1337skills - Cheat Sheet e Guide di Cybersecurity

Bash - Bourne Again Shell¶

# Check if Bash is installed
which bash
/bin/bash

# Check Bash version
bash --version
GNU bash, version 5.1.16(1)-release (x86_64-pc-linux-gnu)

# Check current shell
echo $SHELL
/bin/bash

# Check available shells
cat /etc/shells
```# Bash - Bourne Again Shell

<div class="cheat-sheet-actions">
  ```bash
# Set Bash as default shell for current user
chsh -s /bin/bash

# Set Bash as default shell for specific user (as root)
sudo chsh -s /bin/bash username

# Verify shell change
echo $SHELL

Bash (Bourne Again Shell) è una shell Unix e un linguaggio di comandi scritto da Brian Fox per il Progetto GNU come sostituto gratuito della Bourne Shell. Rilasciato per la prima volta nel 1989, Bash è diventato la shell predefinita sulla maggior parte delle distribuzioni Linux ed è una delle shell più utilizzate nell'ecosistema Unix/Linux. Combina le funzionalità della shell Bourne originale con funzionalità aggiuntive tra cui il completamento dei comandi, la cronologia dei comandi e capacità di scripting migliorate.

Installazione e Configurazione¶

Verifica dell'Installazione di Bash¶

Impostare Bash come Shell Predefinita¶

Installazione di Bash su Diversi Sistemi¶

Sintassi e Comandi Base di Bash¶

Struttura dei Comandi¶

Variabili e Ambiente¶

Sostituzione dei Comandi¶

Virgolettatura ed Escape¶

Operazioni e Navigazione File¶

Navigazione Directory¶

Elenco File e Directory¶

Operazioni sui File¶

Permessi e Proprietà dei File¶

Elaborazione e Manipolazione Testo¶

Operazioni sul Contenuto dei File¶

Ricerca e Filtraggio Testo¶

Strumenti di Elaborazione Testo¶

Reindirizzamento Input/Output e Pipe¶

Operatori di Reindirizzamento¶

Pipe e Concatenazione Comandi¶

Gestione Processi¶

Controllo Processi¶

Informazioni sui Processi¶

Fondamenti di Scripting Bash¶

Struttura dello Script¶

Note: - I've maintained the markdown formatting - Technical terms like "Bash" remain in English - The structure and punctuation are preserved - Translations are provided in the same numbered format

Would you like me to proceed with translating the specific sections you mentioned?```bash

