ExifTool – Read, Write and Edit Meta Information
Practical use, before uploading files publicly, I often want to remove some important metadata.  exiftool makes it really easy:<p><pre><code>    # List all metadata of a file (exif)
    exiftool -s screenshot.png

    # Remove GPS coords in a file
    exiftool -gps:all= filename.jpg

    # Clear out all metadata
    exiftool -all= filename.jpg somesong.mp3</code></pre>