title: [ :Unexpected operator in shell programming
body: <p>My code:</p>
  
  <pre><code>    #!/bin/sh
      #filename:choose.sh
      read choose
      [ "$choose" == "y" -o "$choose" == "Y" ] &amp;&amp; echo "Yes" &amp;&amp; exit 0
      [ "$choose" == "n" -o "$choose" == "N" ] &amp;&amp; echo "No"  &amp;&amp; exit 0
      echo "Wrong Input" &amp;&amp; exit 0
  </code></pre>
  
  <p>But when I execute </p>
  
  <pre><code>    sh ./choose.sh
  </code></pre>
  
  <p>terminal prompt me that</p>
  
  <pre><code>   [: 4: n: :Unexpected operator
     [: 5: n: :Unexpected operator
  </code></pre>
  
  <p>Is there any mistake in my bash script?
  Thanks!</p>