请设计一段c语言代码，通过fork()两个子进程并用nice()改变其优先级，输出字符，比较不同优先级下进程调度的差异

在C语言中，你可以使用`fork()`函数创建子进程，并利用`nice()`函数调整它们的优先级。下面是一个简单的示例，展示了如何通过`fork()`复制进程，然后分别给每个子进程设置不同的niceness值：

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/resource.h>

#define HIGH_PRIORITY -5  // 高优先级
#define LOW_PRIORITY -20  // 低优先级

int main() {
    pid_t child_pid;
    
    // 创建高优先级子进程
    if ((child_pid = fork()) > 0) {  // 父进程
        printf("Parent process PID: %d\n", getpid());
        
        // 设置子进程优先级为高
        struct rlimit limits;
        getrlimit(RLIMIT_NICE, &limits);
        limits.rlim_cur = limits.rlim_max = HIGH_PRIORITY;
        setrlimit(RLIMIT_NICE, &limits);

        wait(NULL);  // 等待子进程结束
    } else if (child_pid == 0) {  // 子进程
        printf("Child process with high priority, PID: %d\n", getpid());
        char msg[] = "High Priority Child Process";
        while (write(1, msg, sizeof(msg)) != sizeof(msg));
        exit(EXIT_SUCCESS);
    } else {
        perror("Fork failed");
        return -1;
    }

    // 为另一个子进程设置低优先级
    if ((child_pid = fork()) > 0) {  // 父进程
        printf("Parent process PID: %d\n", getpid());

        // 设置子进程优先级为低
        limits.rlim_cur = limits.rlim_max = LOW_PRIORITY;
        setrlimit(RLIMIT_NICE, &limits);

        wait(NULL);  // 等待子进程结束
    } else if (child_pid == 0) {  // 另一个子进程
        printf("Child process with low priority, PID: %d\n", getpid());
        char msg[] = "Low Priority Child Process";
        while (write(1, msg, sizeof(msg)) != sizeof(msg));
        exit(EXIT_SUCCESS);
    } else {
        perror("Second fork failed");
        return -1;
    }
    
    return 0;
}