File Operations Skill Skill

File Operations Skill

Master file system operations with production-ready patterns

Learning Objectives

After completing this skill, you will be able to:

[ ] Manage file permissions (chmod, chown)
[ ] Search files efficiently with find and fd
[ ] Create and extract archives (tar, zip)
[ ] Synchronize files with rsync
[ ] Work with symbolic and hard links

Prerequisites

Bash basics
Understanding of file systems
Command line navigation

Core Concepts

1. Permission Management

# Numeric notation
chmod 755 script.sh       # rwxr-xr-x
chmod 644 file.txt        # rw-r--r--
chmod 600 secret.key      # rw-------

# Symbolic notation
chmod u+x script.sh       # Add execute for owner
chmod g-w file.txt        # Remove write for group
chmod a+r public.txt      # Add read for all

# Ownership
chown user:group file
chown -R user:group dir/

# Common patterns
chmod 600 ~/.ssh/id_rsa   # SSH private key
chmod 755 /var/www/html/  # Web directory

2. Find Command

# By name
find . -name "*.txt"
find . -iname "*.TXT"     # Case insensitive

# By type
find . -type f            # Files
find . -type d            # Directories
find . -type l            # Symlinks

# By size/time
find . -size +100M        # Larger than 100MB
find . -mtime -7          # Modified in 7 days

# Actions
find . -name "*.tmp" -delete
find . -type f -exec chmod 644 {} +

3. Archive Operations

# Create archives
tar -cvf archive.tar dir/
tar -czvf archive.tar.gz dir/   # gzip
tar -cjvf archive.tar.bz2 dir/  # bzip2

# Extract archives
tar -xvf archive.tar
tar -xzvf archive.tar.gz -C /dest/

# ZIP
zip -r archive.zip dir/
unzip archive.zip

4. Rsync

# Local sync
rsync -avz source/ dest/

# Remote sync
rsync -avz local/ user@host:/remote/

# With delete (mirror)
rsync -avz --delete source/ dest/

# Dry run
rsync -avzn source/ dest/

Common Patterns

Safe Delete Pattern

# With confirmation
rm -i file.txt

# With variable check
rm -rf "${DIR:?}/"   # Fails if DIR empty

Backup Pattern

# Timestamped backup
backup() {
    local src="$1"
    local timestamp=$(date +%Y%m%d_%H%M%S)
    cp -a "$src" "${src}.${timestamp}.bak"
}

Find and Process

# Fix permissions
find /var/www -type d -exec chmod 755 {} +
find /var/www -type f -exec chmod 644 {} +

# Delete old files
find /tmp -type f -mtime +7 -delete

Anti-Patterns

| Don't | Do | Why | |-------|-----|-----| | rm -rf $VAR/ | rm -rf "${VAR:?}/" | Empty VAR = delete / | | find \| xargs rm | find -delete | Handles spaces | | cp -r for sync | rsync -a | rsync is smarter |

Practice Exercises

Permission Fixer: Script to fix web dir permissions
Old File Cleaner: Remove files older than N days
Backup Script: Timestamped backup with rotation
Sync Tool: Two-way directory sync

Troubleshooting

Common Errors

| Error | Cause | Fix | |-------|-------|-----| | Permission denied | Wrong permissions | Check with ls -la | | No such file | Path typo | Verify path exists | | Directory not empty | rm without -r | Add -r flag | | Cross-device link | Hard link across fs | Use symlink |

Debug Techniques

# Check permissions
stat file.txt
ls -la file.txt

# Trace find
find . -name "*.txt" -print

# Dry-run rsync
rsync -avzn source/ dest/

Safety Guidelines

Always dry-run rsync with --delete first
Quote paths with spaces: "$path"
Verify paths before rm -rf
Use trash instead of rm when possible
Backup before bulk operations

Agent Skills: File Operations Skill

Skill Files