A simple function to shrunken a Unix path to a descriptive fixed size string. I use this for my prompt.

shrunken_dir.sh

function shrunken_dir(){
  SEP="/"
  ESC_SEP="\\$SEP"
  HEADER_SIZE=5
  SIZE_MAX=$1
  current_disp=`pwd`
  seen_path_max_length=$((SIZE_MAX-HEADER_SIZE))
  current_seen_path=$(echo "$current_disp"|tr -s "$SEP")
  nb_dirs=0                 
  seen_path_length=$(expr length "$current_seen_path")
  while [ $seen_path_length -gt $seen_path_max_length ]; do
    current_seen_path=$(echo $current_seen_path|sed "s/^$ESC_SEP//"|grep -oE "$SEP.*")
    seen_path_length=$(expr length "$current_seen_path")
    nb_dirs=$((nb_dirs+1))
  done
  header="{$nb_dirs}"
  padding=""
  for i in $(seq $(expr length $header) $((SIZE_MAX-seen_path_length))); do
    padding="$padding "                            
  done                                             
  printf "${header}${current_seen_path}${padding}" 
}