def get_free_diskbytes(dir_):
    r"""
    Args:
        dir_ (str):

    Returns:
        int: bytes_ folder/drive free space (in bytes)

    References::
        http://stackoverflow.com/questions/51658/cross-platform-space-remaining-on-volume-using-python
        http://linux.die.net/man/2/statvfs

    CommandLine:
        python -m utool.util_cplat --exec-get_free_diskbytes
        python -m utool.util_cplat --exec-get_free_diskbytes --dir /media/raid
        python -m utool.util_cplat --exec-get_free_diskbytes --dir E:

    Example:
        >>> # ENABLE_DOCTEST
        >>> from utool.util_cplat import *  # NOQA
        >>> import utool as ut
        >>> dir_ = ut.get_argval('--dir', type_=str, default=ut.truepath('~'))
        >>> bytes_ = get_free_diskbytes(dir_)
        >>> result = ('bytes_ = %s' % (str(bytes_),))
        >>> print(result)
        >>> print('Unused space in %r = %r' % (dir_, ut.byte_str2(bytes_)))
        >>> print('Total space in %r = %r' % (dir_, ut.byte_str2(get_total_diskbytes(dir_))))
    """
    if WIN32:
        import ctypes
        free_bytes = ctypes.c_ulonglong(0)
        outvar = ctypes.pointer(free_bytes)
        dir_ptr = ctypes.c_wchar_p(dir_)
        ctypes.windll.kernel32.GetDiskFreeSpaceExW(dir_ptr, None, None, outvar)
        bytes_ = free_bytes.value
        return bytes_
    else:
        st = os.statvfs(dir_)
        # blocks avaiable * block size
        bytes_ = st.f_bavail * st.f_frsize
        #bytes_ = st.f_bfree * st.f_frsize  # includes root only space
        return bytes_
r"""
    Args:
        dir_ (str):

    Returns:
        int: bytes_ folder/drive free space (in bytes)

    References::
        http://stackoverflow.com/questions/51658/cross-platform-space-remaining-on-volume-using-python
        http://linux.die.net/man/2/statvfs

    CommandLine:
        python -m utool.util_cplat --exec-get_free_diskbytes
        python -m utool.util_cplat --exec-get_free_diskbytes --dir /media/raid
        python -m utool.util_cplat --exec-get_free_diskbytes --dir E:

    Example:
        >>> # ENABLE_DOCTEST
        >>> from utool.util_cplat import *  # NOQA
        >>> import utool as ut
        >>> dir_ = ut.get_argval('--dir', type_=str, default=ut.truepath('~'))
        >>> bytes_ = get_free_diskbytes(dir_)
        >>> result = ('bytes_ = %s' % (str(bytes_),))
        >>> print(result)
        >>> print('Unused space in %r = %r' % (dir_, ut.byte_str2(bytes_)))
        >>> print('Total space in %r = %r' % (dir_, ut.byte_str2(get_total_diskbytes(dir_))))