU vs BSD)
diff file1 file2                       # Show line-by-line differences
diff -u file1 file2                    # Unified format (readable, useful for patches)
diff -c file1 file2                    # Context format (3 lines of context)
diff -y file1 file2                    # Side-by-side comparison
diff -u file1 file2 > changes.patch    # Generate patch file
diff -r dir1 dir2                      # Recursively compare directories
diff -i file1 file2                    # Ignore case differences
diff --ignore-all-space file1 file2    # Ignore whitespace
man diff                               # Full manual and options

Safety Notes

Area	Guardrail
Line endings	Windows (CRLF) vs Unix (LF) differences can obscure real changes. Use `--ignore-all-space` or normalize with `dos2unix` first.
Binary files	diff marks binary files as "Binary files ... differ" and does not show content. Use `xxd`, `hexdump`, or `cmp` for binary inspection.
Large files	Comparing very large files (>100 MB) can be slow. Use `cmp` for byte-level checking or `diff -q` for existence check.
Patch direction	Patches are directional: `diff -u original modified` (old → new). Reversed order creates inverting patch (`-R`).
Character encoding	diff may produce garbled output for non-UTF-8 files. Convert with `iconv` or check with `file`.
Exit codes	Exit 0 (identical), 1 (differ), 2 (error). Scripts must check `$?` carefully.

Source Policy

Treat the installed diff behavior and man diff as runtime truth.
Use GNU Coreutils documentation (gnu.org/software/diffutils) for GNU-specific features.
Use BSD diff manual for BSD variant behavior differences.

Resource Index

scripts/install.sh — Install diff (GNU diffutils) on macOS or Linux.
scripts/install.ps1 — Install diff on Windows or any platform via PowerShell.