title: Redirecting ffmpeg result into another file
body: <p>I'm trying to get the size of an input video using ffmpeg, below is the code that I use, what I'm trying to do is to first store the result into a txt file and then do some parsing to get the size of the video:</p>
  
  <pre><code>$ ffmpeg -i TheNorth.mp4 
  </code></pre>
  
  <p>The terminal says "At least one output file must be specified"
  Then I tried this:</p>
  
  <pre><code>$ ffmpeg -i TheNorth.mp4 result.txt
  </code></pre>
  
  <p>The terminal says "Unable to find a suitable output format for 'size.txt'"</p>
  
  <p>So how could I get the result and save it to the specified file?</p>