# File lib/bundler/definition.rb, line 327
    def lock(file, preserve_unknown_sections = false)
      contents = to_lock

      # Convert to \r\n if the existing lock has them
      # i.e., Windows with `git config core.autocrlf=true`
      contents.gsub!(/\n/, "\r\n") if @lockfile_contents.match("\r\n")

      if @locked_bundler_version
        locked_major = @locked_bundler_version.segments.first
        current_major = Gem::Version.create(Bundler::VERSION).segments.first

        if updating_major = locked_major < current_major
          Bundler.ui.warn "Warning: the lockfile is being updated to Bundler #{current_major}, " \
                          "after which you will be unable to return to Bundler #{@locked_bundler_version.segments.first}."
        end
      end

      preserve_unknown_sections ||= !updating_major && (Bundler.frozen_bundle? || !(unlocking? || @unlocking_bundler))

      return if file && File.exist?(file) && lockfiles_equal?(@lockfile_contents, contents, preserve_unknown_sections)

      if Bundler.frozen_bundle?
        Bundler.ui.error "Cannot write a changed lockfile while frozen."
        return
      end

      SharedHelpers.filesystem_access(file) do |p|
        File.open(p, "wb") {|f| f.puts(contents) }
      end
    end