Ubuntu/Debian¶

sudo apt update && sudo apt install bash

CentOS/RHEL/Fedora¶

sudo dnf install bash

macOS (using Homebrew for latest version)¶

brew install bash

Arch Linux¶

sudo pacman -S bash

FreeBSD¶

pkg install bash

## Basic Bash Syntax and Commands

### Command Structure
```bash
# Basic command structure
command [options] [arguments]

# Examples
ls -la /home
cp file1.txt file2.txt
grep -r "pattern" /path/to/search

Variables and Environment¶

# Variable assignment (no spaces around =)
name="John Doe"
age=30
path="/home/user"

# Using variables
echo $name
echo $\\\\{name\\\\}
echo "Hello, $name"

# Environment variables
export PATH="/usr/local/bin:$PATH"
export EDITOR="vim"

# Special variables
echo $0    # Script name
echo $1    # First argument
echo $#    # Number of arguments
echo $@    # All arguments
echo $    # Process ID
echo $?    # Exit status of last command

Command Substitution¶

# Using $() (preferred)
current_date=$(date)
file_count=$(ls|wc -l)
user_home=$(eval echo ~$USER)

# Using backticks (legacy)
current_date=`date`
file_count=`ls|wc -l`

# Nested command substitution
echo "Today is $(date +%A), $(date +%B) $(date +%d)"

Quoting and Escaping¶

# Single quotes (literal)
echo 'The variable $HOME is not expanded'

# Double quotes (variable expansion)
echo "Your home directory is $HOME"

# Escaping special characters
echo "The price is \$10"
echo "Use \"quotes\" inside quotes"

# Here documents
cat << EOF
This is a multi-line
text block that can contain
variables like $HOME
EOF

# Here strings
grep "pattern" <<< "$variable"

# Change directory
cd /path/to/directory
cd ~                    # Home directory
cd -                    # Previous directory
cd ..                   # Parent directory
cd ../..                # Two levels up

# Print working directory
pwd

# Directory stack operations
pushd /path/to/dir      # Push directory onto stack
popd                    # Pop directory from stack
dirs                    # Show directory stack

File and Directory Listing¶

# Basic listing
ls
ls -l                   # Long format
ls -la                  # Long format with hidden files
ls -lh                  # Human readable sizes
ls -lt                  # Sort by modification time
ls -lS                  # Sort by size
ls -lR                  # Recursive listing

# Advanced listing options
ls -la --color=auto     # Colored output
ls -la --time-style=full-iso  # ISO time format
ls -la --group-directories-first  # Directories first

File Operations¶

# Create files
touch file.txt
touch file1.txt file2.txt file3.txt

# Copy files and directories
cp source.txt destination.txt
cp -r source_dir/ destination_dir/
cp -p file.txt backup.txt    # Preserve attributes
cp -u source.txt dest.txt    # Update only if newer

# Move and rename
mv old_name.txt new_name.txt
mv file.txt /path/to/destination/
mv *.txt /path/to/directory/

# Remove files and directories
rm file.txt
rm -f file.txt              # Force removal
rm -r directory/            # Recursive removal
rm -rf directory/           # Force recursive removal
rm -i *.txt                 # Interactive removal

# Create directories
mkdir directory_name
mkdir -p path/to/nested/directory
mkdir -m 755 directory_name  # With specific permissions

File Permissions and Ownership¶

# Change permissions
chmod 755 file.txt
chmod u+x script.sh         # Add execute for user
chmod g-w file.txt          # Remove write for group
chmod o=r file.txt          # Set read-only for others
chmod -R 644 directory/     # Recursive permission change

# Change ownership
chown user:group file.txt
chown -R user:group directory/
chgrp group file.txt        # Change group only

# View permissions
ls -l file.txt
stat file.txt               # Detailed file information

Text Processing and Manipulation¶

File Content Operations¶

# View file contents
cat file.txt                # Display entire file
less file.txt               # Paginated view
more file.txt               # Simple paginated view
head file.txt               # First 10 lines
head -n 20 file.txt         # First 20 lines
tail file.txt               # Last 10 lines
tail -n 20 file.txt         # Last 20 lines
tail -f file.txt            # Follow file changes

# File comparison
diff file1.txt file2.txt
diff -u file1.txt file2.txt  # Unified format
cmp file1.txt file2.txt      # Binary comparison

Text Search and Filtering¶

# grep - pattern searching
grep "pattern" file.txt
grep -i "pattern" file.txt   # Case insensitive
grep -r "pattern" directory/ # Recursive search
grep -n "pattern" file.txt   # Show line numbers
grep -v "pattern" file.txt   # Invert match
grep -E "pattern1|pattern2" file.txt  # Extended regex

# Advanced grep options
grep -A 3 "pattern" file.txt # Show 3 lines after match
grep -B 3 "pattern" file.txt # Show 3 lines before match
grep -C 3 "pattern" file.txt # Show 3 lines around match
grep -l "pattern" *.txt      # Show only filenames
grep -c "pattern" file.txt   # Count matches

Text Processing Tools¶

# sed - stream editor
sed 's/old/new/' file.txt           # Replace first occurrence
sed 's/old/new/g' file.txt          # Replace all occurrences
sed '1,5s/old/new/g' file.txt       # Replace in lines 1-5
sed '/pattern/d' file.txt           # Delete lines matching pattern
sed -n '1,10p' file.txt             # Print lines 1-10

# awk - pattern scanning and processing
awk '\\\\{print $1\\\\}' file.txt           # Print first column
awk '\\\\{print $NF\\\\}' file.txt          # Print last column
awk '/pattern/ \\\\{print $0\\\\}' file.txt # Print lines matching pattern
awk -F: '\\\\{print $1\\\\}' /etc/passwd    # Use : as field separator
awk '\\\\{sum += $1\\\\} END \\\\{print sum\\\\}' file.txt  # Sum first column

# cut - extract columns
cut -d: -f1 /etc/passwd             # Extract first field
cut -c1-10 file.txt                 # Extract characters 1-10
cut -f2,4 file.txt                  # Extract fields 2 and 4

# sort and uniq
sort file.txt                       # Sort lines
sort -n file.txt                    # Numeric sort
sort -r file.txt                    # Reverse sort
sort -k2 file.txt                   # Sort by second field
uniq file.txt                       # Remove duplicate lines
sort file.txt|uniq -c             # Count occurrences

Input/Output Redirection and Pipes¶

Redirection Operators¶

# Output redirection
command > file.txt              # Redirect stdout to file (overwrite)
command >> file.txt             # Redirect stdout to file (append)
command 2> error.log            # Redirect stderr to file
command 2>> error.log           # Redirect stderr to file (append)
command &> output.log           # Redirect both stdout and stderr
command > output.log 2>&1       # Redirect both stdout and stderr

# Input redirection
command < input.txt             # Read input from file
command << EOF                  # Here document
line 1
line 2
EOF

# Advanced redirection
command 3> file.txt             # Redirect to file descriptor 3
exec 3> file.txt                # Open file descriptor 3
echo "text" >&3                 # Write to file descriptor 3
exec 3>&-                       # Close file descriptor 3

Pipes and Command Chaining¶

# Basic pipes
ls -l|grep "txt"              # List files and filter for .txt
ps aux|grep "process_name"    # Show processes and filter
cat file.txt|sort|uniq      # Sort and remove duplicates

# Complex pipe chains
cat /var/log/access.log|grep "404"|awk '\\\\{print $1\\\\}'|sort|uniq -c|sort -nr
find . -name "*.log"|xargs grep "ERROR"|cut -d: -f1|sort|uniq

# Tee command (split output)
command|tee file.txt          # Write to file and stdout
command|tee -a file.txt       # Append to file and stdout

Process Management¶

Job Control¶

# Background and foreground jobs
command &                       # Run command in background
jobs                           # List active jobs
fg %1                          # Bring job 1 to foreground
bg %1                          # Send job 1 to background
kill %1                        # Kill job 1

# Process control signals
Ctrl+C                         # Interrupt (SIGINT)
Ctrl+Z                         # Suspend (SIGTSTP)
Ctrl+\                         # Quit (SIGQUIT)

Process Information¶

# Process listing
ps                             # Show current processes
ps aux                         # Show all processes
ps -ef                         # Full format listing
pstree                         # Show process tree
top                            # Real-time process monitor
htop                           # Enhanced process monitor

# Process management
kill PID                       # Terminate process
kill -9 PID                    # Force kill process
killall process_name           # Kill all processes by name
pkill pattern                  # Kill processes matching pattern
nohup command &                # Run command immune to hangups

Bash Scripting Fundamentals¶

Script Structure¶

