One of the simplifying assumptions that is built into this idea is that the input and output to the program are simple streams ( a file, a terminal ). Not surprisingly that makes things a lot less complex so you can focus on the programming.
Since a Raspberry Pi is only $35 or $50 with enough stuff to program it, that is one way to get started. Of course taking an older tossed of PC and installing Linux on it works too (which can often be done for free if there are businesses around)
You can download complete Linux VM images that just work from the net. VirtualBox is free and is installed in 5 minutes. It's hardly frustrating. Certainly less so than getting a RPi up and running, not to mention you end up with an odd, underpowered device secondary to your regular machine.
That's not to say the RPi isn't an interesting, rewarding experience on its own merits -- that's why I got one --, but I wouldn't recommend it to anybody interested primarily in getting a *nix environment for experimentation or programming.
Since a Raspberry Pi is only $35 or $50 with enough stuff to program it, that is one way to get started. Of course taking an older tossed of PC and installing Linux on it works too (which can often be done for free if there are businesses around)