title: What does " 2>&1 " mean?
body: <p>To combine <code>stderr</code> and <code>stdout</code> into the <code>stdout</code> stream, we append this to a command:</p>
  <pre><code>2&gt;&amp;1
  </code></pre>
  <p>e.g. to see the first few errors from compiling <code>g++ main.cpp</code>:</p>
  <pre><code>g++ main.cpp 2&gt;&amp;1 | head
  </code></pre>
  <p>What does <code>2&gt;&amp;1</code> mean, in detail?</p>