char db_items[] = {
    isc_info_user_names,
    isc_info_end
 };

 char res_buffer[ 1024 ], *p, item;
 int length;

....
 isc_attach_database(.......);
.....

 isc_database_info(status,
 &handle,        /* Set in previous isc_attach_database() call. */ 
 sizeof(db_items),
 db_items,
 sizeof(res_buffer),
 res_buffer);

 if (status[ 0 ] ==  1  && status[ 1 ]) {
                    isc_print_status(status);
    return( 1 );
 };

  /* Extract the values returned in the result buffer. */ 

 if (res_buffer[ 0 ]==isc_info_truncated) {
  printf( "Result buffer is too small.\n" );
  return(- 1 );
 }
 for (p = res_buffer; *p != isc_info_end ; ) {
    int i;
    item = *p++;
    if (item!=isc_info_user_names) break;
    length = isc_vax_integer(p,  2 );
    p +=  2 ;
    printf( "%.*s\n" , length,p);
    p += length;
 };