title: Find Unique Characters in a File
body: <p>I have a file with 450,000+ rows of entries. Each entry is about 7 characters in length. What I want to know is the unique characters of this file.</p>
  
  <p>For instance, if my file were the following;</p>
  
  <blockquote>
  <pre><code>Entry
  -----
  Yabba
  Dabba
  Doo
  </code></pre>
  </blockquote>
  
  <p>Then the result would be</p>
  
  <blockquote>
    <p>Unique characters: {abdoy}</p>
  </blockquote>
  
  <p>Notice I don't care about case and don't need to order the results. Something tells me this is very easy for the Linux folks to solve.</p>
  
  <h2>Update</h2>
  
  <p>I'm looking for a very fast solution. I really don't want to have to create code to loop over each entry, loop through each character...and so on. I'm looking for a nice script solution.</p>
  
  <h2>Update 2</h2>
  
  <p>By <strong>Fast</strong>, I mean fast to implement...not necessarily fast to run.</p>