--- a/src/ut/lu/lu.go	Sat Jun 23 09:38:15 2018 +0900
+++ b/src/ut/lu/lu.go	Sat Jun 23 12:27:35 2018 +0900
@@ -416,3 +416,22 @@
     }
 }
 
+/* tee: done. */
+func Tee( file string ) {
+    if _, err := os.Stat( file ); !os.IsNotExist( err ) {
+        if err := os.Remove( file ); err != nil {
+            log.Fatal( err )
+        }
+    }
+    f, err := os.OpenFile( file, os.O_RDWR|os.O_CREATE, 0644 )
+    if err != nil {
+        log.Fatal( err )
+    }
+    defer f.Close()
+
+    w := io.MultiWriter( f, os.Stdout )
+    if _, err := io.Copy( w, os.Stdin ); err != nil {
+        log.Fatal( err )
+    }
+}
+