Introduction

In this tutorial, we’ll explore fundamental Bash commands that every developer should master. We’ll start with disk space analysis and expand to cover essential file operations.

Disk Space Analysis

Basic Command

Here’s a useful command to list files by size:

du -sh * | sort -h

Command Breakdown

  • du -sh *:

    • du = disk usage
    • -s = summary (total only for directories)
    • -h = human-readable format (KB, MB, GB)
    • * = all files/directories in current folder

  • sort -h: sorts human-readable values numerically

Useful Variations

# Top 10 largest files/directories
du -sh * | sort -hr | head -10

# Recursive analysis with details
du -ah . | sort -hr | head -20

# Directories only, excluding files
du -sh */ | sort -hr

# Analysis of specific directory
du -sh /home/user/* | sort -hr

Free Disk Space

# Free space on filesystems
df -h

# Information about specific partition
df -h /home

Finding Large Files

# Files larger than 100MB
find . -type f -size +100M -exec du -sh {} + | sort -hr

# Files larger than 1GB in current directory
find . -maxdepth 1 -type f -size +1G -exec ls -lh {} +

Practical Script

Create a script to monitor disk space:

#!/bin/bash
# monitor_space.sh

echo "=== Disk Space Analysis ==="
echo "Current directory: $(pwd)"
echo ""

echo "Top 10 items by size:"
du -sh * 2>/dev/null | sort -hr | head -10

echo ""
echo "Free space:"
df -h .

Make it executable:

chmod +x monitor_space.sh
./monitor_space.sh

File Operations

Basic File Commands

# List files with details
ls -la

# Copy files
cp source.txt destination.txt
cp -r source_dir/ destination_dir/

# Move/rename files
mv old_name.txt new_name.txt

# Remove files (be careful!)
rm file.txt
rm -rf directory/

Text File Operations

# View file contents
cat file.txt
less file.txt
head -n 10 file.txt    # First 10 lines
tail -n 10 file.txt    # Last 10 lines
tail -f log_file.txt   # Follow file changes

# Search in files
grep "pattern" file.txt
grep -r "pattern" directory/
grep -i "case-insensitive" file.txt

Process Management

Viewing Processes

# List running processes
ps aux
ps -ef

# Interactive process viewer
top
htop  # If installed

# Process tree
pstree

Process Control

# Run command in background
command &

# List background jobs
jobs

# Bring job to foreground
fg %1

# Send to background
bg %1

# Kill processes
kill PID
killall process_name
pkill pattern

Pro Tips

System Information

Hardware Information

# CPU information
lscpu
cat /proc/cpuinfo

# Memory information
free -h
cat /proc/meminfo

# Storage devices
lsblk
fdisk -l

# USB devices
lsusb

# PCI devices
lspci

System Status

# System uptime
uptime

# Who's logged in
who
w

# System load average
cat /proc/loadavg

# Kernel information
uname -a

Environment Variables

Common Variables

# View all environment variables
env
printenv

# Important variables
echo $HOME     # Home directory
echo $USER     # Current user
echo $PATH     # Executable paths
echo $SHELL    # Current shell
echo $PWD      # Current directory

Setting Variables

# Temporary variable (current session)
export MY_VAR="value"

# Permanent variable (add to ~/.bashrc)
echo 'export MY_VAR="value"' >> ~/.bashrc
source ~/.bashrc

Next Steps

In the next tutorial, we’ll cover:

  • Advanced text processing with awk and sed
  • Network commands and troubleshooting
  • Automating tasks with cron jobs
  • Shell scripting best practices

Practice Exercises

Try these exercises to reinforce your learning:

  1. Disk Cleanup: Find and list all files larger than 500MB in your home directory
  2. Log Analysis: Use tail -f to monitor system logs in /var/log/
  3. Process Monitoring: Create a script that shows the top 5 CPU-consuming processes
  4. File Organization: Write a script that organizes files by extension into subdirectories

Resources

Remember: Practice makes perfect! The more you use these commands, the more natural they’ll become.