diff --git a/src/main.rs b/src/main.rs
index c0eacd4..9e078e5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,27 +2,40 @@ use std::env;
 use std::fs;
 use std::io;
 use std::io::Write;
+use crate::rlox::RLox;
+use std::process;
+
+pub mod rlox;
+
+// Exit codes from #include <sysexits.h>
+const EX_OK: i32 = 0;
+const EX_DATAERR: i32 = 65;
+const EX_USAGE : i32 = 66;
 
 fn main() {
     let args: Vec<String> = env::args().collect();
 
-    match args.len() {
+    let exit_code = match args.len() {
         1 => run_prompt(),
         2 => run_file(&args[1]),
         _ => {
             println!("Usage : rlox [script]");
+            EX_USAGE
         }
-    }
+    };
+
+    process::exit(exit_code);
 }
 
-fn run_file( file_path: &str ) {
+fn run_file( file_path: &str ) -> i32 {
     let contents = fs::read_to_string(file_path)
         .expect(&format!("Should have been able to read the file {file_path}"));
 
-    run(contents);
+    run(contents)
 }
 
-fn run_prompt() {
+fn run_prompt() -> i32 {
+    let mut exit_code = EX_OK;
     loop {
         print!("> ");
         io::stdout().flush().expect("Unable to flush stdout");
@@ -36,12 +49,15 @@ fn run_prompt() {
             break;
         }
 
-        run(line);
+        exit_code = run(line);
     }
+    exit_code
 }
 
-fn run( _script: String ) {
+fn run( script: String ) -> i32 {
+    let rlox_interpreter = RLox { had_error: false };
 
+
+    if rlox_interpreter.had_error { EX_DATAERR } else { EX_OK }
 }
 
-// http://www.craftinginterpreters.com/scanning.html#error-handling
\ No newline at end of file
diff --git a/src/rlox.rs b/src/rlox.rs
new file mode 100644
index 0000000..8066210
--- /dev/null
+++ b/src/rlox.rs
@@ -0,0 +1,16 @@
+
+
+pub struct RLox {
+    pub had_error: bool,
+}
+
+
+impl RLox {
+    fn error( &self, line: u32, message: String ) {
+        self.report(line, String::from(""), message);
+    }
+
+    fn report( &self, line: u32, place: String, message: String ) {
+        println!("[line {line}] Error {place}: {message}");
+    }
+}