title: What does “1>&2” mean in bash?
body: <p>What does <code>1&gt;&amp;2</code> mean in a bash script?</p>
  <p>For instance, what does the following line from a bash script do?</p>
  <pre><code>echo &quot;$1 is not a directory!&quot; 1&gt;&amp;2
  </code></pre>
  <p>I use MacOS X. My bash script is:</p>
  <pre><code>if [ ! -d $1 ]; then
      echo &quot;$1 is not a directory&quot; 1&gt;&amp;2
      exit 1
  fi
  </code></pre>