shell腳本實現算術運算且輸入的不能為非數字的值

#!/bin/bash


c=1

while [ ${c} -eq  1 ]
do
echo "請輸入第一個數"
read a
echo "請輸入第二個數"
read b

if [[ ${b} != *[!0]* ]] && [[ ${a} != *[!0123456789]* ]] && [ -n "${a}"  ] && [ -n "${b}" ]  ;

then
sleep 1
echo "   "
echo "   "
echo "和為:"`echo $(( ${a} + ${b} ))`
echo "差為:"`echo $(( ${a} - ${b} ))`
echo "積為:"`echo $(( ${a} * ${b}))`
echo "   "
sleep 2
echo -e "\033[33m除數為0,無法進行除法運算以及取餘運算！\033[0m"

c=$(( ${c} + 1 ))
elif [[ ${a} != *[!0123456789]* ]] && [[ ${b} != *[!0123456789]* ]] && [ -n "${a}" ] && [ -n "${b}" ] ;

then
sleep 1
echo "  "
echo "  "
echo "和為:"`echo $(( ${a} + ${b} ))`
echo "差為:"`echo $(( ${a} - ${b} ))`
echo "商為:"`echo $(( ${a} / ${b} ))`
echo "積為:"`echo $(( ${a} * ${b}))`
echo "餘數為:"`echo  $(( ${a} % ${b}))`

c=$(( ${c} + 1 ))

else

sleep 3

echo "  "

echo -e "\033[31m輸入錯誤，請從新輸入正確的值！\033[0m"

echo "  "
fi

done