How to run JRuby from a Ruby script on a Windows PC

I'm doing some crazy things at the moment, basically calling JRuby from a Ruby script on a Windows 2000 system. I'm doing this because there are a bunch of JRuby scripts that I want to run sequentially, and I also want to check for errors after each run, so what better way to invoke them and look for resulting errors than with Ruby, especially on a Windows system? :)

Unfortunately this creates a slight problem, at least on the Windows 2000 PC I'm currently using. I don't understand the error output yet, but as you can see from the following irb output I can't invoke JRuby from Ruby like this on the Windows system:

irb(main):008:0> `jruby foo2.rb`
Errno::ENOEXEC: Exec format error - jruby foo2.rb
        from (irb):8:in ``'
        from (irb):8

As you can see that leads to the dreaded "Errno::ENOEXEC: Exec format error" error message from hell.

Instead, I just learned that I have to invoke JRuby using the full name of the jruby command file, which is really jruby.bat. With this slight change I call my jruby script like this:

irb(main):009:0> `jruby.bat foo2.rb`
=> "foo2\n"

And yes, that's all foo2.rb does, is print the string "foo2", so this works. So if you see the dreaded "Errno::ENOEXEC: Exec format error" error message you may have to be more explicit in how you refer to the system program you're trying to run.

Speaking of the word "system", I had a similar problem trying to run jruby by invoking ruby's system method. Again using irb to demonstrate the problem, calling jruby as shown below causes the system method to return false:

irb(main):001:0> system("jruby foo2.rb")
=> false

But adding the ".bat" extension to the jruby file works, as shown here:

irb(main):002:0> system("jruby.bat foo2.rb")
=> true

Notice that the system method returns true when the system call succeeds, and false when it does not succeed.