Carl Ambroselli IT-Systems Engineering Student Software Engineer, UI Designer, Snowboarder, wannabe DJ.

Never pass unsanitized input to your mongodb. Never.

Get Mac resolution in terminal

I have a folder for scripts in ~/.bin and added that folder to my $PATH. I put the following script into ~/.bin/resolution and made executable with chmod +x ~/.bin/resolution.

This allows me to quickly get the current resolution of the connected screens (including the interal MacBook screen) by just running the command resolution in my terminal.

system_profiler SPDisplaysDataType | grep Resolution | sed -e 's/^[^R]*//g'

Extract any file with a single command

I have a folder for scripts in ~/.bin and added that folder to my $PATH.

Having the following script placed in ~/.bin/extract and made executable with chmod +x ~/.bin/extract allows me to use the same command to extract any file like extract or extract file.tar.gz. If you are missing an executable used by this script just install it with homebrew.

#! /bin/bash
if [ -f $1 ]
  case $1 in
      *.tar.bz2)  tar -jxvf $1                        ;;
      *.tar.gz)   tar -zxvf $1                        ;;
      *.bz2)      bunzip2 $1                          ;;
      *.dmg)      hdiutil mount $1                    ;;
      *.gz)       gunzip $1                           ;;
      *.tar)      tar -xvf $1                         ;;
      *.tbz2)     tar -jxvf $1                        ;;
      *.tgz)      tar -zxvf $1                        ;;
      *.zip)      unzip $1                            ;;
      *.ZIP)      unzip $1                            ;;
      *.pax)      cat $1 | pax -r                     ;;
      *.pax.Z)    uncompress $1 --stdout | pax -r     ;;
      *.rar)      unrar x $1                          ;;
      *.Z)        uncompress $1                       ;;
      *)          echo "'$1' cannot be extracted/mounted via extract()" ;;
  echo "$1 is not a valid file"

Introduction to machine learning

Disclaimer: The information and graphics here are mainly taken and summerized from the Stanford machine learning course by Andrew Ng.

Chances are high that you use machine learning every day without knowing it. Everytime you search with Google, get recommended articles on Amazon or send a letter via post you get the results because of machine learning. But lets jump straight to knowledge.

Supervised learning

When you have a dataset like shown here you could apply different leadning algorithms. One would be to find a straight line that matches the dataset to make predictions like so: House price prediction With this prediction a house with the size of 750 square feet would cost around $150,000.

But maybe it is better to use a different learning algorithm like a quadratic polinomial function which would output a prediction like so: House price prediction This would lead to a prediction around $200,000 for a house of 750 square meter. Both examples are using supervised learning which refers to the fact, that “correct answers” are given. It is also a regression problem, which means it predicts a continuous valued output (price).