```bash

!/bin/bash¶

Script description and metadata¶

Author: Your Name¶

Date: YYYY-MM-DD¶

Version: 1.0¶

Script content starts here¶

echo "Hello, World!" ### Variabili e Tipi di Datibash

String variables¶

name="John Doe" message='Hello, World!' multiline="This is a multi-line string"

Numeric variables¶

number=42 pi=3.14159

Arrays¶

fruits=("apple" "banana" "orange") numbers=(1 2 3 4 5)

Associative arrays (Bash 4+)¶

declare -A colors colors[red]="#FF0000" colors[green]="#00FF00" colors[blue]="#0000FF"

Array operations¶

echo $\\{fruits[0]\\} # First element echo $\\{fruits[@]\\} # All elements echo $\\{#fruits[@]\\} # Array length fruits+=("grape") # Append element ### Istruzioni Condizionalibash

if-then-else¶

if [ condition ]; then echo "Condition is true" elif [ other_condition ]; then echo "Other condition is true" else echo "No condition is true" fi

Test conditions¶

if [ "$var" = "value" ]; then # String equality if [ "$num" -eq 10 ]; then # Numeric equality if [ "$num" -gt 5 ]; then # Greater than if [ "$num" -lt 20 ]; then # Less than if [ -f "file.txt" ]; then # File exists if [ -d "directory" ]; then # Directory exists if [ -r "file.txt" ]; then # File is readable if [ -w "file.txt" ]; then # File is writable if [ -x "script.sh" ]; then # File is executable

Logical operators¶

if [ condition1 ] && [ condition2 ]; then # AND if [ condition1 ]||[ condition2 ]; then # OR if [ ! condition ]; then # NOT

