CyberLeo/Scraps/BashPrompt

This goes into your .bashrc

__prompt_command() {
  # global variables to cache bits of information to detect changes
  # __last_col - Stores the last width of the terminal
  # __last_git - Stores the last output of __git_ps1
  # __last_pwd - Stores the last working directory

  # Compute status code and prompt colour
  local res="${?}" # Must be first!
  local clr=""
  if [ "${res}" -eq 0 ]
  then
    __ls=""
    __lc=2
  else
    __ls=${res}
    __lc=3
  fi

  # Compute directory name to be no wider than terminal; ellipsis in the middle.
  local git tag dir width have need left right
  type -t __git_ps1 >/dev/null && git="$(__git_ps1)"
  # Don't bother updating if the width, git status, or PWD has not changed.
  if [ "${__last_col}" != "${COLUMNS}" -o "${__last_git}" != "${git}" -o "${__last_pwd}" != "${PWD}" ]
  then
    # Something changed! Cache the values and recompute the prompt data
    __last_col="${COLUMNS}"
    __last_git="${git}"
    __last_pwd="${PWD}"

    tag="${FLAG:+(########)}${USER}@${HOSTNAME%%.*} "
    dir="${PWD}"
    # Replace homedir with ~ to save space
    [ "${dir##${HOME}}" == "${dir}" ] || dir="~${dir##${HOME}}"
    width="$(printf "%s%s" "${tag}" "${git}" | wc -c)"
    have="$(( ${COLUMNS:-80} - ${width} ))"
    need="$(echo "${dir}" | wc -c)"

    # If there is enough space to show something useful, but not enough to show
    # everything, then show the beginning and end, with ellipsis in the middle.
    if [ "${have}" -ge 15 -a "${have}" -lt "${need}" ]
    then
      have=$(( ${have} - 3 ))
      half=$(( ${have} / 2 ))
      left="${half}"
      right="$(( ${need} - ${half} ))"
      [ $(( ${have} % 2 )) -gt 0 ] && left="$(( ${left} + 1 ))"
      dir="$(echo "${dir}" | cut -c1-${left})...$(echo "${dir}" | cut -c${right}-${need})"
    fi

    __ld="${dir}"
    __lg="${git}"
  fi

  # Set xterm title
  echo -ne "\033]0;${HOSTNAME%%.*}(${USER})\007"
}
PROMPT_COMMAND=__prompt_command
PS1="${FLAG+(${FLAG})}"'\[\033[1;32m\]\u@\h \[\033[1;36m\]${__ld}\[\033[1;35m\]${__lg}\[\033[00m\]\n\[\033[1;31m\]${__ls}\[\033[1;3${__lc}m\]\$\[\033[00m\] '