UNIX for Advanced & Expert Users

#!/bin/ksh
# add 27 hours to a "timestamp"

sub_times()  # seconds diff: $1 - now
{
    perl -e '
        use Time::Local;
        
#  get current time

        $tm="$ARGV[0]";
        (  $sec,
           $min,
           $hr,
           $mday,
           $mon,
           $yr,
           $wday,
           $yday,
           $isdst)=localtime(time);
           
# alter to 23:45 or ARGV[0] 
        $sec=0;
        $min=substr($tm,3,2);
        $hr=substr($tm,0,2); 
        
# epochtm is number of seconds at ARGV[0] in future 

        $epochtm=timelocal($sec,$min,$hr,$mday,$mon,$yr);
        if($epochtm > time)
        {
           	$epochtm=$epochtm - time;
           	print "$epochtm", "\n";
        } 
        else    #  we have an error ie., time is > 23:45 
        {
        	print "0\n";	
        }    '   "$1"
}

# example use of sub_times:

sleep_time=$( sub_times "23:45")
echo "$sleep_time"
sleep_time=$( sub_times "00:00")
echo "$sleep_time"

#!/bin/bash
date2stamp () {
    date -u --date "$1" +%s
}

dateDiff (){
    dte1=$(date2stamp $1)
    dte2=$(date2stamp $2)
    diffSec=$((dte2-dte1))
    if ((diffSec < 0)); then abs=-1; else abs=1; fi
    echo $((diffSec*abs))
}

dateDiff "15:30:15" "15:35:18"