Rust and Nix = easier Unix systems programming

Adding new abstraction layers rarely helps when doing systems programming. You (as in "the developer") want to be as near to the machine as possible. C does this pretty well.

Perhaps I'm just getting old :-(

The original API is not "broken" per se, it's just limited by the language features ("magical" return values vs. tagged unions or whatever they're called in Rust, I don't remember.)

Nobody is claiming that C makes it impossible to cleanly do the right thing—obviously the whole world runs on C.

The point is that nothing about the C language, libraries, or toolchain discourage the example given in the blogpost compared to your more correct code. Unless you remember exactly the right details from the manpages, there's nothing about the example in the blogpost that's less natural to write than your more correct code. (And people do forget those details: http://rachelbythebay.com/w/2014/08/19/fork/ )

By contrast, as illustrated in the blogpost, the most natural way to do the same thing in Rust turns out to be the more correct thing. If you wanted the bad behavior to happen, you'd have to go out of your way to pass -1 to kill(). Hence in this example, Rust's design is an improvement.

It's great that C gives you enough rope to hang yourself with, but it's even better if tying yourself to things safely is easy, and to hang yourself you have to really go out of your way.

    if let Some(child) = fork() {
        do_only_child_stuff(); 
    } else {
        do_only_parent_stuff();
    }

    if let Some(ForkResult::Child) = fork() {
        do_only_child_stuff();
    } else {
        do_only_parent_stuff();
    }

By the way, you can also write your own wrapper functions in C, that transform the return value into something like

    struct fork_status {
        enum { ERROR, PARENT, CHILD } state;
        int ret;
    };

That said, the libc bindings in Rust are pretty low-level and a project that offers higher-level wrappers can be very helpful, so I hope my comment doesn't create the impression that I'm ripping on the project itself.