Simple Ruby Example

$Header: /cvs/projects/SWIG/Examples/ruby/simple/index.html,v 1.1 2000/07/05 18:58:47 ttn Exp $

This example illustrates how you can hook Ruby to a very simple C program containing a function and a global variable.

The C Code

Suppose you have the following C code:
/* File : example.c */

/* A global variable */
double Foo = 3.0;

/* Compute the greatest common divisor of positive integers */
int gcd(int x, int y) {
  int g;
  g = y;
  while (x > 0) {
    g = x;
    x = y % x;
    y = g;
  return g;

The SWIG interface

Here is a simple SWIG interface file:
/* File: example.i */
%module example

extern int gcd(int x, int y);
extern double Foo;


  1. swig -ruby example.i

  2. Compile example_wrap.c and example.c to create the extension

Using the extension

Click here to see a script that calls our C functions from Ruby.

Key points

  • Use the require function to load your extension library from Ruby. For example:
    require 'example'
  • C functions work just like Ruby functions. For example:
    g = Example.gcd(42,105)
  • C global variables are accessed through module method. For example:
    a = Example.Foo