Shell Cheatsheet

File & Directory Operations

List Files: ls

Display files and directories in the current location.

# List files in current directory
ls
# List with detailed information
ls -l
# Show hidden files
ls -a
# List with human-readable file sizes
ls -lh
# Sort by modification time
ls -lt

Create Files: touch

Create empty files or update timestamps.

# Create a new file
touch newfile.txt
# Create multiple files
touch file1.txt file2.txt file3.txt
# Update timestamp of existing file
touch existing_file.txt

Create Directories: mkdir

Create new directories.

# Create a directory
mkdir my_directory
# Create nested directories
mkdir -p parent/child/grandchild
# Create multiple directories
mkdir dir1 dir2 dir3

Copy Files: cp

Copy files and directories.

# Copy a file
cp source.txt destination.txt
# Copy directory recursively
cp -r source_dir dest_dir
# Copy with confirmation prompt
cp -i file1.txt file2.txt
# Preserve file attributes
cp -p original.txt copy.txt

Move/Rename: mv

Move or rename files and directories.

# Rename a file
mv oldname.txt newname.txt
# Move file to directory
mv file.txt /path/to/directory/
# Move multiple files
mv file1 file2 file3 target_directory/

Delete Files: rm

Remove files and directories.

# Delete a file
rm file.txt
# Delete directory and contents
rm -r directory/
# Force delete without confirmation
rm -f file.txt
# Interactive deletion (confirm each)
rm -i *.txt

Navigation & Path Management

Current Directory: pwd

Print the current working directory path.

# Show current directory
pwd
# Example output:
/home/user/documents

Change Directory: cd

Change to a different directory.

# Go to home directory
cd ~
# Go to parent directory
cd ..
# Go to previous directory
cd -
# Go to specific directory
cd /path/to/directory

Directory Tree: tree

Display directory structure in tree format.

# Show directory tree
tree
# Limit depth to 2 levels
tree -L 2
# Show only directories
tree -d

Text Processing & Search

View Files: cat / less / head / tail

Display file contents in different ways.

# Display entire file
cat file.txt
# View file page by page
less file.txt
# Show first 10 lines
head file.txt
# Show last 10 lines
tail file.txt
# Show last 20 lines
tail -n 20 file.txt
# Follow file changes (useful for logs)
tail -f logfile.txt

Search in Files: grep

Search for patterns in text files.

# Search for pattern in file
grep "pattern" file.txt
# Case-insensitive search
grep -i "pattern" file.txt
# Search recursively in directories
grep -r "pattern" directory/
# Show line numbers
grep -n "pattern" file.txt
# Count matching lines
grep -c "pattern" file.txt

Find Files: find

Locate files and directories based on criteria.

# Find files by name
find . -name "*.txt"
# Find files by type
find . -type f -name "config*"
# Find directories
find . -type d -name "backup"
# Find files modified in last 7 days
find . -mtime -7
# Find and execute command
find . -name "*.log" -delete

Text Manipulation: sed / awk / sort

Process and manipulate text data.

# Replace text in file
sed 's/old/new/g' file.txt
# Extract specific columns
awk '{print $1, $3}' file.txt
# Sort file contents
sort file.txt
# Remove duplicate lines
sort file.txt | uniq
# Count word frequency
cat file.txt | tr ' ' '\n' | sort | uniq -c

File Permissions & Ownership

View Permissions: ls -l

Display detailed file permissions and ownership.

# Show detailed file information
ls -l
# Example output:
# -rw-r--r-- 1 user group 1024 Jan 1 12:00 file.txt
# d = directory, r = read, w = write, x = execute

Change Permissions: chmod

Modify file and directory permissions.

# Give execute permission to owner
chmod +x script.sh
# Set specific permissions (755)
chmod 755 file.txt
# Remove write permission for group/others
chmod go-w file.txt
# Recursive permission change
chmod -R 644 directory/

Change Ownership: chown / chgrp

Change file owner and group.

# Change owner
chown newowner file.txt
# Change owner and group
chown newowner:newgroup file.txt
# Change group only
chgrp newgroup file.txt
# Recursive ownership change
chown -R user:group directory/

Permission Numbers

Understanding numeric permission notation.

# Permission calculation:
# 4 = read (r), 2 = write (w), 1 = execute (x)
# 755 = rwxr-xr-x (owner: rwx, group: r-x, others: r-x)
# 644 = rw-r--r-- (owner: rw-, group: r--, others: r--)
# 777 = rwxrwxrwx (full permissions for all)
# 600 = rw------- (owner: rw-, group: ---, others: ---)

Process Management

View Processes: ps / top / htop

Display information about running processes.

