请写一个用c语言实现学生信息管理系统其功能包括学生信息链表创建、学生信息输入、学生信息 查询、学生信息修改、学生信息删除、学生信息输出（全部或部分输出）或保存到文件，学生相关排序的代码

好的，以下是一个简单的学生信息管理系统的代码，实现了创建链表、输入、查询、修改、删除、输出和保存到文件的功能。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// 学生信息结构体
typedef struct student {
    int id;             // 学号
    char name[20];      // 姓名
    int age;            // 年龄
    float score;        // 成绩
    struct student *next;   // 指向下一个节点的指针
} Student;

// 创建新的学生信息节点
Student* create_student(int id, char* name, int age, float score) {
    Student* s = (Student*)malloc(sizeof(Student));
    s->id = id;
    strcpy(s->name, name);
    s->age = age;
    s->score = score;
    s->next = NULL;
    return s;
}

// 在链表末尾添加新的学生信息节点
void add_student(Student* head, Student* new_student) {
    Student* p = head;
    while (p->next != NULL) {
        p = p->next;
    }
    p->next = new_student;
}

// 输入新的学生信息
void input_student(Student* head) {
    int id, age;
    char name[20];
    float score;
    printf("请输入学号：");
    scanf("%d", &id);
    printf("请输入姓名：");
    scanf("%s", name);
    printf("请输入年龄：");
    scanf("%d", &age);
    printf("请输入成绩：");
    scanf("%f", &score);
    Student* new_student = create_student(id, name, age, score);
    add_student(head, new_student);
    printf("添加成功！\n");
}

// 根据学号查询学生信息
void search_student(Student* head) {
    int id;
    printf("请输入要查询的学号：");
    scanf("%d", &id);
    Student* p = head->next;
    while (p != NULL) {
        if (p->id == id) {
            printf("学号：%d，姓名：%s，年龄：%d，成绩：%.2f\n", p->id, p->name, p->age, p->score);
            return;
        }
        p = p->next;
    }
    printf("未找到该学生！\n");
}

// 根据学号修改学生信息
void modify_student(Student* head) {
    int id, age;
    char name[20];
    float score;
    printf("请输入要修改的学号：");
    scanf("%d", &id);
    Student* p = head->next;
    while (p != NULL) {
        if (p->id == id) {
            printf("请输入新的姓名：");
            scanf("%s", name);
            printf("请输入新的年龄：");
            scanf("%d", &age);
            printf("请输入新的成绩：");
            scanf("%f", &score);
            strcpy(p->name, name);
            p->age = age;
            p->score = score;
            printf("修改成功！\n");
            return;
        }
        p = p->next;
    }
    printf("未找到该学生！\n");
}

// 根据学号删除学生信息
void delete_student(Student* head) {
    int id;
    printf("请输入要删除的学号：");
    scanf("%d", &id);
    Student* p = head;
    while (p->next != NULL) {
        if (p->next->id == id) {
            Student* temp = p->next;
            p->next = temp->next;
            free(temp);
            printf("删除成功！\n");
            return;
        }
        p = p->next;
    }
    printf("未找到该学生！\n");
}

// 输出所有学生信息
void output_all_students(Student* head) {
    Student* p = head->next;
    while (p != NULL) {
        printf("学号：%d，姓名：%s，年龄：%d，成绩：%.2f\n", p->id, p->name, p->age, p->score);
        p = p->next;
    }
}

// 保存学生信息到文件
void save_students_to_file(Student* head) {
    FILE* fp;
    fp = fopen("students.txt", "w");
    if (fp == NULL) {
        printf("文件打开失败！\n");
        return;
    }
    Student* p = head->next;
    while (p != NULL) {
        fprintf(fp, "%d %s %d %.2f\n", p->id, p->name, p->age, p->score);
        p = p->next;
    }
    fclose(fp);
    printf("保存成功！\n");
}

// 根据成绩排序学生信息
void sort_students_by_score(Student* head) {
    Student* p = head->next;
    int count = 0;
    while (p != NULL) {
        count++;
        p = p->next;
    }
    Student* students[count];
    p = head->next;
    for (int i = 0; i < count; i++) {
        students[i] = p;
        p = p->next;
    }
    for (int i = 0; i < count - 1; i++) {
        for (int j = 0; j < count - i - 1; j++) {
            if (students[j]->score < students[j+1]->score) {
                Student* temp = students[j];
                students[j] = students[j+1];
                students[j+1] = temp;
            }
        }
    }
    printf("按成绩排序后的学生信息：\n");
    for (int i = 0; i < count; i++) {
        printf("学号：%d，姓名：%s，年龄：%d，成绩：%.2f\n", students[i]->id, students[i]->name, students[i]->age, students[i]->score);
    }
}

int main() {
    Student* head = create_student(0, "", 0, 0);
    int choice = 0;
    while (1) {
        printf("请选择操作：\n");
        printf("1. 添加学生信息\n");
        printf("2. 查询学生信息\n");
        printf("3. 修改学生信息\n");
        printf("4. 删除学生信息\n");
        printf("5. 输出所有学生信息\n");
        printf("6. 保存学生信息到文件\n");
        printf("7. 按成绩排序学生信息\n");
        printf("8. 退出\n");
        scanf("%d", &choice);
        switch (choice) {
            case 1:
                input_student(head);
                break;
            case 2:
                search_student(head);
                break;
            case 3:
                modify_student(head);
                break;
            case 4:
                delete_student(head);
                break;
            case 5:
                output_all_students(head);
                break;
            case 6:
                save_students_to_file(head);
                break;
            case 7:
                sort_students_by_score(head);
                break;
            case 8:
                printf("再见！\n");
                return 0;
            default:
                printf("无效的选项！\n");
                break;
        }
    }
}

注意：这个代码只是一个示例，可能还有很多需要改进和完善的地方。比如，可以加上输入信息时的数据验证，避免输入不合法的数据；在删除学生信息时，可以让用户再次确认是否要删除等。