FIFO_PATH
if (unlink(FIFO_PATH) && errno != ENOENT)
err(1, "unlink %s", FIFO_PATH);
if (mkfifo(FIFO_PATH, 0600))
err(1, "mkfifo %s", FIFO_PATH);
retval[0] = open(FIFO_PATH, O_RDONLY);
if (unlink(FIFO_PATH) && errno != ENOENT)
err(1, "unlink %s", FIFO_PATH);