linux shell 计算时间差

#!/bin/bash
#Program: time spent
#set -x

function timespent() {

date_begin=$1
date_end=$2

declare -i date_total_s=$(($date_end-$date_begin))

declare -i date_d=$(($date_total_s/60/60/24))

declare -i date_h=$(($(($date_total_s-$date_d*60*60*24))/60/60))

declare -i date_m=$(($(($date_total_s-$date_d*60*60*24-$date_h*60*60))/60))

declare -i date_s=$(($date_total_s-$date_d*60*60*24-$date_h*60*60-$date_m*60))

echo " The program have spent: $date_d days,$date_h hours,$date_m minutes,$date_s seconds."

}

declare -i date_s=`date +%s`

sleep 2

declare -i date_e=`date +%s`


timespent $date_s $date_e