shell写个计算器

#!/bin/bash
if [ $# -ne 3 ]

then

echo "Usage: $0 num1 + num2"

fi

case $2 in

+)

echo $1$2$3=`expr $1 + $3`

;;

-)

echo $1$2$3=`expr $1 - $3`

;;

*)

echo $1$2$3=`expr $1 \* $3`

;;

/)

echo $1$2$3=`expr $1 / $3`

;;

*)

echo must in \'+-*/\'

;;

esac

#####################################

#!/bin/bash
operator="+ - \* / exit"
echo -n "please input two number:"
read no1 no2
echo number is : $no1 $no2
select i in $operator
do
case $i in
+)
result=$(($no1+$no2))
echo "$result"
;;

-)
result=$(($no1-$no2))
echo "$result"
;;

*)
result=$(($no1 \* $no2))
echo ${result}
;;

/)
result=$(($no1 / $no2))
echo "$result"
;;

exit)
echo "exit.."
exit
;;
esac
done