LFCS Part 52: Bash Startup Files and Configuration (FINAL POST!)

# Method 1: Check $0
echo $0

# If output is "-bash" (with leading dash) = login shell
# If output is "bash" (no dash) = non-login shell

# Method 2: Use shopt
shopt login_shell

# If output is "login_shell on" = login shell
# If output is "login_shell off" = non-login shell

# Method 3: Check with grep
shopt | grep login_shell

# View the file
cat ~/.bashrc

# Count lines
wc -l ~/.bashrc

# View with line numbers
cat -n ~/.bashrc

# Page through it
less ~/.bashrc

# Search for specific content (like aliases)
grep alias ~/.bashrc

# List all aliases
alias

# Count how many aliases you have
alias | wc -l

# Search for specific alias
alias | grep ls

# Check if a specific alias exists
alias ll 2>/dev/null || echo "Alias 'll' not defined"

# Create the alias
alias mydate='date +%Y-%m-%d'

# Test it
mydate
# Output: 2026-01-12

# Verify it exists
alias mydate

# Start a new shell
bash

# Try the alias - it won't work
mydate
# Output: bash: mydate: command not found

# Exit the subshell
exit

# The alias still works in original shell
mydate
# Output: 2026-01-12

# View the file
cat /etc/profile

# View with pagination
less /etc/profile

# See if it sources /etc/profile.d/
grep profile.d /etc/profile

# Count lines
wc -l /etc/profile

# Check permissions
ls -l /etc/profile

# First, test the alias
alias ll='ls -lah --color=auto'

# Test it
ll

# If it works, make it permanent
echo "alias ll='ls -lah --color=auto'" >> ~/.bashrc

# Reload .bashrc
source ~/.bashrc

# Verify it's in the file
grep "alias ll" ~/.bashrc

# Test in a new shell
bash
ll
exit

# Create the function (test first)
mkcd() {
    mkdir -p "$1" && cd "$1"
}

# Test it
mkcd /tmp/test-dir
pwd  # Should show /tmp/test-dir
cd ~

# Make it permanent - add to .bashrc
cat >> ~/.bashrc << 'EOF'

# Create directory and cd into it
mkcd() {
    mkdir -p "$1" && cd "$1"
}
EOF

# Reload configuration
source ~/.bashrc

# Test in new shell
bash
mkcd /tmp/another-test
pwd
exit

# Create the directory
mkdir -p ~/bin

# Create a test script
cat > ~/bin/hello << 'EOF'
#!/bin/bash
echo "Hello from ~/bin/hello!"
EOF

# Make it executable
chmod +x ~/bin/hello

# Try to run it - won't work yet
hello
# Output: bash: hello: command not found

# Add ~/bin to PATH in .bash_profile
echo 'export PATH="$HOME/bin:$PATH"' >> ~/.bash_profile

# Reload
source ~/.bash_profile

# Now it should work
hello
# Output: Hello from ~/bin/hello!

# Verify PATH
echo $PATH | tr ':' '\n' | grep bin

# Test in new login shell
bash -l
hello
exit

# Test the prompt first
export PS1='\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '

# If you like it, make it permanent in .bashrc
echo "export PS1='\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '" >> ~/.bashrc

# Reload
source ~/.bashrc

# Test different colors (red user):
export PS1='\[\033[01;31m\]\u\[\033[00m\]@\[\033[01;32m\]\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '

# Explanation:
# \u = username
# \h = hostname
# \w = full path
# \W = basename only
# \033[01;32m = green color
# \033[01;34m = blue color
# \033[00m = reset color

# Test first
export EDITOR=vim
export VISUAL=vim

# Verify
echo $EDITOR
echo $VISUAL

# Make permanent in .bash_profile
cat >> ~/.bash_profile << 'EOF'

# Set default editor
export EDITOR=vim
export VISUAL=vim
EOF

# Reload
source ~/.bash_profile

# Test with crontab (will use your editor)
crontab -e
# (Press :q to quit without changes)

# Verify in new shell
bash -l
echo $EDITOR
exit

# Test the settings first
export HISTSIZE=10000
export HISTFILESIZE=20000
export HISTCONTROL=ignoreboth:erasedups
export HISTTIMEFORMAT="%F %T "

