title: batch rename to change only single character
body: <p>How to rename all the files in one directory to new name using the command mv. Directory have 1000s of files and requirement is to change the last character of each file name to some specific char. Example: files are</p>
  
  <pre><code>abc.txt
  asdf.txt
  zxc.txt
  ...
  ab_.txt
  asd.txt
  </code></pre>
  
  <p>it should change to</p>
  
  <pre><code>ab_.txt
  asd_.txt
  zx_.txt
  ...
  ab_.txt
  as_.txt
  </code></pre>