Implemented the exec builtin

Fixed readline and terminal interactions using stdin instead of /dev/tty

src/builtin/dirstack.rs

@@ -158,7 +158,7 @@ pub fn pushd(node: Node, io_stack: &mut IoStack, job: &mut JobBldr) -> ShResult<
 			let dirs = m.dirs_mut();
 			dirs.push_front(cwd);
 			match idx {
-				StackIdx::FromTop(n) => dirs.rotate_left(n + 1),
+				StackIdx::FromTop(n) => dirs.rotate_left(n),
 				StackIdx::FromBottom(n) => dirs.rotate_right(n + 1),
 			}
 			dirs.pop_front()

src/builtin/exec.rs

@@ -0,0 +1,50 @@
+use nix::{errno::Errno, unistd::execvpe};
+
+use crate::{
+  builtin::setup_builtin,
+  jobs::JobBldr,
+  libsh::error::{ShErr, ShErrKind, ShResult},
+  parse::{NdRule, Node, execute::ExecArgs},
+  procio::IoStack,
+  state,
+};
+
+pub fn exec_builtin(node: Node, io_stack: &mut IoStack, job: &mut JobBldr) -> ShResult<()> {
+  let NdRule::Command {
+    assignments: _,
+    argv,
+  } = node.class
+  else {
+    unreachable!()
+  };
+
+  let (expanded_argv, guard) = setup_builtin(argv, job, Some((io_stack, node.redirs)))?;
+  if let Some(g) = guard {
+    // Persist redirections so they affect the entire shell,
+    // not just this command call
+    g.persist()
+  }
+
+  if expanded_argv.is_empty() {
+    state::set_status(0);
+    return Ok(());
+  }
+
+  let args = ExecArgs::from_expanded(expanded_argv)?;
+
+  let cmd = &args.cmd.0;
+  let span = args.cmd.1;
+
+  let Err(e) = execvpe(cmd, &args.argv, &args.envp);
+
+  // execvpe only returns on error
+  let cmd_str = cmd.to_str().unwrap().to_string();
+  match e {
+    Errno::ENOENT => {
+      Err(ShErr::full(ShErrKind::CmdNotFound(cmd_str), "", span))
+    }
+    _ => {
+      Err(ShErr::full(ShErrKind::Errno(e), format!("{e}"), span))
+    }
+  }
+}

src/builtin/mod.rs

@@ -26,11 +26,12 @@ pub mod test; // [[ ]] thing
 pub mod trap;
 pub mod zoltraak;
 pub mod dirstack;
+pub mod exec;
 
-pub const BUILTINS: [&str; 24] = [
+pub const BUILTINS: [&str; 25] = [
   "echo", "cd", "read", "export", "pwd", "source", "shift", "jobs", "fg", "bg", "alias", "unalias",
   "return", "break", "continue", "exit", "zoltraak", "shopt", "builtin", "command", "trap",
-	"pushd", "popd", "dirs"
+	"pushd", "popd", "dirs", "exec",
 ];
 
 /// Sets up a builtin command