The vfscanf function is the same as the fscanf function except
    that instead of being called with a variable number of arguments,
    it is called with an argument list that has been initialized by
    va_start (and possibly subsequent va_arg calls).

    If no conversion specifications are given, you can omit the input
    pointers. Otherwise, the function calls must have exactly as
    many input pointers as there are conversion specifications, and
    the conversion specifications must match the types of the input
    pointers.

    Conversion specifications are matched to input sources in left-
    to-right order. Excess input pointers, if any, are ignored.

    For more information about format and conversion specifications
    and their corresponding arguments, see the "Understanding Input
    and Output" chapter of the HP C RTL Reference Manual.

    This function returns the number of successfully matched and
    assigned input items.

    See also vscanf and vsscanf.