Magic

Ruby FFI wrapper to the “magic” library, that determines content type and encoding of files and strings. The library does three types of tests: filesystem tests, magic number tests, and language tests. The first test that succeeds causes the file type to be returned.

Installation

gem install magic --source http://gemcutter.org

Linux

Install magic library using your package manager, e.g.:

sudo apt-get install file

Mac OS

If you don’t have libmagic.1.dylib file in your system, you need to install it via port command:

sudo port install file

Sometimes you also need to set your DYLD_FALLBACK_LIBRARY_PATH environment variable to the directory where the libmagic.1.dylib is:

export DYLD_FALLBACK_LIBRARY_PATH=/opt/local/lib

Windows

Install File for Windows. You also need to set your PATH environment variable to the directory where the magic1.dll is:

set PATH=C:\Program Files\GnuWin32\bin;%PATH%

It might be also required to add database option explicitly:

Magic.guess_string_mime(
  "Magic® File™",
  :database => 'C:\Program Files\GnuWin32\share\misc\magic.mgc'
)

Usage

require "magic"

Magic.guess_file_mime("public/images/rails.png")
# => "image/png; charset=binary"

Magic.guess_file_mime_encoding("public/images/rails.png")
# => "binary"

Magic.guess_file_mime_type("public/images/rails.png")
# => "image/png"

Magic.guess_string_mime("Magic® File™")
# => "text/plain; charset=utf-8"

Magic.guess_string_mime_encoding("Magic® File™")
# => "utf-8"

Magic.guess_string_mime_type("Magic® File™")
# => "text/plain"

Magic.guess(:mime_type, :database => "/etc/magic") { |db| db.buffer("Magic® File™") }
# => "text/plain"

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Jakub Kuźma