Use getopt_long() to reject flags w/usage output

bin/ax25dump.c

@@ -2,6 +2,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>
+#include <getopt.h>
 #include <unistd.h>
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -36,6 +37,10 @@ static void usage(int argc, char **argv, const char *message, ...) {
 int main(int argc, char **argv) {
     patty_client *client;
 
+    struct option opts[] = {
+        { NULL, 0, NULL, 0 }
+    };
+
     uint8_t buf[4096];
     ssize_t readlen;
 
@@ -45,6 +50,12 @@ int main(int argc, char **argv) {
 
     struct stat st;
 
+    int ch;
+
+    if ((ch = getopt_long(argc, argv, "", opts, NULL)) >= 0) {
+        usage(argc, argv, NULL);
+    }
+
     if (argc < 2) {
         usage(argc, argv, "Not enough arguments provided");
     }