在 Orgmode 中，有没有办法仅在匹配（或不匹配）特定标签的子树中缠结块？
比如下面的代码
* A
#+BEGIN_SRC c
printf("Not exported");
#+END_SRC
* B :D:
#+BEGIN_SRC c
printf("Exported");
#+END_SRC
沿标签D导出，tangle C 文件将只包含printf("Exported");
我正在使用org-mode 来组织我的emacs 配置，我的目标是派生不同的配置 从主emacs-config.org。 （例如，只标记特定的 lightconfig）
【问题讨论】：
要实现此行为，您可以利用以下事实：除了 yes 和 no，Org Babel 代码块的 :tangle 标头参数还有 understands file names；即，对于任何给定的代码块，您可以告诉 Org Babel 您希望该块与哪个文件纠缠在一起。我的想法是在给标题添加标签时，自动为某个标题下的每个代码块设置文件名：
(defun org-babel-set-tangle-file ()
(let ((tag (car (org-get-local-tags))))
(org-narrow-to-subtree)
(while (re-search-forward "\\(:tangle \\).*" nil t)
(replace-match (concat "\\1" tag ".el")))
(widen)))
(add-hook 'org-after-tags-change-hook 'org-babel-set-tangle-file)
由此产生的行为是当你为当前文件调用org-babel-tangle时，所有属于的代码块
请注意，上面的函数将标签特定的缠结文件的文件扩展名设置为.el；因为您提到您希望生成不同的 Emacs 配置，所以我认为这将是一个合理的默认值（即使您在示例中显示 C 代码）。
【讨论】：
我不久前尝试对此进行研究，但没有找到快速的答案。
我最终修改了org-babel-tangle-collect-blocks 来实现这个功能
这里是修改后的函数。 org-babel-tags 列表是 ok 标签的列表。对于您的示例，您需要将其设置为 (setq org-babel-tags '("D"))
（我在第一次调用“除非”之后添加了前 4 行）
(defvar org-babel-tags nil
"only tangle entries that has a tag in this list")
(defun org-babel-tangle-collect-blocks (&optional language)
"Collect source blocks in the current Org-mode file.
Return an association list of source-code block specifications of
the form used by `org-babel-spec-to-string' grouped by language.
Optional argument LANG can be used to limit the collected source
code blocks by language."
(let ((block-counter 1) (current-heading "") blocks)
(org-babel-map-src-blocks (buffer-file-name)
((lambda (new-heading)
(if (not (string= new-heading current-heading))
(progn
(setq block-counter 1)
(setq current-heading new-heading))
(setq block-counter (+ 1 block-counter))))
(replace-regexp-in-string "[ \t]" "-"
(condition-case nil
(or (nth 4 (org-heading-components))
"(dummy for heading without text)")
(error (buffer-file-name)))))
(let* ((start-line (save-restriction (widen)
(+ 1 (line-number-at-pos (point)))))
(file (buffer-file-name))
(info (org-babel-get-src-block-info 'light))
(src-lang (nth 0 info)))
(unless (or (string= (cdr (assoc :tangle (nth 2 info))) "no")
(null (intersection (mapcar 'intern org-babel-tags)
(save-excursion
(org-back-to-heading)
(mapcar 'intern (org-get-tags))))))
(unless (and language (not (string= language src-lang)))
(let* ((info (org-babel-get-src-block-info))
(params (nth 2 info))
(extra (nth 3 info))
(cref-fmt (or (and (string-match "-l \"\\(.+\\)\"" extra)
(match-string 1 extra))
org-coderef-label-format))
(link ((lambda (link)
(and (string-match org-bracket-link-regexp link)
(match-string 1 link)))
(org-no-properties
(org-store-link nil))))
(source-name
(intern (or (nth 4 info)
(format "%s:%d"
current-heading block-counter))))
(expand-cmd
(intern (concat "org-babel-expand-body:" src-lang)))
(assignments-cmd
(intern (concat "org-babel-variable-assignments:" src-lang)))
(body
((lambda (body) ;; run the tangle-body-hook
(with-temp-buffer
(insert body)
(when (string-match "-r" extra)
(goto-char (point-min))
(while (re-search-forward
(replace-regexp-in-string "%s" ".+" cref-fmt) nil t)
(replace-match "")))
(run-hooks 'org-babel-tangle-body-hook)
(buffer-string)))
((lambda (body) ;; expand the body in language specific manner
(if (assoc :no-expand params)
body
(if (fboundp expand-cmd)
(funcall expand-cmd body params)
(org-babel-expand-body:generic
body params
(and (fboundp assignments-cmd)
(funcall assignments-cmd params))))))
(if (org-babel-noweb-p params :tangle)
(org-babel-expand-noweb-references info)
(nth 1 info)))))
(comment
(when (or (string= "both" (cdr (assoc :comments params)))
(string= "org" (cdr (assoc :comments params))))
;; from the previous heading or code-block end
(funcall
org-babel-process-comment-text
(buffer-substring
(max (condition-case nil
(save-excursion
(org-back-to-heading t) ; sets match data
(match-end 0))
(error (point-min)))
(save-excursion
(if (re-search-backward
org-babel-src-block-regexp nil t)
(match-end 0)
(point-min))))
(point)))))
by-lang)
;; add the spec for this block to blocks under it's language
(setq by-lang (cdr (assoc src-lang blocks)))
(setq blocks (delq (assoc src-lang blocks) blocks))
(setq blocks (cons
(cons src-lang
(cons (list start-line file link
source-name params body comment)
by-lang)) blocks)))))))
;; ensure blocks in the correct order
(setq blocks
(mapcar
(lambda (by-lang) (cons (car by-lang) (reverse (cdr by-lang))))
blocks))
blocks))
【讨论】：
ob-tangle函数出处，代码和签名都不一样：签名(defun org-babel-tangle-collect-blocks (&optional language tangle-file)
use-package 我有一个解决方法。还是谢谢！ :)