Shell scripting: How to check if an input argument is a Math operator

Question

I want to build a basic calculator where i will give as arguments two numbers and one of these +,-,/,* . Example 1+2=3 . I know how to check if an argument is a number but how about the symbols?

Answer 1

Use case :

case "$op" in
    '*') result=$(($arg1 * $arg2))
        ;;
    /) # code for division
        ;;
    -) # code for subtraction
        ;;
    +) # code for addition
        ;;
    *) echo "Unknown operator '$op'"
        ;;
esac