title: Append to file names in folder
body: <p>How to append filenames in a folder </p>
  
  <pre><code>Filenames: 
  abc.wav
  wjejrt.wav
  13567tin.wav
  
  Desired Output
  abc_ENG.wav
  wjejrt_ENG.wav
  13567tin_ENG.wav
  </code></pre>
  
  <p>Tried this line code below but getting an error, maybe because I don't know the right use of file.rename function. Please help...</p>
  
  <pre><code>file.rename(list.files(pattern="*.wav"), paste0("_ENG"))
  </code></pre>