title: Error in the following process: unzip .pptx -> modify content -> rezip to .pptx
body: <p>I am trying to unzip a Microsoft Office file (.docx and .pptx), modify some content, and then rezip to a new .docx or .pptx file.</p>
  
  <p>I was successful in doing this with a .docx file:</p>
  
  <p>1) <code>$ unzip .../test.docx</code></p>
  
  <p>2) modify some content in the <code>document.xml</code> file</p>
  
  <p>3) <code>$ zip -r rezipped.docx *</code></p>
  
  <p>Using the above process I can then successfully open the new document (rezipped.docx) in Microsoft Word and see the changed content.</p>
  
  <p>I then tried the same process for .pptx but have not found success.</p>
  
  <p>1) <code>$ unzip .../test.pptx</code></p>
  
  <p>2) modify some content in the <code>slide1.xml</code> file<br>
  For example, a simple text change: <code>&lt;a:t&gt;Hello World&lt;/a:t&gt;</code> to <code>&lt;a:t&gt;Hi World&lt;/a:t&gt;</code></p>
  
  <p>3) <code>$ zip -r rezipped.pptx *</code></p>
  
  <p>When I try to open rezipped.pptx in Microsoft PowerPoint 2008 for Mac Version 12.0 I get the following error message: </p>
  
  <blockquote>
    <p>There was an error accessing Macintosh rezipped.pptx</p>
  </blockquote>
  
  <p>However, I can open the file without any issues in Keynote.</p>
  
  <p>I tried the same experiment but I only modified a file in the <code>docProps</code> folder (i.e. app.xml or core.xml) and I was able to rezip it and open it with no problem in Microsoft PowerPoint. So it is only if I edit a file in the <code>ppt</code> folder that I experience this issue.</p>
  
  <p><strong>What is causing this corruption when I edit the contents of slide1.xml and then rezip the files?</strong> Is there another file somewhere in the .pptx structure that is tracking content/modifications?</p>
  
  <p>I also tried resetting the modified date of the file after changing it to see if this had any effect but it did not: <code>touch -m -t 198001010000 slide1.xml</code></p>