syntastic/syntax_checkers/ruby.vim

"============================================================================
"File:        ruby.vim
"Description: Syntax checking plugin for syntastic.vim
"Maintainer:  Martin Grenfell <martin.grenfell at gmail dot com>
"License:     This program is free software. It comes without any warranty,
"             to the extent permitted by applicable law. You can redistribute
"             it and/or modify it under the terms of the Do What The Fuck You
"             Want To Public License, Version 2, as published by Sam Hocevar.
"             See http://sam.zoy.org/wtfpl/COPYING for more details.
"
"============================================================================
if exists("loaded_ruby_syntax_checker")
    finish
endif
let loaded_ruby_syntax_checker = 1

"bail if the user doesnt have ruby installed
if !exists('g:ruby_path') && !executable("ruby")
    finish
endif

function! SyntaxCheckers_ruby_GetLocList()
  if exists('g:ruby_path')
    let makeprg = 'RUBYOPT= ' . g:ruby_path . ' -W1 -c %'
  else
    let makeprg = 'RUBYOPT= ruby -W1 -c %'
  endif
    let errorformat =  '%-GSyntax OK,%E%f:%l: syntax error\, %m,%Z%p^,%W%f:%l: warning: %m,%Z%p^,%-C%.%#'

    return SyntasticMake({ 'makeprg': makeprg, 'errorformat': errorformat })
endfunction