How can the last command's wall time be put in the Bash prompt?

Question

Is there a way to embed the last command\'s elapsed wall time in a Bash prompt? I\'m hoping for something that would look like this:

[last: 0s][/my/dir]$ sl         


        

Answer 1

A version with split hours, minutes and seconds inspired by the zsh spaceship prompt, based on Ville's answer and this time conversion function by perreal.

I also added a threshold variable so that the timer only displays for long running commands.

time_threshold=5;

function convert_secs {
    ((h=${1}/3600))
    ((m=(${1}%3600)/60))
    ((s=${1}%60))
    if [ $h -gt 0 ]; then printf "${h}h "; fi
    if [ $h -gt 0 ] || [ $m -gt 0 ]; then printf "${m}m "; fi
    if [ $s -gt 0 ]; then printf "${s}s "; fi
}

function timer_start {
    timer=${timer:-$SECONDS}
}

function timer_stop {
    timer_time=$(($SECONDS - $timer))
    
    if [ ! -z $timer_time ] && [ $timer_time -ge ${time_threshold} ]; then
        timer_show="took $(convert_secs $timer_time)"
    else
        timer_show=""
    fi

    unset timer
}

trap 'timer_start' DEBUG
PROMPT_COMMAND=timer_stop

PS1='\n\w ${timer_show}\n\\$ '

For the coloured output in my screenshot:

bold=$(tput bold)
reset=$(tput sgr0)
yellow=$(tput setaf 3)
cyan=$(tput setaf 6)

PS1='\n${bold}${cyan}\w ${yellow}${timer_show}${reset}\n\\$ '