title: bash empty string/command
body: <p>I found some strange thing in bash and I can't understand how it works.</p>
  
  <pre><code>[test ~]$ a=""
  [test ~]$ $a &amp;&amp; echo 1
  1
  
  [test ~]$ $a
  [test ~]$ echo $?
  0
  </code></pre>
  
  <p>Why does $a (which is empty) return 0? Is it somehow transformed to empty command?
  If I add quotes or write empty string before <code>&amp;&amp;</code>, it will return error. While empty command returns 0.</p>
  
  <pre><code>[test ~]$ "$a" &amp;&amp; echo 1
  -bash: : command not found
  
  [test ~]$ "" &amp;&amp; echo 1
  -bash: : command not found
  
  [test ~]$ `` &amp;&amp; echo 1
  1
  </code></pre>
  
  <p>So, what is happening when I type $a?</p>