Unix and Linux

When Linux appeared in the first half of the 1990’s, I used to hear a lot: „yes, this is a nice thing, but it is not a real Unix“.

So why was there a different name, even though it was behaving almost the same? It was Posix, but Unix was a trademark, that could not be applied to Linux.

Unix was very important in the 90’s and in the 2000’s, but now it has lost almost all of its relevance.

Newer systems almost always use Linux and systems that still run Unix (Solaris or Aix) are usually considered as something that needs to be migrated to Linux sooner or later.

There is nothing wrong with Unix. It brought us great concepts and these concepts are relevant today. And inventing and standardizing these concepts was a good thing and a success story. But all the good stuff can now be found in Linux and since the progress is happening there, it has surpassed the Unixes. Of course it was a factor that HP in the late 90’s or so announced that they saw no future for their HP/UX, which they revoked, but it had created damage to that system. Oracle had bought SUN and that weakened Solaris. Many other Unix-variants have already lost their relevance long ago or are still lively and good niche systems, like BSD.

The success story behind this is that standards that work across companies have been established and allow systems to work together and to behave similarly.

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Orthodox Christmas 2019/2020

Orthodox Christmas 2019/2020 in Ukraine and probably some other countries is on 2020-01-07.


God Jul! — Feliĉan Kristnaskon! — ميلاد مجيد — Natale hilare! — Hyvää Joulua! — Срећан Божић! — Prettige Kerstdagen! — クリスマスおめでとう ; メリークリスマス — З Рiздвом Христовим! — Buon Natale! — Joyeux Noël! — С Рождеством! — Frohe Weihnachten! — ¡Feliz Navidad! — Crăciun fericit! — Merry Christmas! — καλά Χριστούγεννα! — God Jul!

This text was generated with a C# program (using Mono on Linux):

using System;
using System.Collections.Generic;
using static System.Collections.Generic.KeyValuePair;
using System.Linq;

class OrthodoxChristmas20192020 {
    private static string[] arr = new string[] {
        "Prettige Kerstdagen!",
        "God Jul!",
        "Crăciun fericit!",
        "クリスマスおめでとう ; メリークリスマス",
        "God Jul!",
        "Feliĉan Kristnaskon!",
        "Hyvää Joulua!",
        "ميلاد مجيد",
        "Срећан Божић!",
        "καλά Χριστούγεννα!",
        "З Рiздвом Христовим!",
        "Natale hilare!",
        "Buon Natale!",
        "Joyeux Noël!",
        "Frohe Weihnachten!",
        "С Рождеством!",
        "Merry Christmas!",
        "¡Feliz Navidad!"
    };

    public static void Main() {
        Random rnd = new Random();

        var shuffled = from item in arr.Select(s => new KeyValuePair<int, string>(rnd.Next(), s)) orderby item.Key select item.Value;
        int count = 0;
        foreach (string s in shuffled) {
            if (count++ > 0) {
                Console.Write(" — ");
            }
            Console.Write(s);
        }
        Console.WriteLine();
    }
}

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How to replace svn:keywords?

In the old days we used svn, cvs, rcs or other systems for source code management, that allowed enabling something like svn:keywords. This resulted in certain strings in the source code being replaced by strings containing some version information.

More often than we might think these were useful. The question „what version are we running?“ is often answered, but surprisingly often not correctly.

Now putting the version information into a comment or even better into a string that might even be logged or that might at least be extracted by using something like

strings xyz |egrep '\$Id.*\$'

allows to find out.

Now we are using git instead of svn, or at least we should be using git or plan our migration to git. There are other tools like Mercurial, that are probably just as good as git, but git is most common and every developer knows it or has to learn it anyway to stay in business.

Now git is not supporting these svn:keywords or at least not as easily, because it relies sha-checksums, which does not allow for changing file contents. There are some tricks like pre-checking and post-checkout scripts that might solve such issues, but this is kind of difficult to tame, due to the distributed characters of git including a local repo on each developers machine.

