\version "2.19.81"

% Print table of contents entries to <basename>.toc
% Based on
% http://lilypond.org/doc/v2.19/Documentation/usage-big-page#sharing-the-table-of-contents
% Pointed to by "Thomas Morley"
#(define (oly:create-toc-file layout pages)
   (let*
    ((label-table (ly:output-def-lookup layout 'label-page-table))
     (toc-items (toc-items)))
    (if (not (null? label-table))
        (let*
         ( ;; We need a page-offset so entries are offset to begin with p.1
           ;; (for use in \includepdf)
           (page-offset (- (ly:output-def-lookup layout 'first-page-number) 1))
           (format-line
            (lambda (toc-item)
              (let*
               ((label (car toc-item))
                (display text  (caddr toc-item))
                (page (- (assoc-ref label-table label) page-offset)))
               (format #f "~a,subsection,2,{~a},~a" page text label))))
           (formatted-toc-items (map format-line toc-items))
           (whole-string (string-join formatted-toc-items ",\n"))
           (output-name (ly:parser-output-name))
           (outfilename (format "~a.toc" output-name))
           (outfile (open-output-file outfilename)))
         (if (output-port? outfile)
             (display whole-string outfile)
             (ly:warning (_ "Unable to open output file ~a for the TOC information") outfilename))
         (close-output-port outfile)))))

\paper {
  first-page-number = 20
  print-first-page-number = ##t
  #(define (page-post-process layout pages) (oly:create-toc-file layout pages))
}

\bookpart {
  \tocItem \markup "A TOC entry"
  { c' }
}

\bookpart {
  \tocItem \markup "Another TOC entry"
  { d' e' }
}