参考方法：

//gcc version 7.4.0

#include <stdio.h>

typedef struct
{
    int number;
    char name[20];
    float Chinese,Math,English;
    float avg;
}Student;

int main()
{
    Student stu[5],*ptr=NULL;
    ptr=stu;
    FILE *file=NULL;
    file=(FILE *)fopen("./stud","w");
    printf("请输入五个学生的信息：顺序为学号，姓名，语，数，外\n例子：1 张三 80 92 78\n");
    for(int i=0;i<5;i++)
    {
        scanf("%d %20s %f %f %f",&((ptr+i)->number),(ptr+i)->name,&((ptr+i)->Chinese),&((ptr+i)->Math),&((ptr+i)->English));
        (ptr+i)->avg = ((ptr+i)->Chinese + (ptr+i)->Math + (ptr+i)->English)/3;
    }

    int result=fprintf(file,"学号\t%-20s\t语文\t数学\t英语\t平均成绩\n","姓名");
    if(result<0)
    {
        printf("写入文件stud失败！\n");
        return -1;
    }

    for(int i=0;i<5;i++)
    {
        result=fprintf(file,"%-3d\t%-20s\t%3.1f\t%3.1f\t%3.1f\t%3.1f\n",(ptr+i)->number,(ptr+i)->name,(ptr+i)->Chinese,(ptr+i)->Math,(ptr+i)->English,(ptr+i)->avg);
        if(result<0)
        {
            printf("写入文件stud失败！\n");
            return -1;
        }
    }

    printf("写入文件stud成功！\n");
    fclose(file);
    return 0;
}