# File lib/phusion_passenger/platform_info/apache.rb, line 306
        def self.httpd_infer_envvar(varname, options = nil)
                if envfile = httpd_envvars_file(options)
                        result = `. '#{envfile}' && echo $#{varname}`.strip
                        if $? && $?.exitstatus == 0
                                return result
                        else
                                return nil
                        end
                else
                        return nil
                end
        end