Recursion in a shell script

In shell scripts, the variables are global by default. So recursive calls require the local keyword to be used to display identity locals so that recursive calls to functions can be implemented. Wrote a recursive calculation of factorial script, found that when n=7 before the normal, and then the result is wrong. The upper limit of this number is small when the return value of the function is found, only to 255. So then a global variable was used to hold the result of each recursive.

#!/bin/bash

n=$1
ret=1

function multi ()
{
    local local_n=$1
    local local_n_sub_1=$ ($LOCAL _ N-1))

    if [$LOCAL _n_sub_1-lt 1]
    then
        ret=1
    else
        multi $LOCAL _n_sub_1
        ret= ' expr $LOCAL _n \* $RET '
    fi
}

multi $N

echo $RET