Corrects a bug when no output file are present

README.md

@@ -13,8 +13,8 @@ OPTIONS:
 	set amount of measurements per second.
 -t|--time <time>
 	set duration value (seconds). If 0, then loops infinitely.
--o|--logfile <file>
-	specify a log file.
+-o|--option <output file> or <port number>
+	specify a log file for MojitO/S or a port number for prometeus_mojitO/S.
 -s|--overhead-stats
 	enable overhead statistics (nanoseconds).
 

src/display_manager.c

@@ -9,13 +9,13 @@ extern FILE *output;
 extern char* output_option;
 
 void init_manager(char** labels, int nb_sensors, int stat_mode) {
-
-  if ((output = fopen(output_option, "wb")) == NULL) {
-    perror("fopen");
-    PANIC(1, "-o %s", output_option);
+  if (output_option != NULL) {
+    if ((output = fopen(output_option, "wb")) == NULL) {
+      perror("fopen");
+      PANIC(1, "-o %s", output_option);
+    }
   }
 
-
   fprintf(output, "#timestamp ");
   
   for (int i = 0; i < nb_sensors; i++) {