Add help message for improper usage

2 files changed, 5 insertions, 1 deletions

diff --git a/wtf8.c b/wtf8.c
index ea8950a..1b99d63 100644
--- a/wtf8.c
+++ b/wtf8.c
@@ -92,8 +92,10 @@ int main(int argc, char **argv) {
 	/*
 	 * Check we have one and only one argument
 	 */
-	if (argc != 2)
+	if (argc != 2) {
+		fprintf(stderr, "%s: Need one argument\n", PROGRAM_NAME);
 		exit(EXIT_FAILURE);
+	}
 
 	/*
 	 * Print the sole argument first as hex octets, then as characters, spaced
diff --git a/wtf8.h b/wtf8.h
index e8a40f4..f02e31b 100644
--- a/wtf8.h
+++ b/wtf8.h
@@ -2,6 +2,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+#define PROGRAM_NAME "wtf8"
+
 #define BYTE_SEP '-'
 #define CHAR_SEP ' '