Determine file type in Ruby

Question

How does one reliably determine a file\'s type? File extension analysis is not acceptable. There must be a rubyesque tool similar to the UNIX file(1) comman

Answer 1

For those who came here by the search engine, a modern approach to find the MimeType in pure ruby is to use the mimemagic gem.

require 'mimemagic'

MimeMagic.by_magic(File.open('tux.jpg')).type # => "image/jpeg" 

If you feel that is safe to use only the file extension, then you can use the mime-types gem:

MIME::Types.type_for('tux.jpg') => [#<MIME::Type: image/jpeg>]

Answer 2

I found shelling out to be the most reliable. For compatibility on both Mac OS X and Ubuntu Linux I used:

file --mime -b myvideo.mp4
video/mp4; charset=binary

Ubuntu also prints video codec information if it can which is pretty cool:

file -b myvideo.mp4
ISO Media, MPEG v4 system, version 2

Answer 3

I recently found mimetype-fu.

It seems to be the easiest reliable solution to get a file's MIME type.

The only caveat is that on a Windows machine it only uses the file extension, whereas on *Nix based systems it works great.

Answer 4

If you're on a Unix machine try this:

mimetype = `file -Ib #{path}`.gsub(/\n/,"")

I'm not aware of any pure Ruby solutions that work as reliably as 'file'.

Edited to add: depending what OS you are running you may need to use 'i' instead of 'I' to get file to return a mime-type.

Answer 5

The best I found so far:

http://bogomips.org/mahoro.git/

Answer 6

You could give a go with MIME::Types for Ruby.

This library allows for the identification of a file’s likely MIME content type. The identification of MIME content type is based on a file’s filename extensions.