thread vs threads

[rsip22]

Chapter 1 of the book uses the program "thread" (singular), while the code in this repository is in a file called "threads" (plural). I would suggest fixing either here (which seems easier) or in the book to be consistent.

Chapter 1, page 8:

[francesco1119]

I think a good way to help you @remzi-arpacidusseau is to put the whole book on GitHub divided in chapters.
This way if we find a typo we can automatically edit the book and you will always have the book ready to be published.