Suppose that I've got a foreach loop in which I write output to a file:

    auto f = File("test.txt", "w"); f.close();  // to start with a blank file
    foreach(i; iota(0, 100))
    {
        f = File("test.txt", "a");
        f.writeln(i);
        f.close();
    }

I'm guessing it is at least potentially unsafe to parallelize the loop without also considering the file interactions:

    foreach(i; parallel(iota(0, 100), 20))
    {
        f = File("test.txt", "a");  // What happens if 2 threads want to
        f.writeln(i);               // open this file at the same time?
        f.close();
    }

... so, is there a way that I can ensure that the file appending takes place successfully but also safely in each thread?  Let's assume that I don't care about the order of writing, only that it takes place.