linux17：时间间隔计算脚本练习——距离你的生日还有多少天

echo $(($(date --date="2022/01/01" +%s)/86400+1))

#！/bin/bash

#name——timeDistance.sh


#function

#input a date, to calculate how many days to this day
#2022.1.18 daxiong


read -p  "please input your date like YYYYMMDD ex>20150716 : "  date2

#test whether or not have eight numbers
date_test=$(echo ${date2} | grep '[0-9] \ {8\} ')
if [ "${date_test}" == "" ] ; then
	echo "you must input the right date format... "
	exit 1
fi

#calculate
declare -i date_des=$(date --date="${date2}" +%s)
declare -i date_now=$(date +%s)
declare -i distanceSec=$((${date_des}-${date_now}))

declare -i distanceDay=$(( ${distanceSec}/60/60/24 ))

if [ "$distanceDay" -gt 0 ]; then
        echo "That day hasn't come yet. "
        echo "You have $((${distanceDay}+1)) days."

elif [ "$distanceDay" -eq 0 ]; then
        echo "Just do it now!"
else [ "$distanceDay" -lt 0 ] 
        echo "That day has passed, $((0-${distanceDay})) days ago. "
fi