Oh my zsh custom script to growl on completion of all commands which take more than 10secs

growl-long.zsh

preexec_functions+='save_preexec_time'
save_preexec_time() {
  export PREEXEC_CMD="$(history $HISTCMD | tail -n 1 | sed 's/ *[0-9]* *//')"
  export PREEXEC_TIME=$(date +'%s')
}

precmd_functions+='growl_about_long_running_commands'
growl_about_long_running_commands() {
  exitstatus=$?
  if [ $exitstatus -eq 0 ]; then
    img="$HOME/.oh-my-zsh/custom/growl-pass.png"
  else
    img="$HOME/..oh-my-zsh/custom/growl-fail.png"
  fi

  stop=$(date +'%s')
  start=${PREEXEC_TIME:-$stop}
  let elapsed=$stop-$start
  max=${PREEXEC_MAX:-10}

  if [ $elapsed -gt $max ]; then
    growlnotify -w -H localhost --image="$img" -n "LongRunningCommandGrowler" -m "Exited with status $exitstatus after $elapsed secs" ${PREEXEC_CMD:-Some command}
  fi
  PREEXEC_TIME=
  PREEXEC_CMD=
}