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

this is my version

• use date to format time, only calc days
• set terminal title
• use \$ in PS1 for user $ + root #
• show return code / exit code
• use date -u to disable DST
• use hidden names like _foo

_x_dt_min=1 # minimum running time to show delta T
function _x_before {
    _x_t1=${_x_t1:-$(date -u '+%s.%N')} # float seconds
}
function _x_after {
    _x_rc=$? # return code
    _x_dt=$(echo $(date -u '+%s.%N') $_x_t1 | awk '{printf "%f", $1 - $2}')
    unset _x_t1
    #_x_dt=$(echo $_x_dt | awk '{printf "%f", $1 + 86400 * 1001}') # test
    # only show dT for long-running commands
    # ${f%.*} = int(floor(f))
    (( ${_x_dt%.*} >= $_x_dt_min )) && {
        _x_dt_d=$((${_x_dt%.*} / 86400))
        _x_dt_s='' # init delta T string
        (( $_x_dt_d > 0 )) && \
            _x_dt_s="${_x_dt_s}${_x_dt_d} days + "
        # format time
        # %4N = four digits of nsec
        _x_dt_s="${_x_dt_s}$(date -u -d0+${_x_dt}sec '+%T.%4N')"
        PS1='rc = ${_x_rc}\ndT = ${_x_dt_s}\n\$ '
    } || {
        PS1='rc = ${_x_rc}\n\$ '
    }
    # set terminal title to terminal number
    printf "\033]0;%s\007" $(tty | sed 's|^/dev/\(pts/\)\?||')
}
trap '_x_before' DEBUG
PROMPT_COMMAND='_x_after'
PS1='\$ '

sample output:

$ sleep 0.5
rc = 0
$ sleep 1
rc = 0
dT = 00:00:01.0040
$ sleep 1001d
rc = 0
dT = 1001 days + 00:00:00.0713
$ false
rc = 1
$