# View history with timestamps
history | tail -20

# Make permanent in .bashrc
cat >> ~/.bashrc << 'EOF'

# Enhanced history configuration
export HISTSIZE=10000
export HISTFILESIZE=20000
export HISTCONTROL=ignoreboth:erasedups
export HISTTIMEFORMAT="%F %T "
shopt -s histappend
EOF

# Reload
source ~/.bashrc

# Verify settings
echo $HISTSIZE
echo $HISTFILESIZE
echo $HISTCONTROL
echo $HISTTIMEFORMAT

# Run some commands and check history
ls
pwd
date
history | tail -5

# Create .bash_logout
cat > ~/.bash_logout << 'EOF'
# Clear screen for privacy
clear

# Log logout time
echo "Logged out at: $(date)" >> ~/logout.log

# Display goodbye message
echo "Goodbye, $USER!"
EOF

# Test by logging out and back in
# For SSH:
exit
# Then reconnect

# Check the log file
cat ~/logout.log

# Alternative: Test in a login subshell
bash -l
exit
# Check output

# Create the directory (simulate custom app)
sudo mkdir -p /opt/custom/bin

# Create a test script
echo '#!/bin/bash' | sudo tee /opt/custom/bin/custom-app
echo 'echo "Custom app running!"' | sudo tee -a /opt/custom/bin/custom-app
sudo chmod +x /opt/custom/bin/custom-app

# Try to run - won't work yet
custom-app
# Output: bash: custom-app: command not found

# Create system-wide PATH configuration
sudo tee /etc/profile.d/custom-path.sh << 'EOF'
# Add custom application directory to PATH
export PATH="/opt/custom/bin:$PATH"
EOF

# Make it executable
sudo chmod +x /etc/profile.d/custom-path.sh

# For the change to take effect, start a new login shell
bash -l

# Now test
custom-app
# Output: Custom app running!

# Verify PATH
echo $PATH | tr ':' '\n' | grep custom

exit

# Check current .bash_profile
cat ~/.bash_profile

# Backup first
cp ~/.bash_profile ~/.bash_profile.backup

# Add sourcing of .bashrc (if not already there)
cat >> ~/.bash_profile << 'EOF'

# Source .bashrc for interactive shell settings
if [ -f ~/.bashrc ]; then
    . ~/.bashrc
fi
EOF

# Reload
source ~/.bash_profile

# Test: Create an alias in .bashrc
echo "alias testcmd='echo This is a test'" >> ~/.bashrc

# Start a login shell and test
bash -l
testcmd
# Output: This is a test
exit

# Verify the sourcing is in .bash_profile
grep -A 3 "Source .bashrc" ~/.bash_profile

# Create separate configuration files

# 1. Aliases file
cat > ~/.bash_aliases << 'EOF'
# Enhanced ls commands
alias ll='ls -lah --color=auto'
alias la='ls -A'
alias l='ls -CF'

# Safety aliases
alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'

# Shortcuts
alias c='clear'
alias h='history'
EOF

# 2. Functions file
cat > ~/.bash_functions << 'EOF'
# Create directory and cd into it
mkcd() {
    mkdir -p "$1" && cd "$1"
}

# Quick backup
backup() {
    cp "$1" "$1.backup-$(date +%Y%m%d-%H%M%S)"
}

# Search history
hs() {
    history | grep "$1"
}
EOF

# 3. Prompt file
cat > ~/.bash_prompt << 'EOF'
# Colorful prompt with user@host:path
export PS1='\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
EOF

# 4. Update .bashrc to source these files
cat >> ~/.bashrc << 'EOF'

# Source modular configuration files
if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases
fi

if [ -f ~/.bash_functions ]; then
    . ~/.bash_functions
fi

if [ -f ~/.bash_prompt ]; then
    . ~/.bash_prompt
fi
EOF

# Reload configuration
source ~/.bashrc

# Test aliases
ll

# Test functions
mkcd /tmp/modular-test
pwd
cd ~

# Verify all files
ls -la ~/.bash_*

# Create the function
cat >> ~/.bash_functions << 'EOF'

# Parse Git branch for prompt
parse_git_branch() {
    git branch 2> /dev/null | sed -e '/^[^*]/d' -e 's/* \(.*\)/ (\1)/'
}
EOF

# Create the prompt
cat > ~/.bash_prompt << 'EOF'
# Git-aware prompt: user@host:path (branch)$
export PS1='\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[33m\]$(parse_git_branch)\[\033[00m\]\$ '
EOF

