title: Count all occurrences of a string in lots of files with grep
body: <p>I have a bunch of log files. I need to find out how many times a string occurs in all files.</p>
  
  <pre><code>grep -c string *
  </code></pre>
  
  <p>returns</p>
  
  <pre><code>...
  file1:1
  file2:0
  file3:0
  ...
  </code></pre>
  
  <p>Using a pipe I was able to get only files that have one or more occurrences:</p>
  
  <pre><code>grep -c string * | grep -v :0
  
  ...
  file4:5
  file5:1
  file6:2
  ...
  </code></pre>
  
  <p>How can I get only the combined count? (If it returns <code>file4:5, file5:1, file6:2</code>, I want to get back 8.)</p>