Shell bluetooth car control in bash

#!/bin/bash

#Shell bluetooth car control in bash

#what is your car's MAC address?
#type the below command:
#sudo hcitool lescan
#result sample:
#00:3C:A0:03:F5:7A QCAR-03F57A
MAC="00:3C:A0:03:F5:7A"

function default_state()
{
    # "set default state"
    gatttool -b "$MAC" --char-write-req -a 0x0012 -n "025e695a48ff2a438ca680f83e04e45d"

}

function go()
{
    len="$2"
    if [ -z "$len" ]; then
        len=1
    fi
    for (( i=1; i<=len; i++ ))
    do
        # "send command to car $i"
        gatttool -b "$MAC" --char-write-req -a 0x0012 -n "$1"
        sleep 0.1
    done
}

function forward()
{
    go "29609c664852cff1b0f0cbb98014bd2c" "$1"
}

function backward()
{
    go "03209909ba9da1c8b986163c6d484655" "$1"
}

function fast_forward()
{
    go "e65567da8e6c560d09d3733a7f47ff06" "$1"
}

function fast_backward()
{
    go "cec2ff1d7acc163cd13b7e6153ad5c45" "$1"
}
function forward_left()
{
    go "9928e590dfe821485f414fbb633d5c4e" "$1"
}
function forward_right()
{
    go "0f2ce56662d4fd9d32a44f102bf20aa7" "$1"
}

function backward_left()
{
    go "98ce981d58d115afe11960bf4613925c" "$1"
}
function backward_right()
{
    go "f2520fba3144fb11468fe080c6c2c23c" "$1"
}

function left()
{
    go "51382112135cccdb46cf8921b705499a" "$1"
}
function right()
{
    go "1b5769cdf13e8ab627080ff3cefc3bc0" "$1"
}