# Reload
source ~/.bashrc

# Test in a Git repository
cd ~
mkdir -p ~/git-test
cd ~/git-test
git init
# Notice: prompt shows (master) or (main)

# Create a branch
git checkout -b feature-branch
# Notice: prompt shows (feature-branch)

# Clean up
cd ~
rm -rf ~/git-test

# Add to .bash_functions
cat >> ~/.bash_functions << 'EOF'

# Universal extract function
extract() {
    if [ -f "$1" ]; then
        case "$1" in
            *.tar.gz|*.tgz)  tar xzf "$1"     ;;
            *.tar.bz2|*.tbz2) tar xjf "$1"    ;;
            *.tar.xz)        tar xJf "$1"     ;;
            *.tar)           tar xf "$1"      ;;
            *.zip)           unzip "$1"       ;;
            *.gz)            gunzip "$1"      ;;
            *.bz2)           bunzip2 "$1"     ;;
            *.rar)           unrar x "$1"     ;;
            *.7z)            7z x "$1"        ;;
            *)               echo "Unknown archive format: $1" ;;
        esac
    else
        echo "File not found: $1"
    fi
}
EOF

# Reload
source ~/.bashrc

# Test with different archive types
cd /tmp

# Create test tar.gz
mkdir test-dir
echo "test content" > test-dir/file.txt
tar czf test.tar.gz test-dir/
rm -rf test-dir

# Extract using the function
extract test.tar.gz

# Verify
ls test-dir/
cat test-dir/file.txt

# Clean up
rm -rf test-dir test.tar.gz

# Add to .bash_functions
cat >> ~/.bash_functions << 'EOF'

# System information summary
sysinfo() {
    echo "========================================="
    echo " System Information"
    echo "========================================="
    echo "Hostname      : $(hostname)"
    echo "Kernel        : $(uname -r)"
    echo "OS            : $(cat /etc/os-release 2>/dev/null | grep PRETTY_NAME | cut -d= -f2 | tr -d '\"' || uname -s)"
    echo "Uptime        : $(uptime -p 2>/dev/null || uptime)"
    echo "Load Average  : $(uptime | awk -F'load average:' '{print $2}')"
    echo "Memory (Used) : $(free -h 2>/dev/null | awk 'NR==2{print $3 "/" $2}' || echo 'N/A')"
    echo "Disk (/)      : $(df -h / 2>/dev/null | awk 'NR==2{print $3 "/" $2 " (" $5 ")"}' || echo 'N/A')"
    echo "CPU Cores     : $(nproc 2>/dev/null || echo 'N/A')"
    echo "Current User  : $USER"
    echo "Shell         : $SHELL"
    echo "========================================="
}
EOF

# Reload
source ~/.bashrc

# Test the function
sysinfo

# Create an alias for quick access
echo "alias si='sysinfo'" >> ~/.bash_aliases
source ~/.bash_aliases

# Test the alias
si

# Create the function in .bash_profile
cat >> ~/.bash_profile << 'EOF'

# Safe PATH addition function
pathadd() {
    if [ -d "$1" ] && [[ ":$PATH:" != *":$1:"* ]]; then
        export PATH="$1:$PATH"
        echo "Added to PATH: $1"
    else
        if [ ! -d "$1" ]; then
            echo "Directory does not exist: $1"
        else
            echo "Already in PATH: $1"
        fi
    fi
}
EOF

# Reload
source ~/.bash_profile

# Test the function
echo "Current PATH entries:"
echo $PATH | tr ':' '\n'

# Try adding a directory
mkdir -p ~/test-bin
pathadd ~/test-bin
# Output: Added to PATH: /home/user/test-bin

# Try adding the same directory again
pathadd ~/test-bin
# Output: Already in PATH: /home/user/test-bin

# Try adding a non-existent directory
pathadd ~/does-not-exist
# Output: Directory does not exist: /home/user/does-not-exist

# Verify PATH
echo $PATH | tr ':' '\n' | grep test-bin

# ===== STEP 1: Backup existing configuration =====
cd ~
mkdir -p bash-config-backup
cp .bashrc .bash_profile .bash_logout bash-config-backup/ 2>/dev/null || true
echo "Backup created in ~/bash-config-backup/"

