| PMBEFORESELECT(3) | PMBEFORESELECT(3) | 
int pmBeforeSelect(pmContext *pmc);
pmContext * | 
  pmc | 
  pmContext object | 
pmBeforeSelect() must be called before calling
select(2).
pmBeforeSelect(), all messages in the receive
queue must be extracted by pmReceive().
PM_SUCCESS | 
  Success |