 <p>You have not loaded library <code>comint</code>. You need to do that before Emacs can know about <code>comint-check-proc</code>.</p> <p>Add a <code>(require 'comint)</code>, either in your init file or near the beginning of <code>run-plink</code> - somewhere before it tries to use <code>comint-check-proc</code>.</p>