def read_str(path: str) -> str | None:
    """Read a sysfs file, returning its stripped contents.

    Args:
        path: path under /sys.

    Returns:
        The file contents, or None if it cannot be read.
    """
    try:
        with open(path) as f:
            return f.read().strip()
    except OSError:
        return None


def read_int(path: str) -> int | None:
    """Read a sysfs file as an integer.

    Args:
        path: path under /sys.

    Returns:
        The parsed value, or None if the file cannot be read or does
        not contain an integer.
    """
    v = read_str(path)
    if v is None:
        return None
    try:
        return int(v)
    except ValueError:
        return None


def read_float(path: str) -> float | None:
    """Read a sysfs file as a float.

    Args:
        path: path under /sys.

    Returns:
        The parsed value, or None if the file cannot be read or does
        not contain a number.
    """
    v = read_str(path)
    if v is None:
        return None
    try:
        return float(v)
    except ValueError:
        return None