free software

Translating a lookup-dictionary to bash: Much simpler than I thought

I wanted to name Transcom Regions in my plots by passing their names to the command-line tool, but I only had their region-number and a lookup dictionary in Python. To avoid tampering with the tool, I needed to translate the dictionary to a bash function, and thanks to the case statement it was much simpler than I had expected.

This is the original dictionary:

GNU Guix in 5 minutes

So you get excited when you hear about surviving a power-outage during updates without a hitch and you want to give Guix a try — but woes, you only have 5 minutes of time?

Fear not, that’s enough to get it up and running — all the way to per-user environments and package install as non-priviledged user!

The instructions here are from the official docs, specialized for a GNU Linux host and cut to what I need in a working system.

as user:

$ cd /tmp
$ wget

Gratis py2guile from Freenet

py2guile book

py2guile is a book I wrote about Python and Guile Scheme. It’s selling at 0.01 ฿ | 2.99 € for the ebook and 14.95 € for the printed softcover.

To fight the new german data retention laws, you can get the ebook gratis: Just install Freenet, then the following links work:

Escape total surveillance and get an ebook about the official GNU extension language for free today!

BY-SA and GPL: creativecommons closed the chasm in the sharealike/copyleft community

This is the biggest news item for free culture and free software in the past 5 years: The creativecommons attribution sharealike license is now one-way compatible to the GPL — see the message from creativecommons and from the Free Software Foundation.

Some license compatibility legalese might sound small, but the impact of this is hard to overestimate.

Going from Python to Guile Scheme - a natural progression

py2guile book

Python is the first language I loved. I dreamt in Python, I planned in Python, I thought I would never need anything else.

 - Free: html | pdf
 - Ebook: 2.99 €
   epub format
 - Softcover: 14.95 €
   with pdf, epub, mobi
 - Source: download
   free licensed under GPL

Using Guile Scheme Wisp for low ceremony embedded languages

Update 2017: A matured version of the work shown here was presented at FOSDEM 2017 as Natural script writing with Guile. There is also a video of the presentation (held by Christopher Allan Webber; more info…). Happy Hacking!

Programming languages allow expressing ideas in non-ambiguous ways. Let’s do a play.

say Yes, I do!
Yes, I do!

Staying sane with Emacs (when facing drudge work)

I have to sift through 6 really boring config files. To stay sane, I call in Emacs for support.

My task looks like this:

(click for full size)

GnuPG/PGP signature, short explanation

»What is the .asc file?« This explanation is intended to be copied as-is into emails when someone asks about your signature.

The .asc file is a signature which can be used to verify that the email was really sent by me and wasn’t tampered with.[1] It can be verified with standard email security tools like Enigmail[2], Gpg4win[3] or MacGPG[4] - and others tools supporting OpenPGP[5].

Conveniently convert CamelCase to words_with_underscores using a small emacs hack

I currently cope with refactoring in an upstream project to which I maintain some changes which upstream does not merge. One nasty part is that the project converted from CamelCase for function names to words_with_underscores. And that created lots of merge errors.

Today I finally decided to speed up my work.

The first thing I needed was a function to convert a string in CamelCase to words_with_underscores.

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 ☺ 

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.

Free Software

„Free, Reliable, Ethical and Efficient“
„Frei, Robust, Ethisch und Innovativ”
„Libre, Inagotable, Bravo, Racional y Encantado“

Articles connected to Free Software (mostly as defined by the GNU Project).

A bitcoin-marketplace using Freenet?

A few days ago, xor, the developer of the Web of Trust in Freenet got in contact with the brain behind the planned Web of Trust for Openbazaar, and toad, the former maintainer of Freenet questioned whether we would actually want a marketplace using Freenet.

I took a a few days to ponder the question, and I think a marketplace using Freenet would be a good idea - for Freenet as well as for society.

Freenet is likely the most secure way for implementing a digital market, which means it can work safely for small sums, but not for large ones - except if you can launder huge amounts of digital money. As such it is liberating for small people, but not for syndicates. For example a drug cartel needs to be able to turn lots of money into clean cash to pay henchmen abroads. Since you can watch bitcoin more easily than cash and an anonymous network makes it much harder to use scare-tactics against competing sellers, moving the marketplace from the street to the internet weakens syndicates and other organized crime by removing part of their options for creating a monopoly by force.

If a bitcoin marketplace with some privacy for small-scale users should become a bigger problem than the benefit it brings by weakening organized crime, any state or other big player can easily force the majority of users to reveal their identities by using the inherent tracability of bitcoin transactions.

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 ☺). 

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!

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?

