ads' corner - Languages

Read number lines in a file - in LaTeX

nospam@example.com (Andreas 'ads' Scherbaum) — Sun, 28 Feb 2010 19:05:00 +0100

Andreas 'ads' Scherbaum

Probably a rare needed feature, but i had to count the number lines in a text file - in LaTeX.
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Generate random number in LaTeX

nospam@example.com (Andreas 'ads' Scherbaum) — Sat, 27 Feb 2010 20:51:58 +0100

Andreas 'ads' Scherbaum

It is possible to generate random numbers in a TeX document. For a gimmick i wanted a random line from a text file in my slides. The first step was to find a random number.

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Include and exclude latex-beamer frames

nospam@example.com (Andreas 'ads' Scherbaum) — Tue, 08 Dec 2009 22:46:46 +0100

Andreas 'ads' Scherbaum

For my slides i sometimes want to disable parts of the presentation, as example: if the operating system is Linux, i don't need Solaris installation instructions. The \ifthenelse{<condition>}{...true...}{...false...} from the ifthen package works very well for normal frames, but it fails, if there are examples (verbatim environment) in the code.

In such a case \iftrue and \iffalse are much more lazy than \ifthenelse and compiling the examples results no longer in latex parser errors. The downside of this solution: i need to predefine the condition, but in my case i have them in a separate file anyway.

The definition looks like:

\newboolean{usesolaris}
\ifthenelse{\equal{\targetos}{solaris}}{
  \setboolean{usesolaris}{true}
}{
  \setboolean{usesolaris}{false}
}

I have defined the variable \targetos, which contains a string with the currently used platform name for my presentation. If the string matches "solaris", the boolean \usesolaris is set to "true", else to "false". Latex compiles the "\ifusesolaris" definition from the boolean, which i later can use to include or exclude frames:

\ifusesolaris
\begin{frame}[fragile]
  ... frame content
\end{frame}
\fi

In addition, it is also possible to add code for the case where \usesolaris is false. Just add \else and the code before \fi.

Making life easy for new (and old) PWN translators

nospam@example.com (Andreas 'ads' Scherbaum) — Fri, 16 Oct 2009 19:40:40 +0200

Andreas 'ads' Scherbaum

I released version 3.0 of the pwn-translation script. Although the version number is already 3.0, this is the first public available version.

What does it do? You feed one of David Fetter's PostgreSQL weekly news mails into the script and it generates a new mail with all known text parts translated into your native language. This should make life very easy for new - and already existing - pwn translators.

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Unterlagen für Tutorial beim Perl-Workshop in Frankfurt/Main

nospam@example.com (Andreas 'ads' Scherbaum) — Wed, 25 Feb 2009 16:52:14 +0100

Andreas 'ads' Scherbaum

Die Unterlagen für das Tutorial beim Perl-Workshop 2009 in Frankfurt/Main am 25.02.2009 sind unter:

http://andreas.scherbaum.la/writings/

zu finden. Folgende Änderungen wurden gegenüber dem Vortrag vorgenommen:

- ein falscher Variablenbezeichner im "Perl" Teil wurde korrigiert

- Beispiele für Nutzung von SPI in Perl Stored Procedures wurden aufgenommen

Viel Spass mit den Unterlagen

Update: Die Unterlagen aller Vorträge gibt es im Wiki: http://conferences.yapceurope.org/gpw2009/wiki?node=Slides

PostgreSQL and the Perl Workshop 2009 in Frankfurt (Main)

nospam@example.com (Andreas 'ads' Scherbaum) — Sat, 27 Dec 2008 14:24:53 +0100

Andreas 'ads' Scherbaum

There will be a workshop "optimize PostgreSQL, combine Perl and PostgreSQL" at the Perl Workshop 2009 on february 25 in Frankfurt/Main in Germany.

More details (in german) are available at: http://www.perl-workshop.de/talks/151/view

The full timetable (also mostly in german) for the workshop is available at: http://www.perl-workshop.de/en/2009/zeitplan.html

xPyrus community framework released by UniHelp e.V.

nospam@example.com (Andreas 'ads' Scherbaum) — Thu, 09 Oct 2008 23:00:00 +0200

Andreas 'ads' Scherbaum

UniHelp e.V. - a registered student association in Magdeburg/Germany - announces the release of xPyrus, a framework for operating communities and document sharing platforms.

The framework is based on PHP 5 and PostgreSQL and has been running the students' community UniHelp.de (a platform for exchanging study-related documents and connecting students) in Magdeburg since 2002.

The entire framework is released under the GNU Affero General Public License v3 at http://www.xpyrus.org. A unix-based server is required for installation and use of all features, however, a hosting service can be provided by UniHelp e.V. on request, especially for student organizations.

The press release can be found at:
UniHelp Blogs - Press release

Further information can be found at:
- Homepage of the framework: http://www.xpyrus.org
- Reference application: http://magdeburg.unihelp.de
- Homepage of the publisher: http://magdeburg.unihelp.de/imprint

Single line input for psql copy command

nospam@example.com (Andreas 'ads' Scherbaum) — Wed, 08 Oct 2008 22:26:05 +0200

Andreas 'ads' Scherbaum

I have the following problem:

A database server and another client machine. I have to execute several \copy commands in psql on the client machine to retrieve data and store the output in CSV files. The PostgreSQL COPY command is not an option because it stores the results on the database server, not the client machine. All \copy commands are executed from several files containing SQL commands, which are concated together by a makefile and feeded into psql. So far so good.

