diff --git a/src/command/builtins.rs b/src/command/builtins.rs
index 848daa0..e06b35a 100644
--- a/src/command/builtins.rs
+++ b/src/command/builtins.rs
@@ -1,5 +1,6 @@
 use crate::error;
 use crate::error::CdError;
+use crate::error::IllegalNumberError;
 use crate::exit_code::ExitCode;
 
 use std::env;
@@ -33,3 +34,23 @@ pub(super) fn cd(args: &Vec<String>, exit_code: &mut ExitCode) {
 pub(super) fn colon(_args: &Vec<String>, exit_code: &mut ExitCode) {
     exit_code.set_success();
 }
+
+pub(crate) fn exit(args: &Vec<String>, exit_code: &mut ExitCode) {
+    let raw_exit_code: Result<i32, IllegalNumberError>;
+
+    if args.is_empty() {
+        raw_exit_code = Ok(i32::from(exit_code.get()));
+    } else {
+        raw_exit_code = match args[0].parse::<usize>() {
+            Ok(parsed) => Ok(i32::try_from(parsed % 256).unwrap()),
+            Err(_e) => Err(IllegalNumberError::new("exit", args[0].as_str())),
+        };
+    }
+
+    if raw_exit_code.is_ok() {
+        println!("exit");
+        std::process::exit(raw_exit_code.unwrap());
+    } else {
+        error::print(Box::new(raw_exit_code.unwrap_err()));
+    }
+}
diff --git a/src/command/mod.rs b/src/command/mod.rs
index 7e450ed..e78cff0 100644
--- a/src/command/mod.rs
+++ b/src/command/mod.rs
@@ -1,4 +1,4 @@
-mod builtins;
+pub mod builtins;
 pub mod command_builder;
 pub mod command_sequence;
 
@@ -27,6 +27,7 @@ impl Builtin {
 
         let function: Option<BuiltinFunction> = match program.as_str() {
             "cd" => Some(builtins::cd),
+            "exit" => Some(builtins::exit),
             ":" => Some(builtins::colon),
             _ => None,
         };
diff --git a/src/control.rs b/src/control.rs
index 22107d8..5254d7f 100644
--- a/src/control.rs
+++ b/src/control.rs
@@ -1,15 +1,10 @@
+use crate::command::builtins;
 use crate::command::Command;
 use crate::exit_code::ExitCode;
 use crate::interface::get_user_input;
 use crate::parser::parse;
 use crate::variables::Variables;
 
-fn exit(code: &ExitCode) {
-    let code = i32::from(code.get());
-    println!("exit");
-    std::process::exit(code);
-}
-
 pub fn run() {
     let mut current_exit_code = ExitCode::new(0);
     let mut variables = Variables::new();
@@ -25,7 +20,7 @@ pub fn run() {
             }
         } else {
             println!();
-            exit(&current_exit_code);
+            builtins::exit(&vec![], &mut current_exit_code);
         }
     }
 }
diff --git a/src/error.rs b/src/error.rs
index 020fee5..6f93e82 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -5,6 +5,7 @@ use std::path::Path;
 
 type Error = Box<dyn Display>;
 
+#[derive(Debug)]
 pub struct CdError {
     entry_name: String,
 }
@@ -23,6 +24,7 @@ impl Display for CdError {
     }
 }
 
+#[derive(Debug)]
 pub struct CommandNotFoundError {
     command: String,
 }
@@ -41,6 +43,7 @@ impl Display for CommandNotFoundError {
     }
 }
 
+#[derive(Debug)]
 pub struct UnmatchedQuoteError {
     index: usize,
 }
@@ -51,6 +54,31 @@ impl Display for UnmatchedQuoteError {
     }
 }
 
+#[derive(Debug)]
+pub struct IllegalNumberError {
+    command_invoked: String,
+    illegal_number: String,
+}
+
+impl IllegalNumberError {
+    pub fn new(command_invoked: &str, illegal_number: &str) -> Self {
+        Self {
+            command_invoked: String::from(command_invoked),
+            illegal_number: String::from(illegal_number),
+        }
+    }
+}
+
+impl Display for IllegalNumberError {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(
+            f,
+            "{}: '{}' is not a valid number",
+            self.command_invoked, self.illegal_number
+        )
+    }
+}
+
 pub fn print(error: Error) {
     let name = env::args().next().unwrap_or(String::from("rash"));
     let name = Path::new(&name).file_name().unwrap().to_str().unwrap();