org-mode ob-dot

gistfile1.txt

(defun org-babel-execute:dot (body params)
  "Execute a block of Dot code with org-babel.
This function is called by `org-babel-execute-src-block'."
  (let* ((out-file (cdr (or (assq :file params)
                            (error "You need to specify a :file parameter"))))
         (cmdline (or (cdr (assq :cmdline params))
                      (format "-T%s" (file-name-extension out-file))))
         (cmd (or (cdr (assq :cmd params)) "dot"))
         (coding-system-for-read 'utf-8) ;use utf-8 with sub-processes
         (coding-system-for-write 'utf-8)
         (in-file (org-babel-temp-file "dot-"))
         (script-file (org-babel-temp-file "dot-script-"))) ;;; when use script-file
    (with-temp-file in-file
      (insert (org-babel-expand-body:dot body params)))

    ;; org-babel-eval
    (with-temp-file script-file
      (insert (concat cmd
                      " " (org-babel-process-file-name in-file)
                      " " cmdline
                      " -o " (org-babel-process-file-name out-file))))
    (set-file-modes script-file #o755)
    (org-babel-eval script-file "")
;;    ;; original
;;    (org-babel-eval
;;     (concat cmd
;;             " " (org-babel-process-file-name in-file)
;;             " " cmdline
;;             " -o " (org-babel-process-file-name out-file)) "")
    nil))

gistfile2.txt

#+BEGIN_SRC dot :file o.svg :results file :exports both00
digraph {
    A -> B;
  }
#+END_SRC