# ===== STEP 2: Create modular configuration files =====

# .bash_aliases
cat > ~/.bash_aliases << 'EOF'
# ~/.bash_aliases - Personal command aliases

# Safety first
alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'

# Enhanced ls
alias ll='ls -lah --color=auto'
alias la='ls -A --color=auto'
alias l='ls -CF --color=auto'

# Directory navigation
alias ..='cd ..'
alias ...='cd ../..'
alias ....='cd ../../..'

# Git shortcuts
alias gs='git status'
alias ga='git add'
alias gc='git commit'
alias gp='git push'
alias gl='git log --oneline --graph --all'
alias gd='git diff'

# System shortcuts
alias c='clear'
alias h='history'
alias ports='netstat -tulanp'
alias listening='ss -tulpn'
alias psg='ps aux | grep -v grep | grep -i -e VSZ -e'

# Disk usage
alias df='df -h'
alias du='du -h'
alias free='free -h'
EOF

# .bash_functions
cat > ~/.bash_functions << 'EOF'
# ~/.bash_functions - Personal shell functions

# Create directory and cd into it
mkcd() {
    mkdir -p "$1" && cd "$1"
}

# Quick backup with timestamp
backup() {
    if [ -f "$1" ]; then
        cp "$1" "$1.backup-$(date +%Y%m%d-%H%M%S)"
        echo "Backed up: $1"
    else
        echo "File not found: $1"
    fi
}

# Universal extract function
extract() {
    if [ -f "$1" ]; then
        case "$1" in
            *.tar.gz|*.tgz)   tar xzf "$1"    ;;
            *.tar.bz2|*.tbz2) tar xjf "$1"    ;;
            *.tar.xz)         tar xJf "$1"    ;;
            *.tar)            tar xf "$1"     ;;
            *.zip)            unzip "$1"      ;;
            *.gz)             gunzip "$1"     ;;
            *.bz2)            bunzip2 "$1"    ;;
            *)                echo "Unknown format: $1" ;;
        esac
    else
        echo "File not found: $1"
    fi
}

# Search in command history
hs() {
    history | grep "$1"
}

# System information summary
sysinfo() {
    echo "========================================="
    echo " System Information"
    echo "========================================="
    echo "Hostname      : $(hostname)"
    echo "Kernel        : $(uname -r)"
    echo "Uptime        : $(uptime -p 2>/dev/null || uptime)"
    echo "Load Average  : $(uptime | awk -F'load average:' '{print $2}')"
    echo "Memory        : $(free -h 2>/dev/null | awk 'NR==2{print $3 "/" $2}' || echo 'N/A')"
    echo "Disk (/)      : $(df -h / 2>/dev/null | awk 'NR==2{print $3 "/" $2 " (" $5 ")"}' || echo 'N/A')"
    echo "Current User  : $USER"
    echo "========================================="
}

# Safe PATH addition
pathadd() {
    if [ -d "$1" ] && [[ ":$PATH:" != *":$1:"* ]]; then
        export PATH="$1:$PATH"
    fi
}
EOF

# .bash_prompt
cat > ~/.bash_prompt << 'EOF'
# ~/.bash_prompt - Prompt customization

# Git branch parser
parse_git_branch() {
    git branch 2> /dev/null | sed -e '/^[^*]/d' -e 's/* \(.*\)/ (\1)/'
}

# Colorful Git-aware prompt
# Format: user@host:path (git-branch)$
export PS1='\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[33m\]$(parse_git_branch)\[\033[00m\]\$ '
EOF

# ===== STEP 3: Create main .bashrc =====
cat > ~/.bashrc << 'EOF'
# ~/.bashrc - Main interactive shell configuration

# Source system-wide definitions
if [ -f /etc/bashrc ]; then
    . /etc/bashrc
elif [ -f /etc/bash.bashrc ]; then
    . /etc/bash.bashrc
fi

# If not running interactively, don't do anything
case $- in
    *i*) ;;
      *) return;;
esac

# ===== HISTORY CONFIGURATION =====
export HISTSIZE=50000
export HISTFILESIZE=100000
export HISTCONTROL=ignoreboth:erasedups
export HISTTIMEFORMAT="%F %T "
shopt -s histappend

