Minimal skills

[xpetrl]

> The common language of FreeBSD and CS/E is C.

With the following platform, you can practice coding in more that 50 
languages of your choice:

https://exercism.io

I stated practice in C and Perl (5), IMHO is very useful and funny: 
after every exercise I made (starting from the classic "hello world!"), 
a mentor is checking you code giving you advises how to improve your 
skills. It is 100% free.