set iTerm2 tab chrome background color according to the current working directory

auto_set_tab_chrome_background_color.sh

function auto_set_tab_chrome_background_color {
  # Red component value is calculated from the full path of current directory
  RR=`pwd | wc -m`
  let RR=(RR%25)*10

  # Green component value is calculated from the basename of current directory
  GG=`basename \`pwd\` | wc -m`
  let GG=(GG%25)*10*2

  # Blue component value is calculated from the full total files and directories count under this directory
  BB=`ls | wc -l`
  let BB=(BB%25)*10

  # start to set background color of tab chrome
  # Documents: http://iterm2.com/documentation-escape-codes.html
  echo -en "\033]6;1;bg;red;brightness;${RR}\a"         # -n: ignore newline
  echo -en "\033]6;1;bg;green;brightness;${GG}\a"
  echo -en "\033]6;1;bg;blue;brightness;${BB}\a"
}

hack_builtin_cd_function.sh

function cd {
  # actually change the directory with all args passed to the function
  builtin cd "$@"

  auto_set_tab_chrome_background_color;
}

# should append this line to ~/.bashrc or ~/.bash_profile so that the function will get running
# when each time you open a new shell window
auto_set_tab_chrome_background_color;