Case statement¶

case $variable in pattern1) echo "Matched pattern1" ;; pattern2|pattern3) echo "Matched pattern2 or pattern3" ;; *) echo "No pattern matched" ;; esac ### Ciclibash

for loop¶

for i in \\{1..10\\}; do echo "Number: $i" done

for file in *.txt; do echo "Processing: $file" done

for item in "$\\{array[@]\\}"; do echo "Item: $item" done

C-style for loop¶

for ((i=1; i<=10; i++)); do echo "Counter: $i" done

while loop¶

counter=1 while [ $counter -le 10 ]; do echo "Counter: $counter" ((counter++)) done

until loop¶

counter=1 until [ $counter -gt 10 ]; do echo "Counter: $counter" ((counter++)) done

Loop control¶

for i in \\{1..10\\}; do if [ $i -eq 5 ]; then continue # Skip iteration fi if [ $i -eq 8 ]; then break # Exit loop fi echo $i done ### Funzionibash

Function definition¶

function greet() \\{ echo "Hello, $1!" \\}

Alternative syntax¶

greet() \\{ echo "Hello, $1!" \\}

Function with return value¶

calculate_sum() \\{ local num1=$1 local num2=$2 local sum=$((num1 + num2)) echo $sum \\}

Function with local variables¶

process_file() \\{ local filename=$1 local line_count=$(wc -l < "$filename") echo "File $filename has $line_count lines" \\}

Function usage¶

greet "World" result=$(calculate_sum 5 3) echo "Sum: $result" ## Funzionalità Avanzate di Bashbash

Basic parameter expansion¶

echo $\\{variable\\} echo $\\{variable:-default\\} # Use default if unset echo $\\{variable:=default\\} # Set default if unset echo $\\{variable:+alternate\\} # Use alternate if set echo $\\{variable:?error\\} # Error if unset

String manipulation¶

string="Hello, World!" echo $\\{string#Hello\\} # Remove shortest match from beginning echo $\\{string##/\\} # Remove longest match from beginning echo $\\{string%World!\\} # Remove shortest match from end echo $\\{string%%/\\} # Remove longest match from end echo $\\{string/Hello/Hi\\} # Replace first occurrence echo $\\{string//l/L\\} # Replace all occurrences

Substring extraction¶

echo $\\{string:0:5\\} # Extract substring (position:length) echo $\\{string:7\\} # Extract from position to end echo $\\{#string\\} # String length ### Espansione dei Parametribash

Arithmetic expansion¶

result=$((5 + 3)) result=$((10 * 2)) result=$((20 / 4)) result=$((17 % 5)) # Modulo

Increment/decrement¶

((counter++)) ((counter--)) ((counter += 5)) ((counter -= 3))

Arithmetic with variables¶

num1=10 num2=5 sum=$((num1 + num2)) product=$((num1 * num2))

Floating point arithmetic (using bc)¶

result=$(echo "scale=2; 10/3"|bc) result=$(echo "scale=4; sqrt(16)"|bc -l) ### Operazioni Aritmetichebash

Exit on error¶

set -e # Exit on any error set -u # Exit on undefined variable set -o pipefail # Exit on pipe failure

Error handling in scripts¶

command||\\{ echo "Command failed" exit 1 \\}

Trap signals¶

trap 'echo "Script interrupted"; exit 1' INT TERM trap 'cleanup_function' EXIT

Function error handling¶

safe_command() \\{ if ! command_that_might_fail; then echo "Error: Command failed" >&2 return 1 fi \\} ### Gestione degli Erroribash

System-wide configuration¶

/etc/bash.bashrc # System-wide bashrc /etc/profile # System-wide profile

User-specific configuration¶

~/.bashrc # User's bashrc ~/.bash_profile # User's profile ~/.bash_login # Login shell configuration ~/.profile # POSIX shell profile ~/.bash_logout # Logout script ## Configurazione e Personalizzazionebash

~/.bashrc example configuration¶

Source global definitions¶

if [ -f /etc/bashrc ]; then . /etc/bashrc fi

User specific environment¶

export EDITOR="vim" export BROWSER="firefox" export PAGER="less"

Custom PATH¶

export PATH="$HOME/bin:$HOME/.local/bin:$PATH"

Aliases¶

alias ll='ls -alF' alias la='ls -A' alias l='ls -CF' alias grep='grep --color=auto' alias fgrep='fgrep --color=auto' alias egrep='egrep --color=auto'

