# Ruby-FFI https://github.com/ffi/ffi/wiki [](https://travis-ci.com/ffi/ffi) [](https://ci.appveyor.com/project/larskanis/ffi-aofqa/branch/master)
## Description
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](https://github.com/ffi/ffi/wiki/why-use-ffi).
## Features
* 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
## Synopsis
```ruby
require 'ffi'
module MyLib
extend FFI::Library
ffi_lib 'c'
attach_function :puts, [ :string ], :int
end
MyLib.puts 'Hello, World using libc!'
```
For less minimalistic and more examples you may look at:
* the `samples/` folder
* the examples on the [wiki](https://github.com/ffi/ffi/wiki)
* the projects using FFI listed on the wiki: https://github.com/ffi/ffi/wiki/projects-using-ffi
## Requirements
When installing the gem on CRuby (MRI), you will need:
* A C compiler (e.g., Xcode on macOS, `gcc` or `clang` on everything else)
Optionally (speeds up installation):
* The `libffi` library and development headers - this is commonly in the `libffi-dev` or `libffi-devel` packages
The ffi gem comes with a builtin libffi version, which is used, when the system libffi library is not available or too old.
Use of the system libffi can be enforced by:
```
gem install ffi -- --enable-system-libffi # to install the gem manually
bundle config build.ffi --enable-system-libffi # for bundle install
```
or prevented by `--disable-system-libffi`.
On Linux systems running with [PaX](https://en.wikipedia.org/wiki/PaX) (Gentoo, Alpine, etc.), FFI may trigger `mprotect` errors. You may need to disable [mprotect](https://en.wikibooks.org/wiki/Grsecurity/Appendix/Grsecurity_and_PaX_Configuration_Options#Restrict_mprotect.28.29) 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).
## Installation
From rubygems:
[sudo] gem install ffi
From a Gemfile using git or GitHub
gem 'ffi', github: 'ffi/ffi', submodules: true
or from the git repository on github:
git clone git://github.com/ffi/ffi.git
cd ffi
git submodule update --init --recursive
bundle install
rake install
### Install options:
* `--enable-system-libffi` : Force usage of system libffi
* `--disable-system-libffi` : Force usage of builtin libffi
* `--enable-libffi-alloc` : Force closure allocation by libffi
* `--disable-libffi-alloc` : Force closure allocation by builtin method
## License
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](https://github.com/ruby/spec), the MIT license.
## Credits
The following people have submitted code, bug reports, or otherwise contributed to the success of this project:
* Alban Peignier <alban.peignier@free.fr>
* Aman Gupta <aman@tmm1.net>
* Andrea Fazzi <andrea.fazzi@alcacoop.it>
* Andreas Niederl <rico32@gmx.net>
* Andrew Cholakian <andrew@andrewvc.com>
* Antonio Terceiro <terceiro@softwarelivre.org>
* Benoit Daloze <eregontp@gmail.com>
* Brian Candler <B.Candler@pobox.com>
* Brian D. Burns <burns180@gmail.com>
* Bryan Kearney <bkearney@redhat.com>
* Charlie Savage <cfis@zerista.com>
* Chikanaga Tomoyuki <nagachika00@gmail.com>
* Hongli Lai <hongli@phusion.nl>
* Ian MacLeod <ian@nevir.net>
* Jake Douglas <jake@shiftedlabs.com>
* Jean-Dominique Morani <jdmorani@mac.com>
* Jeremy Hinegardner <jeremy@hinegardner.org>
* Jesús García Sáez <blaxter@gmail.com>
* Joe Khoobyar <joe@ankhcraft.com>
* Jurij Smakov <jurij@wooyd.org>
* KISHIMOTO, Makoto <ksmakoto@dd.iij4u.or.jp>
* Kim Burgestrand <kim@burgestrand.se>
* Lars Kanis <kanis@comcard.de>
* Luc Heinrich <luc@honk-honk.com>
* Luis Lavena <luislavena@gmail.com>
* Matijs van Zuijlen <matijs@matijs.net>
* Matthew King <automatthew@gmail.com>
* Mike Dalessio <mike.dalessio@gmail.com>
* NARUSE, Yui <naruse@airemix.jp>
* Park Heesob <phasis@gmail.com>
* Shin Yee <shinyee@speedgocomputing.com>
* Stephen Bannasch <stephen.bannasch@gmail.com>
* Suraj N. Kurapati <sunaku@gmail.com>
* Sylvain Daubert <sylvain.daubert@laposte.net>
* Victor Costan
* beoran@gmail.com
* ctide <christide@christide.com>
* emboss <Martin.Bosslet@googlemail.com>
* hobophobe <unusualtears@gmail.com>
* meh <meh@paranoici.org>
* postmodern <postmodern.mod3@gmail.com>
* wycats@gmail.com <wycats@gmail.com>
* Wayne Meissner <wmeissner@gmail.com>
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