http://winged.ch/ Recent content on Winged.ch Hugo -- gohugo.io en Wed, 19 Dec 2018 00:00:00 +0000 http://winged.ch/exploding_load/ Wed, 19 Dec 2018 00:00:00 +0000 http://winged.ch/exploding_load/ Today, I had an interesting problem to solve. Since a few weeks, I’d sporadically get bugged by the on-call team about a production server with a legacy app that generate excessively high load. The on-call guys usually check the obvious things like disk capacity, memory etc, but it’s always good to double-chek. But again - Disk - IO is fine, capacity is fine (and the app mainly just reads and writes to DB). http://winged.ch/snake_again/ Mon, 18 Jul 2016 00:00:00 +0000 http://winged.ch/snake_again/ When at FOSDEM, I was inspired to hack up a simple Snake game. And today, I saw the awesome talk by Nicholas Tollervey about what the BBC does with the micro:bit at EuroPython 2016. Well, nice, I thought, but just as we left the talk, Nicholas announced that every attendee will get a free micro:bit to play with. AWESOME! So after a bit of tinkering with the device, I had the idea to use the LEDs on the device to implement the game again. http://winged.ch/lpask/ Sat, 21 May 2016 00:00:00 +0000 http://winged.ch/lpask/ So I've often wanted to send something out from vim (or indeed any other console tool). GVim on Windows shows you the system print dialog, but neovim certainly does not. You could always pass in the appropriate printer name to the lp tool, but really, do you always remember the exact name of your printer? Especially if you have some auto discovery in CUPS and may at times be at one office and other times in another office (With different printers around). http://winged.ch/goblin_700_dismount_autorotation/ Thu, 19 May 2016 00:00:00 +0000 http://winged.ch/goblin_700_dismount_autorotation/ I’m currently trying to learn some new tricks on my RC helis - got some attemts on dismount autorotations on video: Sorry for the vertical video… Need to have a talk with my camera man. And this is what it should look like when it’s perfected: http://winged.ch/tail_recursion_in_python/ Mon, 09 May 2016 00:00:00 +0000 http://winged.ch/tail_recursion_in_python/ So I've had a very recursive problem that needed to be solved in python. Now as we know, python does not support tail recursion, so if your problem is a wee bit too complex, you're running out of space. Luckily, it's quite easy to hack up some kind of workaround, so this is exactly what I did. I'm sure there are cleaner / better solutions out there, but half the fun is doing it yourself. http://winged.ch/erlang_strings/ Tue, 15 Mar 2016 00:00:00 +0000 http://winged.ch/erlang_strings/ I’m currently diving head-first into Erlang and all it’s awesomeness. If you’ve never really jumped in, Erlang may seem kinda… weird. And if you had a closer look, it may seem even weirder. Well, I feel like I’m now slowly getting past the weird phase and start to enjoy it quite a lot. But there’s still some things that surprise you. For example, how strings are built. When you look at any tutorial, they will tell you that strings are basically just list of integers, which then get interpreted as ASCII (or UTF8) when printing out (which leads to some more weirdness if you actually try to print a list of integers that just accidentally are ASCII-representable). http://winged.ch/some_vim_tips_and_tricks/ Fri, 19 Feb 2016 00:00:00 +0000 http://winged.ch/some_vim_tips_and_tricks/ This started out as an internal training at Adfinis SyGroup to show off some Vim features and how to work best with it. I’m assuming that you know the absolute basics, like Vim’s primary modes like insert, normal, ex, and what each one does. Preparations It’s essential that you get some text somewhere to play around. How about some Samuel L. Jackston Lorem Ipsum text? Go and grab some paragraphs of that. http://winged.ch/headaches/ Wed, 10 Feb 2016 00:00:00 +0000 http://winged.ch/headaches/ I had a request from a customer to review an existing legacy web app to see if my company would take over it's maintenance. The app uses some "max framework" or something, which had some .. uhm .. shall we say "pretty interesting" bits of code. I'm sharing some of those nuggets here. Sometimes I'm very happy to be able to turn down customers! So - it seems that the authors of this framework really are lazy. http://winged.ch/snaaaake/ Mon, 01 Feb 2016 00:00:00 +0000 http://winged.ch/snaaaake/ So, I was at FOSDEM this last weekend, and had quite a lot of fun. One of the cooler talks was actually Yuri Numerov's talk about making simple console-based games in Python. I thought hey, I can do that too! and started hacking on a Snake implementation right away. You know, that game you used to waste all your time back in the Nokia 3210 days? Yep, that one. Turns out, you can do that in less than 100 lines of python. http://winged.ch/btrfs_minimal_backup_script/ Mon, 06 Jan 2014 00:00:00 +0000 http://winged.ch/btrfs_minimal_backup_script/ My /home partition is a BTRFS volume. Since it allows for very easy snapshotting, I decided to use it for providing a very simple history functionality. Note that this is not a REAL backup, because it doesn't protect against disk or machine failures. However it