Essential Linux Command Line Tools

1. File and Directory Operations

• ls: List directory contents
  ls -l # Long format listing ls -a # Show hidden files ls -lh # Human-readable file sizes
• cd: Change directory
  cd /path/to/directory cd .. # Go up one directory cd ~ # Go to home directory
• pwd: Print working directory
  pwd
• mkdir: Make directory
  mkdir new_folder mkdir -p parent/child/grandchild
• rm: Remove files or directories
  rm file.txt rm -r directory # Remove directory and contents rm -f file.txt # Force remove without prompting
• cp: Copy files or directories
  cp source.txt destination.txt cp -r source_dir destination_dir
• mv: Move or rename files or directories
  mv old_name.txt new_name.txt mv file.txt /path/to/new/location/

2. File Viewing and Editing

• cat: Concatenate and display file content
  cat file.txt
• less: View file content page by page
  less large_file.txt
• head: Display the beginning of a file
  head -n 10 file.txt # Show first 10 lines
• tail: Display the end of a file
  tail -n 20 file.txt # Show last 20 lines tail -f log_file.txt # Follow file updates in real-time
• nano: Simple text editor
  nano file.txt
• vim: Advanced text editor
  vim file.txt

3. System Information and Process Management

• top: Display and manage system processes
  top
• ps: Report process status
  ps aux # Display all processes
• kill: Terminate processes
  kill PID kill -9 PID # Force kill
• df: Report file system disk space usage
  df -h # Human-readable sizes
• du: Estimate file space usage
  du -sh directory # Summarize directory size
• free: Display amount of free and used memory
  free -h # Human-readable sizes

4. Networking

• ping: Send ICMP ECHO_REQUEST to network hosts
  ping google.com
• ifconfig or ip: Configure network interface
  ifconfig ip addr show
• netstat: Print network connections, routing tables, etc.
  netstat -tuln # Show active listening ports
• ssh: Secure shell client (remote login program)
  ssh username@remote_host
• scp: Secure copy (remote file copy program)
  scp file.txt username@remote_host:/path/to/destination

5. File Permissions

• chmod: Change file mode bits
  chmod 755 file.txt chmod u+x script.sh # Make executable for user
• chown: Change file owner and group
  chown user:group file.txt

6. Search and Text Processing

• grep: Search for patterns in files
  grep "pattern" file.txt grep -r "pattern" directory # Recursive search
• find: Search for files in a directory hierarchy
  find /path -name "*.txt" find /path -type d # Find directories
• sed: Stream editor for filtering and transforming text
  sed 's/old/new/g' file.txt # Replace text
• awk: Pattern scanning and processing language
  awk '{print $1}' file.txt # Print first column

Further Learning

To deepen your command line skills, consider exploring:

• Bash Scripting Fundamentals
• Advanced Text Processing with sed and awk
• Linux System Administration via Command Line