Recent Posts

A git hook to prevent pushes with untracked source files (August 08, 2014)

Hey all,

do you know this: You work on something locally in git, ensure everything compiles and the tests pass, then commit and hit git push.What could possibly go wrong at that point, eh? Well, far too often I forgot to git add some new source file. Best-case I’ll notice this directly, worst-case I’ll see my CI complaining. But, like yesterday in kdev-clang, I might be afk at that point and someone else will have to revert my change and I’ll have to fix it up the day after, polluting the git history while at it…

Thanks to some simple shell scripting and the powerful git hook architecture, it is pretty simple to protect oneself against such issues:

    # A hook script to verify that a push is not done with untracked source file
    # To use it, either symlink this script to $your-git-clone/.git/hooks/pre-push
    # or include it in your existing pre-push script.
    # Perl-style regular expression which limits the files we interpret as source files.
    # The default pattern here excludes CMakeLists.txt files and any .h/.cpp/.cmake files.
    # Extend/adapt this to your needs. Alternatively, set the pattern in your repo via:
    #     git config hooks.prepush.sourcepattern "$your-pattern"
    pattern=$(git config --get hooks.prepush.sourcepattern)
    if [ -z "$pattern" ]; then
    files=$(git status -u --porcelain --no-column | sed "s/^?? //" | grep -P "$pattern")
    if [ -z "$files" ]; then
      exit 0
    echo "ERROR: Preventing push with untracked source files:"
    echo "$files" | sed "s/^/    /"
    echo "Either include these files in your commits, add them to .gitignore"
    echo "or stash them with git stash -u."
    exit 1

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Maxwell distribution in C++11 (July 29, 2014)

Hey all,

I recently needed to generate values following a Maxwell distribution. Wikipedia gives the hint that this is a Gamma distribution, which in C++11 is easily useable. Thus, thanks to <random>, we can setup a Maxwell distribution in a few lines of code:

    #include <random>
    #include <chrono>
    #include <iostream>
    using namespace std;
    int main()
        unsigned seed = chrono::system_clock::now().time_since_epoch().count();
        default_random_engine generator(seed);
        // Boltzmann factor times temperature
        const double k_T = 0.1;
        // setup the Maxwell distribution, i.e. gamma distribution with alpha = 3/2
        gamma_distribution<double> maxwell(3./2., k_T);
        // generate Maxwell-distributed values
        for (int i = 0; i < 10000; ++i) {
            cout << maxwell(generator) << endl;
        return 0;

Pretty neat, I have to say!

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Styling Apache Indexes (February 13, 2013)

The default output of Apaches Options +Indexes doesn’t look good at all. Very 1990 something… But - as with pretty much any open source open source software - there are tons of options, which enable you to change everything to your likings!

The contents of .htaccess

    # default order: descending by name
    IndexOrderDefault Descending Name
    # set the following options:
    # - ignore case
    # - don't display the description column
    # - display folders first
    # - set the width of the name column to 40 chars
    # - don't display the default HTML output (doctype, head, ..., starting <body> tag)
    # - use Fancy Indexing
    # - set IconHeight und Width to 16 pixels (FamFams Icons use these dimensions)
    IndexOptions +IgnoreCase +SuppressDescription +FoldersFirst +NameWidth=40 +SuppressHTMLPreamble +FancyIndexing +IconHeight=16 +IconWidth=16
    # we want to use indexes for this folder!
    Options +Indexes
    # the header template, which is displayed before the list
    HeaderName ../list_header.html
    # the footer template, which is displayed after the list
    ReadmeName ../list_footer.html
    # don't display the link to the root folder
    IndexIgnore ..
    # set the default icon to a fancy famfam icon
    DefaultIcon ../images/bricks.png

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Git commit message highlighting in nano (November 24, 2012)

For those who use nano as their CLI editor of choice: Here’s a syntax highlighting file for Git commit messages which also supports the special KDE commit hook keywords.

    ##  syntax highlighting for git commit messages of KDE projects
    syntax "patch" ".git/COMMIT_EDITMSG$"
    # overlong lines
    color brightred "^.{70,}.+$"
    # KDE commit hook keywords, see:
    color yellow "(SVN_SILENT|GIT_SILENT|SVN_MERGE)"
    # comment
    color blue "^#.*$"
    # special comment lines
    color green "^# Changes to be committed:"
    color red "^# Changes not staged for commit:"
    color brightblue "^# Untracked files:"
    color brightblue "^# On branch .+$"
    color brightblue "^# Your branch is ahead of .+$"
    # diff files
    # meh - cannot match against \t ... should be: ^#\t.*$
    color cyan "^#[^ a-zA-Z0-9][^ ].*$"

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Access klipper clipboard on CLI under KDE4 (August 04, 2012)

NOTE: find most recent version on github:

Here’s a little script you can save in your path and do things like

    # paste current clipboard into file
    clipboard > "some_file"
    # copy some file into clipboard
    cat "some_file" | clipboard

Actually I find it rather useful so I thought I should share it.

