#!/bin/bash
#===============================================================================
# Bash Cheatsheet
# Author: Claude (AI Language Model)
# Date: 2023-06-13
#===============================================================================
#===============================================================================
# Table of Contents
#===============================================================================
# 1. Basic Commands
# 2. Variables
# 3. Input/Output
# 4. Conditionals
# 5. Loops
# 6. Functions
# 7. Arrays
# 8. Strings
# 9. File Operations
# 10. Process Handling
# 11. Debugging
# 12. Whiptail Commands
# 13. Tips and Tricks
#===============================================================================
# 1. Basic Commands
#===============================================================================
# Print working directory
pwd
# List files and directories
ls
ls -l # List in long format
ls -a # List all files (including hidden)
ls -t # List files sorted by modification time
ls -R # List files recursively
# Change directory
cd
cd /path/to/directory # Change to specific directory
cd ~ # Change to home directory
cd - # Change to previous directory
# Create directory
mkdir directory_name
mkdir -p /path/to/directory # Create intermediate directories if they don't exist
# Remove empty directory
rmdir directory_name
# Remove files and directories
rm file_name
rm -r directory_name # Remove directory and its contents recursively
rm -f file_name # Force removal without confirmation
# Copy files and directories
cp source_file destination_file
cp -r source_directory destination_directory # Copy directory recursively
# Move or rename files and directories
mv old_name new_name
# Create symbolic link
ln -s /path/to/file link_name
# Print file contents
cat file_name
cat file1 file2 # Concatenate files and print
# Print file contents with pagination
less file_name
# Print first 10 lines of a file
head file_name
head -n 5 file_name # Print first 5 lines
# Print last 10 lines of a file
tail file_name
tail -n 5 file_name # Print last 5 lines
# Search for patterns in files
grep pattern file_name
grep -r pattern directory_name # Search recursively in directory
grep -i pattern file_name # Case-insensitive search
grep -v pattern file_name # Invert match (lines not containing pattern)
# Find files and directories
find /path/to/directory -name "pattern" # Find by name
find /path/to/directory -type f # Find only files
find /path/to/directory -type d # Find only directories
find /path/to/directory -size +100M # Find files larger than 100MB
# Execute command with root privileges
sudo command
#===============================================================================
# 2. Variables
#===============================================================================
# Declare a variable
variable_name="value"
# Access a variable
echo $variable_name
# Read-only variable
readonly variable_name="value"
# Delete a variable
unset variable_name
# Variable scope (local)
local variable_name="value"
# Environment variables
export variable_name="value"
# Command substitution
variable_name=$(command)
# Arithmetic expansion
result=$((expression))
#===============================================================================
# 3. Input/Output
#===============================================================================
# Read user input
read variable_name
read -p "Prompt: " variable_name # Prompt for input
read -s variable_name # Read input silently (for passwords)
# Print to stdout
echo "Hello, World!"
