In this case, the second parameter is a n.c., but the third parameter must be a pointer to an integer with a value of zero (0) or one (1), which will have the following effect:
Notice that if you employ this call you must install another method for obtaining the PEN - for example using call POLL_oob() when reading is possible on the file handle supplied by PEN_GET_HANDLE() (see section 11.7.2).