Shell Script To Simulate a Simple Calculator

#!/bin/bash
# Shell Program to simulate a simple calculator
# --------------------------------------------------------------------
# This is a free shell script under GNU GPL version 2.0 or above
# Copyright (C) 2005 nixCraft project.
# Feedback/comment/suggestions : http://cyberciti.biz/fb/
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
a=$1
op="$2"
b=$3
 
if [ $# -lt 3 ]
then
	echo "$0 num1  opr num2"
	echo "opr can be +, -, / , x"
	exit 1
fi
 
case "$op" in
	+) echo $(( $a + $b ));;
	-) echo $(( $a - $b ));;
	/) echo $(( $a / $b ));;
	x) echo $(( $a * $b ));;
	*) echo "Error ";;
esac