diff --git a/main.go b/main.go
index ab47e80..66a958e 100644
--- a/main.go
+++ b/main.go
@@ -12,6 +12,19 @@ import (
 	"github.com/hymkor/go-windows1x-virtualterminal"
 )
 
+func loop(ptmx pty.Pty) error {
+	watcher := NewWatcher(ptmx)
+
+	sh := ptmx.Command("cmd.exe")
+	if err := sh.Start(); err != nil {
+		return err
+	}
+
+	_ = watcher.Expect("100")
+	io.WriteString(ptmx, "exit\r")
+	return sh.Wait()
+}
+
 func mains() error {
 	disableStdout, err := virtualterminal.EnableStdout()
 	if err != nil {
@@ -43,16 +56,7 @@ func mains() error {
 	}
 	defer term.Restore(int(os.Stdin.Fd()), oldState)
 
-	go io.Copy(ptmx, os.Stdin)
-	go io.Copy(os.Stdout, ptmx)
-
-	// sh := ptmx.Command(fields[0], fields[1:]...)
-	// if err := sh.Start(); err != nil {
-	//	return err
-	// }
-	// return sh.Wait()
-
-	return nil
+	return loop(ptmx)
 }
 
 func main() {
diff --git a/watcher.go b/watcher.go
new file mode 100644
index 0000000..6fa7103
--- /dev/null
+++ b/watcher.go
@@ -0,0 +1,59 @@
+package main
+
+import (
+	"io"
+	"os"
+	"strings"
+
+	"github.com/aymanbagabas/go-pty"
+)
+
+type Watcher struct {
+	ch       <-chan string
+	lastline string
+}
+
+func NewWatcher(ptmx pty.Pty) *Watcher {
+	pipeline := make(chan string, 1024)
+	go io.Copy(ptmx, os.Stdin)
+	go func() {
+		for {
+			var buffer [1024]byte
+			n, err := ptmx.Read(buffer[:])
+			if err != nil {
+				close(pipeline)
+				return
+			}
+			// If the code below spends a lot of time,
+			// It hangs up to io.Copy(ptmx, os.Stdin)
+			// The reason is unknown.
+			os.Stdout.Write(buffer[:n])
+			pipeline <- string(buffer[:n])
+		}
+	}()
+
+	return &Watcher{ch: pipeline}
+}
+
+func (W *Watcher) updateLastLine() {
+	newLinePos := strings.LastIndexByte(W.lastline, '\n')
+	if newLinePos >= 0 {
+		W.lastline = W.lastline[newLinePos+1:]
+	} else {
+		W.lastline = ""
+	}
+}
+
+func (W *Watcher) Expect(words ...string) int {
+	for frag := range W.ch {
+		W.lastline += frag
+		for i, word := range words {
+			if strings.Contains(W.lastline, word) {
+				W.updateLastLine()
+				return i
+			}
+		}
+		W.updateLastLine()
+	}
+	return -1
+}