# Show processes for current user
ps
# Show all processes with details
ps aux
# Show processes in tree format
ps -ef --forest
# Interactive process viewer
top
# Enhanced process viewer (if available)
htop

Background Jobs: & / jobs / fg / bg

Manage background and foreground processes.

# Run command in background
command &
# List active jobs
jobs
# Bring job to foreground
fg %1
# Send job to background
bg %1
# Suspend current process
Ctrl+Z

Kill Processes: kill / killall

Terminate processes by PID or name.

# Kill process by PID
kill 1234
# Force kill process
kill -9 1234
# Kill all processes with name
killall firefox
# Send specific signal
kill -TERM 1234

System Monitoring: free / df / du

Monitor system resources and disk usage.

# Show memory usage
free -h
# Show disk space
df -h
# Show directory size
du -sh directory/
# Show largest directories
du -h --max-depth=1 | sort -hr

Input/Output Redirection

Redirection: > / >> / <

Redirect command output and input.

# Redirect output to file (overwrite)
command > output.txt
# Append output to file
command >> output.txt
# Redirect input from file
command < input.txt
# Redirect both output and errors
command > output.txt 2>&1
# Discard output
command > /dev/null

Pipes: |

Chain commands together using pipes.

# Basic pipe usage
command1 | command2
# Multiple pipes
cat file.txt | grep "pattern" | sort | uniq
# Count lines in output
ps aux | wc -l
# Page through long output
ls -la | less

Tee: tee

Write output to both file and stdout.

# Save output and display it
command | tee output.txt
# Append to file
command | tee -a output.txt
# Multiple outputs
command | tee file1.txt file2.txt

Here Documents: <<

Provide multi-line input to commands.

# Create file with here document
cat << EOF > file.txt
Line 1
Line 2
Line 3
EOF
# Send email with here document
mail user@example.com << EOF
Subject: Test
This is a test message.
EOF

Variables & Environment

Variables: Assignment & Usage

Create and use shell variables.

# Assign variables (no spaces around =)
name="John"
count=42
# Use variables
echo $name
echo "Hello, $name"
echo "Count: ${count}"
# Command substitution
current_dir=$(pwd)
date_today=$(date +%Y-%m-%d)

Environment Variables: export / env

Manage environment variables.

# Export variable to environment
export PATH="/new/path:$PATH"
export MY_VAR="value"
# View all environment variables
env
# View specific variable
echo $HOME
echo $PATH
# Unset variable
unset MY_VAR

Special Variables

Built-in shell variables with special meanings.

# Script arguments
$0  # Script name
$1, $2, $3...  # First, second, third argument
$#  # Number of arguments
$@  # All arguments as separate words
$*  # All arguments as single word
$?  # Exit status of last command
# Process information
$$  # Current shell PID
$!  # PID of last background command

Parameter Expansion

Advanced variable manipulation techniques.

# Default values
${var:-default}  # Use default if var is empty
${var:=default}  # Set var to default if empty
# String manipulation
${var#pattern}   # Remove shortest match from
beginning
${var##pattern}  # Remove longest match from
beginning
${var%pattern}   # Remove shortest match from end
${var%%pattern}  # Remove longest match from end

Scripting Basics

Script Structure

Basic script format and execution.

#!/bin/bash
# This is a comment
# Variables
greeting="Hello, World!"
user=$(whoami)
# Output
echo $greeting
echo "Current user: $user"
# Make script executable:
chmod +x script.sh
# Run script:
./script.sh

Conditional Statements: if

Control script flow with conditions.

#!/bin/bash
if [ -f "file.txt" ]; then
    echo "File exists"
elif [ -d "directory" ]; then
    echo "Directory exists"
else
    echo "Neither exists"
fi
# String comparison
if [ "$USER" = "root" ]; then
    echo "Running as root"
fi
# Numeric comparison
if [ $count -gt 10 ]; then
    echo "Count is greater than 10"
fi

Loops: for / while

Repeat commands using loops.

#!/bin/bash
# For loop with range
for i in {1..5}; do
    echo "Number: $i"
done
# For loop with files
for file in *.txt; do
    echo "Processing: $file"
done
# While loop
count=1
while [ $count -le 5 ]; do
    echo "Count: $count"
    count=$((count + 1))
done

Functions

Create reusable code blocks.

#!/bin/bash
# Define function
greet() {
    local name=$1
    echo "Hello, $name!"
}
# Function with return value
add_numbers() {
    local sum=$(($1 + $2))
    echo $sum
}
# Call functions
greet "Alice"
result=$(add_numbers 5 3)
echo "Sum: $result"

Network & System Commands

Network Commands

Test connectivity and network configuration.

