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Using Macros to avoid tedious tasks (screencast)

Because I am lazy,1 and that makes me fast.


(download (ogg theora video))

Using Macros to avoid tedious tasks

  1. I have lots of stuff to do, so I cannot afford not being lazy ☺ 

Ambition the Film: This is where magic happens

I just watched the short film Ambition from ESA, and I still have tears in my eyes.

The film is awesome.

don’t change your habits - fix your tools!

→ In don't run 'strings' on untrusted files Michal Zalewski complained that running the strings-utility for computer forensics or other fields of information security could make you vulnerable yourself, so you should not use that. Given that strings is Free Software, I find a different conclusion from the vulnerability of tools used by professional forensics people.

I’d say if you’re actually using these tools to earn money, it is high time to go in and fix them.

I now have a spam-resistant, decentralized comment system via Freenet

In the last years, spam became worse and worse. The more my site grew, the more time I had to spend deleting blatant advertisements. Even captchas did not help anymore: Either they were so hard that I myself needed 3 tries on average to get through, or I got hundreds of spam messages per day. A few years ago, I caved in and disabled comments. The alternative would have been to turn my Website into a mere PR-outlet of Facebook, twitter or one of the commenting platforms out there.

But this all changed now. I finally have decentralized, spam-resistant comments using babcom with Freenet as backend!

» babcom: decentralized, spam-resistant comments! «

Lots of site uploads into freenet

I just finished lots of new uploads of sites into freenet - with the new freesitemgr (which actually uploads quickly when WoT is disabled, check todays IRC-logs tomorrow to get background on that). You can get the new freesitemgr from or via infocalypse:

hg clone freenet://USK@kDVhRYKItV8UBLEiiEC8R9O8LdXYNOkPYmLct9oT9dM%2CdcEYugEmpW6lb9fe4UzrJ1PgyWfe0Qto2GCdEgg-OgE%2CAQACAAE/pyfreenet.R1/14 

The sites are also available via my freenet inproxy:

freenet-team - an introduction of most of the freenet hackers I know.

mathmltest - example of mathml in freenet.

winterface-deadlines - deadlines for the Winterface GSoC project

freenet-funding - the freenet fundraising plan, still lacking good design and crisp presentation slides or a video

freenet-meltdown - on the recent massive performance degradation which lasted a few month and ended with the link length fix.

fix-link-length - background on the link-length fix which made freenet actually do small world routing again instead of random routing (into which it had degraded, partially due to local requests, partially due to having so many peers per node that random routing actually worked for the current network size, so the pressure by routing-success to go back to small world routing was too weak compared to the pressure from local requests to randomize the connections)

download-web-site - how to download a single page from a website - for example to mirror it into freenet. Hint: For all the sites on or you are allowed to do so freely (licensed under GPL).

guiledocs - the online documentation for GNU Guile with a focus on Scheme (using Guile): A powerful lisp-like language with multiple implementations.

decorrespondent-metadata - experiment how much information one can glean about your life from just one week of metadata, in dutch.

netzpolitiz-metadaten - same article translated to german. License: cc by-nc-sa

Adventures of a Pythonista in Schemeland - the adventures of a Pythonista in Schemeland: A deep understanding of Scheme for Python users. I learned to love Scheme with this. BSD license.

programming-languages - The Programming languages lecture. License: cc by-nc-sa

tao of programming - "When you have learned to snatch the error code from the trap frame, it will be time for you to leave."

Download one page from a website with all its prerequisites

Often I want to simply backup a single page from a website. Until now I always had half-working solutions, but today I found one solution using wget which works really well, and I decided to document it here. That way I won’t have to search it again, and you, dear readers, can benefit from it, too ☺

In short: This is the command:

wget --no-parent --timestamping --convert-links --page-requisites --no-directories --no-host-directories --span-hosts --adjust-extension --no-check-certificate -e robots=off -U 'Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20070802 SeaMonkey/1.1.4' [URL]

Optionally add --directory-prefix=[target-folder-name]

(see the meaning of the options and getting wget for some explanation)

Exact Math to the rescue - with Guile Scheme

I needed to calculate the probability that for every freenet user there are at least 70 others in a distance of at most 0.01. That needs binomial coefficients with n and k on the order of 4000. My old Python script failed me with an OverflowError: integer division result too large for a float. So I turned to Guile Scheme and exact math.

