I recently posted about using Emacs for scripts (http://kitchingroup.cheme.cmu.edu/blog/2014/08/06/Writing-scripts-in-Emacs-lisp/ ). Someone was probably wondering, why would you do that, when you could use shell, python or perl? A good reason is to write scripts that can access data or code inside an org-file! This would allow you to leverage the extensive support for org-mode in Emacs, without a user necessarily even needing to use Emacs. Let us consider some examples.
1 Extracting tables from an org-file
If tables are named in org-mode, it is possible to extract the contents. Here is a table:
Another table might look like
It would be convenient to have a command-line utility that could extract the data from that table with a syntax like:
extract-org-table tblname orgfile --format lisp|csv|tab
Here is one way to do it:
;; org-table tblname orgfile lisp|csv|tab (let ((tblname (pop command-line-args-left)) (org-file (pop command-line-args-left)) (format) (table) (content)) (when command-line-args-left (setq format (pop command-line-args-left))) (find-file org-file) (setq table (org-element-map (org-element-parse-buffer) 'table (lambda (element) (when (string= tblname (org-element-property :name element)) element)) nil ;info t )) ; first-match (unless table (error "no table found for %s" tblname)) (when table (goto-char (org-element-property :contents-begin table)) (let ((contents (org-table-to-lisp))) (if (string= format "lisp") (print contents) ;else (dolist (row contents) (unless (eq row 'hline) (cond ((string= format "csv") (princ (mapconcat 'identity row ","))) ((string= format "tab") (princ (mapconcat 'identity row "\t"))) (t (error "unsupported format: %s" format))) (princ "\n")))))))
Let us try it out. org-babel-tangle
./extract-org-table data-2 org-outside-emacs.org lisp
(("a" "b") ("1" "1") ("2" "8") ("3" "27"))
./extract-org-table data-1 org-outside-emacs.org csv
x,y 1,1 2,4 3,9
./extract-org-table data-2 org-outside-emacs.org tab
a b 1 1 2 8 3 27
That looks pretty reasonable, and you could even pipe the output to another classic unix command like cut to get a single column. Let us get the second column here.
./extract-org-table data-1 org-outside-emacs.org csv | cut -d , -f 2
y 1 4 9
That is starting to look like using data from an org-file, but outside of org. Of course, we are using org-mode, via emacs, but the point is a user might not have to know that, as long as a fairly recent Emacs and org-mode was installed on their system.
2 Running code in an org-file
It may be that there is code in an org-file that you might want to use, but for some reason choose not to cut and paste from the org-file to some script. Here is a simple code block:
import time with open('results.dat', 'w') as f: f.write(time.asctime())
To call this externally we have to find the block and then run it.
;; org-run blockname org-file ;; run a code block in an org file (let ((blockname (pop command-line-args-left)) (org-file (pop command-line-args-left)) (src)) (find-file org-file) (setq src (org-element-map (org-element-parse-buffer) 'src-block (lambda (element) (when (string= blockname (org-element-property :name element)) element)) nil ;info t )) ; first-match (when src (goto-char (org-element-property :begin src)) ;; since we start with a fresh emacs, we have to configure some things. (org-babel-do-load-languages 'org-babel-load-languages '((python . t))) (let ((org-confirm-babel-evaluate nil)) (org-babel-execute-src-block))))
./org-call.el python-block org-outside-emacs.org cat results.dat
Mon Aug 11 20:17:01 2014
That demonstrates it is possible to call source blocks, but this is pretty limited in capability. You can only call a block; we did not capture any output from the block, only its side effects, e.g. it changed a file that we can examine. We have limited capability to set data into the block, other than through files. It might be possible to hack up something that runs org-babel-execute-src-block with constructed arguments that enables something like a var to be passed in. That is beyond today's post. When I get around to it, here is a reminder of how it might be possible to feed stdin to an emacs script: http://stackoverflow.com/questions/2879746/idomatic-batch-processing-of-text-in-emacs .
Copyright (C) 2014 by John Kitchin. See the License for information about copying.
Org-mode version = 8.2.6