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This is a good book if you want to do Unixy things on Unixy platforms, from simple concepts like how pipes work to more advanced process control or TTY's: https://en.wikipedia.org/wiki/Advanced_Programming_in_the_Unix_Environment

And alongside this one is great for network/socket stuff, equally good: https://en.wikipedia.org/wiki/UNIX_Network_Programming

At least skim over those before touching Unix/Posix API's. I'm not really shocked how little people know about very basic things like pipes and how they work, but it's a problem those books can potentially fix 🙂