printf "Hello, %s!\n" "John"
# Redirect stdout to a file
command > file_name
command >> file_name # Append to a file
# Redirect stderr to a file
command 2> file_name
command 2>> file_name # Append to a file
# Redirect both stdout and stderr to a file
command &> file_name
command &>> file_name # Append to a file
# Redirect stdin from a file
command < file_name
# Here Document
command << EOF
input
input
EOF
# Here String
command <<< "input"
#===============================================================================
# 4. Conditionals
#===============================================================================
# If statement
if [[ condition ]]; then
# commands
elif [[ condition ]]; then
# commands
else
# commands
fi
# Case statement
case "$variable" in
pattern1)
# commands
;;
pattern2)
# commands
;;
*)
# default commands
;;
esac
# Conditional expressions
[[ -z "$variable" ]] # Check if variable is empty
[[ -n "$variable" ]] # Check if variable is not empty
[[ "$str1" == "$str2" ]] # String equality
[[ "$str1" != "$str2" ]] # String inequality
[[ $num1 -eq $num2 ]] # Numeric equality
[[ $num1 -ne $num2 ]] # Numeric inequality
[[ $num1 -lt $num2 ]] # Less than
[[ $num1 -le $num2 ]] # Less than or equal to
[[ $num1 -gt $num2 ]] # Greater than
[[ $num1 -ge $num2 ]] # Greater than or equal to
#===============================================================================
# 5. Loops
#===============================================================================
# For loop
for variable in item1 item2 item3; do
# commands
done
# C-style for loop
for ((i=0; i<10; i++)); do
# commands
done
# While loop
while [[ condition ]]; do
# commands
done
# Until loop
until [[ condition ]]; do
# commands
done
# Break and continue
for item in list; do
if [[ condition ]]; then
break
fi
if [[ condition ]]; then
continue
fi
# commands
done
#===============================================================================
# 6. Functions
#===============================================================================
# Define a function
function function_name() {
# commands
}
# Call a function
function_name arg1 arg2
# Function arguments
$1 # First argument
$2 # Second argument
$@ # All arguments as separate words
$* # All arguments as a single word
$# # Number of arguments
# Return value
return_value=0
return $return_value
#===============================================================================
# 7. Arrays
#===============================================================================
# Declare an array
array_name=(item1 item2 item3)
# Access array elements
echo ${array_name[0]} # First element
echo ${array_name[*]} # All elements
echo ${array_name[@]} # All elements
echo ${#array_name[@]} # Number of elements
# Modify array elements
array_name[0]="new_item"
# Iterate over array elements
for item in "${array_name[@]}"; do
# commands
done
#===============================================================================
# 8. Strings
#===============================================================================
# String length
length=${#string}
# Substring
substring=${string:start:length}
# String replacement
new_string=${string//pattern/replacement}
# String splitting
IFS=","
read -ra arr <<< "$string"
# String concatenation
result="$str1$str2"
#===============================================================================
# 9. File Operations
#===============================================================================
# Check if file exists
if [[ -e "$file" ]]; then
# commands
fi
# Check if directory exists
if [[ -d "$directory" ]]; then
# commands
fi
# Create file
touch file_name
# Remove file
rm file_name
# Rename file
mv old_name new_name
# Copy file
cp source_file destination_file
# Symlink
ln -s /path/to/file link_name
# File permissions
chmod 644 file_name # Set read/write for owner, read for others
chmod +x file_name # Add execute permission for everyone
chmod -R 755 directory_name # Set permissions recursively
#===============================================================================
# 10. Process Handling
#===============================================================================
# Run command in background
command &
# List running jobs
jobs
# Bring background job to foreground
fg job_id
# Suspend current foreground job
Ctrl+Z
# Resume suspended job in background
bg job_id
# Terminate a process
kill pid
kill -9 pid # Force terminate
# Check process status
ps
