Homework & Coursework Questions

Hey folks, thanks in advance for any help or advice.

1. The problem statement, all variables and given/known data:

I'm supposed to write a script that takes 3 arguments, like "compute.sh 1 + 2" where the middle one will be +,-,/, or * and output the operation and the result.

2. Relevant commands, code, scripts, algorithms:

It is in bourne shell.

3. The attempts at a solution (include all code and scripts):

Code:

#!/bin/sh

compute()
{
	if [ $# -eq 3 ]; then
		if [ $2 = "+" -o $2 = "-" -o $2 = "/" -o $2 = "*" ]; then
			answer=`expr $1 $2 $3`
			echo $answer
		else
		echo "Please enter proper arguments."		
		
		fi

	else
		echo "Please only enter three arguments."
	fi
}

compute $1 $2 $3

4. Complete Name of School (University), City (State), Country, Name of Professor, and Course Number (Link to Course):
University of Notre Dame, IN; Freeland, CSE30189



This script works for +, -, and /, but when I get to the *, it fails the if test. I think it has something to do with * being a wildcard? However, I thought the quotes would make it literal...

Hi, you need to double quote $2 as well, otherwise the * will get expanded by the shell.

You can also use a case statement, then you do not need to quote the variable

Code:

case $2 in 
  \*|+|-|/)  blabla      ;;
esac