1 files changed, 7 insertions, 1 deletions
diff --git a/main.cpp b/main.cpp
index e862ee1..9f3028e 100644
--- a/main.cpp
+++ b/main.cpp
@@ -327,9 +327,15 @@ void got_packet(u_char *args, const struct pcap_pkthdr *header, const u_char *pa
 }
 
 int main(int argc, char *argv[]) {
-    char *dev = argv[1];
     char errbuf[1000];
 
+    if (argc != 2) {
+        fprintf(stderr, "usage: %s [interface]\n", argv[0]);
+	return EXIT_FAILURE;
+    }
+
+    char *dev = argv[1];
+
     pcap_t *handle;
 
     handle = pcap_open_live(dev, BUFSIZ, 1, 1000, errbuf);