Mayabatch problem

Hi all,

Does anyone know how to use the cmd, currentCtx, in the Mayabatch. Here is my
mel scprit.

  string $s3dPaintCtx = `art3dPaintToolScript 4`;
  setToolTo $s3dPaintCtx;
  string $ sCurrentCtx = `currentCtx`;
  print $sCurrentCtx;  

On script editon,  it always print the string as same as $s3dPaintCtx, but the
scrpit prints nothing when I use mayabatch to execute  it. 

Does anyone can help me?

Thanks,