The Internet Security Architecture

19. Januar 2023 in Society, Graphics, Multimedia.

Eine Bemerkung über das Funktionieren

16. Dezember 2022 in Society, Technology.

Nach einer Weile hört man immer mal wieder gewisse Sprüche über das Funktionieren irgendwelcher Produkte, Technologien, Techniken, Lösungswege, Praktiken oder Konfigurationen X:

  • “Was funktioniert [also X], ist gut.”
  • “X ist nicht schön, aber es funktioniert.”
  • “Hauptsache, es [gemeint ist X] funktioniert.”
  • “Wieso, es [X] funktioniert doch!”
  • “Wir wissen zwar nicht warum, aber es [X] funktioniert.”

Lösungen für drängende Probleme müssen gefunden werden, und es gibt Situationen, da müssen Nägel mit Köpfen gemacht werden. Zuweilen muss ich aber auch mal auf die Bremse treten, so etwa, wenn ich erkenne, dass ein Lösungsvorschlag X (vielleicht) momentan eine Lösung darstellt, auf Dauer aber zum Problem werden wird.

Die Geisteshaltung “was funktioniert, ist gut” ist mitreißend, und die Sprüche sind eingängig, also habe ich mir für den Fall, dass ich dagegen halten muss, eine ähnlich eingängige Gegenbemerkung zurechtgelegt:

“X ist total super, solange es funktioniert.”

Es gibt auch eine universelle Form:

“Alles ist total super, solange es funktioniert.”

 The Way Home

20. Juli 2025 in Music.

 

 

  • Electronic, 117bpm

Removing the Builtin Inline CSS from WordPress

27. August 2022 in Programming.

Should you – as i did – wonder why WordPress renders a bucket of inline CSS into the HTML output (such as --wp--preset--font-size--normal in <html> or  --wp--preset--color--white in <body>): This is done to accomodate frontend editing with Gutenberg. If you – as i do – are not using Gutenberg frontend editing, then the following PHP code can be included in the functions.php of a custom theme or the php file of a custom plugin. Sorry, Gutenberg folks – no means no. 🙂

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Updated Common Prefix Notation Transformation

2. Februar 2024 in Programming.

This is an update to my previous article on determining the common prefixes of a set of strings (passed a sequence of lines) and printing them in common prefix notation (CPN). The problem of reconstructing strings from the original input that are complete prefixes of other input strings is addressed.

The code is now in a Git repository:

Project information not readable.

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Print XDG Desktop Definition for Application

3. November 2024 in Administration, GNU/Linux.

Update Nov 3 2024:

For an application given by “application name” or “executable name”, output the corresponding .desktop file, if any:

#!/bin/sh
IFS=":"
xdg_data_dirs=${XDG_DATA_DIRS:-/usr/local/share:/usr/share}
search=$1

for i in $xdg_data_dirs ; do
  a="$i/applications"

  [ -d $a ] && for d in "$a"/*.desktop ; do
    grep -q -e "^Name=.*$search" -e "^Exec=.*$search" "$d" && {
      echo "# $d:"
      grep -Ev '^(Comment|GenericName|Keywords|Name\[)' "$d"
    }
  done
done

To try this code out, save it to /usr/local/bin/xdg-desktop-search, make it executable and test it, for example, as follows:

xdg-desktop-search gnome-terminal

Transforming Sets of Strings to their Common Prefix Notation

26. Juli 2025 in Programming.

Update Aug 20 2022:

Any two strings s1, s2 have a common prefix cp, which is the string of characters that s1 and s2 have in common up from the start. If s1, s2 have no such common characters, cp is the empty string. Let s̅1, s̅2 be the remainders or suffixes of s1 and s2 if cp is removed from them. Then, the common prefix notation (CPN) of s1, s2 – in short, cpn(s1,s2) – shall be:

cpn(s1,s2) := cp{s̅1,s̅2}

Given the definition above, for any given CPN of a set of strings s1, s2, …, sn, the CPN of the set extended by an additional string sn+1 is defined as follows:

Case 1: If the suffix of sn+1 with cp removed, s̅n+1, has no nonempty common prefix with any of the suffixes s̅1, s̅2, …, s̅n:

cpn(s1,s2,…,sn+1) := cp{s̅1,s̅2,…,s̅n+1}

Case 2: Otherwise, since the first characters of s̅1, s̅2, …, s̅n are distinct, there can only be one element s̅m that has a nonempty common prefix with s̅n+1. Given s̅m to be that element:

cpn(s1,s2,…,sn+1) := cp{s̅1,s̅2,…,cpn(s̅m,s̅n+1),…,s̅n}

Examples:

cpn("a", "b") = "{a,b}"
cpn("aa", "ab") = "a{a,b}"
cpn("aa", "ab", "abc", "abd") = "a{a,b{c,d}}"
cpn("a", "ab", "abc") = "{a{b{c}}}"

Note: For the sake of reasoning, strings containing the CPN’s reserved characters {, } and , shall be considered invalid input. In a practical implementation, a syntax for “escaping” these reserved characters should be available.

Given a set of strings, one per line, on standard input, the following Python program prints the CPN of these strings on standard output: /ref/trie1.py

Try the examples:

./trie1.py << EOF
a
b
EOF
./trie1.py << EOF
aa
ab
EOF
./trie1.py << EOF
aa
ab
abc
abd
EOF

The following example renders the wrong output, because a trie does not actually store the common prefix (this is what a suffix tree would accomplish), it just stores different prefix paths, and a, ab and abc have no different prefix paths, it’s just a degenerate tree a → b → c:

./trie1.py << EOF
a
ab
abc
EOF

So my guess is, i must implement one of these fancy suffix tree algorithms to get it done right. (see the update instead) 🙂

In the meantime, try this:

find /etc -type d | ./trie1.py

🙂

Pinguin-Patenschaft

31. Dezember 2021 in Other.

Mein Arbeitgeber, B1 Systems GmbH hat in meinem Namen eine Patenschaft für einen afrikanischen Pinguin gesponsert. 🙂

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