僅有三次機會，判斷密碼是否正確

#!/bin/bash
str=wgw
for ((i=1;i<=3;i++))
do
read -p "請輸入密碼: " nb
    if [ ${nb}a = ${str}a ];then
            echo "密碼輸入正確"
            break
    else
            echo "密碼輸入錯誤。第$i次機會"
    fi
done