How to alternately select m rows every n rows in oracle sql
For m=10 and n=100 add the following where clause WHERE mod(rownum, 100)
kostas
Check if shared library is installed on Mac OS X
One way to check whether a library is installed is to use ld, e.g. check that zlib is installed: ld -lzlib If library is installed you’ll get something like this: ld: warning: -arch not specified ld: could not find entry…
Checking for disc overload on linux
The trick is to use vmstat and look at the number for “wait on acknowledge”. vmstat -S m 1 100 Look under “cpu” and the “wa” column. If this number is high, it is bad. It should be zero. Some…
OpenStreetMap tiles in EPSG:25832 projection using GeoServer
Warning: This is a description of how to create a OpenStreetMap WMS with GeoServer. It works fine up to the point where the layers published as an unstyled WMS. This is where I’ve not been able to produce a good…
Fetching static JSON files cross site with jQuery.
Say you have a static JSON file sitting on a web server, e.g. mystaticfiles.com on Amazon S3 or a CDN. For the sake of argument, let’s imagine that it’s a configuration file. The contents of the file looks like this:…
Reprojecting shapefiles with ogr2ogr
If you have an ESRI Shapefile (.shp) that you want to reproject, you can use ogr2ogr ogr2ogr -t_srs newfile.shp oldfile.shp The EPSG code could be for instance epsg:28532.
Creating a word cloud from PDF documents
Warning: This is not the hardest way to create a word cloud from pdf-documents, but it’s up there. Say you have directory containing pdf documents: $ ls a.pdf b.pdf c.pdf …
Easy two column layout in latex
Include the packages. The blindtext package is just an easy way to type Lorem ipsum etc. \usepackage{multicol} \usepackage{blindtext} Make a two column section of a page. \begin{multicols}{2}[\textbf{Example for a two column text}] \blindtext \end{multicols}
Run OpenSolaris in your OS with VirtualBox
The following recipe should work for any OS. Download and install VirtualBox Download OpenSolaris image Start VM If you want to try an other image than OpenSolaris, you can find many others images (CentOS, FreeBSD, etc) here:
If only more people wrote like Lamport
I’m half way through the Part-time parliament on Paxos article by Leslie Lamport. It is an article that describes a three-phase consensus protocol by telling a story of a (fictional) parliement on the greek island of Paxos, complete with fat…