Bash script to calculate time elapsed

Question

I am writing a script in bash to calculate the time elapsed for the execution of my commands, consider:

STARTTIME=$(date +%s)
#command block that takes time to complete...
#........
ENDTIME=$(date +%s)
echo "It takes $($ENDTIME - $STARTTIME) seconds to complete this task..."

I guess my logic is correct however I end up with the following print out:

"It takes seconds to complete this task..."

Anything wrong with my string evaluation?

I believe bash variables are untyped, I would love if there is a "string to integer" method in bash nevertheless.

Answer 1

I find it very clean to use the internal variable "$SECONDS"

SECONDS=0 ; sleep 10 ; echo $SECONDS

Answer 2

    #!/bin/bash

    time_elapsed(){
    appstop=$1; appstart=$2

    ss_strt=${appstart:12:2} ;ss_stop=${appstop:12:2}
    mm_strt=${appstart:10:2} ;mm_stop=${appstop:10:2}
     hh_strt=${appstart:8:2} ; hh_stop=${appstop:8:2}
     dd_strt=${appstart:6:2} ; dd_stop=${appstop:6:2}
     mh_strt=${appstart:4:2} ; mh_stop=${appstop:4:2}
     yy_strt=${appstart:0:4} ; yy_stop=${appstop:0:4}

    if [ "${ss_stop}" -lt "${ss_strt}" ]; then ss_stop=$((ss_stop+60)); mm_stop=$((mm_stop-1)); fi
    if [ "${mm_stop}" -lt "0" ]; then mm_stop=$((mm_stop+60)); hh_stop=$((hh_stop-1)); fi
    if [ "${mm_stop}" -lt "${mm_strt}" ]; then mm_stop=$((mm_stop+60)); hh_stop=$((hh_stop-1)); fi
    if [ "${hh_stop}" -lt "0" ]; then hh_stop=$((hh_stop+24)); dd_stop=$((dd_stop-1)); fi
    if [ "${hh_stop}" -lt "${hh_strt}" ]; then hh_stop=$((hh_stop+24)); dd_stop=$((dd_stop-1)); fi

    if [ "${dd_stop}" -lt "0" ]; then dd_stop=$((dd_stop+$(mh_days $mh_stop $yy_stop))); mh_stop=$((mh_stop-1)); fi
    if [ "${dd_stop}" -lt "${dd_strt}" ]; then dd_stop=$((dd_stop+$(mh_days $mh_stop $yy_stop))); mh_stop=$((mh_stop-1)); fi

    if [ "${mh_stop}" -lt "0" ]; then mh_stop=$((mh_stop+12)); yy_stop=$((yy_stop-1)); fi
    if [ "${mh_stop}" -lt "${mh_strt}" ]; then mh_stop=$((mh_stop+12)); yy_stop=$((yy_stop-1)); fi

    ss_espd=$((10#${ss_stop}-10#${ss_strt})); if [ "${#ss_espd}" -le "1" ]; then ss_espd=$(for((i=1;i<=$((${#ss_stop}-${#ss_espd}));i++)); do echo -n "0"; done; echo ${ss_espd}); fi
    mm_espd=$((10#${mm_stop}-10#${mm_strt})); if [ "${#mm_espd}" -le "1" ]; then mm_espd=$(for((i=1;i<=$((${#mm_stop}-${#mm_espd}));i++)); do echo -n "0"; done; echo ${mm_espd}); fi
    hh_espd=$((10#${hh_stop}-10#${hh_strt})); if [ "${#hh_espd}" -le "1" ]; then hh_espd=$(for((i=1;i<=$((${#hh_stop}-${#hh_espd}));i++)); do echo -n "0"; done; echo ${hh_espd}); fi
    dd_espd=$((10#${dd_stop}-10#${dd_strt})); if [ "${#dd_espd}" -le "1" ]; then dd_espd=$(for((i=1;i<=$((${#dd_stop}-${#dd_espd}));i++)); do echo -n "0"; done; echo ${dd_espd}); fi
    mh_espd=$((10#${mh_stop}-10#${mh_strt})); if [ "${#mh_espd}" -le "1" ]; then mh_espd=$(for((i=1;i<=$((${#mh_stop}-${#mh_espd}));i++)); do echo -n "0"; done; echo ${mh_espd}); fi
    yy_espd=$((10#${yy_stop}-10#${yy_strt})); if [ "${#yy_espd}" -le "1" ]; then yy_espd=$(for((i=1;i<=$((${#yy_stop}-${#yy_espd}));i++)); do echo -n "0"; done; echo ${yy_espd}); fi

