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diff and patch are fundamental UNIX utilities for comparing files and applying changes. diff computes the differences between two files or directories and outputs them in various formats. patch reads a diff output (a "patch file") and applies those changes to the original file.

Что это: diff и patch — базовые UNIX-утилиты для сравнения файлов и применения изменений. diff вычисляет различия между двумя файлами или каталогами. patch читает вывод diff ("файл патча") и применяет эти изменения к оригиналу.

Common use cases / Типичные случаи использования:

Status / Статус: ✅ Actively maintained, universally available on all UNIX/Linux systems. Part of POSIX standard. No modern replacement needed — diff and patch remain the foundation for version control and change management.

Installation

Install diff & patch

[!NOTE] diff and patch are part of GNU diffutils and are pre-installed on virtually all Linux distributions. diff и patch входят в состав GNU diffutils и предустановлены практически во всех дистрибутивах Linux.

# Verify installation
diff --version                                 # Show diff version / Версия diff
patch --version                                # Show patch version / Версия patch

# Install if missing
sudo apt install diffutils patch               # Debian/Ubuntu
sudo dnf install diffutils patch               # RHEL/Fedora
sudo pacman -S diffutils patch                 # Arch Linux

Install Enhanced Tools

sudo apt install colordiff diffstat            # Colored diff + statistics / Цветной diff + статистика
sudo apt install meld                          # GUI diff/merge tool / GUI инструмент diff/merge
sudo apt install wdiff                         # Word-level diff / Diff на уровне слов

diff — Compare Files

Basic Comparison

diff file1.txt file2.txt                     # Compare two files / Сравнить два файла
diff -q file1.txt file2.txt                   # Brief (quiet) mode / Краткий режим
diff -s file1.txt file2.txt                   # Report identical files / Сообщить об идентичных файлах
diff -i file1.txt file2.txt                   # Ignore case / Игнорировать регистр
diff -w file1.txt file2.txt                   # Ignore whitespace / Игнорировать пробелы
diff -b file1.txt file2.txt                   # Ignore blank lines / Игнорировать пустые строки

Output Formats

The unified format (-u) is the most widely used and recommended for patches and code review. Context format (-c) provides more surrounding context. Side-by-side (-y) is best for visual comparison in a terminal.

Унифицированный формат (-u) — самый распространённый и рекомендуемый для патчей и ревью кода. Контекстный формат (-c) предоставляет больше окружающего контекста. Бок о бок (-y) лучше всего подходит для визуального сравнения в терминале.

diff -u file1.txt file2.txt                   # Unified format (recommended) / Унифицированный формат (рекомендуется)
diff -c file1.txt file2.txt                   # Context format / Контекстный формат
diff -y file1.txt file2.txt                   # Side-by-side / Бок о бок
diff -y -W 200 file1.txt file2.txt            # Side-by-side wide / Бок о бок широко
diff --normal file1.txt file2.txt             # Normal format / Нормальный формат

Output Format Comparison

Format Flag Description (EN / RU) Best For / Лучше для
Unified -u Shows +/- with context lines / Показывает +/- с контекстом Patches, code review / Патчи, ревью кода
Context -c Extended context with ! markers / Расширенный контекст с маркерами ! Detailed review / Детальный обзор
Side-by-side -y Two columns / Два столбца Visual comparison / Визуальное сравнение
Normal (default) Line ranges with </> / Диапазоны строк с </> Scripts, legacy tools / Скрипты, устаревшие инструменты
Brief -q Only reports if files differ / Только сообщает о различиях Quick checks / Быстрая проверка

Save to Patch File

diff -u old.conf new.conf > change.patch      # Create unified patch / Создать унифицированный патч
diff -Naur old/ new/ > changes.patch          # Recursive patch / Рекурсивный патч
diff -u file1.txt file2.txt | tee change.patch  # Save and display / Сохранить и показать

Color Output

diff --color=always file1.txt file2.txt       # Colored diff / Цветной diff
diff --color=auto file1.txt file2.txt         # Auto color / Авто цвет
colordiff file1.txt file2.txt                 # Using colordiff (requires package) / С помощью colordiff

patch — Apply Changes

Basic Patching

patch file.txt < change.patch                 # Apply patch / Применить патч
patch -p0 < change.patch                      # Apply at current level / Применить на текущем уровне
patch -p1 < change.patch                      # Strip one directory / Убрать один каталог
patch -p2 < change.patch                      # Strip two directories / Убрать два каталога

Reverse & Test

patch -R file.txt < change.patch              # Reverse patch / Откатить патч
patch --dry-run -p1 < change.patch            # Test without applying / Тест без применения
patch -b file.txt < change.patch              # Backup original / Резервная копия оригинала
patch -b -V numbered file.txt < change.patch  # Numbered backups / Нумерованные резервные копии

[!TIP] Always use --dry-run before applying patches in production to verify they apply cleanly. Всегда используйте --dry-run перед применением патчей в продакшене.