So it is better to accept that the time of this svn:keywords-stuff is over and look for something new. As an example we will consider the world of Java and JVM languages. Most use a Jenkins server to compile the software.

To create a release, even a temporary release or a release just for testing, the right way is to first label the head of the branch we are working on, then check out based on this label, compile that and upload it to the artifactory, if it is successful. Maybe rename the label or and another label. If not, maybe delete the label, depending on the processes.

Now the jar-files contain a META-INF-directory and a MANIFEST.MF. This should be the right place to put version information during such a build. More or less this can provide the same benefit as the svn:keywords, but it works with git and needs only be done in one place.

Details about how to do it will can be found out when needed.

I assume that the same approach can also be accomplished for other environments. We can even find ways that the software logs its version by changing a string in a source code file during the build process.

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Happy New Year 2020

Un an nou fericit! — Onnellista uutta vuotta! — Feliĉan novan jaron! — Καλή Χρονια! — ¡Feliz año nuevo! — С новым годом! — FELIX SIT ANNUS NOVUS — Godt nytt år! — Щасливого нового року! — Frohes neues Jahr! — Felice anno nuovo! — Bonne année! — Gott nytt år! — Срећна нова година! — عام سعيد — Gullukkig niuw jaar! — Happy new year!

This is generated with a Java 13 program using Lambdas and secure random numbers:

import java.security.SecureRandom;
import java.util.List;
import java.util.stream.Stream;
import java.util.stream.Collectors;

public class HappyNewYearJava8 {

    private static final class Element implements Comparable<Element> {
        Element(Long sortKey, String text) {
            this.sortKey = sortKey;
            this.text = text;
        }

        private Long sortKey;
        private String text;

        public String getText() {
            return text;
        }

        public int compareTo(Element e) {
            return this.sortKey.compareTo(e.sortKey);
        }
    }

    public static void main(String[] args) {
        SecureRandom random = new SecureRandom();
        List<String> list = Stream.of("Frohes neues Jahr!",
                                      "Happy new year!",
                                      "Gott nytt år!",
                                      "¡Feliz año nuevo!",
                                      "Bonne année!",
                                      "FELIX SIT ANNUS NOVUS",
                                      "С новым годом!",
                                      "عام سعيد",
                                      "Felice anno nuovo!",
                                      "Godt nytt år!",
                                      "Gullukkig niuw jaar!",
                                      "Feliĉan novan jaron!",
                                      "Onnellista uutta vuotta!",
                                      "Срећна нова година!",
                                      "Un an nou fericit!",
                                      "Щасливого нового року!",
                                      "Καλή Χρονια!")
            .map(s->new Element(random.nextLong(), s))
            .sorted()
            .map(Element::getText)
            .collect(Collectors.toList());

        System.out.println(String.join(" — ", list));
    }
}

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Christmas 2019

Joyeux Noël! — ميلاد مجيد — Crăciun fericit! — God Jul! — God Jul! — Natale hilare! — С Рождеством! — З Рiздвом Христовим! — Prettige Kerstdagen! — Hyvää Joulua! — クリスマスおめでとう ; メリークリスマス — καλά Χριστούγεννα! — Buon Natale! — Срећан Божић! — Frohe Weihnachten! — ¡Feliz Navidad! — Feliĉan Kristnaskon! — Merry Christmas!

