title: sed: how to replace CR and/or LF with "\r" "\n", so any file will be in one line
body: <p>I have files like</p>
  
  <blockquote>
    <p>aaa</p>
    
    <p>bbb</p>
    
    <p>ccc</p>
  </blockquote>
  
  <p>I need them to sed into <code>aaa\r\nbbb\r\nccc</code></p>
  
  <p>It should work either for unix and windows replacing them with <code>\r</code> or <code>\r\n</code> accordingly</p>
  
  <p>The problem is that <code>sed</code> adds <code>\n</code> at the end of line but keeps lines separated. How can I fix it?</p>