    echo -e "${yy_espd}-${mh_espd}-${dd_espd} ${hh_espd}:${mm_espd}:${ss_espd}"
    #return $(echo -e "${yy_espd}-${mh_espd}-${dd_espd} ${hh_espd}:${mm_espd}:${ss_espd}")
    }

    mh_days(){
    mh_stop=$1; yy_stop=$2; #also checks if it's leap year or not

    case $mh_stop in
     [1,3,5,7,8,10,12]) mh_stop=31
     ;;
     2) (( !(yy_stop % 4) && (yy_stop % 100 || !(yy_stop % 400) ) )) && mh_stop=29 || mh_stop=28
     ;;
     [4,6,9,11]) mh_stop=30
     ;;
    esac

    return ${mh_stop}
    }

    appstart=$(date +%Y%m%d%H%M%S); read -p "Wait some time, then press nay-key..." key; appstop=$(date +%Y%m%d%H%M%S); elapsed=$(time_elapsed $appstop $appstart); echo -e "Start...: ${appstart:0:4}-${appstart:4:2}-${appstart:6:2} ${appstart:8:2}:${appstart:10:2}:${appstart:12:2}\nStop....: ${appstop:0:4}-${appstop:4:2}-${appstop:6:2} ${appstop:8:2}:${appstop:10:2}:${appstop:12:2}\n$(printf '%0.1s' "="{1..30})\nElapsed.: ${elapsed}"

    exit 0


-------------------------------------------- return
Wait some time, then press nay-key...
Start...: 2017-11-09 03:22:17
Stop....: 2017-11-09 03:22:18
==============================
Elapsed.: 0000-00-00 00:00:01

Answer 3

Try the following code:

start=$(date +'%s') && sleep 5 && echo "It took $(($(date +'%s') - $start)) seconds"

Answer 4

start=$(date +%Y%m%d%H%M%S);
for x in {1..5};
do echo $x;
sleep 1; done;
end=$(date +%Y%m%d%H%M%S);
elapsed=$(($end-$start));
ftime=$(for((i=1;i<=$((${#end}-${#elapsed}));i++));
        do echo -n "-";
        done;
        echo ${elapsed});
echo -e "Start  : ${start}\nStop   : ${end}\nElapsed: ${ftime}"

Start  : 20171108005304
Stop   : 20171108005310
Elapsed: -------------6

Answer 5

Either $(()) or $[] will work for computing the result of an arithmetic operation. You're using $() which is simply taking the string and evaluating it as a command. It's a bit of a subtle distinction. Hope this helps.

As tink pointed out in the comments on this answer, $[] is deprecated, and $(()) should be favored.

Answer 6

You can use Bash's time keyword here with an appropriate format string

TIMEFORMAT='It takes %R seconds to complete this task...'
time {
    #command block that takes time to complete...
    #........
 }

Here's what the reference says about TIMEFORMAT:

The value of this parameter is used as a format string specifying how the timing information for pipelines prefixed with the time reserved word should be displayed. The ‘%’ character introduces an escape sequence that is expanded to a time value or other information. The escape sequences and their meanings are as follows; the braces denote optional portions.

%%

    A literal ‘%’.
%[p][l]R

    The elapsed time in seconds.
%[p][l]U

    The number of CPU seconds spent in user mode.
%[p][l]S

    The number of CPU seconds spent in system mode.
%P

    The CPU percentage, computed as (%U + %S) / %R. 

The optional p is a digit specifying the precision, the number of fractional digits after a decimal point. A value of 0 causes no decimal point or fraction to be output. At most three places after the decimal point may be specified; values of p greater than 3 are changed to 3. If p is not specified, the value 3 is used.

The optional l specifies a longer format, including minutes, of the form MMmSS.FFs. The value of p determines whether or not the fraction is included.

If this variable is not set, Bash acts as if it had the value

$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'

If the value is null, no timing information is displayed. A trailing newline is added when the format string is displayed.