title: Replace single quotes to double and vice versa in file by single command line
body: <p>Are there ways to do it more clean/simple than this:</p>
  
  <pre><code>$ tr '"' '?' &lt; f.txt &gt; f1.txt &amp;&amp; tr "'" '"' &lt; f1.txt &gt; f.txt \
      &amp;&amp; tr '?' "'" &lt; f.txt &gt; f1.txt &amp;&amp; rm f.txt &amp;&amp; mv f1.txt f.txt 
  </code></pre>