improves help print output of weights2vtk tool

contrib/weights2vtk.c

@@ -569,11 +569,11 @@ void write_data_to_file(char const * filename, struct grid * src_grid,
   free(points);
 }
 
-void interpret_grid_arg(struct grid_config * grid_config, char * arg, char * str) {
+int interpret_grid_arg(struct grid_config * grid_config, char * arg, char * str) {
 
   if (arg == NULL) {
     fprintf(stderr, "-%c argument is missing\n", str[0]);
-    exit(EXIT_FAILURE);
+    return 1;
   }
 
   switch (grid_config->type) {
@@ -581,7 +581,7 @@ void interpret_grid_arg(struct grid_config * grid_config, char * arg, char * str
       grid_config->config.cube.n = atoi(arg);
       if (grid_config->config.cube.n == 0) {
         fprintf(stderr, "invalid N for cubed sphere %s grid\n", str);
-        exit(EXIT_FAILURE);
+        return 1;
       }
       break;
     case CURVE:
@@ -593,12 +593,37 @@ void interpret_grid_arg(struct grid_config * grid_config, char * arg, char * str
     case NONE:
     default:
       fprintf(stderr, "invalid %s grid type\n", str);
-      exit(EXIT_FAILURE);
+      return 1;
   }
 
   return 0;
 }
 
+void print_help(char * command) {
+  fprintf(stderr, "Usage: %s -S src_grid_type -T tgt_grid_type "
+                  "-s src_filename -t tgt_filename -w weight_filename "
+                  "-o vtk_filename\n\n"
+                  "   grid_type can have the following values:\n"
+                  "      'c', 'C': cubed sphere grid (instead of a "
+                  "filename provide N, where\n"
+                  "                N = sqrt(n/6), with n being the "
+                  "total number of cells\n"
+                  "      'm', 'M': curvilinear grid\n"
+                  "      'i', 'I': unstructured grid\n"
+                  "\n"
+                  "Example:\n"
+                  "  Configuration:\n"
+                  "    source grid type: unstructured\n"
+                  "    source grid file: src_grid.nc\n"
+                  "    target grid type: cubed sphere\n"
+                  "    target grid file: 100 (N instead of filename)\n"
+                  "    weight file name: weight_file.nc\n"
+                  "    vtk file name:    weights.vtk\n"
+                  "  Command:\n"
+                  "     %s -S i -T c -s src_grid.nc -t 100 -w weight_file.nc "
+                  "-o weights.vtk\n", command, command);
+}
+
 void parse_arguments(int argc, char ** argv,
                      struct grid_config * src_grid_config,
                      struct grid_config * tgt_grid_config,
@@ -610,6 +635,8 @@ void parse_arguments(int argc, char ** argv,
   *weight_filename = NULL;
   *vtk_filename = NULL;
 
+  int error = 0;
+
   char * src_arg = NULL;
   char * tgt_arg = NULL;
 
@@ -660,32 +687,38 @@ void parse_arguments(int argc, char ** argv,
       break;
     case '?':
     default:
-      fprintf(stderr, "Usage: %s -S src_grid_type -T tgt_grid_type "
-                      "-s src_filename -t tgt_filename -w weight_filename "
-                      "-o vtk_filename\n\n"
-                      "   grid_type can have the following values:\n"
-                      "      'c', 'C': cubed sphere grid (instead of a "
-                      "filename provide N, where\n"
-                      "                N = sqrt(n/6), with n being the "
-                      "total number of cells\n"
-                      "      'm', 'M': curvilinear grid\n"
-                      "      'i', 'I': unstructured grid\n", argv[0]);
-      exit(EXIT_FAILURE);
+      error = 1;
     }
   }
+  if (optind < argc) {
+    printf("non-option ARGV-elements: ");
+    while (optind < argc)
+        printf ("%s ", argv[optind++]);
+    printf("\n");
+    error = 1;
+  }
+
+  if (argc == 1) error = 1;
 
-  if (*weight_filename == NULL) {
+  if ((!error) && (*weight_filename == NULL)) {
     fputs("weight_filename argument is missing\n", stderr);
-    exit(EXIT_FAILURE);
+    error = 1;
   }
 
-  if (*vtk_filename == NULL) {
+  if ((!error) && (*vtk_filename == NULL)) {
     fputs("vtk_filename argument is missing\n", stderr);
-    exit(EXIT_FAILURE);
+    error = 1;
   }
 
-  interpret_grid_arg(src_grid_config, src_arg, "source");
-  interpret_grid_arg(tgt_grid_config, tgt_arg, "target");
+  if (!error)
+    error |= interpret_grid_arg(src_grid_config, src_arg, "source");
+  if (!error)
+    error |= interpret_grid_arg(tgt_grid_config, tgt_arg, "target");
+
+  if (error) {
+    print_help(argv[0]);
+    exit(EXIT_FAILURE);
+  }
 }
 
 struct grid * create_grid(struct grid_config grid_config) {