add tangle to code block

src/posts/0011-export-tangle-names/index.org

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+#+title: Add links to code block during orgmode export
+#+date: [2020-02-29 Sat]
+#+author: Yann Esposito
+#+EMAIL: yann@esposito.host
+#+keywords: org-mode, blog
+#+DESCRIPTION: add links to code block during orgmode export
+#+OPTIONS: auto-id:t toc:t
+#+STARTUP: overview
+
+I wanted to add a link to the file I export with org tangle.
+And it was surprisingly difficult to find.
+Apparently I am one of the few people that use orgmode the way I do.
+
+Using orgmode file as markdown to blog.
+And exporting to a different file some code block.
+So I often endup writing something like:
+
+#+begin_src org
+..begin_src elisp :tangle foo.el
+#+end_src
+
+I tangle the source code that export the code block to an external file.
+Then I use this hook during HTML export to add a caption with the link the
+file I tangled:
+
+#+begin_src elisp :tangle org_html_export_show_tangle.el
+(defun my-add-link-to-tangled-files (backend)
+  "Add a link just before source code block with tangled files.
+BACKEND is the export backend. Used as symbol."
+  (while ;; (re-search-forward )
+      (re-search-forward "^\\( *\\)#\\+begin_src .*:tangle \\([^\s\n]*\\)" nil t)
+    (replace-match "\\1#+CAPTION: [[./\\2][=\\2=]]\n\\&")))
+
+(add-hook 'org-export-before-processing-hook
+          'my-add-link-to-tangled-files)
+#+end_src
+
+And this article is an example of the result.
+The link with the listing is generated automatically for me.
+
+A small note regarding CSS.
+My =pre= have a =margin-top=.
+But I wanted to get rid of it when the previous block was a =label=.
+This is achievable with:
+
+#+begin_src css
+label + pre {margin-top: 0;}
+#+end_src
+
+That's it.
+It took me really a long time to just think about using caption, and not
+trying something smarter like injecting html code, etc...
+So I hope it could help someone.

src/posts/0011-export-tangle-names/org_html_export_show_tangle.el

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+(defun my-add-link-to-tangled-files (backend)
+  "Add a link just before source code block with tangled files.
+BACKEND is the export backend. Used as symbol."
+  (while ;; (re-search-forward )
+      (re-search-forward "^\\( *\\)#\\+begin_src .*:tangle \\([^\s\n]*\\)" nil t)
+    (replace-match "\\1#+CAPTION: [[./\\2][=\\2=]]\n\\&")))
+
+(add-hook 'org-export-before-processing-hook
+          'my-add-link-to-tangled-files)