Add usage.
diff --git a/regress/tryopen.c b/regress/tryopen.c
index 313928a..7d44fe4 100644
--- a/regress/tryopen.c
+++ b/regress/tryopen.c
@@ -48,7 +48,11 @@
 #include "zip.h"
 #include "compat.h"
 
-const char *usage = "usage: %s [-cent] file\n";
+const char *usage = "usage: %s [-cent] file\n\n"
+    "\t-c\tcheck consistency\n"
+    "\t-e\texclusively open archive\n"
+    "\t-n\tcreate new file\n"
+    "\t-t\ttruncate file to size 0\n";