diff --git a/main.go b/main.go
index f3b3d7f..383a140 100644
--- a/main.go
+++ b/main.go
@@ -7,16 +7,68 @@ import (
 	"os"
 )
 
-func check(r io.Reader) {
+func input() io.ReadCloser {
+	if flag.Arg(1) == "" {
+		return os.Stdin
+	} else {
+		f, err := os.Open(flag.Arg(1))
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "error: %s\n", err)
+			os.Exit(1)
+		}
+		return f
+	}
+}
+
+func check() {
+	r := input()
+	defer r.Close()
+
 	_, err := parse(r)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "%s\n", err)
 	}
 }
 
+func lexx() {
+	r := input()
+	defer r.Close()
+
+	c := lex(r)
+	for t := range c {
+		fmt.Println(t)
+	}
+}
+
+func parsse() {
+	r := input()
+	defer r.Close()
+
+	n, err := parse(r)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error: %s", err)
+		os.Exit(1)
+	}
+	if err := n.pretty(os.Stdout, ""); err != nil {
+		fmt.Fprintf(os.Stderr, "error: %s\n", err)
+		os.Exit(1)
+	}
+}
+
 func main() {
 	flag.Parse()
-	if flag.NArg() == 0 {
-		check(os.Stdin)
+	switch flag.Arg(0) {
+	case "check":
+		check()
+	case "lex":
+		lexx()
+	case "parse":
+		parsse()
+	case "":
+		fmt.Fprintf(os.Stderr, "specify an action (check)\n")
+		os.Exit(1)
+	default:
+		fmt.Fprintf(os.Stderr, "no such action: %s\n", flag.Arg(0))
+		os.Exit(1)
 	}
 }
diff --git a/node.go b/node.go
index 5ab6b6c..06b5170 100644
--- a/node.go
+++ b/node.go
@@ -1,8 +1,11 @@
 package main
 
 import (
+	"bufio"
 	"bytes"
 	"fmt"
+	"io"
+	"strings"
 )
 
 type nodeType int
@@ -14,9 +17,12 @@ const (
 	n_assignment
 )
 
+var indent = "  "
+
 type node interface {
 	Type() nodeType
 	parse(*parser) error
+	pretty(io.Writer, string) error
 }
 
 type rootNode struct {
@@ -73,6 +79,17 @@ func (n *rootNode) String() string {
 	return buf.String()
 }
 
+func (n *rootNode) pretty(w io.Writer, prefix string) error {
+	fmt.Fprintf(w, "%sroot{\n", prefix)
+	for _, child := range n.children {
+		if err := child.pretty(w, prefix+indent); err != nil {
+			return err
+		}
+	}
+	fmt.Fprintf(w, "%s}\n", prefix)
+	return nil
+}
+
 type commentNode struct {
 	body string
 }
@@ -89,6 +106,26 @@ func (n *commentNode) String() string {
 	return fmt.Sprintf("{comment: %s}", n.body)
 }
 
+func (n *commentNode) pretty(w io.Writer, prefix string) error {
+	r := bufio.NewReader(strings.NewReader(n.body))
+	fmt.Fprintf(w, "%scomment{\n", prefix)
+	for {
+		line, err := r.ReadString('\n')
+		if err == io.EOF {
+			if line != "" {
+				fmt.Fprintf(w, "%s%s%s\n", prefix, indent, line)
+			}
+			break
+		}
+		if err != nil {
+			return err
+		}
+		fmt.Fprintf(w, "%s%s%s\n", prefix, indent, line)
+	}
+	fmt.Fprintf(w, "%s}\n", prefix)
+	return nil
+}
+
 type assignmentNode struct {
 	name  string
 	value interface{}
@@ -122,5 +159,13 @@ func (n *assignmentNode) String() string {
 	return fmt.Sprintf("{assign: name=%s, val=%v}", n.name, n.value)
 }
 
+func (n *assignmentNode) pretty(w io.Writer, prefix string) error {
+	fmt.Fprintf(w, "%sassign{\n", prefix)
+	fmt.Fprintf(w, "%s%sname: %s\n", prefix, indent, n.name)
+	fmt.Fprintf(w, "%s%svalue: %v\n", prefix, indent, n.value)
+	fmt.Fprintf(w, "%s}\n", prefix)
+	return nil
+}
+
 type list []interface{}
 type object map[string]interface{}