title: unzip command ends successfully without unzipping file
body: <p>There are double compressed files with extension xxx.zip.gz</p>
  
  <p>On gunzip - xxx.zip file is created of size 0.25 GB<br>
  On unzip after gunzip - xxx.zip file extension does not change</p>
  
  <p>Output of unzip : </p>
  
  <pre><code>Archive:  xxx.zip
    inflating: xxx.txt
  </code></pre>
  
  <p>also </p>
  
  <pre><code>echo $? shows 0 
  </code></pre>
  
  <p>so, even though zip command completed successfully and still the file remains with zip extension , any help ?</p>
  
  <p>OS - SunOS 5.10 </p>