int main() {
    pipe(fd);
    int pid = fork();
    if (pid == 0) {
        close(fd[0]);
        struct sigaction sa;
        sa.sa_handler = send_one;
        sa.sa_flags = 0;
        sigemptyset(&sa.sa_mask);
        sigaction(SIGUSR1, &sa, NULL);
        while (1)
            ;
    } else if (pid > 0) {
        close(fd[1]);
        int count = 0;
        while (1) {
        }
    }
    return 0;
}