title: How to create an empty file by elisp?
body: <p>I set an explicit file to customization created via the UI. It's named <code>custom.el</code>. Currently, I use the followed snippets to create this file if not exist.</p>
  
  <pre><code>(defconst custom-file (expand-file-name "custom.el" user-emacs-directory))
  (unless (file-exists-p custom-file)
    (shell-command (concat "touch " custom-file)))
  </code></pre>
  
  <p>There is an ugly shell-command <code>touch</code> in, any other elisp functions can do this?</p>