Shell Script to implement a recursive shell function to find the factorial of a given positive integer

fact()
{
    if(( $1<=1 ))
    then
        echo 1
    else
        (( t=$1-1 ))
        (( res=`fact $t` * $1 ))
        echo $res
    fi
}
  
echo -e "Enter an integer: \c"
read n
if(( n<0 ))
then
    echo ERROR: Invalid argument
else
    echo -e "Factorial of \"$n\" is `fact $n`"
fi