USK and Date-Hints: Finding the newest version of a site in Freenet's immutable datastore

Freenet provides a global, anonymous datastore where you can upload sites which then work like normal websites. But different from websites, they have a version-number.

The reason for this is, that you can only upload to a given key once1. This data then gets stored in the network and is effectively immutable (much like immutable data structures in functional programming).

  1. If you try to upload to a given key twice, you can get collisions. In that case, it isn’t clear which data a client will retrieve - similar to race conditions in threaded programs. That’s why we do not write to the same key twice in practice (though there is a key-type which can be used for passwords or simple file-names. It is called KSK and was the first key-type freenet provided. That led to wars on overwriting files like gpl.txt - similar to the edit-wars we nowadays get on Wikipedia, but with real anonymity thrown in ☺). 

comment on scientific consensus: distorting a debate to hide the majority view

I just discussed with “sceptics” on twitter about climate change. There Ronan Connolly ‏(@RonanConnolly) showed me his article which tries to give the impression that there is no scientific consensus that climate change is man-made.

De-Orchestrating Freenet with the QUEEN program

So Poul-Henning Kamp thought this just a thought experiment …

In Fosdem2014 Poul-Henning Kamp talked about a hypothetical “Project ORCHESTRA” by the NSA with the goal of disrupting internet security: Information, Slides, Video (with some gems not in the slides).

One of the ideas he mentioned was the QUEEN program: Psy-Ops for Nerds.

I’ve been a contributor to the Freenet Project for several years. And in that time, I experienced quite a few of these hypothetical tactics first-hand.

“If you like what I do, why don’t you help me?”

Almost every free software developer made the experience that many people like his or her work, but very few actually provide help. If you experience this, don’t let it disheart you. Verbal support without practical help sounds inconsistent at first, but it actually is the result of limited time.

Most people who have the skills to help are already committed to other projects, so they cannot help you on yours. They can encourage you from the sidelines (“This is cool!

Huge datafiles in free culture projects under GPL

4 ways how large raw artwork files are treated in free culture projects to provide the editable source.1

In the discussion about license compatibility of the creativecommons sharealike license towards the GPL, Anthony asked how the source-requirement is solved for artwork which often has huge raw files. These are the 4 basic ways I described in my answer.

  1. The die was created by Trudy Wenzel (2013) and is licensed under GPLv3 or later. 

shell basics (bash)

These are the notes to a short tutorial I gave to my working group as part of our groundwork group meetings. Some parts here require GNU Bash.

1 Outline

1.1 Outline

  • user-output: echo
  • pipes: |, xargs, - (often stdin)
  • text-processing: cat/tac, sed, grep, cut, head/tail
  • variables (foo=1; echo ${foo})
  • subshell: $(command)
  • loops (for; do; done) (while; do; done)
  • conditionals (if; then; fi)
  • scripts: shebang
  • return values: $?
  • script-arguments: $1, $#, $@ and getopt
  • command chaining: ;, &, && and ||
  • functions and function-arguments
  • math: $((1+2))
  • help: man and info

The assisted brain and the chained brain

PDF (to print)

Org (to change)

Who serves whom? Our tools can be our allies or our masters. Do your tools assist or chain?

The exhaustive guide to German Streets

This is no absolute truth.

complex number compiler and libc bugs (cexp+conj) on OSX and with the intel compiler (icc)

Today a bug in complex number handling surfaced in guile which only appeared on OSX.

This is a short note just to make sure that the bug is reported somewhere.

Test-code (written mostly by Mark Weaver who also analyzed the bug - I only ran the code on a few platforms I happened to have access to):

keep auto-complete from competing with org-mode structure-templates

For a long time it bothered me that auto-complete made it necessary for me to abort completion before being able to use org-mode templates.

