doc"><p>Execute the command. Do a left fold over the lines of output from the processe's stdout. Wraps the accumulated output in the output type.</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-fold_err"><a href="#val-fold_err" class="anchor"></a><code><span><span class="keyword">val</span> fold_err : 
  <span><span><span>(<span class="type-var">'stdin</span>, <span class="type-var">'stdout</span>, <a href="../Core/index.html#type-stderr">Core.stderr</a>)</span> <a href="../Co