This time the greetings were generated with a C program:

#include <stdio.h>
#include <stdint.h>
#include <openssl/rand.h>

#define N 18
static const uint32_t n = N;

int main(int argc, char **argv) {
  char greetings[N][60] = {
    "С Рождеством!",
    "Hyvää Joulua!",
    "καλά Χριστούγεννα!",
    "Buon Natale!",
    "Prettige Kerstdagen!",
    "З Рiздвом Христовим!",
    "Merry Christmas!",
    "Срећан Божић!",
    "God Jul!",
    "¡Feliz Navidad!",
    "ميلاد مجيد",
    "クリスマスおめでとう ; メリークリスマス",
    "Natale hilare!",
    "Joyeux Noël!",
    "God Jul!",
    "Frohe Weihnachten!",
    "Crăciun fericit!",
    "Feliĉan Kristnaskon!" };
  int32_t i, j;
  uint32_t x;
  uint32_t idx[N];
  int rtc;
  uint64_t r = 0;
  for (i = n-1; i >= 0; i--) {
    idx[i] = i;
  }
  RAND_bytes((char *) &r, sizeof(r));
  for (i = n-1; i > 0; i--) {
    j = r % i;
    r = r / i;
    x = idx[i];
    idx[i] = idx[j];
    idx[j] = x;
  }
  for (i = 0; i < n; i++) {
    if (i > 0) {
      printf(" — ");
    }
    printf("%s", greetings[idx[i]]);
  }
  printf("\n");
}

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Poor mans profiling with LOGs

We have professional profiling tools and we should use them.. They give really useful and extensive information.

So why bother about doing „poor man’s profiling“?

About ten years ago, running profilers was kind of constrained to very small examples and computers with really huge memory. We have this huge memory now on every development machine. But we can only run such tests on development and test systems.

Sometimes it is possible to copy data from the productive system to the test system and really simulate what is happening on the productive system. Often this is quite far away from what is really happening on the productive system and we often only know about a problem when it has already occurred.

What we usually do have are log files. Each entry has a time stamp and can somehow be connected to a line of code where it is created. We always know the class or the file or something like that from where the log statement was issued and since there is only a limited number of log statements, they can often be recognized. Sometimes it is a good idea to actually help finding where it was logged. For example could we artificially put the source code line number or some uniq number or a short random string into the source code for each log statement. Then we can find several pieces of information in the log statement:

  • The timestamp (please use ISO-format!!! And at least milliseconds)
  • The source code location (line number, class name, random string, relative position in file, meaningful description like entering/leaving methods etc.)
  • The thread and/or process
  • The payload information of the log

Now log statements analyzed by thread. The first step is to look from which pairs of locations in the source code we observe successive log statements from the same thread, ignoring all logging from other threads and processes. We can also estimate the time that was spent for going from the first to the second location. Aggregating this by basically adding up thes timestamp deltas for each such pair over all threads and the whole log file will already indicate some hotspots where time is spent. Sometimes it is even interesting to look at sequences of three log statements (from the same thread). This was useful, when DB-commits, i.e. one such pair like „begin commit“ to „commit done“ used around 50% of the time, if not more. This was not interesting without knowing the statement that was committed, which was found out by looking at the previous log entry of the same thread just before the commit.

Such analysis can be done with scripts for example in Perl, Ruby or Python. I use Perl for this kind of task. Maybe log analysis tools provide this out of the box or with a little bit of tweaking. A concept about what entries in log files look like that make recognizing the location of the program that created the log entry, are very helpful. Sometimes we actually want to see, with which kins of data the problem occurred, which means looking also into the payload.

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50 years of internet

According to some the RFC1, which was published on 1969-04-07, was the start of the internet. Many RFCs have since this time been published and they describe the standards of the internet.

The early internet did contain functionality to communicate between computers, but it did of course not include http, html and the WWW, which were introduced much later in the early nineties.

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Orthodox Christmas 2018/2019

Orthodox Christmas in some countries, for example in Ukraine is on 7th of January.
So to all readers, who have Christmas on 7th of January:


С Рождеством! — Hyvää Joulua! — καλά Χριστούγεννα! — Buon Natale! — Prettige Kerstdagen! — З Рiздвом Христовим! — Merry Christmas! — Срећан Божић! — God Jul! — ¡Feliz Navidad! — ميلاد مجيد — クリスマスおめでとう ; メリークリスマス — Natale hilare! — Joyeux Noël! — God Jul! — Frohe Weihnachten! — Crăciun fericit! — Feliĉan Kristnaskon!

