How to correctly disconnect from the kernel?

Question

I'm connecting to and disconnecting from the kernel but I'm doing something wrong. I crash the text formatting in the terminal and got some warnings. There are some instructions to connecting to the kernel, but I almost didn't find anything about the disconnecting from the kernel. This question is related to connection to the remote machine and particularly to my this answer.

I'm doing the following (based on this instructions):

1. Open terminal and run math

   Mathematica 9.0 for Linux x86 (64-bit)
   Copyright 1988-2013 Wolfram Research, Inc.
   In[1]:= y=x^2
   
            2
   Out[1]= x
   

   OK, it works fine.

2. Open regular Mathematica.

   Create a new kernel configuration (Evaluation menu -> Kernel Configuration Options...)

   Select Advanced Options.

   Arguments to MLOpen:

   -LinkName [email protected],[email protected] -LinkMode Listen -LinkProtocol TCPIP -LinkOptions MLDontInteract -LinkHost 127.0.0.1
   

   Shell command to launch kernel: leave empty (we will do it manually)

   Set the notebook's kernel to the one you just set up, and evaluate something (2+2).

3. In the terminal evaluate the following:

   link=LinkConnect["[email protected],[email protected]",LinkProtocol->"TCPIP"] 
   (* connect to front end link *)
   
   $ParentLink = link; (* set the front end link as parent link *)
   

4. Now in the notebook you see that 2+2=4 :)

   Disconnect from the kernel:

   links = {$ParentLink, MathLink`$ServiceLink, MathLink`$PreemptiveLink}; 
       $ParentLink = Null; LinkClose /@ links;
   

5. In the terminal evaluate y=x^2 one more time

   In[8]:= y=x^2
   
   Out[8]= RawBoxes[SuperscriptBox[x, 2]]
   

   It's not what you expect to see. Moreover, you can see that $FrontEnd isn`t empty

   In[9]:= $FrontEnd
   
   Out[9]= RawBoxes[InterpretationBox[PanelBox[TooltipBox[
          C FrontEndObject  C, InterpretationBox[StyleBox[FrontEndObject\
            [LinkObject["[email protected],[email protected]", 58, 1]], 
                   ShowStringCharacters -> True, NumberMarks -> True], 
          FrontEndObject[LinkObject["[email protected],[email protected]",\
            58, 1]], Editable -> True, AutoDelete -> True]], 
        FrameMargins -> {{4, 5}, {4, 4}}], -FrontEndObject-, 
       Editable -> False]]  
   

6. Evaluate 2+2 in the notebook and

   link=LinkConnect["[email protected],[email protected]",LinkProtocol->"TCPIP"] 
   $ParentLink = link;
   

   in the terminal one more time. The notebook is now reconnected to the kernel, but you can see warnings like

   SetDelayed::write: Tag UpdateDynamicObjects in UpdateDynamicObjects[] is Protected. >>
   SetDelayed::write: Tag UpdateDynamicObjectsSynchronous in UpdateDynamicObjectsSynchronous[] is Protected. >>
   

Except the bad formatting in the terminal and these warnings everything works fine.

The first I can temporary fix by

In[16]:= $Post=TextForm;

Out[16]//TextForm= Null

In[17]:= y=x^2
                    2
Out[17]//TextForm= x

But it produces annoying //TextForm.

The messages come from the reevaluation of $InstallationDirectory/SystemFiles/FrontEnd/TextResources/GetFEKernelInit.tr which contain the following lines

UpdateDynamicObjects[] := (
       FrontEnd`Private`changes = Internal`GetTrackChanges[];
       If[Length[FrontEnd`Private`changes] =!= 0,

       MathLink`CallFrontEnd[FrontEnd`UpdateDynamicObjectsSynchronous[
                            FrontEnd`Private`changes]]];
   )

UpdateDynamicObjectsSynchronous[] := 
   MathLink`CallFrontEnd[FrontEnd`UpdateDynamicObjectsSynchronous[
            Internal`GetTrackChanges[]]];

Do you have any experience with disconnecting from the kernel?

Answer 1

The formatting you're seeing on the command-line is caused as a result of settings the FE makes to the "stdout" stream. Internally, the FE calls this function:

FE`SetResultForm[FE`form_] :=
    SetOptions["stdout", FormatType -> FE`form];

with the argument for form being whatever the default output format should be. This setting doesn't get reset when the kernel disconnects from the FE, but it's easy enough for you to do call this directly:

SetOptions["stdout", FormatType->OutputForm]

That's your problem #1 solved.

I wasn't able to reproduce your second problem, but if the problem is just the warning, then surely you could shut the warning off. You can't bracket the FE's evaluation of the code in FEKernelInit.tr directly using Quiet, but you could issue an Off command in the terminal followed by an On command in the FE.