7

By default when org-mode documents are exported to HTML, the section and sub-section links look like

file:///path/to/export/location/doc.html#sec-1-1

The problem is that the above link won't point to the correct section if I rearrange the sections.

How can we have permalinks for each section auto-generated that look like below?

file:///path/to/export/location/doc.html#introduction
9

You can get this result by setting the CUSTOM_ID property.

From the following file:

* Test
:PROPERTIES:
:CREATED:  [2014-10-02 Thu 11:48]
:END:
** Sub no custom
:PROPERTIES:
:CREATED:  [2014-10-02 Thu 11:49]
:END:
** Sub custom
:PROPERTIES:
:CREATED:  [2014-10-02 Thu 11:49]
:CUSTOM_ID: Custom
:END:

I get the following Export (C-c C-e h H):

<div id="text-table-of-contents">
<ul>
<li><a href="#sec-1">1. Test</a>
<ul>
<li><a href="#sec-1-1">1.1. Sub no custom</a></li>
<li><a href="#Custom">1.2. Sub custom</a></li>
</ul>
</li>
</ul>
</div>
</div>
<div id="outline-container-sec-1" class="outline-2">
<h2 id="sec-1"><span class="section-number-2">1</span> Test</h2>
<div class="outline-text-2" id="text-1">
</div>
<div id="outline-container-sec-1-1" class="outline-3">
<h3 id="sec-1-1"><span class="section-number-3">1.1</span> Sub no custom</h3>
<div class="outline-text-3" id="text-1-1">
</div>
</div>
<div id="outline-container-Custom" class="outline-3">
<h3 id="Custom"><a id="sec-1-2"></a><span class="section-number-3">1.2</span> Sub custom</h3>

So Sub no custom is linked to by #sec-1-1 while Sub custom uses #custom as the reference.


AutoGenerating IDs

Adding org-id to the list of loaded org-modules or directly evaluating (require 'org-id) will allow for IDs to be generated using org-id-get-create. The following will insert IDs automatically and use them on export.

;; Use custom ID if present, otherwise create a new one when trying to
;; resolve links
(setq org-id-link-to-org-use-id
      'create-if-interactive-and-no-custom-id)

;; Based on org-expiry-insinuate
(add-hook 'org-insert-heading-hook 'org-id-get-create)
(add-hook 'org-after-todo-state-change-hook 'org-id-get-create)
(add-hook 'org-after-tags-change-hook 'org-id-get-create)

This should look through your existing headlines in a buffer and update the IDs. It will only create IDs if none are present.

(defun my/org-update-ids ()
  (interactive)
  (let* ((tree (org-element-parse-buffer 'headline))
         (map (org-element-map tree 'headline
                (lambda (hl)
                  (org-element-property :begin hl)))))
    (save-excursion
      (cl-loop for point in map do
               (goto-char point)
               (org-id-get-create)))))

Note. This will not fix TOC links to point to the correct IDs. TOC is only configured to use CUSTOM_ID or sec-#-# for generating links. You can however access the sections by their ID's (I would suggest changing org-id-method to org from uuid to shorten the ID length if you intend to use it this way.

CUSTOM_ID is still probably your best bet if you actually want human-legible IDs for the headlines. my/org-update-ids should be able to be used as a starting point for that (map through the buffer for each headline, go to headline then perform action).

A starting point would be (org-entry-put (point) "CUSTOM_ID" id) for setting and (org-entry-get (point) "CUSTOM_ID") for getting. Determinining what to use as id is dependant on how you want them named.

  • Thanks! I will cook up something to auto generate the :CUSTOM_ID: values and post here. This is my plan: It would be cumbersome to type the :PROPERTIES: block for each sub-section. Instead an elisp code can generate those for me and auto generate the :CUSTOM_ID: if one doesn't exist; all in the org-export-before-processing-hook so that the source org file is not modified. It might take me some time to implement this, but will post it here when done. – Kaushal Modi Oct 2 '14 at 15:56
  • I've provided a method to create :ID: properties for each (and to update your buffer to include them where missing). If you create a function to dynamically assign IDs to headlines (based on headline name?) you can substitute it in for org-id-get-create and it will use create the :Custom_ID: instead. – Jonathan Leech-Pepin Oct 2 '14 at 16:54

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