Re: [jruby-user] rescue error?

If you don’t want to do the test on Windows, then I believe you can rely on the existence of the 'which' command.  In that case:

system(‘which factor’)

…will return true if it’s available, and false if it’s not.  This is from my Mac, which does not have factor:

2.1.2 :003 > system('which ls')
/bin/ls
 => true
2.1.2 :004 > system('which factor')
 => false

Of course, this does not guarantee that the ‘factor’ executable found is the one you want.

You could do something like this:

def factor_available?
  RUBY_PLATFORM != ‘mswin’ && system(‘which factor’)
end

You might need to tweak the platform test; there are other values of RUBY_PLATFORM that are Windows, but some of them (e.g. ‘cygwin’, and maybe ‘mingw’?) simulate Unix so may not need to be excluded.

- Keith

> On Mar 21, 2015, at 12:45 AM, Jabari Z. <[email protected]> wrote:
> 
> 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
> 
> -- 
> Posted via http://www.ruby-forum.com/.
> 
> ---------------------------------------------------------------------
> To unsubscribe from this list, please visit:
> 
>    http://xircles.codehaus.org/manage_email
> 
> 


---------------------------------------------------------------------
To unsubscribe from this list, please visit:

    http://xircles.codehaus.org/manage_email