Welcome

This is my home in the virtual world, where I write about things that I want to share. The freely available software that I've written as well as some of the photographs I've taken over the years can also be found here. Please use the navigation links on the right if you are looking for something.

Recent articles

1. Buildworld benchmark on my new workstation

   As a real-world benchmark I rebuilt the FreeBSD OS after the most recent published vulnerabilities.

2. Writing speed on FreeBSD 12.1-STABLE amd64

   This is a repeat of the tests I ran in 2010 and 2012, on my current hardware.

   The test is …

3. Playing a sound when the battery is low

   Although I have a battery indicator on the bottom of my laptop screen I don’t alway check that often enough. That’s why I wanted to add an extra warning in the form of an audio signal. So even if I’m turned away from the laptop, it should still catch my attention.

4. Generating barcodes with “BWIPP”

   Originally I looked for a Python module to generate barcodes, and I found the treepoem module. This used Pillow to create bitmaps, and I preferred to have PDF or other resolution independant formats. Looking through the README, I found that treepoem is a wrapper for bwipp. This is a set of PostScript procedures to generate barcodes.

   Since I’m familiar with using PostScript, I decided to use bwipp directly.

5. On the nature of GUI programs

   This is based on an answer I gave on stackoverflow. That answer is specific to the tkinter toolkit that comes with Python. The principles apply to other GUI toolkits and languages as well but the terminology used (like mainloop and idle task) may be different.

6. Have Python log to syslog

   This article documents how I set up Python and the syslog daemon so that Python programs can log to syslogd.

7. Command-line versus GUI program

   TL;DR

   When you are exploring a problem, in general first write a command-line program whenever possible.

   It will take less effort to write then a full-blown GUI.

   Introduction

   Recently I wrote a program to remove the protection from ms-excel files.

   The original version was written as a command-line program. Later I re-used the relevant code for a GUI program for use on ms-windows. This was mainly for the benefit of some colleagues who are not comfortable with using the command-line.

   In this article I want to contrast the two programs.

8. Creating a screenshot in X11

   Creating a screenshot from a terminal, using standard UNIX tools.

9. How convenient is multithreading compared to multiprocessing?

   There are basically two ways in which one can make use of a modern CPU with multiple cores for computationally intensive work.

   1. Using multiple threads within one program (multithreading).
   2. Using multiple (single-threaded) programs that communicate (multiprocessing).

   In the first case, all data is implicitly shared. In the second case, data must be explicitly shared or communicated.

   The first option is often said to be more convenient. I would like to make the case that this usually makes the task more difficult, because of the need to manage all shared data.

10. Roll back a FreeBSD port with svnlite

    Sometimes I’m too hasty with updating ported applications, and I need to roll them back to a working version. Since I use svnlite to manage my ports tree, this is relatively easy. But since it is different than I’m used to (since I mostly use git), I thought I would document it here for convenience.