simple sed examples

“sed” is a powerful tool to automatically edit strings or streams (sed = Stream EDitor). It comes with every modern Linux or Unix system and you can use in many different cases. It’s syntax is not very intuitive but it is definitely worth it to learn it’s basics . Example use cases: Recursively replace a […]


Simply serve local directory via HTTP with python webserver 1

Sometimes you quickly need to exchange some files between networked machines. A really easy way that mostly also works through firewalls is to serve them via a local webserver. Python offers a really simple module for that: python -m SimpleHTTPServer To serve a local directory just run: [email protected]:~$ python -m SimpleHTTPServer Serving HTTP on 0.0.0.0 […]


find log-file location of Linux process with lsof

If you are testing or debugging a software you often need to know where the logfiles of that process are located (for example apache httpd logfiles or mysql logfiles). Many people tend to look into the default location – or try to find that information in the default location of the configuration files or an […]


machines that learn better than people with deep learning

Machines are starting to learn and understand better than humans. Technologist Jeremy Howard shows new developments in the fast-moving field of deep learning. The TED talk below shows both wonderful and terrifying implications.

Today machines are able to learn from massive amounts of data. And we already know that companies are using this to recommend products, find friends in social networks and optimize advertising campaigns.

But there is a lot of other development going on. Companies are inventing self driving cars that can recognize a street sign or a human being and that can make reasonable decisions on events like that.  They are inventing systems that can understand speech and translate them in real time – and they do not write a translating program – instead they let the system learn the languages from massive amounts of data. Companies and researchers are using the deep learning algorithm to solve a variety of problems that couldn’t be solved before.

  • Computers are able to learn.
  • Computers start to get better than humans in many fields.
  • They can listen and see.
  • Computers can read and write.
  • They can understand!

The input is not restricted to machine readable text any more. It can be images, audio and video as well. Machines will be able to beat human performance in learning and understanding very soon … and they will not be limited to a single brain without “RAM extension slots”.

See more TED talks on www.ted.com


How to save a remote server SSL / TLS certificate locally as a file

In linux you can just use the openssl commandline tools to download any certificate from a remote web-server and store it in a local file. Show the certificate chain and public key of a web-server openssl s_client -connect slash4.de:443 -showcerts To directly extract the certificate and save it to a file you can use these […]


see invisible motion and hear silent sounds using videoscope – a motion microscope

Michael Rubinstein has developed the “motion microscope” that can highlight tiny movements in videos taken by normal cameras. You can watch a baby breathe, see the pulse of an actor or see a glass vibrating from sound waves.

In his talk he recreates a conversation by amplifying the movements from sound waves bouncing off a bag of chips … quite impressive:

 


How can I download an entire website to static files and harden my CMS?

You can easily harden your wordpress/CMS installation by downloading it to static files and only publishing those static files to the internet. Security vulnerabilities are regularly found in all common used CMS systems – if you just need your CMS to publish content (no interaction like comments) then the following is an option to really […]


how to read n random characters from /dev/urandom

If you want to create random chars in a bash script – e.g. to generate a password – you can get these chars from /dev/urandom or /dev/random. It can be very useful in automated deployments to generate a new good password with each deployment. The difference between /dev/random and /dev/urandom is basically that /dev/random will […]


wordpress friendly URLs

In the basic settings wordpress does not have a very good URL structure. Your first posts URL will most probably look like this : http://slash4.de/blog/?p=15 The above number 15 (the post ID) does not mean anything to your users and it does not contain any keywords that could be found by a search engine. Change […]


Carol Dweck researches “growth mindset” — the idea that we can grow our brain’s capacity … a great introduction to this field.