Schick mir eine verschlüsselte E-Mail

Eine verschlüsselte E-Mail zu schicken ist einfach. Hier will ich dir in 3 Schritten zeigen, wie du mich erreichen kannst. Ich zeige die Schritte für eine Reihe verschiedener Programme, sowohl für Windows als auch für OSX und GNU/Linux.

Das Programm dafür ist GnuPG: Frei lizensiert und der langjährige Standard für sichere Verschlüsselung von E-Mails.

Org-mode with Parallel Babel

Update 2017: a block with sem -j ... seems to block in recent versions of Emacs until all subtasks are done. It would be great if someone could figure out why (though it likely is the right thing to do). To circumvent that, you can daemonize the job in sem, but that might have unwanted side-effects: sem "[job] &"

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.

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.

Fix Quod Libet empty panes on Gentoo GNU/Linux (bug solving process)

PDF-version (for printing)

orgmode-version (for editing)

For a few days now my Quod Libet has been broken, showing only empty space instead of information panes.


I investigated halfheartedly, but did not find the cause with quick googling. Today I decided to change that. I document my path here, because I did not yet write about how I actually tackle problems like these - and I think I would have profited from having a writeup like this when I started, instead of having to learn it by trial-and-error.

Update: Quodlibet 2.6.3 is now in the Gentoo portage tree - using my ebuild. The update works seamlessly. So to get your Quodlibet 2.5 running again, just call emerge =media-sound/quodlibet-2.6.3 =media-plugins/quodlibet-plugins-2.6.3. Happy Hacking!

Update: I got a second reply in the bug tracker which solved the plugins problem: I had user-plugins which require Quod Libet 3. Solution: mv ~/.quodlibet/plugins ~/.quodlibet/plugins.for-ql3. Quod Libet works completely again.

Solution for the impatient: Update to Quod Libet 2.5.1. In Gentoo that’s easy.

Top 5 systemd troubles - a strategic view for distros

systemd is a new way to start a Linux-system with the expressed goal of rethinking all of init. These are my top 5 gripes with it. (»skip the updates«)

Update (2016-09-28): Systemd is an exploit kit just waiting to be activated. And once it is active, only those who wrote it will be able to defuse it — and check whether it is defused. And it is starting: How to crash systemd in one tweet? Alternatives? Use OpenRC for system services. That’s simple and fast and full-featured with minimal fuss. Use runit for process supervision of user-services and system-services alike.

Update (2014-12-11): One more deconstruction of the strategies around systemd: systemd: Assumptions, Bullying, Consent. It shows that the attitude which forms the root of the dangers of systemd is even visible in its very source code.

Update (2014-11-19): The Debian General Resolution resulted in “We do not need a general resolution to decide systemd”. The vote page provides detailed results and statistics. Ian Jackson resigned from the Technical Committee: “And, speaking personally, I am exhausted.”

Update (2014-10-16): There is now a vote on a General Resolution in Debian for preserving the ability to switch init systems. It is linked under “Are there better solutions […]?” on the site Shall we fork Debian™? :^|.

Update (2014-10-07): Lennart hetzt (german) describes the rhetoric tricks used by Lennart Poettering to make people forget that he is a major part of the communication problems we’re facing at times - and to hide valid technical, practical, pragmatical, political und strategical criticism of Systemd.

Update (2014-09-24): boycott systemd calls for action with 12 reasons against systemd: “We do recognize the need for a new init system in the 21st century, but systemd is not it.”

Update (2014-04-03): And now we have Julian Assange warning about NSA control over Debian, Theodore Ts’o, maintainer of ext4, complaining about incomprehensible systemd, and Linus Torvalds (you know him, right?) rant against disrupting behavior from systemd developers, going as far as refusing to merge anything from the developers in question into Linux. Should I say “I said so”? Maybe not. After all, I came pretty late. Others saw this trend 2 years before I even knew about systemd. Can we really assume that there won’t be intentional disruption? Maybe I should look for solutions. It could be a good idea to start having community-paid developers.

Update (2014-02-18): An email to the mailing list of the technical committee of debian summarized the strategic implications of systemd-adoption for Debian and RedHat. It was called conspiracy theory right away, but the gains for RedHat are obvious: RedHat would be dumb not to try this. And only a fool trusts a company. Even the best company has to put money before ethics.

