lines</code> to the process stdin, which will be separated with a newline character by default. Use the optional <code>sep</code> parameter to change this to another string. While all that is happening, fold over lines from stdout. This function uses asynchronous I/O internally, so the optional <code>sleep</code> parameter is provided as a means to pause briefly if output is expected to be slow to avoid pegging the CPU with a loop that does nothing.</p></div></div><div class="odoc-spec"><div class="spec val