title: How to write shell script to create zip file for the files that had same string in file name
body: <p>How to write simple shell script to create zip file.<br>
  I want to create zip file by collecting files with same string pattern in their file names from a folder.  </p>
  
  <p>For example, there may be many files under a folder.  </p>
  
  <ul>
  <li>xxxxx_20140502_xxx.txt</li>
  <li>xxxxx_20140502_xxx.txt</li>
  <li>xxxxx_20140503_xxx.txt</li>
  <li>xxxxx_20140503_xxx.txt</li>
  <li>xxxxx_20140504_xxx.txt</li>
  <li>xxxxx_20140504_xxx.txt  </li>
  </ul>
  
  <p>After running the shell script, the result must be following three zip files.  </p>
  
  <ul>
  <li>20140502.zip  </li>
  <li>20140503.zip  </li>
  <li>20140504.zip</li>
  </ul>
  
  <p>Please give me right direction to create simple shell script to output the result as above.</p>