groups.diff

diff --git a/core/src/main/java/org/jruby/RubyProcess.java b/core/src/main/java/org/jruby/RubyProcess.java
index 91006dd..e7622db 100644
--- a/core/src/main/java/org/jruby/RubyProcess.java
+++ b/core/src/main/java/org/jruby/RubyProcess.java
@@ -573,7 +573,16 @@ public class RubyProcess {

     @JRubyMethod(name = "groups", module = true, visibility = PRIVATE)
     public static IRubyObject groups(IRubyObject recv) {
-        throw recv.getRuntime().newNotImplementedError("Process#groups not yet implemented");
+        if(Platform.IS_WINDOWS) {
+            throw recv.getRuntime().newNotImplementedError("groups() function is unimplemented on this machine");
+        } else {
+            long[] groups = (new com.sun.security.auth.module.UnixSystem()).getGroups();
+            RubyArray ary = RubyArray.newArray(recv.getRuntime(), groups.length);
+            for(int i = 0; i < groups.length; i++) {
+                ary.push(RubyFixnum.newFixnum(recv.getRuntime(), groups[i]));
+            }
+            return ary;
+        }
     }

     @JRubyMethod(name = "setrlimit", rest = true, module = true, visibility = PRIVATE)