diff --git a/src/bin/code_gen.rs b/src/bin/code_gen.rs
index 0657048..040a79a 100644
--- a/src/bin/code_gen.rs
+++ b/src/bin/code_gen.rs
@@ -53,7 +53,7 @@ impl FromStr for RadiusAttributeValueType {
 }
 
 fn print_usage(program: &str, opts: &Options) {
-    let brief = format!("Usage: {} FILE [options]", program);
+    let brief = format!("Usage: {} [options] DICT_FILE OUT_FILE", program);
     print!("{}", opts.usage(&brief));
     process::exit(0);
 }
@@ -68,13 +68,18 @@ where
 
 fn main() {
     let args: Vec<String> = env::args().collect();
-    let _program = args[0].clone();
+    let program = args[0].clone();
 
-    let opts = Options::new();
+    let mut opts = Options::new();
+    opts.optflag("h", "help", "print this help menu");
     let matches = opts
         .parse(&args[1..])
         .unwrap_or_else(|f| panic!(f.to_string()));
 
+    if matches.opt_present("h") {
+        print_usage(&program, &opts);
+    }
+
     let dict_file_path = Path::new(&matches.free[0]);
     if !dict_file_path.exists() {
         panic!("no such dictionary file => {}", &matches.free[0]);