diff --git a/contrib/20.repl/CMakeLists.txt b/contrib/20.repl/CMakeLists.txt
index c0a24065..91bec1b8 100644
--- a/contrib/20.repl/CMakeLists.txt
+++ b/contrib/20.repl/CMakeLists.txt
@@ -1 +1,3 @@
 list(APPEND PICLIB_CONTRIB_LIBS ${PROJECT_SOURCE_DIR}/contrib/20.repl/repl.scm)
+list(APPEND PICRIN_CONTRIB_SOURCES ${PROJECT_SOURCE_DIR}/contrib/20.repl/repl.c)
+list(APPEND PICRIN_CONTRIB_INITS repl)
\ No newline at end of file
diff --git a/contrib/20.repl/repl.c b/contrib/20.repl/repl.c
new file mode 100644
index 00000000..bdc54e65
--- /dev/null
+++ b/contrib/20.repl/repl.c
@@ -0,0 +1,25 @@
+#include "picrin.h"
+#include "picrin/data.h"
+#include "picrin/pair.h"
+#include "picrin/string.h"
+#include "picrin/cont.h"
+
+#include <unistd.h>
+
+
+static pic_value
+pic_repl_tty_p(pic_state *pic)
+{
+
+  pic_get_args(pic, "");
+
+  return pic_bool_value((isatty(STDIN_FILENO)));
+}
+
+void
+pic_init_repl(pic_state *pic)
+{
+  pic_deflibrary (pic, "(picrin repl)") {
+    pic_defun(pic, "tty?", pic_repl_tty_p);
+  }
+}
diff --git a/contrib/20.repl/repl.scm b/contrib/20.repl/repl.scm
index 2b9d4812..bed94d0e 100644
--- a/contrib/20.repl/repl.scm
+++ b/contrib/20.repl/repl.scm
@@ -11,7 +11,7 @@
    (else
     (begin
       (define (readline str)
-        (display str)
+        (if (tty?) (display str))
         (read-line))
       (define (add-history str)
         #f))))