When the author says that threads are out, he means that they are a difficult way to write concurrent code. Pre-fork is just one (classic) example of how to wri

When the author says that threads are out, he means that they are a difficult way to write concurrent code. Pre-fork is just one (classic) example of how to write concurrent code without shared state. Instead of threads communicating via shared state, you have processes communicating over pipes or sockets. That said, you're right about portability. The attraction of Ruby's Thread is that it works identically across operating systems.