diff --git a/main.go b/main.go
index 8605409..7d097c5 100644
--- a/main.go
+++ b/main.go
@@ -71,9 +71,28 @@ func getMode() string {
   return mode
 }
 
+func checkArg() []byte {
+  var data []byte
+  arg := os.Args[1:]
+  if len(arg) != 1 {
+    fmt.Println("hns only takes file name as arg")
+    os.Exit(1)
+  }
+  filename := arg[0]
+  if _, err := os.Stat(filename); err == nil {
+    data = file2data(filename)
+  } else {
+    fmt.Println("No such file")
+    os.Exit(1)
+  }
+  return data
+}
+
 func main() {
+  data := checkArg()
   mode := getMode()
   fmt.Println(mode)
+  fmt.Println(len(data))
   /*
   var passwd string = "ThisAnnPassphrase"
   fmt.Println(passwd)