provides easy access to earlier versions of the file system. Here's how it works: Run it on a hourly basis Creates a separate snapshot for every hour the machine is running Creates a snapshot for every day of the month Creates a snapshot for every month of the year The script is really very simple: http://winged.ch/the_next_web/ Tue, 23 Apr 2013 00:00:00 +0000 http://winged.ch/the_next_web/ Recently, I've started to get really frustrated by what the web is becoming. It seems that everything is going to become more and more centralised. Google and Facebook currently control a huge amount of the world's communication systems. Everything seems to move "to the cloud", which is provided by a few large companies. Many businesses stopped using local installations of Microsoft Office or OpenOffice, putting everything on Google Docs instead. http://winged.ch/vundle_autoinstall/ Sat, 16 Mar 2013 00:00:00 +0000 http://winged.ch/vundle_autoinstall/ My setup (especially my config files in my $HOME) are synced across many machines using a dedicated git repository. Up until now, I've used TPlugin and a bunch of subdirectories in ~/.vim/bundle to handle it. Unfortunately, this never really worked well. So, I switched to Vundle, which is AWESOME. Now, how do I install vundle on all my machines? Some of them are only used rarely and it's quite possible that I'll forget where to get vundle from in that moment. http://winged.ch/pelican_article_series/ Fri, 22 Feb 2013 00:00:00 +0000 http://winged.ch/pelican_article_series/ My first idea was to just use tags, and then list all the articles in a specific tag together. However, tags should be pretty short, and I wanted my series to have a bit more of a descriptive name. After toying around a bit, I stumbled upon the fact that you can put arbitrary metadata in your articles, which you can then use in the templates. So, after thinking a bit, a plan was born - and promptly implemented. http://winged.ch/language-fun/dvm01_now_with_labels/ Wed, 20 Feb 2013 00:00:00 +0000 http://winged.ch/language-fun/dvm01_now_with_labels/ In my previous article, I came to the conclusion that programming in DVM01 is, in fact, quite troublesome. The trickiest part, by far, was getting the correct addresses when you need to jump to another code location. The stack implementation (link above) used a bunch of NOPs to help with aiming the jumps. While this helps a bit, it’s still only a hack. So I decided to give you… http://winged.ch/pages/about/ Sun, 17 Feb 2013 00:00:00 +0000 http://winged.ch/pages/about/ This is the personal blog of David Vogt, from Switzerland. This site is mainly about my adventures in software development. Some stories are about things I learn at work, other stories are about my private projects. I try to keep this site about technical stuff, mostly programming and other software topics, but may occasionally also write about my hobbies, like mountain biking or RC helicopters. About the author I’m working as head of the software development department at Adfinis SyGroup AG in Bern, a company dedicated to providing open source technologies to businesses and organisations in Switzerland and it’s neighbouring countries. http://winged.ch/vim_outliner/ Tue, 04 Dec 2012 00:00:00 +0000 http://winged.ch/vim_outliner/ To organise my tasks, I have defined some handy shortcuts in vim to quickly add a new TODO line, and to jump to the next item with a given priority. Just add the following lines to your .vimrc: " Search helpers for finding unfinished tasks, by priority au FileType vo_base nmap <buffer><silent><leader>1 gg/^\s*\[_\]\ P1.*<cr> au FileType vo_base nmap <buffer><silent><leader>2 gg/^\s*\[_\]\ P2.*<cr> au FileType vo_base nmap <buffer><silent><leader>3 gg/^\s*\[_\]\ P3.*<cr> au FileType vo_base nmap <buffer><silent><leader>4 gg/^\s*\[_\]\ P4. http://winged.ch/language-fun/stack/ Tue, 03 Jul 2012 00:00:00 +0000 http://winged.ch/language-fun/stack/ As with past code examples, I’m mainly going to show pieces of code along with some commentary. Also, the complete source is at my github archive, so all you need is a browser and/or node.js installed to play around :) Okay, so what about the design decisions? Here’s what I want / need in a stack implementation: (Just as a reminder): A stack consists of a piece memory that acts in a first in, last out way. http://winged.ch/natd_ssh_connections/ Mon, 09 Apr 2012 00:00:00 +0000 http://winged.ch/natd_ssh_connections/ At our company, we have to SSH into a client server via port forwarding on their gateway, like this: :::shell ssh gateway -l root -p 1349 Which is, of course, quite troublesome. Fortunately, SSH (in combination with netcat) can be configured to work around this. You can even make a pretty “alias” for that connection. Add the following lines to your .ssh/config file: Host my_alias ProxyCommand nc gateway 1349 Now, you can simply connect to the NAT’d server like this: http://winged.ch/language-fun/erathosthenes/ Mon, 09 Apr 2012 00:00:00 +0000 http://winged.ch/language-fun/erathosthenes/ Okay, so how do we implement this in DVM01? Since we (currently) have poorno support for memory management, the first thing I thought was that we need some agreement over how to do the marking. Usually, you