c - 如何修复正在修改二进制文件中的记录的子程序

Question

我的二进制文件中有三个记录。当我修改记录并打开包含可读记录的文本文件时，修改名称的记录只是重复并且没有任何更改。此外，有时控制台会说该记录不存在，即使它存在。 2 个子程序用于创建二进制文件和包含二进制文件中的记录的文本文件。

#include<stdio.h>
typedef struct {
    char CNP[14];// CNP = Personal Identification Number
    char nume[30]; // nume=name
    int an;        // an=year
    int grupa;     // grupa=group
    int nrDisc;    // nrDisc=number of classes           
    int note[20];  // note=grades
}STUDENT;

void creare(char*nume) {       // creare=creation
    FILE*f;
    STUDENT s;
    fopen_s(&f, nume, "wb");
    if (!f)
        printf("Eroare");
    else {
        printf("CNP:");
        gets(s.CNP);
        while (!feof(stdin)){
            printf("Nume:");
            gets(s.nume);
            printf("An:");
            scanf_s("%d", &s.an);
            printf("Grupa:");
            scanf_s("%d", &s.grupa);
            printf("Nr. discipline:");
            scanf_s("%d", &s.nrDisc);
            for (int i = 0; i < s.nrDisc; i++)
            {
                printf("Nota[%d] este:", i);
                scanf_s("%d", &s.note[i]);
            }
            fwrite(&s, sizeof(s), 1, f);
            getchar();
            printf("CNP:");
            gets(s.CNP);
        }
        fclose(f);
    }
}


void raport(char*nume_binar, char*nume_text) {   // raport=report
    FILE*f;
    fopen_s(&f, nume_binar, "rb");
    if (!f)
        printf("Eroare");
    else {
        FILE*g;
        STUDENT s;
        fopen_s(&g, nume_text, "w");
        fprintf(g,"     CNP             Nume           An       Grupa    Nr discipline\n\n");
        while(fread(&s, sizeof(s), 1, f)==1)
         {          
            fprintf(g,"%s   %s  %5d  %9d  %9d\n", s.CNP, s.nume, s.an, s.grupa, s.nrDisc);
            for (int i = 0; i < s.nrDisc; i++)
            {
                fprintf(g, "Nota %d este:", i);
                fprintf(g, "%d\n", s.note[i]);

            }
            fprintf(g, "\n");
        }

        fclose(g);

    }
    fclose(f);
}


void modificare(char*nume) {  // modificare=modifying
    FILE*f;
    STUDENT s;
    int grupa;
    fopen_s(&f, nume, "rb+");
    if (!f)
        printf("Eroare");
    else {
        printf("Grupa:");
        scanf_s("%d", &grupa);
        while (!feof(stdin)) {
            int g=0;
            char nume[20];
            fread(&s, sizeof(s), 1, f);
            if (grupa == s.grupa) {
                g = 1;
                printf("Numele initial este:%s\n", s.nume);
                printf("Noul nume este:");
                getchar();
                gets(nume);
                fseek(f,ftell(f)-sizeof(s), 0);
                fwrite(&s, sizeof(s), 1, f);
            }

            if (g == 0)
                printf("Nu exista\n");

            printf("Grupa:");
            scanf_s("%d", &grupa);


        }
        fclose(f);

    }
}

void main() {
    char nume_fisier[] = "Student.dat";
    char nume_fisier_txt[] = "Raport.txt";
    //creare(nume_fisier);
    //raport(nume_fisier, nume_fisier_txt);
    modificare(nume_fisier);
}

Answer 1

while (fread(&s, sizeof(s), 1, f)) {
            int g=0;
            char nume[30]; //size of nume here should be same as that of structure

            if (grupa == s.grupa) {
                g = 1;
                printf("Numele initial este:%s\n", s.nume);
                printf("Noul nume este:");
                getchar();
                gets(nume);
                fseek(f,-sizeof(s), SEEK_CUR)) ; //Using macros helps clarify code
                fwrite(&s, sizeof(s), 1, f);
                break;  //break after modifying content

            }
            if (feof(f))
               break;