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) ist eine Unix-Shell und Befehlssprache, die von Brian Fox für das GNU-Projekt als freier Software-Ersatz für die Bourne Shell entwickelt wurde. Erstmals 1989 veröffentlicht, ist Bash zur Standardshell auf den meisten Linux-Distributionen geworden und ist eine der am häufigsten verwendeten Shells im Unix/Linux-Ökosystem. Sie kombiniert die Funktionen der ursprünglichen Bourne Shell mit zusätzlichen Funktionen wie Befehlsergänzung, Befehlsverlauf und verbesserten Skriptfähigkeiten.

## Installation und Einrichtung

### Bash-Installation überprüfen
```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 als Standardshell festlegen¶

# 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

Bash-Installation auf verschiedenen Systemen¶

# Basic command structure
command [options] [arguments]

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

Grundlegende Bash-Syntax und Befehle¶

Befehlsstruktur¶

# 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

Variablen und Umgebung¶

# 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)"

Befehlssubstitution¶

# 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"

Anführungszeichen und Escaping¶

# 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

Verzeichnisnavigation¶

# 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

Datei- und Verzeichnislisting¶

# 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

Dateioperationen¶

# 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

Dateiberechtigungen und Besitz¶

# 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

Textverarbeitung und -manipulation¶

Dateiinhaltsoperationen¶

# 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

Textsuche und Filterung¶

# 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

Textverarbeitungstools¶

# 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

Ein-/Ausgabe-Umleitung und Pipes¶

Umleitungsoperatoren¶

# 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

Pipes und Befehlsverkettung¶

# 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)

Prozessverwaltung¶

Jobkontrolle¶

# 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

Prozessinformationen¶

```bash

!/bin/bash¶

Script description and metadata¶

Author: Your Name¶

Date: YYYY-MM-DD¶

Version: 1.0¶

Script content starts here¶

echo "Hello, World!" ### Variablen und Datentypenbash

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 ### Bedingte Anweisungenbash

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 ### Schleifenbash

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 ### Funktionenbash

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" ## Erweiterte Bash-Funktionenbash

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 ### Parameterexpansionbash

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) ### Arithmetische Operationenbash

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 \\} ### Fehlerbehandlungbash

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 ## Konfiguration und Anpassungbash

~/.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 ### Bash-Konfigurationsdateienbash

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 ### .bashrc anpassenbash

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 ### Bash-Optionen und Einstellungenbash

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 ## Befehlszeilenbearbeitung und Verlaufbash

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 \\} ### Befehlszeilenbearbeitungbash

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 ### Verlaufsverwaltungbash

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 ## Debugging und Fehlerbehebungbash

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 ### Debugging von Skriptenbash

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 ### Fehlerüberprüfungbash

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 )) ```### Leistungsüberwachung

Bash - Bourne Again Shell¶

Bash als Standardshell festlegen¶

Bash-Installation auf verschiedenen Systemen¶

Grundlegende Bash-Syntax und Befehle¶

Befehlsstruktur¶

Variablen und Umgebung¶

Befehlssubstitution¶

Anführungszeichen und Escaping¶

Dateioperationen und Navigation¶

Verzeichnisnavigation¶

Datei- und Verzeichnislisting¶

Dateioperationen¶

Dateiberechtigungen und Besitz¶

Textverarbeitung und -manipulation¶

Dateiinhaltsoperationen¶

Textsuche und Filterung¶

Textverarbeitungstools¶

Ein-/Ausgabe-Umleitung und Pipes¶

Umleitungsoperatoren¶

Pipes und Befehlsverkettung¶

Prozessverwaltung¶

Jobkontrolle¶

Prozessinformationen¶

!/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¶

Arithmetic expansion¶

Increment/decrement¶

Arithmetic with variables¶

Floating point arithmetic (using bc)¶

Exit on error¶

Error handling in scripts¶

Trap signals¶

Function error handling¶

System-wide configuration¶

User-specific configuration¶

~/.bashrc example configuration¶

Source global definitions¶

User specific environment¶

Custom PATH¶

Aliases¶

Custom functions¶

Prompt customization¶

History configuration¶

Shell options¶

Set options¶

Shopt options¶

Emacs mode (default)¶

Vi mode¶

History commands¶

History expansion¶

History search¶

History configuration¶

Debug modes¶

Debug options in script¶