ps aux # List all processes
# Wait for a process to finish
wait pid
#===============================================================================
# 11. Debugging
#===============================================================================
# Enable debugging mode
set -x
# Disable debugging mode
set +x
# Print trace of function calls
set -o functrace
# Print shell input lines as they are read
set -v
# Print commands and their arguments as they are executed
set -x
# Ignore errors and continue execution
command || true
# Exit immediately if a command exits with a non-zero status
set -e
# Print an error message and exit
echo "Error: Something went wrong" >&2
exit 1
#===============================================================================
# 12. Whiptail Commands
#===============================================================================
# Display a message box
whiptail --title "Message" --msgbox "Hello, World!" 8 40
# Display an input box
result=$(whiptail --title "Input" --inputbox "Enter your name:" 8 40 3>&1 1>&2 2>&3)
# Display a password box
password=$(whiptail --title "Password" --passwordbox "Enter your password:" 8 40 3>&1 1>&2 2>&3)
# Display a yes/no box
if whiptail --title "Confirmation" --yesno "Are you sure?" 8 40; then
# User selected "Yes"
else
# User selected "No"
fi
# Display a menu
options=("Option 1" "Option 2" "Option 3")
choice=$(whiptail --title "Menu" --menu "Choose an option:" 15 40 3 "${options[@]}" 3>&1 1>&2 2>&3)
# Display a checklist
options=("Option 1" "Option 2" "Option 3")
selected=$(whiptail --title "Checklist" --checklist "Select options:" 15 40 3 "${options[@]}" 3>&1 1>&2 2>&3)
# Display a radio list
options=("Option 1" "Option 2" "Option 3")
selected=$(whiptail --title "Radio List" --radiolist "Select an option:" 15 40 3 "${options[@]}" 3>&1 1>&2 2>&3)
# Display a gauge
for ((i=0; i<=100; i+=10)); do
sleep 1
echo $i
done | whiptail --title "Progress" --gauge "Please wait..." 6 50 0
#===============================================================================
# 13. Tips and Tricks
#===============================================================================
# Brace expansion
echo {1..10} # Sequence: 1 2 3 4 5 6 7 8 9 10
echo {a..z} # Sequence: a b c ... x y z
echo {A..Z} # Sequence: A B C ... X Y Z
echo file{1..3}.txt # File names: file1.txt file2.txt file3.txt
# Parameter expansion
${variable:-default} # Use default value if variable is unset or empty
${variable:=default} # Set variable to default value if unset or empty
${variable:?error} # Display error if variable is unset or empty
${variable:+value} # Use alternative value if variable is set and not empty
# Shebang
#!/bin/bash # Specify bash as the interpreter for the script
# Conditionally execute command based on exit status
command1 && command2 # Execute command2 only if command1 succeeds
command1 || command2 # Execute command2 only if command1 fails
# Redirection
command > file # Redirect stdout to file (overwrite)
command >> file # Redirect stdout to file (append)
command 2> file # Redirect stderr to file (overwrite)
command 2>> file # Redirect stderr to file (append)
command &> file # Redirect both stdout and stderr to file (overwrite)
command < file # Redirect file to stdin
# Here Document
command << EOF
input
input
EOF
# Arithmetic expansion
result=$((expression)) # Perform arithmetic operation and store result in variable
# Process substitution
diff <(command1) <(command2) # Compare output of command1 and command2
# Subshell
(cd /path/to/directory && command) # Execute command in a subshell with a different working directory
# Traps
trap 'echo "Interrupted!"' INT # Execute command when interrupt signal (Ctrl+C) is received
trap 'echo "Terminated!"' TERM # Execute command when termination signal is received
trap 'echo "Exiting..."; exit' EXIT # Execute command when script exits
# Bash options
set -e # Exit immediately if a command exits with a non-zero status
set -u # Treat unset variables as an error and exit immediately
set -x # Print commands and their arguments as they are executed
set -o pipefail # Return value of a pipeline is the status of the last command to exit with a non-zero status
# Aliases
alias ll='ls -alF' # Create an alias for a commonly used command
# Prompt customization
PS1="\u@\h \w $ " # Customize the prompt to show username, hostname, and current directory
# History
history # View command history