    # Access your KDE 4 klipper on the command line
    # usage:
    #  ./clipboard
    #    will output current contents of klipper
    #  echo "foobar" | ./clipboard
    #    will put "foobar" into your clipboard/klipper
    # check for stdin
    if ! tty -s && stdin=$(</dev/stdin) && [[ "$stdin" ]]; then
      # get the rest of stdin
      # oh, nice - user input! we set that as current
      # clipboard content
      qdbus org.kde.klipper /klipper setClipboardContents "$stdin"
    # if we reach this point no user input was given and we
    # print out the current contents of the clipboard
    qdbus org.kde.klipper /klipper getClipboardContents

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Tracking Memory Consumption Using Pmap (March 19, 2012)

Massif is a really nifty tool which is very powerful, especially paired with my visualizer. The caveat of course is that it slows down the application considerably, I’ve seen anything up to a factor of 100… I see no alternative to Massif when it comes to investigating where your memory problems come from. But if you just want to see whether you have a problem at all, tracking the total memory consumption should suffice.

A few days ago, I came across pmap on Stack Overflow, which makes it easy to track the RSS memory consumption of an application using the -x switch. Of course I had to write some bash magic to automate this process and visualize the data using Gnuplot! Behold:

memory consumption of PhantomJS
memory consumption of a PhantomJS script over ~30min

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Qt: Tint alphatransparent PNG (September 21, 2011)

Let’s assume you want to display the logo of your company in your Qt app. Most probably that logo has just single color with an alpha channel.But: Having the color hard coded in the image is not nice, there are users (like me!) out there, who use a custom (dark!) color scheme. Meaning: If your logo is black/dark and assumes a bright background and you just embed it blindly in your app, I probably won’t see it since the background will be dark in my case.

Here is a solution for the simple case of a mono-colored PNG with an alpha channel which I came up with:

      QLabel* label = new QLabel;
      // load your image
      QImage img(QString("..."));
      // morph it into a grayscale image
      img = img.alphaChannel();
      // the new color we want the logo to have
      QColor foreground = label->palette().foreground().color();
      // now replace the colors in the image
      for(int i = 0; i < img.colorCount(); ++i) {
        img.setColor(i, foreground.rgba());
      // display the new logo

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syntax highlighting for *.ini files in nano (February 27, 2011)

Use the snippet below in your ~/.nanorc or /etc/nanorc file to highlight *.ini files like php.ini in Nano.

    # ini highlighting
    syntax "ini" "\.ini(\.old|~)?$"
    # values
    color brightred "=.*$"
    # equal sign
    color green "="
    # numbers
    color brightblue "-?[0-9\.]+\s*($|;)"
    # ON/OFF
    color brightmagenta "ON|OFF|On|Off|on|off\s*($|;)"
    # sections
    color brightcyan "^\s*\[.*\]"
    # keys
    color cyan "^\s*[a-zA-Z0-9_\.]+"
    # comments
    color brightyellow ";.*$"

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Take 2: Download script for Ebooks (March 12, 2010)

NOTE: This script is apparently against the licensing contract between universities and Springer, see:

NOTE 2: I do not maintain this script anymore. Please look for an alternative.

Seems like quite some people are interested in my bash script for downloading ebooks from

That script has some quirks, the greatest of all that it was written in bash which makes it kind of hard to implement new features. And one which was requested was support for books which span multiple pages on SpringerLink.

So here I present - a Python rewrite which should handle all the old links and some more. This is the very first program I’ve written in Python. And since it has to run on the Zedat servers it’s limited to Python 2.4.x without any fancy shmancy additions (a pity, since I’d love to use urlgrabber or pycurl).

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Shell helper: running KDE unit tests (ctests) the easy way (March 26, 2009)

Unit tests are in my eyes a very important part of programming. KDE uses them, KDevelop does - the PHP plugin I help writing does as well. cmake comes with a ctest program which does quite well to give you a quick glance on which test suite you just broke with your new fance feature :)

But I am very dissatisfied with it. Right now I usually do the following

    # lets assume I'm in the source directory
    cb && ctest
    # look for failed test suites
    cd $failed_test_suite_path
    ./$ | less
    # search for FAIL
    cd $to_whereever_I_was_before

That’s pretty much for just running a test. Especially all that cding and lessing became very tedious. Tedious is good, because I eventually fix it:

introducing kdetest

I wrote a bash function (with autocompletion!!!) called kdetest. Calling it without any parameter will run all test suites and gives a nice report of failed functions at the end. Here’s an example (run via cs php && kdetest).

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