C语言文件操作编程问题

Question

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

#define NUM_STUDENTS 5
#define NUM_COURSES 3

typedef struct {
    int student_number;
    char name[20];
    float courses[NUM_COURSES];
    float average;
} Student;

int main(int argc, char *argv[]) {
    if (argc != 2) {
        printf("Usage: %s file_name\n", argv[0]);
        return 1;
    }
    char *file_name = argv[1];

    Student students[NUM_STUDENTS];
    for (int i = 0; i < NUM_STUDENTS; i++) {
        printf("Enter student number: ");
        scanf("%d", &students[i].student_number);
        printf("Enter name: ");
        scanf("%s", students[i].name);
        for (int j = 0; j < NUM_COURSES; j++) {
            printf("Enter course %d score: ", j + 1);
            scanf("%f", &students[i].courses[j]);
        }
        students[i].average = (students[i].courses[0] + students[i].courses[1] + students[i].courses[2]) / NUM_COURSES;
    }

    FILE *fp = fopen(file_name, "wb");
    if (fp == NULL) {
        perror("Error opening file");
        return 1;
    }

    for (int i = 0; i < NUM_STUDENTS; i++) {
        fwrite(&students[i], sizeof(Student), 1, fp);
    }

    fclose(fp);

    return 0;
}
嗯，输出结果就是比较不成功。嗯，想要大家再帮我看看代码

Answer 1

输出没问题，只要把平均成绩保留两位后在保存即可，另外可以用fread()函数再次读取文件并打印，以验证写入的数据是否正确，修改如下：

参考链接：

#include <stdio.h>
#include <stdlib.h>
 
#define NUM_STUDENTS 5
#define NUM_COURSES 3
 
typedef struct {
    int student_number;
    char name[20];
    float courses[NUM_COURSES];
    float average;
} Student;
 
int main(int argc, char *argv[]) {
    if (argc != 2) {
        printf("Usage: %s file_name\n", argv[0]);
        return 1;
    }
    char *file_name = argv[1];
 
    Student students[NUM_STUDENTS];
    double avg;
    char temp[20]; 
    for (int i = 0; i < NUM_STUDENTS; i++) {
        printf("Enter student number: ");
        scanf("%d", &students[i].student_number);
        printf("Enter name: ");
        scanf("%s", students[i].name);
        for (int j = 0; j < NUM_COURSES; j++) {
            printf("Enter course %d score: ", j + 1);
            scanf("%f", &students[i].courses[j]);
        }
        
       
        avg= (students[i].courses[0] + students[i].courses[1] + students[i].courses[2]) / NUM_COURSES;
        // https://baike.baidu.com/link?url=_FbRjX1l4bRnFF8hQoqlw9-2HhQr4LDM-23DwSSLil86L0OO-bz5NDL5ljll4dgf47xbtOgMOF1Ny5MCFw67d0BOAsOgb2hbg1VpKI6WcsO
        sprintf(temp,"%.2f",avg);  //   平均成绩保留两位小数 保存为字符串 
        // https://www.runoob.com/cprogramming/c-function-atof.html
        students[i].average = (float)(atof(temp));  // 把保留两位小数的字符串转为浮点数 
    }
 
    FILE *fp = fopen(file_name, "wb");
    if (fp == NULL) {
        perror("Error opening file");
        return 1;
    }
 
    for (int i = 0; i < NUM_STUDENTS; i++) {
        fwrite(&students[i], sizeof(Student), 1, fp);
    }
 
    fclose(fp);
    
    // 读取文件验证写入的数据是否正确 
    fp = fopen(file_name, "r");
    if (fp == NULL) {
        perror("Error opening file");
        return 1;
    }
     Student rstudents[NUM_STUDENTS];
     printf("\n");
    for (int i = 0; i < NUM_STUDENTS; i++) {
        fread(&rstudents[i], sizeof(Student), 1, fp);
    }
    for (int i = 0; i < NUM_STUDENTS; i++) {
        printf("%d %s %f %f %f %f\n",rstudents[i].student_number,rstudents[i].name,
        rstudents[i].courses[0],rstudents[i].courses[1],rstudents[i].courses[2],rstudents[i].average);
    }
    
    fclose(fp);
 
    return 0;
}