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

Here's my take on Thomas'

uses date +%s%3N to get milliseconds as base unit, simplified following code (less zeros)

function t_now {
    date +%s%3N
}

function t_start {
    t_start=${t_start:-$(t_now)}
}

function t_stop {
    local d_ms=$(($(t_now) - $t_start))
    local d_s=$((d_ms / 1000))
    local ms=$((d_ms % 1000))
    local s=$((d_s % 60))
    local m=$(((d_s / 60) % 60))
    local h=$((d_s / 3600))
    if ((h > 0)); then t_show=${h}h${m}m
    elif ((m > 0)); then t_show=${m}m${s}s
    elif ((s >= 10)); then t_show=${s}.$((ms / 100))s
    elif ((s > 0)); then t_show=${s}.$((ms / 10))s
    else t_show=${ms}ms
    fi
    unset t_start
}
set_prompt () {
t_stop
}

trap 't_start' DEBUG
PROMPT_COMMAND='set_prompt' 

Then add $t_show to your PS1