#!/bin/bash

freemb=$(df -h -B 1048576 | grep "/$" | awk -F ' ' '{ print $4 }')
freegb=$(df -h -B 1048576 | grep "/$" | awk -F ' ' '{ print $4/1024 }')

if [ "$freemb" -lt 1024 ]; then
    printf " %0.2fMb" "$freemb"
else
    printf " %0.2fGb" "$freegb"
fi