linux shell脚本获取时间差

#!/bin/sh

timer_start=`date "+%Y-%m-%d %H:%M:%S"`
echo "开始时间：$timer_start"

#测试，睡眠3秒
sleep  3s 

timer_end=`date "+%Y-%m-%d %H:%M:%S"`
echo "结束时间：$timer_end"

start_seconds=$(date --date="$timer_start" +%s);
end_seconds=$(date --date="$timer_end" +%s);
echo "本次运行时间："$((end_seconds-start_seconds)) "秒"