Custom functions¶

mkcd() \\{ mkdir -p "$1" && cd "$1" \\}

extract() \\{ if [ -f $1 ] ; then case $1 in *.tar.bz2) tar xjf $1 ;; *.tar.gz) tar xzf $1 ;; *.bz2) bunzip2 $1 ;; *.rar) unrar e $1 ;; *.gz) gunzip $1 ;; *.tar) tar xf $1 ;; *.tbz2) tar xjf $1 ;; *.tgz) tar xzf $1 ;; *.zip) unzip $1 ;; *.Z) uncompress $1 ;; *.7z) 7z x \(1 ;; *) echo "'$1' cannot be extracted via extract()" ;; esac else echo "'\)1' is not a valid file" fi \\}

Prompt customization¶

PS1='[\033[01;32m]\u@\h[\033[00m]:[\033[01;34m]\w[\033[00m]$ '

History configuration¶

HISTSIZE=10000 HISTFILESIZE=20000 HISTCONTROL=ignoredups:ignorespace shopt -s histappend

Shell options¶

shopt -s checkwinsize shopt -s globstar shopt -s cdspell ### File di Configurazione di Bashbash

Set options¶

set -o vi # Vi editing mode set -o emacs # Emacs editing mode (default) set -o noclobber # Prevent file overwriting set +o noclobber # Allow file overwriting

Shopt options¶

shopt -s autocd # Auto cd to directory shopt -s cdspell # Correct minor spelling errors shopt -s checkwinsize # Update LINES and COLUMNS shopt -s cmdhist # Save multi-line commands shopt -s dotglob # Include hidden files in globbing shopt -s expand_aliases # Expand aliases shopt -s extglob # Extended globbing shopt -s globstar # ** recursive globbing shopt -s histappend # Append to history file shopt -s nocaseglob # Case-insensitive globbing ### Personalizzazione di .bashrcbash

Emacs mode (default)¶

Ctrl+A # Beginning of line Ctrl+E # End of line Ctrl+B # Back one character Ctrl+F # Forward one character Alt+B # Back one word Alt+F # Forward one word Ctrl+D # Delete character Ctrl+H # Backspace Ctrl+K # Kill to end of line Ctrl+U # Kill to beginning of line Ctrl+W # Kill previous word Alt+D # Kill next word Ctrl+Y # Yank (paste) Ctrl+T # Transpose characters Alt+T # Transpose words

Vi mode¶

set -o vi Esc # Enter command mode i # Insert mode a # Append mode A # Append at end of line I # Insert at beginning of line ### Opzioni e Impostazioni di Bashbash

History commands¶

history # Show command history history 10 # Show last 10 commands history -c # Clear history history -d 5 # Delete history entry 5

History expansion¶

!! # Previous command !n # Command number n !string # Last command starting with string !?string # Last command containing string ^oldnew # Replace old with new in previous command

History search¶

Ctrl+R # Reverse search Ctrl+S # Forward search Ctrl+G # Cancel search

History configuration¶

export HISTSIZE=10000 # Commands in memory export HISTFILESIZE=20000 # Commands in file export HISTCONTROL=ignoredups # Ignore duplicates export HISTIGNORE="ls:ll:cd:pwd:bg:fg:history" # Ignore commands export HISTTIMEFORMAT="%F %T " # Add timestamps ## Modifica della Riga di Comando e Cronologiabash

Debug modes¶

bash -x script.sh # Execute with trace bash -n script.sh # Check syntax without execution bash -v script.sh # Verbose mode

Debug options in script¶

set -x # Enable trace set +x # Disable trace set -v # Enable verbose set +v # Disable verbose

Conditional debugging¶

if [ "$DEBUG" = "1" ]; then set -x fi

Debug function¶

debug() \\{ if [ "$DEBUG" = "1" ]; then echo "DEBUG: $*" >&2 fi \\} ### Modifica della Riga di Comandobash

Check command success¶

if command; then echo "Command succeeded" else echo "Command failed" fi

Check exit status¶

command if [ $? -eq 0 ]; then echo "Success" else echo "Failed with exit code $?" fi

Validate input¶

if [ $# -ne 2 ]; then echo "Usage: $0 " exit 1 fi

Check file existence¶

if [ ! -f "$filename" ]; then echo "Error: File $filename does not exist" exit 1 fi ### Gestione della Cronologiabash

