# File Operations
ls -la                      # List all files with details
find . -name "*.php"        # Find PHP files
grep -r "function" ./       # Search for text in files
sed -i "s/old/new/g" file   # Replace text in file
awk "{print $1}" file       # Print first column

# Process Management
ps aux | grep nginx         # Find nginx processes
top                         # Live process viewer
htop                        # Enhanced process viewer
kill -9 PID                 # Force kill process
nohup command &             # Run command in background

# System Info
df -h                       # Disk usage
du -sh *                    # Directory sizes
free -h                     # Memory usage
uname -a                    # System info
lscpu                       # CPU info

# Networking
curl -I https://example.com # Get HTTP headers
wget https://example.com    # Download file
netstat -tulpn              # Open ports
ss -tulpn                   # Socket stats (modern)
ping -c 4 google.com        # Test connectivity
traceroute google.com       # Trace network path

# Permissions
chmod 755 script.sh         # Set permissions
chown user:file file        # Change owner
umask                       # View default permissions

# Compression
tar -czf archive.tar.gz dir/    # Create tar.gz
tar -xzf archive.tar.gz         # Extract tar.gz
zip -r archive.zip dir/         # Create zip
unzip archive.zip               # Extract zip

# Text Editors
vim file.txt                # Open in vim
nano file.txt               # Open in nano
tail -f log.txt             # Follow log file
less large.txt              # View large file

# SSH
ssh user@host               # Connect to remote
scp file user@host:/path/   # Copy file
rsync -av src/ dest/        # Sync directories

# Package Management (Ubuntu/Debian)
apt update                  # Update package list
apt upgrade                 # Upgrade packages
apt install package         # Install package
apt remove package          # Remove package

# Git
git status                  # Check status
git log --oneline           # Compact log
git branch -a               # List branches
git diff                    # Show changes