Irreal

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.

#Emacs: using transpose-chars is a litmus test. If you care enough to save keystrokes to internalize C-t, then you must be a power user.

— Fredrik Appelberg (@appelberg) November 28, 2014

The estimable Mickey Petersen, proprietor of the Mastering Emacs blog, is working on a book. Mickey says that the book is not an encapsulation of his blog but rather is all new material. His announcement has a general outline of what he’s going to cover so read that if you’re interested.

Mickey’s aiming to release the book in February 2015 so we won’t have to wait long. If you sign up to be notified when it’s ready, Mickey will give you 20% off. You can sign up on the announcement page so head on over.