    # File lib/chef/mixin/command.rb, line 82
          def not_if(command, args = {})
            if command.kind_of?(Proc)
              chdir_or_tmpdir(args[:cwd]) do
                res = command.call
                if res
                  return false
                end
              end
            else
              status = run_command({:command => command, :ignore_failure => true}.merge(args))
              if status.exitstatus == 0
                return false
              end
            end
            true
          end