I typed <s and auto-complete showed stuff like <string, forcing me to hit C-g before I could use TAB to complete the template with org-mode.

I fixed this for me by adding all the org-mode structure templates as stop-words:

;; avoid competing with org-mode templates.
(add-hook 'org-mode-hook
          (lambda ()
            (make-local-variable 'ac-stop-words)
            (loop for template in org-structure-template-alist do
                  (add-to-list 'ac-stop-words 
                               (concat "<" (car template))))))

Org-mode with Parallel Babel

Babel in Org

Emacs Org-mode provides the wonderful babel-capability: Including code-blocks in any language directly in org-mode documents in plain text.

In default usage, running such code freezes my emacs until the code is finished, though.

Up to a few weeks ago, I solved this with a custom function, which spawns a new emacs as script runner for the specific code:

; Execute babel source blocks asynchronously by just opening a new emacs.
(defun bab/org-babel-execute-src-block-new-emacs ()
  "Execute the current source block in a separate emacs,
so we do not block the current emacs."
  (let ((line (line-number-at-pos))
        (file (buffer-file-name)))
    (async-shell-command (concat 
                          "TERM=vt200 emacs -nw --find-file " 
                          " --eval '(goto-line "
                          (number-to-string line) 
                          ")' --eval "
     "'(let ((org-confirm-babel-evaluate nil))(org-babel-execute-src-block t))' "
                          "--eval '(kill-emacs 0)'"))))

and its companion for exporting to beamer-latex presentation pdf:

; Export as pdf asynchronously by just opening a new emacs.
(defun bab/org-beamer-export-new-emacs ()
  "Export the current file in a separate emacs,
so we do not block the current emacs."
  (let ((line (line-number-at-pos))
        (file (buffer-file-name)))
    (async-shell-command (concat 
                          "TERM=vt200 emacs -nw --find-file " 
                          " --eval '(goto-line " 
                          (number-to-string line) 
                          ")' --eval "
     "'(let ((org-confirm-babel-evaluate nil))(org-beamer-export-to-pdf))' "
                          "--eval '(kill-emacs 0)'"))))

But for shell-scripts there’s a much simpler alternative:

Recursion wins!

I recently read the little schemer and that got me thinking about recursion and loops.

After starting my programming life with Python, I normally use for-loops to solve problems. But actually they are an inferior mechanism when compared to recursion, if the language provides proper syntactic support for that. Since that claim pretty much damns Python on a theoretical level (even though it is still a very good tool in practice and I still love it!), I want to share a simplified version of the code which made me realize this.

Tutorial: Writing scientific papers for ACPD using emacs org-mode

PDF-version (for printing)

orgmode-version (for editing)

Emacs Org mode is an excellent tool for reproducible research,1 but research is only relevant if people learn about it.2 To reach people with scientific work, you need to publish your results in a Journal, so I show here how to publish in ACPD with Emacs Org mode.3

The translation of NSA is Stasi

Just to give you a short note, if you have been surprised by the NSA acting like the Stasi in former DDR (German Democratic Republic).

Here’s the translation of NSA:

  • N: National = Staatlich
  • S: Security = Sicherheit
  • A: Agency = Ministerium

Let’s put that together:

NSA = Staatliches Sicherheitsministerium
(in more regular German: Ministerium für Staatssicherheit)

Well, that’s long. Shorten it to Staatssicherheit. Still to long for casual discussions. So shorten it once more: Stasi.

NSA = Stasi

Do you still wonder why the NSA acts like the Stasi?

git vs. hg - offensive

In many discussions on DVCS over the years I have been fair, friendly and technical while receiving vitriol and misinformation and FUD. This strip visualizes the impression which stuck to my mind when talking to casual git-users.

Update: I found a very calm discussion at a place where I did not expect it: reddit. I’m sorry to you, guys. Thank you for proving that a constructive discussion is possible from both sides! I hope that you are not among the ones offended by this strip.

