Irreal

Oleh Krehel (abo-abo) has a new blog, (or emacs. There’s only a few posts so far but they’re really excellent. For example, his initial post discusses his packaging of ace-window into a library so that other packages can use the ace-window technology to pick windows to operate on.

I really like ace-window and use it all the time. I didn’t know, though, that with 【Ctrl+u】 it will swap the current window with the selected one and with 【Ctrl+u Ctrl+u】 it will delete the selected window. So I learned something useful from his very first post.

Abo-abo has made many contributions to Emacs other than ace-window so he has interesting things to say. Welcome, abo-abo. We’ll be looking forward to many more posts.

I use iBuffer a lot. That’s probably because I get a little OCD about stray buffers eating up memory for no reason. With my new 16 GB laptop, buffers eating up memory isn’t much of a problem but it’s too late for me to reform my ways.

I especially like to clean up after I upgrade my packages. That process always leaves a Compile-Log buffer at the top of the iBuffer list and a Packages buffer at the bottom. Of course, when I navigate to the head or tail of the buffer I end up in the wrong place—not at the head or tail of the list.

If that seems a little familiar it’s probably because Magnar Sveen had similar problem with dired and solved it with a bit of Elisp. So I shamelessly ripped off Sveen’s code and made a few trivial changes so it does the same thing for iBuffer that Sveen’s did for dired. If you’re having the same problem, the code is below. It’s almost embarrassing to post it because it’s such a rip off but Emacsers who don’t have the wherewithal to figure out which key map to use or who don’t know Elisp may find it useful.

;; Stolen from Magnar's code to do the same thing for dired
;; http://whattheemacsd.com/setup-dired.el-02.html
(defun ibuffer-back-to-top ()
  (interactive)
  (beginning-of-buffer)
  (next-line 3))

(defun ibuffer-jump-to-bottom ()
  (interactive)
  (end-of-buffer)
  (next-line -2))

(eval-after-load 'ibuffer
  '(progn
     (define-key ibuffer-mode-map
       (vector 'remap 'end-of-buffer) 'ibuffer-jump-to-bottom)
     (define-key ibuffer-mode-map
       (vector 'remap 'beginning-of-buffer) 'ibuffer-back-to-top)))

Recently, I needed to sort an Org mode table by a column having IP addresses. For example, given the table

|            IP | 11/01 | 11/02 | 11/03 |
|---------------+-------+-------+-------|
|    10.1.213.5 |     2 |     1 |     0 |
|  172.25.100.1 |     4 |     1 |     1 |
|   10.234.4.55 |     1 |     1 |     5 |
|  192.168.7.11 |     2 |     1 |     3 |
| 10.25.215.200 |     1 |     3 |     1 |
|    172.35.0.1 |     2 |     5 |     1 |

I want to sort on the IP column to get

|            IP | 11/01 | 11/02 | 11/03 |
|---------------+-------+-------+-------|
|    10.1.213.5 |     2 |     1 |     0 |
| 10.25.215.200 |     1 |     3 |     1 |
|   10.234.4.55 |     1 |     1 |     5 |
|  172.25.100.1 |     4 |     1 |     1 |
|    172.35.0.1 |     2 |     5 |     1 |
|  192.168.7.11 |     2 |     1 |     3 |

That turns out to be surprisingly difficult. There’s no built-in method and I couldn’t find an appropriate sort routine that exposed the comparison function so that I could write my own.

The normal Unix sort can sort IP addresses with

sort -n -t . -k 1,1 -k 2,2 -k 3,3 -k 4,4

Not easy or pretty but at least it gets the job done. My first attempt to get this to work was to mark the whole table except for the header line and the following rule line and then pipe it into sort with 【Ctrl+u Meta+|】. Sadly, this didn’t work because of the | that begins each line.

Next, I tried marking the rectangle comprising the data of the table with 【Ctrl+x Space】 and then piping it into sort as before. That didn’t work either.

Finally I remembered that I have cua-selection-mode enabled to mark rectangular regions. I marked the data with that and piped it into sort. Happily, that worked. If you haven’t already enabled cua-selection-mode, you should. It’s really useful.

I wouldn’t think sorting IP addresses would be that unusual but there’s no support for it all in Emacs. Most utilities do no better. Even sort only manages with some trickery. It’s probably just that IP addresses weren’t as ubiquitous as they are now when Emacs and those utilities were written. Or maybe I’m the only one who wants to sort by IP address.

So I solved the problem, sort of, but, really, it’s a terrible solution. After a bit of thought, I ginned up a patch and sent it off to the Org mailing list. Tomorrow, I’ll tell you the rest of the story.

Edgar Aroutiounian has a nice post about adding animations to PDF files with Emacs, Org, and LaTeX. If you’re an OS X user, he also explains how to load a minimal TeX distribution rather than the huge MacTeX distribution.

The real magic is putting an animated graph into a PDF file. It’s surprisingly easy to do and doesn’t require much more than Emacs, Org, and LaTeX. Definitely worth reading if you think you might want to do this someday.