title: Emacs opening and saving encoding
body: <p>I have a Perl source file in utf-8 encoding, LF ending. It contains English and Chinese characters. The questions are:</p>
  
  <p>1.When I open file, the encoding is windows-1251-unix. I have to run these commands:</p>
  
  <pre><code>Alt-x revert-buffer-with-coding-system
  &gt; Coding system for visited file (default nil):
  utf-8-auto-unix
  &gt; Revert buffer from file file_name.pl?
  y
  </code></pre>
  
  <p>How to automatically open it in utf-8-auto-unix?</p>
  
  <p>2.When I edit the file and try to save it, Emacs gives me a question:</p>
  
  <pre><code>&gt; Select coding system (default raw-text):
  utf-8-auto-unix
  </code></pre>
  
  <p>How to automatically save the file in utf-8-auto-unix? And get rid of the question.</p>