To Hg-users: There are git users who really understand what they are doing and who stick to arguments and friendly competition. This comic arose from the many frustrating experiences with the many other git users. Please don’t let this strip trick you into going down to non-constructive arguments. Let’s stay friendly. I already feel slightly bad about this short move into competition-like visualization for a topic where I much prefer friendly, constructive discussions. But it sucks to see contributors stumble over git, so I think it was time for this.

»I also think that git isn’t the most beginner-friendly program. That’s why I’m using only its elementary features«

git vs. hg - offensive

To put the strip in words, let’s complete the quote:

»I also think that git isn’t the most beginner-friendly program.
That’s why I’m using only its elementary features«
<ArneBab> I hear that from many git-users…
»oh, maybe I should have another look at hg after all«

Why this?

Because there are far too many Git-Users who only dare using the most basic commands which makes git at best useless and at worst harmful.

This is not the fault of the users. It is the fault of the tool.

This strip is horrible!

If you are offended by this strip: You knew the title when you came here, right?

And if you are offended enough, that you want to make your own strip and set things right, go grab the source-file, fire up krita and give me what I deserve! This strip is free.1


If you feel that this strip fits Mercurial and Git perfectly, keep in mind, that this is only one aspect of the situation, and that using Git is still much better than being forced to use centralized or proprietary version tracking (and people who survive the initial phase mostly unscarred can actually do the same with Git as they could with Mercurial).

  1. All the graphics in this strip are available under free licenses: creative-commons attribution or GPLv3 or later — you decide which of those you use. If it is cc attribution, call me Arne Babenhauserheide and link to this article. You’ll find all the sources as well as some preliminary works and SVGs in git-vs-hg-offensive.tar_.gz or (whichever you prefer)

    cc by GPLv3

Factual Errors in “Git vs Mercurial: Why Git?” from Atlassian

2 years ago, Atlassian developer Charles O’Farrell published the article Git vs. Mercurial: Why Git? in which he “showed the winning side of Git” as he sees it. This article was part of the Dev Tools series at Atlassian and written as a reply to the article Why Mercurial?. It was spiced with so much misinformation that the comments exploded right away. But the article was never corrected. Just now I was referred to the text again, and I decided to do what I should have done 2 years ago: Write an answer which debunks the myths.

Wicked Words! on Patreon

John Wick is entering the patreon arena with the Wicked Words! Magazine: Adventures, GM Advice, Little Games, Stories, The Works!

There’s an update with a Happy ending on!


This is really good news for online publishing, because it shows by example how roleplaying games and shortstories enter a new stage on the web: Fan-Funded periodicals.

Write multiple images on a single page in org-mode.

How to add show multiple images on one page in the latex-export of emacs org-mode. I had this problem. This is my current solution.

Unicode char \u8:χ not set up for use with LaTeX: Solution (made easy with Emacs)

For years I regularly stumbled over LaTeX-Errors in the form of Unicode char \u8:χ not set up for use with LaTeX. I always took the chickens path and replaced the unicode characters with the tex-escapes in the file. That was easy, but it made my files needlessly unreadable. Today I decided to FIX the problem once and for all. And it worked. Easily.

Firstoff: The problem I’m facing is that my keyboard layout makes it effortless for me to input characters like ℂ Σ and χ. But LaTeX cannot cope with them out-of-the-box.

Publish a single file with emacs org-mode

I often write small articles on some experience I make, and since I want to move towards using static pages more often, I tried using emacs org-mode publishing for that. Strangely the simple usecase of publishing a single file seems quite a bit more complex than needed, so I document the steps here.

This is my first use of org-publish, so I likely do not use it perfectly. But as it stands, it works. You can find the org-publish version of this article at

How to show the abstract before the table of contents in org-mode

I use Emacs Org-Mode for writing all kinds of articles. The standard format for org-mode is to show the table of contents before all other content, but that requires people to scroll down to see whether the article is interesting for them. Therefore I want the abstract to be shown before the table of contents.

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