[!WARNING] Applying patches without backup (-b) in production can make rollback difficult if the patch fails partially. Применение патчей без резервной копии (-b) в продакшене может затруднить откат при частичном сбое.

Interactive & Verbose

patch -i change.patch                         # Read from file / Читать из файла
patch -v -p1 < change.patch                   # Verbose output / Подробный вывод
patch -f -p1 < change.patch                   # Force (skip prompts) / Принудительно (пропустить подтверждения)

Directory Patching

cd /path/to/project                           # Change to project / Перейти в проект
patch -p1 < /path/to/changes.patch            # Apply patch / Применить патч

Patch Strip Level Explanation

The -pN flag strips N leading path components from file paths in the patch. This is critical when the patch was generated in a different directory context.

Флаг -pN убирает N начальных компонентов пути из путей файлов в патче. Это критически важно когда патч был сгенерирован в другом контексте каталогов.

Level Description (EN / RU) Example / Пример
-p0 Apply at current directory / Применить в текущей директории a/src/file.c → a/src/file.c
-p1 Strip top-level directory (most common) / Убрать верхний каталог a/src/file.c → src/file.c
-p2 Strip two levels / Убрать два уровня a/src/file.c → file.c

Directory Comparison

Recursive Comparison

diff -r dir1/ dir2/                           # Recursive diff / Рекурсивный diff
diff -qr dir1/ dir2/                          # Brief recursive / Краткий рекурсивный
diff -ur dir1/ dir2/                          # Unified recursive / Унифицированный рекурсивный
diff -Naur dir1/ dir2/ > changes.patch        # Create patch / Создать патч

Exclude Patterns

diff -r --exclude=".git" dir1/ dir2/          # Exclude .git / Исключить .git
diff -r --exclude="*.log" dir1/ dir2/         # Exclude log files / Исключить файлы логов
diff -r --exclude-from=exclude.txt dir1/ dir2/  # Exclude from file / Исключить из файла

Only Show Differences

diff -qrl dir1/ dir2/                         # List different files / Список различающихся файлов
diff -qr dir1/ dir2/ | grep "^Only in"        # Files only in one dir / Файлы только в одном каталоге
diff -qr dir1/ dir2/ | grep "differ$"         # Files that differ / Различающиеся файлы

Git-Style Diffs

Git Diff Format

diff -u --label="old version" --label="new version" file1.txt file2.txt  # Custom labels / Пользовательские метки
git diff --no-index file1.txt file2.txt       # Git-style diff / Diff в стиле Git
git diff --no-index --color-words file1.txt file2.txt  # Word diff / Diff по словам

Git Patch Creation

git format-patch -1                           # Create patch from commit / Создать патч из коммита
git format-patch HEAD~3..HEAD                 # Patches from last 3 commits / Патчи из последних 3 коммитов
git diff > changes.patch                      # Working tree diff / Diff рабочего дерева
git diff --cached > staged.patch              # Staged changes / Staged изменения

Apply Git Patches

git apply changes.patch                       # Apply patch / Применить патч
git apply --check changes.patch               # Check if applicable / Проверить применимость
git apply --reject changes.patch              # Apply with reject files / Применить с reject файлами
git am < email.patch                          # Apply mail format / Применить формат почты

Advanced Usage

Ignore Specific Changes

diff -I "^#" file1.txt file2.txt              # Ignore lines starting with # / Игнорировать строки начинающиеся с #
diff -I ".*timestamp.*" file1.txt file2.txt   # Ignore lines with pattern / Игнорировать строки с шаблоном
diff -B file1.txt file2.txt                   # Ignore blank lines / Игнорировать пустые строки
diff -w -B file1.txt file2.txt                # Ignore whitespace and blank / Игнорировать пробелы и пустые

Context Lines

diff -U 5 file1.txt file2.txt                 # 5 lines of context / 5 строк контекста
diff -U 0 file1.txt file2.txt                 # No context / Без контекста
diff -C 3 file1.txt file2.txt                 # 3 lines context format / 3 строки контекстного формата

Binary Files

diff --brief file1.bin file2.bin              # Binary comparison / Бинарное сравнение
cmp file1.bin file2.bin                       # Byte-by-byte comparison / Побайтовое сравнение
cmp -l file1.bin file2.bin                    # List all differences / Список всех различий
xxd file1.bin > /tmp/hex1.txt && xxd file2.bin > /tmp/hex2.txt && diff /tmp/hex1.txt /tmp/hex2.txt  # Hex diff / Hex сравнение

Diff Statistics

diff -u file1.txt file2.txt | diffstat        # Show statistics / Показать статистику
diff -u file1.txt file2.txt | wc -l           # Count diff lines / Подсчитать строки diff

