engine: changes output of vlkb-nullvals calc so it is easy to parse

data-access/engine/src/vlkb/src/main.cpp

@@ -136,8 +136,8 @@ int cmd_nullvals(int argc, char * argv[])
             unsigned long long null_cnt;
             unsigned long long total_cnt;
             double fill_ratio = fitsfiles::calc_nullvals(argv[1], /*hdunum*/1, null_cnt, total_cnt);
-            cout << "fill ratio: " << fill_ratio << "%  null_cnt/total_cnt : " << null_cnt 
-               << "/" << total_cnt << endl;
+            //  fill_ratio_[%]   null_cnt   total_cnt 
+            cout << fill_ratio << " " <<  null_cnt << " " << total_cnt << endl;
             rc = EXIT_SUCCESS;
          }
          break;
@@ -146,7 +146,8 @@ int cmd_nullvals(int argc, char * argv[])
          std::cerr
             << "Usage: nullvals <filename.fits>\n"
             << std::endl
-            <<"Calculates number of undefined pixels (null values).\n"
+            <<"Calculates ratio of undefined pixels in image; returns three values:\n"
+            <<"<percentage-of-null-values> <count-of-nulls> <count-of-allpixels>\n"
             << std::endl;
          rc = EXIT_FAILURE;
    }