I created the message and the random ordering using Perl and the Schwartzian transform:

#!/usr/bin/perl
use Math::Random::Secure qw(irand);
my @list = ( "Prettige Kerstdagen!",
          "God Jul!",
          "Crăciun fericit!",
          "クリスマスおめでとう ; メリークリスマス",
          "God Jul!",
          "Feliĉan Kristnaskon!",
          "Hyvää Joulua!",
          "ميلاد مجيد",
          "Срећан Божић!",
          "καλά Χριστούγεννα!",
          "З Рiздвом Христовим!",
          "Natale hilare!",
          "Buon Natale!",
          "Joyeux Noël!",
          "Frohe Weihnachten!",
          "С Рождеством!",
          "Merry Christmas!",
          "¡Feliz Navidad!" );
my @shuffled = map{ $_->[0] }
               sort {$a->[1] <=> $b->[1]}
               map { [ $_, irand() ] }
               @list;
print join(" — ", @shuffled);

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2019 — Happy New Year

Gott nytt år! — Godt nytt år! — Felice anno nuovo! — Καλή Χρονια! — Щасливого нового року! — Срећна нова година! — С новым годом! — Feliĉan novan jaron! — Bonne année! — FELIX SIT ANNUS NOVUS — Gullukkig niuw jaar! — Un an nou fericit! — Frohes neues Jahr! — Happy new year! — ¡Feliz año nuevo! — Onnellista uutta vuotta! — عام سعيد

This was created by a Java-program:

import java.util.Random;
import java.util.List;
import java.util.Arrays;
import java.util.Collections;

public class HappyNewYear {

    public static void main(String[] args) {
        List list = Arrays.asList("Frohes neues Jahr!",
                                          "Happy new year!",
                                          "Gott nytt år!", 
                                          "¡Feliz año nuevo!",
                                          "Bonne année!", 
                                          "FELIX SIT ANNUS NOVUS", 
                                          "С новым годом!",
                                          "عام سعيد",
                                          "Felice anno nuovo!",
                                          "Godt nytt år!", 
                                          "Gullukkig niuw jaar!", 
                                          "Feliĉan novan jaron!",
                                          "Onnellista uutta vuotta!",
                                          "Срећна нова година!",
                                          "Un an nou fericit!",
                                          "Щасливого нового року!", 
                                          "Καλή Χρονια!");
        Collections.shuffle(list);
        System.out.println(String.join(" — ", list));
    }
}

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Christmas 2018


Feliĉan Kristnaskon! — Frohe Weihnachten! — God Jul! — Merry Christmas! — Joyeux Noël! — クリスマスおめでとう ; メリークリスマス — Срећан Божић! — Buon Natale! — Hyvää Joulua! — З Рiздвом Христовим! — ميلاد مجيد — С Рождеством! — Crăciun fericit! — ¡Feliz Navidad! — καλά Χριστούγεννα! — Natale hilare! — God Jul! — Prettige Kerstdagen!

As I said, I am learning some Python, so let’s use it. I created the message above with this program:

#!/usr/bin/python3
import random
arr = [
    "Frohe Weihnachten!",
    "Merry Christmas!",
    "God Jul!",
    "¡Feliz Navidad!",
    "Joyeux Noël!",
    "Natale hilare!",
    "С Рождеством!",
    "ميلاد مجيد",
    "Buon Natale!",
    "God Jul!",
    "Prettige Kerstdagen!",
    "Feliĉan Kristnaskon!",
    "Hyvää Joulua!",
    "クリスマスおめでとう ; メリークリスマス",
    "Срећан Божић!",
    "Crăciun fericit!",
    "З Рiздвом Христовим!",
    "καλά Χριστούγεννα!"
]
random.shuffle(arr)
print(" — ".join(arr))
print("\n")

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