shell中两个输入变量的乘积

Question

The program works fine in case " + " ," - "," /"

Example :

./calculate.sh 1 + 2 ==> output is 3.

But the problem here is when I type :

./calculate.sh 1 * 2 ==>output is "Please ..."

I've tried "\\*" like this but it seem the variable $2 can not get what I want.

Anyone can help me what is the problem here ?

#!/bin/sh
if [ $# -ne 3 ]
 then
      echo "Please input a number , an operator + or - or * or /"
 else
      case "$2" in 
            "+") echo "Sum is `expr $1 + $3`";;
            "-") echo "Substraction is `expr $1 - $3`";;
            "*") echo "Product is `expr $1 \* $3`";;
            "/") echo "Division is `expr $1 / $3`";;
      esac
fi

Answer 1

You should use it like this

./calculate.sh 2 \* 3

Or

./calculate.sh 2 "*" 3

Or

./calculate.sh 2 '*' 3

You are using "\\*" which is wrong.