feat: add builtins module

src/builtins/mod.rs

@@ -0,0 +1,11 @@
+use crate::error::ShellError;
+
+const BUILTINS: &[&str] = &[];
+
+pub fn is_builtin(keyword: &str) -> bool {
+    BUILTINS.contains(&keyword)
+}
+
+pub fn execute_builtin(keyword: &str, args: &[&str]) -> Result<(), ShellError> {
+    Ok(())
+}

src/execute.rs

@@ -1,6 +1,7 @@
 use std::io::ErrorKind::NotFound;
 use std::process::Command;
 
+use crate::builtins::{execute_builtin, is_builtin};
 use crate::error::ShellError;
 use crate::parse::parse_line;
 
@@ -10,10 +11,14 @@ pub fn interpret(line: &str) -> Result<(), ShellError> {
     }
     let (keyword, args) = parse_line(line);
 
-    let mut command = Command::new(keyword);
-    command.args(args);
+    if is_builtin(keyword) {
+        execute_builtin(keyword, &args)?;
+    } else {
+        let mut command = Command::new(keyword);
+        command.args(args);
 
-    execute(command)?;
+        execute(command)?;
+    }
 
     Ok(())
 }

src/main.rs

@@ -1,3 +1,4 @@
+mod builtins;
 mod error;
 mod execute;
 mod parse;