title: bash [[ [a] == [a] ]] not true? square bracket affect compare result
body: <p>Anyone know why this happens? Is this a bug of bash?</p>
  
  <pre><code>x='mnt:[4026532411]'
  
  [[ $x == $x ]] &amp;&amp; echo OK
  </code></pre>
  
  <p>I am expecting result <code>OK</code>, but it did not.</p>
  
  <p>Of course, this works</p>
  
  <pre><code>[[ "$x" == "$x" ]] &amp;&amp; echo OK
  </code></pre>
  
  <p>But as I know, bash [[ ]] have a merit that no need to quote var when compare.</p>
  
  <pre><code>x='a b'
  [[ $x == $x ]] &amp;&amp; echo OK
  </code></pre>
  
  <p>works.</p>
  
  <p>Ironical things is</p>
  
  <pre><code>x='mnt:[4026532411]'
  
  [[ $x != $x ]] &amp;&amp; echo Oh my god
  </code></pre>
  
  <p>result is Oh my god</p>