#!/bin/sh

fact()
{
   if [ $1 -gt 1 ] ; then
        # eval first to do the expr and pass value to fact.  
        eval p=\`fact `expr $1 - 1`\`   
   else
        echo $1
        return      # needed so that you dont echo two things
   fi
   echo `expr $p \* $1`
}

echo "Enter a number you wish to calculate factorial of"
read NUM

echo "Factorial of $NUM is : " `fact $NUM`

p=$( fact $(( $1 - 1)) )