src/Pure/System/isabelle_process.scala

       while (!finished) {
         try {
           //{{{
           receive {
             case Input_Text(text) =>
-              // FIXME echo input?!
               writer.write(text)
               writer.flush
             case Close =>
               writer.close
               finished = true

     command_input ! Input_Chunks(Standard_System.string_bytes(name) :: args.toList)
 
   def input(name: String, args: String*): Unit =
     input_bytes(name, args.map(Standard_System.string_bytes): _*)
 
-  def close(): Unit = command_input ! Close
+  def close(): Unit = { standard_input ! Close; command_input ! Close }
 }