!<number> # Execute a command from history by its number
!! # Execute the last command
!<string> # Execute the most recent command starting with <string>
Ctrl+R # Search command history interactively
# Job control
Ctrl+Z # Suspend the current foreground process
bg # Resume the most recently suspended process in the background
fg # Bring the most recently backgrounded process to the foreground
jobs # List all background jobs
# Bash completion
Tab # Trigger auto-completion
Tab Tab # Display all possible completions
# Multiline commands
command1 \
command2 \
command3
# Heredoc with indentation
<<-EOF
This is a heredoc
with indentation
EOF
# Redirecting file descriptor
exec 3>&1 # Save current stdout to file descriptor 3
exec 1>output.txt # Redirect stdout to a file
echo "This goes to the file"
exec 1>&3 # Restore stdout from file descriptor 3
echo "This goes to the console"
# Temporary files and directories
temp_file=$(mktemp) # Create a temporary file
temp_dir=$(mktemp -d) # Create a temporary directory
# Redirecting output to multiple commands
command | tee file1 file2 > file3
# Case conversion
echo "${string^^}" # Convert to uppercase
echo "${string,,}" # Convert to lowercase
# Random number generation
random_number=$RANDOM # Generate a random number between 0 and 32767
random_number=$((RANDOM % 100 + 1)) # Generate a random number between 1 and 100
# Parsing command-line arguments
while [[ "$#" -gt 0 ]]; do
case $1 in
-o|--option) option="$2"; shift ;;
-h|--help) display_help; exit ;;
*) echo "Unknown argument: $1" >&2; exit 1 ;;
esac
shift
done
# Colorized output
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[0;33m'
NC='\033[0m' # No color
echo -e "${RED}Error: ${NC}Something went wrong"
echo -e "${GREEN}Success: ${NC}Operation completed"
# Keyboard input
read -rsn1 -t5 key # Read a single character without echoing, with a timeout of 5 seconds
case "$key" in
[Yy]) echo "Yes" ;;
[Nn]) echo "No" ;;
*) echo "Invalid input" ;;
esac
# Plotting with Gnuplot
gnuplot <<- EOF
set title "Plot Title"
set xlabel "X-axis label"
set ylabel "Y-axis label"
plot "data.txt" using 1:2 with lines
EOF
# Curses-based interfaces with dialog
dialog --title "Menu" --menu "Choose an option:" 15 40 3 \
1 "Option 1" \
2 "Option 2" \
3 "Option 3"
# Logging
exec > >(tee -a log.txt) # Redirect stdout to both console and log file
exec 2> >(tee -a error.log >&2) # Redirect stderr to both console and error log file
# Sending email
echo "Subject: Alert" | sendmail -s "Alert" user@example.com
# Downloading files
wget -O output.zip https://example.com/file.zip # Download file and save as output.zip
curl -o output.tar.gz https://example.com/file.tar.gz # Download file and save as output.tar.gz
# Extracting archives
tar -xvf archive.tar # Extract tar archive
tar -xzvf archive.tar.gz # Extract gzipped tar archive
unzip archive.zip # Extract zip archive
# SSH commands
ssh user@host # Connect to remote host via SSH
ssh user@host command # Execute command on remote host via SSH
scp file.txt user@host:/path/to/destination # Copy file to remote host via SSH
scp user@host:/path/to/file.txt . # Copy file from remote host via SSH
# Running commands in parallel
command1 &
command2 &
command3 &
wait # Wait for all background commands to finish
# Checking disk space
df -h # Display disk space usage in human-readable format
du -sh /path/to/directory # Display size of a directory in human-readable format
# Checking memory usage
free -h # Display memory usage in human-readable format
vmstat # Display virtual memory statistics
top # Display real-time system information, including memory usage
# Checking CPU usage
top # Display real-time system information, including CPU usage
mpstat # Display CPU usage statistics
sar # Collect, report, and save system activity information
# Network troubleshooting
ping host # Send ICMP echo request to host
traceroute host # Trace route to host
nslookup domain # Query DNS for domain information
netstat -tunlp # Display listening ports and associated processes
# Performance monitoring
iostat # Report CPU and I/O statistics
vmstat # Report virtual memory statistics
sar # Collect, report, and save system activity information
dstat # Versatile tool for generating system resource statistics
# Text manipulation
sed 's/pattern/replacement/g' file # Replace pattern with replacement globally in file
awk '{print $1}' file # Print first column of file
cut -d ',' -f 1,3 file # Cut fields 1 and 3 from CSV file
