Nested coroutines

So I need to run a coroutine that endlessly calls another coroutine like so:

 public IEnumerator terminal_command(string[] args)
 {
     terminal.println("running terminal", Terminal.success_style);
     // Loop forever to wait for inputs
     while (!terminal.window.active)
     {
         string input_string = null;
         //terminal.println(">", Terminal.warning_style);
         yield return StartCoroutine(terminal.getline((x) => input_string = x));
         //terminal.println("hello " + input_string, Terminal.success_style);
         terminal.println("meme", Terminal.warning_style);
     }
     yield return null;
 }

 public IEnumerator getline(System.Action<string> var)
     {
         enable_command_parsing(false);
         while (!submitted)
         {
             yield return null;
         }
         string str = "";
         foreach (TChar tc in line_buffer.get_buffer()[(int)cursor_pos.y - 1].chars)
         {
             str += tc.c;
         }
         var(str);
         enable_command_parsing(true);
     }

esentially the getline waits for the user to press enter, then returns. However, in 'terminal_command', it calls terminal.getline once, and then just exits, when I want it to loop until the window is not active