brew install cxwx/cxbrew/libhv

test do
    (testpath/"test.c").write <<~C
      /* Wait for stdin to become readable, then read and echo the first line. */

      #include <stdio.h>
      #include <stdlib.h>
      #include <unistd.h>
      #include <ev.h>

      ev_io stdin_watcher;

      static void stdin_cb (EV_P_ ev_io *watcher, int revents) {
        char *buf;
        size_t nbytes = 255;
        buf = (char *)malloc(nbytes + 1);
        getline(&buf, &nbytes, stdin);
        printf("%s", buf);
        ev_io_stop(EV_A_ watcher);
        ev_break(EV_A_ EVBREAK_ALL);
      }

      int main() {
        ev_io_init(&stdin_watcher, stdin_cb, STDIN_FILENO, EV_READ);
        ev_io_start(EV_DEFAULT, &stdin_watcher);
        ev_run(EV_DEFAULT, 0);
        return 0;
      }
    C
    system ENV.cc, "test.c", "-I#{include}", "-L#{lib}", "-lev", "-o", "test"
    input = "hello, world\n"
    assert_equal input, pipe_output("./test", input, 0)
  end
end