Detect MIME type of uploaded file in Ruby

ruby-on-rails ruby file-upload swfupload
Vincent picture Vincent · Jan 5, 2011 · Viewed 41.1k times · Source

Is there a bullet proof way to detect MIME type of uploaded file in Ruby or Ruby on Rails? I'm uploading JPEGs and PNGs using SWFupload and content_type is always "application/octet-stream"

Answer

Wayne Conrad picture Wayne Conrad · Jan 5, 2011

The ruby-filemagic gem will do it:

require 'filemagic'

puts FileMagic.new(FileMagic::MAGIC_MIME).file(__FILE__)
# => text/x-ruby; charset=us-ascii

This gem does not look at the file extension at all. It reads a bit of the file contents and uses that to guess the file's type.

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