sort file # Sort lines of file
uniq file # Remove duplicate lines from file
tr 'a-z' 'A-Z' < file # Convert lowercase to uppercase in file
grep -v pattern file # Print lines not matching pattern in file
# Date and time
date # Display current date and time
date +"%Y-%m-%d" # Display current date in YYYY-MM-DD format
date -d "1 day ago" # Display date 1 day ago
date -d "1 week" # Display date 1 week in the future
# Scheduling tasks
echo "command" | at 10:00 # Schedule command to run at 10:00
echo "command" | at now + 1 hour # Schedule command to run 1 hour from now
crontab -e # Edit crontab file to schedule recurring tasks
# Compiling and running C programs
gcc -o program program.c # Compile C program
./program # Run compiled C program
# Compiling and running Java programs
javac Program.java # Compile Java program
java Program # Run compiled Java program
# Compiling and running Python programs
python program.py # Run Python program
# Git commands
git init # Initialize a new Git repository
git clone https://github.com/user/repo.git # Clone a Git repository
git add . # Stage all changes for commit
git commit -m "Commit message" # Commit staged changes with a message
git push origin main # Push commits to the main branch of the origin remote
# Docker commands
docker build -t image:tag . # Build a Docker image from a Dockerfile in the current directory
docker run -d --name container image:tag # Run a Docker container in detached mode
docker ps # List running Docker containers
docker stop container # Stop a running Docker container
docker rm container # Remove a Docker container
# Kubernetes commands
kubectl apply -f deployment.yaml # Apply a Kubernetes deployment from a YAML file
kubectl get pods # List Kubernetes pods
kubectl logs pod # View logs of a Kubernetes pod
kubectl exec -it pod -- bash # Open an interactive shell in a Kubernetes pod
kubectl scale deployment --replicas=3 # Scale a Kubernetes deployment to 3 replicas
# AWS CLI commands
aws ec2 describe-instances # Describe EC2 instances
aws s3 ls # List S3 buckets
aws iam list-users # List IAM users
aws lambda invoke --function-name my-function output.txt # Invoke a Lambda function
aws cloudformation create-stack --stack-name my-stack --template-body file://template.yaml # Create a CloudFormation stack
# GCP CLI commands
gcloud compute instances list # List Compute Engine instances
gcloud storage ls # List Cloud Storage buckets
gcloud iam service-accounts list # List service accounts
gcloud functions deploy my-function --runtime python37 --trigger-http # Deploy a Cloud Function
gcloud deployments create my-deployment --config deployment.yaml # Create a deployment using a YAML configuration file
# Azure CLI commands
az vm list # List virtual machines
az storage account list # List storage accounts
az ad user list # List Azure Active Directory users
az functionapp create --name my-function --resource-group my-resource-group --storage-account my-storage-account # Create a Function App
az deployment group create --resource-group my-resource-group --template-file template.json # Create a deployment using an ARM template
# Terraform commands
terraform init # Initialize a Terraform working directory
terraform plan # Generate and show an execution plan
terraform apply # Apply the changes required to reach the desired state of the configuration
terraform destroy # Destroy the Terraform-managed infrastructure
# Ansible commands
ansible all -m ping # Ping all hosts in the inventory
ansible-playbook playbook.yml # Run an Ansible playbook
ansible-vault encrypt secrets.yml # Encrypt a file containing sensitive data using Ansible Vault
ansible-galaxy init role_name # Initialize a new Ansible role
ansible-doc -l # List available Ansible modules
# Puppet commands
puppet apply manifest.pp # Apply a Puppet manifest
puppet module install author-module # Install a Puppet module from the Puppet Forge
puppet cert list # List all SSL certificates
puppet resource user # Manage user resources using Puppet
puppet agent --test # Run a Puppet agent in test mode
# Chef commands
knife cookbook create cookbook_name # Create a new Chef cookbook
knife node list # List all registered Chef nodes
knife data bag create bag_name # Create a new data bag
knife role create role_name # Create a new role
knife bootstrap node_name # Bootstrap a new node and register it with the Chef server
Generated using Claude Opus Credits: https://devhints.io/bash