title: Awk: gsub("\\\\", "\\\\") yields suprising results
body: <p>Consider the following input:</p>
  <pre><code>$ cat a
  d:\
  
  $ cat a.awk
  { sub(&quot;\\&quot;, &quot;\\\\&quot;); print $0 }
  
  $ cat a_double.awk
  { sub(&quot;\\\\&quot;, &quot;\\\\&quot;); print $0 }
  </code></pre>
  <p>Now running <code>cat a | awk -f a.awk</code> gives</p>
  <pre><code>d:\
  </code></pre>
  <p>and running <code>cat a | awk -f a_double.awk</code> gives</p>
  <pre><code>d:\\
  </code></pre>
  <p>and I expect exactly the other way around. How should I interpret this?</p>
  <pre><code>$ awk -V
  GNU Awk 4.1.4, API: 1.1 (GNU MPFR 4.0.1, GNU MP 6.1.2)
  </code></pre>