Real-World Examples

Compare Configuration Files

# Compare configs and create patch
diff -u /etc/nginx/nginx.conf.backup /etc/nginx/nginx.conf > nginx.patch

# Apply to another server
scp nginx.patch <USER>@<HOST>:/tmp/
ssh <USER>@<HOST> "cd /etc/nginx && sudo patch -p0 < /tmp/nginx.patch"

Sync Directory Changes

# Create patch of all changes
diff -Naur /var/www/old/ /var/www/new/ > website.patch

# Apply to production
cd /var/www/html
patch -p1 < website.patch

# Verify
patch --dry-run -p1 < website.patch

[!CAUTION] Always test patches on staging before applying to production web directories. A broken patch can cause website downtime. Всегда тестируйте патчи на staging перед применением к продакшен веб-каталогам. Сломанный патч может вызвать простой сайта.

Code Review Workflow

# Generate review patch
diff -Naur src.old/ src.new/ > review.patch

# Review changes
less review.patch
vim review.patch

# Apply if approved
cd src.new/
patch -R -p1 < review.patch  # Reverse if needed / Откатить если нужно

Migration Scripts

# Compare database schemas
diff -u schema.old.sql schema.new.sql > migration.patch

# Generate SQL migration
diff -u schema.old.sql schema.new.sql | grep "^+" | sed 's/^+//' > migration.sql

Security Audits

# Check for unauthorized changes
diff -qr /etc.backup/ /etc/ | tee /var/log/config-audit.log

# Detailed diff of changed files
diff -ur /etc.backup/ /etc/ > /var/log/config-changes.patch

Automated Testing

# Compare test outputs
./test.sh > output.new
diff -u output.expected output.new
if [ $? -eq 0 ]; then echo "PASS"; else echo "FAIL"; fi

# Regression testing
diff -qr baselines/ results/ || echo "Regression detected"

Documentation Updates

# Track doc changes
diff -u README.md.old README.md > doc-updates.patch

# Generate changelog from diff
diff -u v1.0/ v2.0/ | grep "^+" | grep -v "^+++" > CHANGES.txt

Backup Verification

# Verify backup integrity
diff -qr /data/ /backup/data/ | tee backup-verification.log

# Find files missing in backup
diff -qr /data/ /backup/data/ | grep "^Only in /data"

Container Image Layers

# Compare Dockerfiles
diff -u Dockerfile.old Dockerfile.new > docker.patch

# Compare container filesystems
docker export container1 | tar -x -C /tmp/c1
docker export container2 | tar -x -C /tmp/c2
diff -qr /tmp/c1 /tmp/c2

Multi-Server Consistency

# Check config consistency
for server in <HOST1> <HOST2> <HOST3>; do
  ssh <USER>@$server "cat /etc/app/config.yml" > config.$server
done
diff -u config.<HOST1> config.<HOST2>
diff -u config.<HOST1> config.<HOST3>

Best Practices

General Recommendations

Useful diff Options

Option Description (EN / RU)
-u Unified format (most readable) / Унифицированный формат
-r Recursive / Рекурсивно
-N Treat absent files as empty / Рассматривать отсутствующие как пустые
-a Treat all files as text / Рассматривать все как текст
-q Brief output / Краткий вывод
-i Ignore case / Игнорировать регистр
-w Ignore whitespace / Игнорировать пробелы

Alternative Tools

Tool Description (EN / RU) Use Case / Применение
vimdiff Visual diff editor / Визуальный diff редактор Terminal-based merge / Слияние в терминале
meld GUI diff tool / GUI инструмент diff Visual file/dir comparison / Визуальное сравнение файлов
kompare KDE diff tool / KDE инструмент diff KDE desktop integration / Интеграция с KDE
colordiff Colored diff / Цветной diff Better terminal readability / Читаемость в терминале
delta Modern diff viewer / Современный просмотрщик diff Git pager, syntax highlighting / Git pager, подсветка синтаксиса
difftastic Structural diff / Структурный diff Language-aware comparison / Сравнение с учётом языка
wdiff Word-level diff / Diff по словам Document comparison / Сравнение документов

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Source: devtoolbox-cheats

On this page

sysadmin Description Installation Install diff &amp; patch Install Enhanced Tools diff — Compare Files Basic Comparison Output Formats Output Format Comparison Save to Patch File Color Output patch — Apply Changes Basic Patching Reverse &amp; Test Interactive &amp; Verbose Directory Patching Patch Strip Level Explanation Directory Comparison Recursive Comparison Exclude Patterns Only Show Differences Git-Style Diffs Git Diff Format Git Patch Creation Apply Git Patches Advanced Usage Ignore Specific Changes Context Lines Binary Files Diff Statistics Real-World Examples Compare Configuration Files Sync Directory Changes Code Review Workflow Migration Scripts Security Audits Automated Testing Documentation Updates Backup Verification Container Image Layers Multi-Server Consistency Best Practices General Recommendations Useful diff Options Alternative Tools Documentation Links