title: Windows 'start' command for files 'in use by another process'
body: <p>I'm making an application that downloads video files from the internet.</p>
  
  <p>The application needs to launch the system's default video player to play these files while they are being downloaded.</p>
  
  <p>I'm not interested in implementing a video (or network) stream to make this work. The videos are being downloaded in sequential order. I need to simulate the process of a user clicking on the video file from file explorer while it is downloading (which always works provided that enough bytes are saved).</p>
  
  <p>To achieve this I spawn a child process that runs</p>
  
  <pre><code>start filepath/filename.avi
  </code></pre>
  
  <p>but it fails saying the file is in use by another process.</p>
  
  <p>This command also fails if I type it in the cmd while the file is downloading.</p>
  
  <p>However, if I double click the file it will start to play normally in the system's default video player.</p>
  
  <p>What command can I use to make the file open in the system's default video player while it is being downloaded (used by another process)?</p>
  
  <p>Thanks.</p>
  
  <p><strong><em>Note</strong>: files may be of any type, not only .avi like in the example</em></p>