nvttest: Improve help

And do help stuff like in nvtsrv.

nvttest/nvttest.c

@@ -16,8 +16,17 @@
 #include "lib/nvt_log.h"
 
 
-#define HELP \
+/**INDENT-OFF**/
-    "Usage: nvttest -dqr [-n loops] [-t threads]\n"
+static const char help_text[] =
+    "Usage: nvttest OPTIONS...\n"
+    "OPTIONS:\n"
+    "  -d         : Enable debug\n"
+    "  -n loops   : Test loops per thread\n"
+    "  -q         : Quiet\n"
+    "  -r         : Insert random delay in loops\n"
+    "  -t threads : N. threads\n"
+    ;
+/**INDENT-ON**/
 
 static const char *dev = "/dev/ttyNVT0";
 
@@ -28,6 +37,13 @@ typedef struct {
     bool            opt_rand_delay;
 } topts_t;
 
+
+static void _usage(int rc)
+{
+    printf(help_text);
+    exit(rc);
+}
+
 static void    *_worker(void *arg)
 {
     topts_t        *topts = arg;
@@ -120,8 +136,8 @@ int main(int argc, char **argv)
         switch (opt)
         {
         default:               /* '?' */
-            fprintf(stderr, HELP);
+            _usage(1);
-            exit(EXIT_FAILURE);
+            break;
         case 'd':
             debug += 1;
             break;