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how to and tips mostly related to programming
awk '!visited[$0]++' or how to remove duplicate lines from files keeping the original order explained
How to remove duplicate lines of a file in Linux without sorting or changing their order (awk one-liner explained).

How to manage nested objects in Elasticsearch documents
How to add, update and delete nested objects in Elasticsearch documents using the Update API and painless scripts.

Change brightness with the function keys on iMac running Ubuntu or Debian

In this post I will describe the steps I had to follow to be able to change the brightness on my iMac using the related keyboard function keys.

How to add a custom HTTP header in Rails
Set custom HTTP headers in responses of a Ruby on Rails application.

How to create a favicon from an image
Quickly create a favicon with imagemagick from an image (png, jpg etc)

Rails radio buttons and required boolean attributes
How to deal with required boolean attributes and radio buttons in Ruby on Rails.

Testing execution of filters with RSpec
I was working on my application and I wanted to write some RSpec tests for some controllers having `before_filter` for some actions....