Shell script to find the factorial of a number

Factorial A

#!/bin/bash

#command to find the factorial of a number
#Syntax :       fact [arg]

declare -i count result

# The script will treat subsequent occurrences of "count", "result" as an integer.

if test -z $1 ; then
        echo "Error     :       Argument missing"
        exit 1
else
        tempvar=$(expr $1 + $1)
        if test -z $tempvar ; then
                echo "Error     :       Non integer argument"
                exit 1
        fi
fi

count=$1
result=1

while [ "$count" != "0"  ]; do
result=result*count
count=count-1
done

echo "$result"
exit 0