time difference

UNIX for Advanced & Expert Users
1

Hi,

i have one hard coded time which will be 23:45 and one will be sysdate (same date) and time less than 23:45.

i want to start my job at 23:45 and the input file will be arriving before that. so i want to make sure that the task starts only at 23:45 and from the input file time till 23:45 the script should go into sleep mode.

for that i need difference between both the times in seconds so that i can use sleep for the difference time.

Please help me on how to get the difference in seconds.

Any other solution to achieve the same requirement is also welcomed.

2 
#!/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"
3

The GNU date command in full of goodies but not when it comes to calculate a date or time difference. Here is what I came up with after looking to more than one solution.

#!/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"
4

start_time=`date +%H:%M`
end_time="23:45"
tme=`TZ=CST+24 date +%Y%m%d`
start_hour=`echo $start_time | cut -d':' -f1`
start_min=`echo $start_time | cut -d':' -f2`
end_hour=`echo $end_time | cut -d':' -f1`
end_min=`echo $end_time | cut -d':' -f2`
hour=`expr $end_hour - $start_hour`
min=`expr $end_min - $start_min`

            if [ $min -lt 0 ]
            then
              min=\`expr $min \+ 60\`
              hour=\`expr $hour - 1\`
            fi

    hour_min=\`expr $hour \\* 60\`
    tot_min=\`expr $hour_min \+ $min\`
    seconds=\`expr $tot_min \\* 60\`

    echo "Total Sec - $seconds"