[jruby-user] rescue error?

I'm creating a gem and have been testing it on MRI, JRuby, and Rubinius.

I have a section of code which checks to see if the Linux/Unix cli
command 'factor' exists on the platform the gem is installed on.  If it
exists I wrap some ruby around it and use it. If 'factor' doesn't exists
then I create pure ruby versions of the same methods.

To do this, I invoke the 'factor' command. If it exists I create the
methods I want using it. If it doesn't exists, an error is thrown which
I use a 'rescue' section to resolve to create pure ruby versions.

Below is code to show the use of 'rescue':

If the system is a RUBY_PlATFORM which has 'factor' (Linux/Unix)

then the line:  `factor 10`.split(' ') != []

will be performed with no error, and the code will proceed in sequence.

If the system doesn't have 'factor' a sys error is thrown and 'rescued'.

I test this on my Linux system by running it with the correct spelling
of 'factor', which outputs 'OS versions'.

I then create a false cli command 'factorz' and run the code, and for
MRI (2.2.1 and 2.1.2) and Rubinius (2.5.2) a sys error is thrown and the
'rescue' section is invoked correctly and 'Ruby versions' is shown.

However, on JRuby 1.7.19, in both cases I get 'OS versions'.

So apparently, JRuby isn't throwing a system error when it attempts to
run a non-existent cli command, which doesn't conform to MRI (2.2; 2.1).

1)Is this a bug in JRuby, or is this allowed behavior?

2)Is there a 'better' more universally transferable way to do this?


  begin

    # Test Operating Systems if *nix cli command 'factor' exists

    `factor 10`.split(' ') != []
    #`factorz 10'.split(' ') != []  # mimic nonexistent on system

    # code would go here to create 'factor' coded methods

    puts 'OS versions'

  rescue # if 'factor' not in system use pure ruby versions

    # code would go here to create pure ruby coded methods

    puts 'Ruby versions'

  end

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