Add a timer for the last command to your bash prompt

gistfile1.txt

# timer prompt, add to ~/.bashrc (tested in bash only thus far)
function timer_start {
  timer=${timer:-$SECONDS}
}

function timer_stop {
  i=$(($SECONDS - $timer))
  ((sec=i%60, i/=60, min=i%60, hrs=i/60))
  timer_show=$(printf "%d:%02d:%02d" $hrs $min $sec)
  unset timer
}

trap 'timer_start' DEBUG

if [ "$PROMPT_COMMAND" == "" ]; then
  PROMPT_COMMAND="timer_stop"
else
  PROMPT_COMMAND="$PROMPT_COMMAND; timer_stop"
fi

PS1='[last: ${timer_show}s] '$PS1