Older articles (12/27)

1. Adding an overlay to each page of a pdf file

   We can use PostScript’s Endpage procedure to e.g. add a signature to each page of a PDF file, using only ghostscript.

2. Install ntpsec on FreeBSD

   A short article on how to install ntpsec on FreeBSD. Tested with 0.9.7 and 1.0.0.

   Note

   There is/was a bug in the ntpdate implementation that set the clock to a completely bogus value. So I’ve since written a simple script that runs from cron to fetch the time from a near NTP server.

3. Transplanting noscript settings and bookmarks to another machine

   After upgrading a laptop to 12-CURRENT, I had problems with firefox 57 choking on some javascript in an extension. So I renamed my ~/.mozilla directory and let firefox create a new one. That solved the problem. But with that I lost my noscript settings and my bookmarks.

4. Using sqlite3 for time management

   After some initial experiments with sqlite as a replacement for a json data file format (which I did not pursue in the end), I have now started using sqlite in earnest. And I must say that I quite like it.

5. Database scheme for resin recipes

   This document explores how an SQLite database could be used to store data for the resin-calculator. Normally, the recipes are a dictionary keyed to the name of the resin. The value of each recipe is a list of (component, parts-by-weight) tuples. Since a database only contains tables, where each row has the same form, how do we store such infomation in a database?

6. Converting RCS history to git

   Before the rise of git, I used rcs as my version control system. Because I want to standardize on git, I am slowly converting old repositories.

   In this article, as an example, I’ll be converting my old perl scripts in ~/src/perl.

7. Compiling asymptote for TeXLive on FreeBSD

   As of TeXLive 2015 there is no TeXLive binary for FreeBSD included anymore. So I’m building my own, using …

8. Doing calculations with Python

   As an engineer I do a lot of calculations. These can be done with pen and paper and a calculator, in an IPython notebook or in a throwaway spreadsheet. All of these methods have shortcomings, though.

   Pen and paper is hard to share and (in my case) hard for others to read. In IPython you can assign the results of calculations to a variable, but you have to perform a separate action to display them. And spreadsheets in general show you the results but not the calculations.

   So I wrote a simple function in Python to help me with that. Using this function I can print both simple assignments and relatively complex calculations. And it shows both the calculation and the result.

9. Improving my Python coding

   With leading white space governing the indentation level and so the grouping of statements, Python code already looks relatively clean.

   Yet there are additional tools that will help you improve your code.

10. Structures in Python

    Sometimes I miss the C’s plain old struct in Python.

    Of course Python has dictionaries, but I prefer to write a.b over a['b'].

    Here are several ways of doing something akin to a struct in Python.