Khushhall Chandra Mahajan खुशहाल चंद्र महाजन bio photo

Khushhall Chandra Mahajan खुशहाल चंद्र महाजन

Software Engineer
Facebook Inc.
Menlo Park, USA

Email Twitter LinkedIn Github


Ruby-FFI Build Status Build status Windows


Ruby-FFI is a gem for programmatically loading dynamically-linked native libraries, binding functions within them, and calling those functions from Ruby code. Moreover, a Ruby-FFI extension works without changes on CRuby (MRI), JRuby, Rubinius and TruffleRuby. Discover why you should write your next extension using Ruby-FFI.


  • Intuitive DSL
  • Supports all C native types
  • C structs (also nested), enums and global variables
  • Callbacks from C to Ruby
  • Automatic garbage collection of native memory


require 'ffi'

module MyLib
  extend FFI::Library
  ffi_lib 'c'
  attach_function :puts, [ :string ], :int

MyLib.puts 'Hello, World using libc!'

For less minimalistic and more examples you may look at:

  • the samples/ folder
  • the examples on the wiki
  • the projects using FFI listed on the wiki:


When installing the gem on CRuby (MRI) or Rubinius, you will need:

  • A C compiler (e.g., Xcode on macOS, gcc or clang on everything else)
  • The libffi library and development headers - this is commonly in the libffi-dev or libffi-devel packages

On Linux systems running with PaX (Gentoo, Alpine, etc.), FFI may trigger mprotect errors. You may need to disable mprotect for ruby (paxctl -m [/path/to/ruby]) for the time being until a solution is found.

On FreeBSD systems pkgconf must be installed for the gem to be able to compile using clang. Install either via packages pkg install pkgconf or from ports via devel/pkgconf.

On JRuby and TruffleRuby, there are no requirements to install the FFI gem, and require 'ffi' works even without installing the gem (i.e., the gem is preinstalled on these implementations).


From rubygems:

[sudo] gem install ffi

or from the git repository on github:

git clone git://
git submodule update --init --recursive
cd ffi
rake install


The ffi library is covered by the BSD license, also see the LICENSE file. The specs are covered by the same license as ruby/spec, the MIT license.


The following people have submitted code, bug reports, or otherwise contributed to the success of this project: