title: Changing multiple filenames that with a number already in the file name in Unix
body: <p>so I want to batch change name files with these type of names (about 400 files):</p>
  
  <pre><code>L1_Mviridis.fasta
  L2_Mviridis.fasta
  L3_Mviridis.fasta...
  </code></pre>
  
  <p>to this:</p>
  
  <pre><code>L1_1_Mviridis.fasta
  L2_2_Mviridis.fasta
  L3_3_Mviridis.fasta
  </code></pre>
  
  <p>I do not have the function "rename" available either.
  Thanks for any suggestion!</p>