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6.5.3 RSS

Some web sites have an RDF Site Summary (RSS). RSS is a format for summarizing headlines from news related sites (such as BBC or CNN). But basically anything list-like can be presented as an RSS feed: weblogs, changelogs or recent changes to a wiki (e.g., http://cliki.net/site/recent-changes).

RSS has a quite regular and nice interface, and it's possible to get the information Gnus needs to keep groups updated.

Note: you had better use Emacs which supports the utf-8 coding system because RSS uses UTF-8 for encoding non-ASCII text by default. It is also used by default for non-ASCII group names.

Use G R from the group buffer to subscribe to a feed—you will be prompted for the location, the title and the description of the feed. The title, which allows any characters, will be used for the group name and the name of the group data file. The description can be omitted.

An easy way to get started with nnrss is to say something like the following in the group buffer: B nnrss RET RET y, then subscribe to groups.

The nnrss back end saves the group data file in nnrss-directory (see below) for each nnrss group. File names containing non-ASCII characters will be encoded by the coding system specified with the nnmail-pathname-coding-system variable or other. Also See Non-ASCII Group Names, for more information.

The nnrss back end generates ‘multipart/alternativeMIME articles in which each contains a ‘text/plain’ part and a ‘text/html’ part.

You can also use the following commands to import and export your subscriptions from a file in OPML format (Outline Processor Markup Language).

— Function: nnrss-opml-import file

Prompt for an OPML file, and subscribe to each feed in the file.

— Function: nnrss-opml-export

Write your current RSS subscriptions to a buffer in OPML format.

The following nnrss variables can be altered:

nnrss-directory
The directory where nnrss stores its files. The default is ~/News/rss/.
nnrss-file-coding-system
The coding system used when reading and writing the nnrss groups data files. The default is the value of mm-universal-coding-system (which defaults to emacs-mule in Emacs or escape-quoted in XEmacs).
nnrss-ignore-article-fields
Some feeds update constantly article fields during their publications, e.g., to indicate the number of comments. However, if there is a difference between the local article and the distant one, the latter is considered to be new. To avoid this and discard some fields, set this variable to the list of fields to be ignored. The default is '(slash:comments).
nnrss-use-local
If you set nnrss-use-local to t, nnrss will read the feeds from local files in nnrss-directory. You can use the command nnrss-generate-download-script to generate a download script using wget.

The following code may be helpful, if you want to show the description in the summary buffer.

     (add-to-list 'nnmail-extra-headers nnrss-description-field)
     (setq gnus-summary-line-format "%U%R%z%I%(%[%4L: %-15,15f%]%) %s%uX\n")
     
     (defun gnus-user-format-function-X (header)
       (let ((descr
              (assq nnrss-description-field (mail-header-extra header))))
         (if descr (concat "\n\t" (cdr descr)) "")))

The following code may be useful to open an nnrss url directly from the summary buffer.

     (require 'browse-url)
     
     (defun browse-nnrss-url (arg)
       (interactive "p")
       (let ((url (assq nnrss-url-field
                        (mail-header-extra
                         (gnus-data-header
                          (assq (gnus-summary-article-number)
                                gnus-newsgroup-data))))))
         (if url
             (progn
               (browse-url (cdr url))
               (gnus-summary-mark-as-read-forward 1))
           (gnus-summary-scroll-up arg))))
     
     (eval-after-load "gnus"
       #'(define-key gnus-summary-mode-map
           (kbd "<RET>") 'browse-nnrss-url))
     (add-to-list 'nnmail-extra-headers nnrss-url-field)

Even if you have added ‘text/html’ to the mm-discouraged-alternatives variable (see Display Customization) since you don't want to see HTML parts, it might be more useful especially in nnrss groups to display ‘text/html’ parts. Here's an example of setting mm-discouraged-alternatives as a group parameter (see Group Parameters) in order to display ‘text/html’ parts only in nnrss groups:

     ;; Set the default value of mm-discouraged-alternatives.
     (eval-after-load "gnus-sum"
       '(add-to-list
         'gnus-newsgroup-variables
         '(mm-discouraged-alternatives
           . '("text/html" "image/.*"))))
     
     ;; Display ‘text/html’ parts in nnrss groups.
     (add-to-list
      'gnus-parameters
      '("\\`nnrss:" (mm-discouraged-alternatives nil)))