Update (2013-11-20): Further reading shows that people have been giving arguments from my list since 2011, and they got answers in the range of “anything short of systemd is dumb”, “this cannot work” (while OpenRC clearly shows that it works well), requests for implementation details without justification and insults and further insults; but the arguments stayed valid for the last 2 years. That does not look like systemd has a friendly community - or is healthy for distributions adopting it. Also an OpenRC developer wrote the best rebuttal of systemd propaganda I read so far: “Alternativlos”: Systemd propaganda (note, though, that I am biased against systemd due to problems I had in the past with udev kernel-dependencies)

Phoronix conclusions distort their results, shown with the example of GCC vs. LLVM/Clang On AMD's FX-8350 Vishera

Phoronix recently did a benchmark of GCC vs. LLVM on AMD hardware. Sadly their conclusion did not fit the data they showed. Actually it misrepresented the data so strongly, that I decided to speak up here instead of having my comments disappear in their forums. This post was started on 2013-05-14 and got updates when things changed - first for the better, then for the worse.

Update 3 (the last straw, 2013-11-09): In the recent most blatant attack by Phoronix on copyleft programs - this time openly targeted at GNU - Michael Larabel directly misrepresented a post from Josh Klint to badmouth GDB (Josh confirmed this1). Josh gave a report of his initial experience with GDB in a Kickstarter Update in which he reported some shortcomings he saw in GDB (of which the major gripe is easily resolved with better documentation2) and concluded with “the limitations of GDB are annoying, but I can deal with it. It's very nice to be able to run and debug our editor on Linux”. Michael Larabel only quoted the conclusion up to “annoying” and abused that to support the claim that game developers (in general) call GDB “crap” and for further badmouthing of GDB. With this he provided the straw which I needed to stop reading Phoronix: Michael Larabel is hostile to copyleft and in particular to GNU and he goes as far as rigging test results3 and misrepresenting words of others to further his agenda. I even donated to Phoronix a few times in the past. I guess I won’t do that again, either. I should have learned from the error of the german pirates and should have avoided reading media which is controlled by people who want to destroy what I fight for (sustainable free software).
Update 2 (2013-07-06): But the next went down the drain again… “Of course, LLVM/Clang 3.3 still lacks OpenMP support, so those tests are obviously in favor of GCC.” — I couldn’t find a better way to say that those tests are completely useless while at the same time devaluing OpenMP support as “ignore this result along with all others where GCC wins”…
Update (2013-06-21): The recent report of GCC 4.8 vs. LLVM 3.3 looks much better. Not perfect, but much better.

  1. Josh Klint from Leadwerks confirmed that Phoronix misrepresented his post and wrote a followup-post: » @ArneBab That really wasn't meant to be controversial. I was hoping to provide constructive feedback from the view of an Xcode / VS user.« » Slightly surprised my complaints about GDB are a hot topic. I can make just as many criticisms of other compilers and IDEs.« » The first 24 hours are the best for usability feedback. I figure if they notice a pattern some of those things will be improved.« » GDB Follwup «@Leadwerks, 2:04 AM - 11 Nov 13, 2:10 AM - 11 Nov 13 and @JoshKlint, 2:07 AM - 11 Nov 13, 8:48 PM - 11 Nov 13

  2. The first-impression criticism from Josh Klint was addressed by a Phoronix reader by pointing to the frame command. I do not blame Josh for not knowing all tricks: He wrote a fair account of his initial experience with GDB (and he said later that he wrote the post after less than 24 hours of using GDB, because he considers that the best time to provide feedback) and his experience can serve as constructive criticism to improve tutorials, documentation and the UI of GDB. Sadly his visibility and the possible impact of his work on free software made it possible for Phoronix to abuse a personal report as support for a general badmouthing of the tool. In contrast the full message of Josh Klint ended really positive: Although some annoyances and limitations have been discovered, overall I have found Linux to be a completely viable platform for application development. — Josh Klint, Leadwerks 

  3. I know that rigging of tests is a strong claim. The actions of Michael Larabel deserve being called rigging for three main reasons: (1) Including compile-time data along with runtime performance without clear distinction between both, even though compile-time of the full code is mostly irrelevant when you use a proper build system and compile time and runtime are completely different classes of results, (2) including pointless tests between incomparable setups whose only use is to relativate any weakness of his favorite system and (3) blatantly lying in the summaries (as I show in this article). 

Making websafe colors safe for colorblind people

I just made the colors of my plotting framework safe for colorblind people (thanks to Paul Tol’s notes) and I want to share a very nice result I got: How to make the really websafe colors safe for colorblind people with minimal changes.

mostly websafe and colorblindsafe websafe but NOT colorblind safe

(the colorblind-safe colors are on the left, the original websafe colors on the right)

To do so, I turned to Color Oracle (for simulation of colorblindness directly on my screen) and Emacs rainbow-mode (for seeing the colors while editing the hex-codes - as shown in the screenshots above) and tweaked the color codes bit by bit, until they were distinguishable in the simulation of Deuteranopia, Protanopia and Tritanopia.

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