# ===== SHELL OPTIONS =====
# Check window size after each command
shopt -s checkwinsize

# Enable recursive globbing with **
shopt -s globstar 2>/dev/null

# ===== TAB COMPLETION =====
# Case-insensitive tab completion
bind "set completion-ignore-case on" 2>/dev/null

# Show all matches if ambiguous
bind "set show-all-if-ambiguous on" 2>/dev/null

# ===== SOURCE MODULAR FILES =====
# Load aliases
if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases
fi

# Load functions
if [ -f ~/.bash_functions ]; then
    . ~/.bash_functions
fi

# Load prompt configuration
if [ -f ~/.bash_prompt ]; then
    . ~/.bash_prompt
fi
EOF

# ===== STEP 4: Create .bash_profile =====
cat > ~/.bash_profile << 'EOF'
# ~/.bash_profile - Login shell initialization

# ===== ENVIRONMENT VARIABLES =====
export EDITOR=vim
export VISUAL=vim
export PAGER=less

# ===== PATH CONFIGURATION =====
# Load pathadd function if available
if [ -f ~/.bash_functions ]; then
    . ~/.bash_functions
fi

# Add user bin directories to PATH
pathadd "$HOME/bin"
pathadd "$HOME/.local/bin"

# ===== SOURCE .BASHRC =====
# Ensure interactive settings work in login shells
if [ -f ~/.bashrc ]; then
    . ~/.bashrc
fi

# ===== LOGIN MESSAGE =====
echo "Welcome back, $USER!"
echo "Login time: $(date '+%Y-%m-%d %H:%M:%S')"
EOF

# ===== STEP 5: Create .bash_logout =====
cat > ~/.bash_logout << 'EOF'
# ~/.bash_logout - Cleanup on logout

# Clear screen for privacy
clear

# Log logout time
echo "Logout: $(date '+%Y-%m-%d %H:%M:%S')" >> ~/.bash_login_history

# Display goodbye message
echo "Goodbye, $USER!"
EOF

# ===== STEP 6: Create user bin directory =====
mkdir -p ~/bin

# Create a sample script
cat > ~/bin/myinfo << 'EOF'
#!/bin/bash
# Display current user information
echo "User: $USER"
echo "Home: $HOME"
echo "Shell: $SHELL"
echo "Current directory: $PWD"
EOF

chmod +x ~/bin/myinfo

# ===== STEP 7: Reload configuration =====
source ~/.bash_profile

# ===== STEP 8: Test everything =====
echo ""
echo "========================================="
echo " Configuration Installation Complete!"
echo "========================================="
echo ""
echo "Testing installed components..."
echo ""

# Test aliases
echo "✓ Aliases loaded: $(alias | wc -l) aliases defined"

# Test functions
echo "✓ Functions loaded: mkcd, backup, extract, hs, sysinfo, pathadd"

# Test prompt
echo "✓ Custom prompt configured"

# Test history
echo "✓ History size: $HISTSIZE commands"

# Test PATH
echo "✓ Custom PATH: ~/bin and ~/.local/bin added"

# Test user script
echo "✓ User script: ~/bin/myinfo created"

echo ""
echo "Run these commands to test:"
echo "  ll              # Enhanced ls"
echo "  sysinfo         # System information"
echo "  myinfo          # User information"
echo "  mkcd testdir    # Create and enter directory"
echo ""
echo "Configuration files:"
echo "  ~/.bashrc       # Main interactive config"
echo "  ~/.bash_profile # Login shell config"
echo "  ~/.bash_aliases # Your aliases"
echo "  ~/.bash_functions # Your functions"
echo "  ~/.bash_prompt  # Prompt configuration"
echo ""
echo "Backup saved in: ~/bash-config-backup/"
echo "========================================="

# 1. Test aliases
ll
c  # clear screen

# 2. Test functions
sysinfo
mkcd /tmp/final-test
pwd
cd ~

# 3. Test user script
myinfo

# 4. Test history
h | tail
hs bash

# 5. Test PATH
echo $PATH | tr ':' '\n' | grep -E 'bin|local'

# 6. Test Git prompt (if in a git repo)
cd ~/some-git-repo
# Prompt should show (branch-name)

# 7. View configuration
cat ~/.bashrc
cat ~/.bash_profile
cat ~/.bash_aliases
cat ~/.bash_functions
cat ~/.bash_prompt

# 8. Test in new shell
bash
ll
sysinfo
exit

# 9. Test login shell
bash -l
# Should see welcome message
exit

# 10. Verify backup
ls -la ~/bash-config-backup/