Time command execution¶

time command time \\{ command1; command2; \\}

Profile script execution¶

PS4='+ $(date "+%s.%N"): ' set -x

Your commands here¶

set +x

Memory usage¶

/usr/bin/time -v command

Disk usage¶

du -sh directory/ df -h ## Debug e Risoluzione dei Problemibash

Use full paths for commands¶

/bin/ls instead of ls /usr/bin/find instead of find

Validate input¶

case "$input" in [a-zA-Z0-9]*) # Valid input ;; *) echo "Invalid input" exit 1 ;; esac

Quote variables¶

rm "$filename" # Correct rm $filename # Dangerous

Use arrays for file lists¶

files=( *.txt ) for file in "$\\\\{files[@]\\\\}"; do process "$file" done ### Debug degli Scriptbash

Use built-in commands when possible¶

[[ condition ]] # Instead of [ condition ] (( arithmetic )) # Instead of [ arithmetic ]

Avoid unnecessary subshells¶

var=$(cat file) # Subshell var=$(<file) # Built-in

Use parameter expansion¶

$\\{var#pattern\\} # Instead of sed/awk for simple operations $\\{var%pattern\\} $\\{var/pattern/replacement\\}

Efficient loops¶

while IFS= read -r line; do # Read file line by line process "$line" done < file.txt ### Controllo degli Erroribash

Use functions for repeated code¶

log_message() \\{ echo "[$(date '+%Y-%m-%d %H:%M:%S')] $*" >&2 \\}

Separate configuration¶

CONFIG_FILE="$\\\\{HOME\\\\}/.myapp.conf" if [ -f "$CONFIG_FILE" ]; then source "$CONFIG_FILE" fi

Use meaningful variable names¶

user_count=10 # Good uc=10 # Poor

Comment complex logic¶

Calculate the number of days between two dates¶

start_date=$(date -d "$1" +%s) end_date=$(date -d "$2" +%s) days=$(( (end_date - start_date) / 86400 )) ```### Monitoraggio delle Prestazioni

Bash - Bourne Again Shell¶

Installazione e Configurazione¶

Verifica dell'Installazione di Bash¶

Impostare Bash come Shell Predefinita¶

Installazione di Bash su Diversi Sistemi¶

Sintassi e Comandi Base di Bash¶

Struttura dei Comandi¶

Variabili e Ambiente¶

Sostituzione dei Comandi¶

Virgolettatura ed Escape¶

Operazioni e Navigazione File¶

Navigazione Directory¶

Elenco File e Directory¶

Operazioni sui File¶

Permessi e Proprietà dei File¶

Elaborazione e Manipolazione Testo¶

Operazioni sul Contenuto dei File¶

Ricerca e Filtraggio Testo¶

Strumenti di Elaborazione Testo¶

Reindirizzamento Input/Output e Pipe¶

Operatori di Reindirizzamento¶

Pipe e Concatenazione Comandi¶

Gestione Processi¶

Controllo Processi¶

Informazioni sui Processi¶

Fondamenti di Scripting Bash¶

Struttura dello Script¶

Ubuntu/Debian¶

CentOS/RHEL/Fedora¶

macOS (using Homebrew for latest version)¶

Arch Linux¶

FreeBSD¶

Variables and Environment¶

Command Substitution¶

Quoting and Escaping¶

File Operations and Navigation¶

Directory Navigation¶

File and Directory Listing¶

File Operations¶

File Permissions and Ownership¶

Text Processing and Manipulation¶

File Content Operations¶

Text Search and Filtering¶

Text Processing Tools¶

Input/Output Redirection and Pipes¶

Redirection Operators¶

Pipes and Command Chaining¶

Process Management¶

Job Control¶

Process Information¶

Bash Scripting Fundamentals¶

Script Structure¶

!/bin/bash¶

Script description and metadata¶

Author: Your Name¶

Date: YYYY-MM-DD¶

Version: 1.0¶

Script content starts here¶

String variables¶

Numeric variables¶

Arrays¶

Associative arrays (Bash 4+)¶

Array operations¶

if-then-else¶

Test conditions¶

Logical operators¶

Case statement¶

for loop¶

C-style for loop¶

while loop¶

until loop¶

Loop control¶

Function definition¶

Alternative syntax¶

Function with return value¶

Function with local variables¶

Function usage¶

Basic parameter expansion¶

String manipulation¶

Substring extraction¶