set up a bunch of memory first, initializing it. Better implementation don’t use a list of booleans, but use every bit separately, thus saving a huge load of space. We won’t do that, because it makes the code more complex. http://winged.ch/language-fun/first_programs_for_dvm01/ Fri, 06 Apr 2012 00:00:00 +0000 http://winged.ch/language-fun/first_programs_for_dvm01/ Anything that can be programmed must have a few things: Documentation, and a few examples. This being about programming, it’s tradition to write a “Hello World” program first. So without further ado, let’s have a go: Hello World! This program just writes out that well-known message to it’s output, then quits: START WRITEC 72 WRITEC 101 WRITEC 108 WRITEC 108 WRITEC 111 WRITEC 32 WRITEC 87 WRITEC 111 WRITEC 114 WRITEC 108 WRITEC 100 WRITEC 33 END Pretty simple, huh? http://winged.ch/language-fun/a_simple_virtual_machine/ Fri, 02 Sep 2011 00:00:00 +0000 http://winged.ch/language-fun/a_simple_virtual_machine/ Many times, I started hacking up a specification of the core features of “my” language, only to discover that such a spec is a huge project in itself: The more spec I wrote, the more details turned up that I just couldn’t keep track of. In the end, I always got demotivated moved on, only to try again a few weeks or months later. So, this time, I’ve decided to try more of a bottom-up approach: Before even starting on another language specification, I wanted to implement something simple, something which could then evolve with my knowledge of the domain. http://winged.ch/javascript_pc_emulator/ Sat, 08 Jan 2011 00:00:00 +0000 http://winged.ch/javascript_pc_emulator/ At first, I really thought it was just some fake emulation of a shell, but then… poking around in the system (and reading the tech info), I saw that it was “real”. There’s even a C compiler, running in your browser! If that’s not cool, I don’t know WHAT is. http://winged.ch/php_exceptions/ Sat, 08 Jan 2011 00:00:00 +0000 http://winged.ch/php_exceptions/ What happend is this: I'm currently hacking away on my diploma thesis, involving some coding in PHP. No problem so far. In doing so, I'm using many features new in PHP 5.3, such as namespaces and some other niceties, which are of no concern for us today. Namespaces do have a few weird side effects, one of which I discovered in the following story: Trying to implement some exception-catching code, I wrote the following lines: http://winged.ch/interesting_times/ Thu, 11 Nov 2010 00:00:00 +0000 http://winged.ch/interesting_times/ Alright, it’s been a while. But here’s a post that I wanted to do a few weeks back already, but didn’t get around to do it. But in the meantime, There were a few more ideas being tossed about, so now it’s about time I write this. So, here’s what it’s about: As a software developer, I have almost anything computer-related set to english. Unfortunately, the english dialects that are acceptable (being en_US and en_GB) both have funny date strings that I do not like. http://winged.ch/mysql_and_enums/ Thu, 02 Sep 2010 00:00:00 +0000 http://winged.ch/mysql_and_enums/ Turns out that a database update wasn’t done, so an ENUM field did not allow the values requested by the application. This in turn caused a weird error message that, in my opinion, just could not be! mysql> CREATE TABLE foo( -> something ENUM('a', 'b', 'c') -> ); Query OK, 0 rows affected (0.12 sec) mysql> INSERT INTO foo -> SET something = 'x'; Query OK, 1 row affected, 1 warning (0. http://winged.ch/pain/ Wed, 16 Sep 2009 00:00:00 +0000 http://winged.ch/pain/ Imagine... Imagine a file with about four thousand lines (yep, that's right, 4000). There, you will find such gems like the following. Note that I've grepped out the "if" statements, as the content in each block is trivial (puts together a single variable). For illustration, look at the first and last entry block to get an idea what the code does. And here we go: if(!empty($searchSubject) && empty($searchLevel) && empty($searchProfile) && empty($searchCountry) && empty($searchVertical) ) { $concat='( partnersMain. http://winged.ch/mel_and_the_lgp30_manual/ Mon, 31 Aug 2009 00:00:00 +0000 http://winged.ch/mel_and_the_lgp30_manual/ Out of a coincidence, we came across the good old jargon file.. again. In it is the great Story Of Mel, who is a Real Programmer For those who don’t know that story yet, here’s a teaser: Since Mel knew the numerical value of every operation code, and assigned his own drum addresses, every instruction he wrote could also be considered a numerical constant. He could pick up an earlier “add” instruction, say, and multiply by it, if it had the right numeric value. http://winged.ch/resizing_bash/ Tue, 04 Aug 2009 00:00:00 +0000 http://winged.ch/resizing_bash/ Finally found that bloody option again for making bash not fuck up when the terminal is resized...Quoting http://www.faqs.org/faqs/unix-faq/shell/bash/: There is a 'checkwinsize' option, settable with the 'shopt' builtin, that will cause bash to check the window size and adjust its idea of the terminal's dimensions each time a process stops or exits and returns control of the terminal to bash. Enable it with 'shopt -s checkwinsize'. Whew. Now let's not forget this option ever again.