My SELECT commands used in the \copy are a bit more complicated and \copy requires to have the entire command on a single line. That can be done in two ways:

- Write the entire command in a single line. But that's hard to debug :-(

- Write the command as i like it and remove the linebreaks before feeding the command into psql.

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Manage Serendipity installations with Spartacus

nospam@example.com (Andreas 'ads' Scherbaum) — Sat, 13 Sep 2008 17:59:20 +0200

Andreas 'ads' Scherbaum

I have to manage some Serendipity (s9y) installations. Only one of them is my personal blog, the others are customer installations, all on different servers. Apart from new serendipity versions there's also the problem with updated plugins. How can one know about available updates without opening each blog in a browser window, open administration, select "Configure Plugins" and check for new sidebar and event plugins?

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role ... cannot be dropped because some objects depend on it

nospam@example.com (Andreas 'ads' Scherbaum) — Wed, 10 Sep 2008 20:11:07 +0200

Andreas 'ads' Scherbaum

I want to drop a ROLE (previously USER/GROUPs) which is still referenced by object(s) in my database. But PostgreSQL has objections:

ERROR: role "xyz" cannot be dropped because some objects depend on it

DETAIL: access to schema public

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new screen_away version for irssi finally online

nospam@example.com (Andreas 'ads' Scherbaum) — Thu, 22 May 2008 18:50:10 +0200

Andreas 'ads' Scherbaum

After exact 364 days the irssi guys published my last screen_away.pl version which includes SILC support.

You can find the script here: http://scripts.irssi.org/

For anyone who don't know about screen_away: if you run irssi in a screen(1), this script set's you away if you detach the screen session and cancels the away status if the screen is reconnected. You can configure the away message and optional also change the nick (but ppl usually don't like nick changes to show the away status).

Install instructions are in the head of the script.

Stupid open_basedir handling in PHP

nospam@example.com (Andreas 'ads' Scherbaum) — Tue, 29 Apr 2008 00:15:00 +0200

Andreas 'ads' Scherbaum

I have an application which has to run on different webservers (or to be more specific on servers with a different directory layout). On one server the php files are in /usr/home, the next one is using /www, the third one /var/www and last but not least my laptop has the files in my home directory which is below /home.

No problem - or?

Since we want a bit security, we have open_basedir activated. Now the script has to check if a specific directory exists. I added this directory name to the open_basedir settings on all webservers. But surprise PHP tries to be intelligent. On servers where the specific directory does not exist, PHP removes the directory name from the open_basedir directory list (note: this cost another stat() call on startup).

You imagine what comes next? Now the is_dir() call on this server fails, because of an "open_basedir restriction in effect" error.

*grrr*

create language if not exist

nospam@example.com (Andreas 'ads' Scherbaum) — Thu, 27 Mar 2008 08:33:14 +0100

Andreas 'ads' Scherbaum

In a customer project i have to setup a database from a Makefile. Part of my problem: on windows the installer may or may not install "plpgsql" into template1 so in consequence this language would be activated in every new database. But that's not predictable. This problem can appear on different Linux/Unix distributions too.

In contrary to some other opinions in #postgresql i dislike filtering error messages and i prefer clean solutions.

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Understanding SQL

nospam@example.com (Andreas 'ads' Scherbaum) — Sun, 13 Jan 2008 15:29:56 +0100

Andreas 'ads' Scherbaum

Just have to port a phpkit database to something else. It seems, the phpkit ppl did not really understand what SQL is for.

The 'phpkit_config' table in this case contains 255(!) columns and a lot of this columns seems to be for extensions.

This is a very good example where you should use normalization: you don't add more and more columns to one table but you have a key/value table and for new entries you add a new key with a value. No need to change the table at all.

BOOLEAN datatype with PHP-compatible output

nospam@example.com (Andreas 'ads' Scherbaum) — Mon, 07 Jan 2008 12:43:31 +0100

Andreas 'ads' Scherbaum

If you use pure PHP (no database abstraction layer) with PostgreSQL, you may run into the problem that your BOOLEAN columns are not recognized by PHP but the value is instead returned as a string. So any code like:

if (!$boolean)

always returns true because the 't' and 'f' are just strings in PHP.

Other programming languages like Perl, Python or Java and even the newer PHP PDO don't have this problem so it's clearly a PHP issue ... but i don't expect this one to be fixed, because this may break a lot existing applications. The column type information is available in the query result information so normally this should not be a big problem.

How to resolve this problem? There are some possibilities, one simple way would be to just use a SMALLINT instead a BOOLEAN but with the disadvantage that you loose the boolean input values. Another way is to create a new BOOLEAN type and change the output to something PHP-compatible. This new type is binary compatible with the existing BOOLEAN type so casts in either way are not a problem.

Note: i asked around, but it seems, there is no easy solution which does not require updates in the PHP or SQL code. Any workaround like explicit casts to integer are error-prone and you cannot easily find out, because your application will work, but in a wrong way.

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