What data set is my C program using?

I wanted to know what data set my C program was using.  There is a facility BPXWDYN: a text interface to dynamic allocation and dynamic output designed for REXX users, but callable from C.

This is not very well documented, so here is my little C program based on the sample IBM provided.

The documentation says use  RTARG dsname = {45,”rtdsn”};  but this is for alloc.  With “info” it gives the error message IKJ56231I TEXT UNIT X’0056′ CONTAINS INVALID KEY .  Which basically means rtdsn is not value.     I had to use RTARG dsname = {45,”INRTDSN”};

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#include <errno.h> 
int main(int argc, char * argv[]) { 
  typedef int EXTF(); 
  #pragma linkage(EXTF,OS) 
  EXTF *bpxwdyn=(EXTF *)fetch("BPXWDY2 "); 
  int i,j,rc; 
  typedef struct s_rtarg { 
    short len; 
    char str[260]; 
   } RTARG;
  char *info ="info DD(APF1) "; 
   
  RTARG dsname = {45,"INRTDSN"}; // not  rtdsn as the doc says
  RTARG ddname = {9,"INRTDDN"}; // not rtddn as the doc says
  RTARG volser = {7,"INRTVOL"}; 
  RTARG msg = {3,"MSG "}; 
  RTARG m[4] = {258,"msg.1",258,"msg.2",258,"msg.3",258,"msg.4"};
 
  rc=bpxwdyn(info,&dsname,&ddname,&volser,
      &msg,&m[0],&m[1],&m[2],&m[3]); 
  if (rc!=0) printf("bpxwdyn rc=%X %i\n",rc,rc);

  if (*ddname.str) printf("ddname=%s\n",ddname.str); 
  if (*dsname.str) printf("dsname=%s\n",dsname.str); 
  if (*volser.str) printf("volser=%s\n",volser.str); 
  for (i=0,j=atoi(msg.str);i<j && i<4;i++) 
     printf("%s\n",m[i].str); 
  
  return; 
}