Shell exclamation mark command
<p>What does this command do?</p>

<pre><code>!g++
</code></pre>

<p>For the history command:</p>

<pre><code>!12
</code></pre>

<p>It runs command #12 of the history, but what about <code>g++</code>, or another:</p>

<pre><code>!cat filename
</code></pre>