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

    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.

    See also scanf, vfscanf, and vsscanf.