extconf.rb

require 'mkmf'

# http://www.ruby-lang.org/ja/old-man/html/mkmf.html
# http://brandish.xrea.jp/BlackCity/labo/labo_ruby_ext_2.html
# http://d.hatena.ne.jp/yarb/20090724/p1
dir_config('lxc')
if have_header('lxc/namespace.h') and have_library('lxc') and have_func("lxc_attach")
  $libs = append_library($libs, "lxc")
  create_makefile("lxc")
else
  raise "lxc_attach is not defined"
end

rb_lxc_attach.c

#include "ruby.h"
#include "lxc/namespace.h"

static VALUE lxc_lxc_attach(VALUE, VALUE);

void
Init_lxc(void){
  VALUE lxc;
  lxc = rb_define_class("Lxc", rb_cObject);
  rb_define_method(lxc, "attach", lxc_lxc_attach, 1);
}

static VALUE
lxc_lxc_attach(VALUE self, VALUE name) {

  char *lxc_name = StringValuePtr(name);
  pid_t pid;
  int   ret;

  pid = get_init_pid(lxc_name);
  if(pid == -1) {
    rb_raise(rb_eRuntimeError, "container '%s' is not running", lxc_name);
  }

  ret = lxc_attach(pid);
  if(ret == -1) {
    rb_raise(rb_eRuntimeError, "failed to lxc_attach (pid %d)", pid);
  }

  return self;
}

ruby1.8 extconf.rb --with-lxc-header=/usr/local/lxc/include/ --with-lxc-lib=/usr/local/lxc/lib/
make
ruby1.8 -r./lxc -e 'Lxc.new.attach("hogehoge"); system("hostname"); '