title: korn shell error [: missing `]'
body: <p>I am learning Korn shell which is based on Bourne shell. Below is my really simple code. </p>
  
  <pre><code>read ab
  if [ $ab = "a" || $ab = "A" ] ; then
      echo hi
  fi
  </code></pre>
  
  <p>For some reason <code>||</code> operator is giving me the error:</p>
  
  <pre><code>[: missing `]'
  a: command not found
  </code></pre>