# Test network connectivity
ping google.com
ping -c 4 google.com  # Send only 4 packets
# DNS lookup
nslookup google.com
dig google.com
# Network configuration
ip addr show  # Show IP addresses
ip route show # Show routing table
# Download files
wget https://example.com/file.txt
curl -O https://example.com/file.txt

System Information: uname / whoami / date

Get system and user information.

# System information
uname -a      # All system info
uname -r      # Kernel version
hostname      # Computer name
whoami        # Current username
id            # User ID and groups
# Date and time
date          # Current date/time
date +%Y-%m-%d # Custom format
uptime        # System uptime

Archive & Compression: tar / zip

Create and extract compressed archives.

# Create tar archive
tar -czf archive.tar.gz directory/
# Extract tar archive
tar -xzf archive.tar.gz
# Create zip archive
zip -r archive.zip directory/
# Extract zip archive
unzip archive.zip
# View archive contents
tar -tzf archive.tar.gz
unzip -l archive.zip

File Transfer: scp / rsync

Transfer files between systems.

# Copy file to remote server
scp file.txt user@server:/path/to/destination
# Copy from remote server
scp user@server:/path/to/file.txt .
# Sync directories (local to remote)
rsync -avz local_dir/ user@server:/remote_dir/
# Sync with delete (mirror)
rsync -avz --delete local_dir/ user@server:/remote_dir/

Command History & Shortcuts

Command History: history

View and reuse previous commands.

# Show command history
history
# Show last 10 commands
history 10
# Execute previous command
!!
# Execute command by number
!123
# Execute last command starting with 'ls'
!ls
# Search history interactively
Ctrl+R

History Expansion

Reuse parts of previous commands.

# Last command's arguments
!$    # Last argument of previous command
!^    # First argument of previous command
!*    # All arguments of previous command
# Example usage:
ls /very/long/path/to/file.txt
cd !$  # Goes to /very/long/path/to/file.txt

Keyboard Shortcuts

Essential shortcuts for efficient command line usage.

# Navigation
Ctrl+A  # Move to beginning of line
Ctrl+E  # Move to end of line
Ctrl+F  # Move forward one character
Ctrl+B  # Move backward one character
Alt+F   # Move forward one word
Alt+B   # Move backward one word
# Editing
Ctrl+U  # Clear line before cursor
Ctrl+K  # Clear line after cursor
Ctrl+W  # Delete word before cursor
Ctrl+Y  # Paste last deleted text
# Process control
Ctrl+C  # Interrupt current command
Ctrl+Z  # Suspend current command
Ctrl+D  # Exit shell or EOF

Command Combinations & Tips

Useful Command Combinations

Powerful one-liners for common tasks.

# Find and replace text in multiple files
find . -name "*.txt" -exec sed -i 's/old/new/g' {} \;
# Find largest files in current directory
du -ah . | sort -rh | head -10
# Monitor log file for specific pattern
tail -f /var/log/syslog | grep "ERROR"
# Count files in directory
ls -1 | wc -l
# Create backup with timestamp
cp file.txt file.txt.backup.$(date +%Y%m%d-%H%M%S)

Aliases & Functions

Create shortcuts for frequently used commands.

# Create aliases (add to ~/.bashrc)
alias ll='ls -alF'
alias la='ls -A'
alias l='ls -CF'
alias ..='cd ..'
alias ...='cd ../..'
# View all aliases
alias
# Create persistent aliases in ~/.bashrc:
echo "alias mycommand='long command here'" >>
~/.bashrc
source ~/.bashrc

Job Control & Screen Sessions

Manage long-running processes and sessions.

# Start command in background
nohup long_running_command &
# Start screen session
screen -S mysession
# Detach from screen: Ctrl+A then D
# Reattach to screen
screen -r mysession
# List screen sessions
screen -ls
# Alternative: tmux
tmux new -s mysession
# Detach: Ctrl+B then D
tmux attach -t mysession

System Maintenance

Common system administration tasks.

# Check disk usage
df -h
du -sh /*
# Check memory usage
free -h
cat /proc/meminfo
# Check running services
systemctl status service_name
systemctl list-units --type=service
# Update package lists (Ubuntu/Debian)
sudo apt update && sudo apt upgrade
# Search for installed packages
dpkg -l | grep package_name

Relevant Links

• Linux Cheatsheet
• Red Hat Enterprise Linux Cheatsheet
• Git Cheatsheet
• Docker Cheatsheet
• Kubernetes Cheatsheet
• Ansible Cheatsheet
• DevOps Cheatsheet
• Python Cheatsheet