I have a variable of $i which is seconds in a shell script, and I am trying to convert it to 24 HOUR HH:MM:SS. Is this possible in shell?
If $i represents some date in second since the Epoch, you could display it with
$i
date -u -d @$i +%H:%M:%S
but you seems to suppose that $i is an interval (e.g. some duration) not a date, and then I don't understand what you want.