This sample sets the current thread priority to Time Critical level 15. It then uses DosGetInfoBlocks to retrieve the priority.

#define INCL_DOSPROCESS
#define INCL_DOSERRORS
#include <os2.h>
#include <stdio.h>

int main(VOID)
{
   PTIB   ptib = NULL;          /* Thread information block structure  */
   PPIB   ppib = NULL;          /* Process information block structure */
   APIRET rc   = NO_ERROR;      /* Return code                         */

   rc = DosSetPriority (PRTYS_THREAD,        /* Change a single thread */
                        PRTYC_TIMECRITICAL,  /* Time critical class    */
                        15L,                 /* Increase by 15         */
                        0L);                 /* Assume current thread  */
   if (rc != NO_ERROR) {
      printf ("DosSetPriority error : rc = %u\n", rc);
      return 1;
   } else {
      rc = DosGetInfoBlocks(&ptib, &ppib);

      if (rc != NO_ERROR) {
         printf ("DosGetInfoBlocks error : rc = %u\n", rc);
         return 1;
      } else {
         printf("Priority Class = %d\n",
               ((ptib->tib_ptib2->tib2_ulpri) >> 8) & 0x00FF);
         printf("Priority Level = %d\n",
               ((ptib->tib_ptib2->tib2_ulpri) & 0x001F) );
      } /* endif */
   }

   return NO_ERROR;
}