两个日期之间相差的天数计算

#!/bin/bash

warning(){
echo "###################################################"
echo " Invalid! Please retype. [ Ctrl+C ] to exit!"
echo "###################################################"
}

while :
do
        read -p "Please enter the 1st date : " datex
        if [[ $datex =~ [0-9]{8}$ ]];then
                break
        else
                warning
                continue
        fi
done
while :
do
        read -p "Please enter the 2nd date : " datey
        if [[ $datey =~ [0-9]{8}$ ]];then
                break
        else
                warning
                continue
        fi
done

a=$(date -d $datex +%s)
b=$(date -d $datey +%s)
if [ $a -lt $b ];then
        z=$(($b-$a))
else
        z=$(($a-$b))
fi

i=$[$z/86400]
if [ $i == 1 ];then
        echo "$i day"
else
        echo "$i days"
fi

[解析]

  输入2个8位的时间日期，然后转换成时间戳，最后相差除以86400(1天的秒数)，得到多少天。