My personally edited .bashrc file.

case $- in
    *i*) ;;
      *) return;;
esac
HISTCONTROL=ignoreboth
shopt -s histappend
HISTSIZE=1000
HISTFILESIZE=2000
shopt -s checkwinsize
if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then
    debian_chroot=$(cat /etc/debian_chroot)
fi
case "$TERM" in
    xterm-color|*-256color) color_prompt=yes;;
esac
force_color_prompt=yes
if [ -n "$force_color_prompt" ]; then
    if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then
        color_prompt=yes
    else
        color_prompt=
    fi
fi
if [ "$color_prompt" = yes ]; then
    if [ "$(id -u)" -eq 0 ]; then
        PS1='${debian_chroot:+($debian_chroot)}\[\033[01;31m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w #\[\033[00m\] '
    else
        PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w \$\[\033[00m\] '
    fi
else
    if [ "$(id -u)" -eq 0 ]; then
        PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w # '
    else
        PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w \$ '
    fi
fi
unset color_prompt force_color_prompt
case "$TERM" in
xterm*|rxvt*)
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"
    ;;
*)
    ;;
esac
if [ -x /usr/bin/dircolors ]; then
    test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"
    alias ls='ls --color=auto'
    alias grep='grep --color=auto'
    alias fgrep='fgrep --color=auto'
    alias egrep='egrep --color=auto'
fi
diffy() {
    diff -y -B <(grep -vE '^\s*#' "$1") <(grep -vE '^\s*#' "$2")
}
alias ll='ls -l'
alias la='ls -la'
alias lh='ls -lah'
alias cd..='cd ..'
if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases
fi
if ! shopt -oq posix; then
  if [ -f /usr/share/bash-completion/bash_completion ]; then
    . /usr/share/bash-completion/bash_completion
  elif [ -f /etc/bash_completion ]; then
    . /etc/bash_completion
  fi
fi

Interactive Shell Check

case $- in
i) ;;
*) return;;
esac

• case $- in ... esac: This checks the current shell options.
• i) ;;: If the shell is interactive (i is present in $-), do nothing (;;).
• *) return;;: If the shell is not interactive, exit the script (return).

History Control

HISTCONTROL=ignoreboth

• HISTCONTROL=ignoreboth: Sets the shell history to ignore duplicate entries and commands that start with a space.

Append to History

shopt -s histappend

• shopt -s histappend: Enables appending to the history file, rather than overwriting it.

History Size

HISTSIZE=1000
HISTFILESIZE=2000

• HISTSIZE=1000: Sets the number of commands to remember in the command history.
• HISTFILESIZE=2000: Sets the maximum number of lines contained in the history file.

Check Window Size

shopt -s checkwinsize

• shopt -s checkwinsize: After each command, checks the window size and updates LINES and COLUMNS if necessary.

Debian Chroot

if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then
debian_chroot=$(cat /etc/debian_chroot)
fi

• Checks if the debian_chroot variable is unset or empty and if /etc/debian_chroot is readable.
• If both conditions are met, it sets debian_chroot to the contents of /etc/debian_chroot.

Terminal Color Check

case "$TERM" in
xterm-color|*-256color) color_prompt=yes;;
esac

• Checks if the terminal supports color (xterm-color or *-256color).
• If so, sets color_prompt=yes.

Force Color Prompt

force_color_prompt=yes

• Forces the color prompt to be enabled.

Color Prompt Setup

if [ -n "$force_color_prompt" ]; then
if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then
color_prompt=yes
else
color_prompt=
fi
fi

• Checks if force_color_prompt is set.
• If tput exists and can set terminal colors, it sets color_prompt=yes.
• Otherwise, it sets color_prompt to empty.

PS1 Prompt Definition

if [ "$color_prompt" = yes ]; then
if [ "$(id -u)" -eq 0 ]; then
PS1='${debian_chroot:+($debian_chroot)}[\033[01;31m]\u@\h[\033[00m]:[\033[01;34m]\w #[\033[00m] '
else
PS1='${debian_chroot:+($debian_chroot)}[\033[01;32m]\u@\h[\033[00m]:[\033[01;34m]\w \$[\033[00m] '
fi
else
if [ "$(id -u)" -eq 0 ]; then
PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w # '
else
PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w $ '
fi
fi
unset color_prompt force_color_prompt

• Sets the prompt (PS1) based on whether color_prompt is set.
• If the user is root (id -u equals 0), the prompt ends with #, otherwise with $.
• The colors are different for root (\033[01;31m for red) and non-root users (\033[01;32m for green).

Xterm Title

case "$TERM" in
xterm*|rxvt*)
PS1="[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a]$PS1"
;;
*)
;;
esac

• If the terminal is xterm or rxvt, sets the terminal title to user@host: dir.

Enable Color Support for ls and Define Aliases

if [ -x /usr/bin/dircolors ]; then test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)" alias ls='ls --color=auto' alias grep='grep --color=auto' alias fgrep='fgrep --color=auto' alias egrep='egrep --color=auto' fi

• Checks if dircolors exists and is executable.
• If ~/.dircolors is readable, evaluates it for setting up color definitions.
• Sets up color aliases for ls, grep, fgrep, and egrep.

Define diffy Function

diffy() {
diff -y -B <(grep -vE '^\s*#' "$1") <(grep -vE '^\s*#' "$2")
}

• Defines the diffy function to compare two files, ignoring lines that start with a comment (#) or are empty.

Define Aliases

alias ll='ls -l'
alias la='ls -la'
alias lh='ls -lah'
alias cd..='cd ..'

• Sets up aliases for common ls commands and a cd shortcut.

Load Additional Aliases

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

• If ~/.bash_aliases exists, sources it to load additional aliases.

Enable Programmable Completion

if ! shopt -oq posix; then
if [ -f /usr/share/bash-completion/bash_completion ]; then
. /usr/share/bash-completion/bash_completion
elif [ -f /etc/bash_completion ]; then
. /etc/bash_completion
fi
fi

• If the shell is not in POSIX mode, checks for bash_completion files and sources them to enable programmable completion features.