c - 关闭文件后丢失文件数据

Question

我正在尝试制作一个文件来保存学校学生的记录，除了一件事之外一切都很好，那就是在我关闭程序后数据丢失了。有什么问题吗？

程序从这里开始:

    #include "stdafx.h"
    #include <stdio.h>
    #include <conio.h>
    #include <iostream>
    #include <string.h>

    using namespace std;

这是将用于处理记录的结构。

    /*a struct ogrenci and name it ogr_t with typedef*/
    typedef struct ogrenci
    {
    int kyt_no, ogrno, vize, final;
    float ort;
    char ad[10];
    char soyad[10];
    }ogr_t;
    /*End struct*/

    void creatfile();//To create the file "Kayit.dat" if it was not created .

函数原型(prototype)和main()

    int menu();
    void addrecord(FILE *ptr); 
    void updaterecord(FILE *ptr);
    void deleterecord(FILE *ptr);
    void listrecords(FILE *ptr);
    void searchrecord(FILE *ptr);
    double findavg(FILE *ptr);

    int _tmain(int argc, _TCHAR* argv[])
    {
    FILE *fp;
    int request;
    int choice;
    printf("1- Creat the File \"Kayit.dat\" if it was not created .\n\n"
           "#NOTE: this choice will clear the data saved if the file was created earlier .\n\n"
           "2- To continue if the file is already created .\n");
    scanf("%d", &choice);
    switch (choice)
    {
    case 1:creatfile();
    case 2:
        system("cls");
        if ((fp = fopen("kayit.dat", "rb+")) == NULL)
        {
            printf("File was not opened.");
        }
        else
        {
            while ((request = menu()) != 6)
            {
                switch (request)
                {
                case 1:addrecord(fp); break;
                case 2:updaterecord(fp); break;
                case 3:deleterecord(fp); break;
                case 4:listrecords(fp); break;
                case 5:searchrecord(fp); break;
                default:printf("undefined\n");break;
                }
            }
            fclose(fp);
        }break;
    default:printf("Undefined\n");break;
    }
    return 0;
    }

在 main() 中询问用户后，该函数创建文件 kayit.dat

    void creatfile()
    {
    FILE *fp;
    ogr_t bos_ogr = { 0, 0, 0, 0, 0.0, "", "" };
    if ((fp = fopen("kayit.dat", "wb")) == NULL)
    {
        printf("File was not opened");
    }
    else
    {   //to create a file and initialize it with an empty 100 student record .
        for (int i = 0; i < 100; i++)
        {
            fwrite(&bos_ogr, sizeof(ogr_t), 1, fp);
        }//end for
    }
    system("cls");
    }

这是用户在 main() 中显示的菜单。

    int menu(void)
    {
    int x;
    printf("What do you want to do :\n\n"
        "1= Add record .\n"
        "2= Update record .\n"
        "3= Delete Record .\n"
        "4= list all the records .\n"
        "5= Search for a specific record .\n"
        "6= Quit .\n");
    scanf("%d", &x);
    system("cls");
    return x;
    }

此函数使用随机访问添加一条新记录。

    void addrecord(FILE *ptr)
    {
    ogr_t record = { 0, 0, 0, 0, 0.0, "", "" };
    int accnum;
    char c;
    /*Enter a record number and search if is was already input*/
    printf(" Enter a record number for the new student < 1 - 100 > .");
    scanf("%d", &accnum);
    fseek(ptr, (accnum - 1)*sizeof(ogr_t), SEEK_SET);
    fread(&record, sizeof(ogr_t), 1, ptr);
    if (record.kyt_no!=0)
    {
        printf("this record is already full .\n");
        printf("press and key to continue...\n");
        if (c = _getche())
        {
            system("cls");
        }
    }
    else
    {
        printf("%-13s%-13s%-13s%-13s%-13s\n", "Name", "SureName", "StudentNum", "MidtermNote", "FinalNote");
        fscanf(stdin, "%s%s%d%d%d", record.ad, record.soyad, &record.ogrno, &record.vize, &record.final);
        record.kyt_no = accnum;
        fseek(ptr, (record.kyt_no - 1)*sizeof(ogr_t), SEEK_SET);
        fwrite(&record, sizeof(ogr_t), 1, ptr);
    }
    system("cls");
    }

更新用户选择的记录。

    void updaterecord(FILE *ptr)
    {
    ogr_t record1 = { 0, 0, 0, 0, 0.0, "", "" };
    int accnum;
    char c;
    printf(" Enter the student's record number that you want to update  < 1 - 100 > .");
    scanf("%d", &accnum);
    fseek(ptr, (accnum - 1)*sizeof(ogr_t), SEEK_SET);
    fread(&record1, sizeof(ogr_t), 1, ptr);
    if (record1.kyt_no == 0)
    {
        printf("This record is empty\n");
        printf("press and key to continue...\n");
        if (c= _getche())
        {
            system("cls");
        }
    }
    else
    {
        printf("Enter the new informations\n");
        printf("%-13s%-13s%-13s%-13s%-13s\n", "Name", "SureName", "StudentNum", "MidtermNote", "FinalNote");
        fscanf(stdin, "%s%s%d%d%d", record1.ad, record1.soyad, &record1.ogrno, &record1.vize, &record1.final);
        record1.kyt_no = accnum;
        fseek(ptr, (record1.kyt_no - 1)*sizeof(ogr_t), SEEK_SET);
        fwrite(&record1, sizeof(ogr_t), 1, ptr);
        system("cls");
    }

    }

检查用户选择的记录是否为空后，删除该记录。

    void deleterecord(FILE *ptr)
    {
    ogr_t bos_ogr = { 0, 0, 0, 0, 0.0, "", "" };
    ogr_t record2;
    int accnum;
    char c;
        printf("Enter the record for the student that you want delete < 1 - 100 >\n");
        fscanf(stdin, "%d", &accnum);
        fseek(ptr, (accnum - 1)*sizeof(ogr_t), SEEK_SET);
        fread(&record2, sizeof(ogr_t), 1, ptr);
        if (record2.kyt_no == 0)
        {
            printf("The record is already empty .\n");
            printf("press and key to continue...\n");
            if (c = _getche())
            {
                system("cls");
            }
        }
        else
        {
            fseek(ptr, (accnum - 1)*sizeof(ogr_t), SEEK_SET);
            fwrite(&bos_ogr, sizeof(ogr_t), 1, ptr);
            system("cls");
        }
    }

列出文件中的所有记录。

void listrecords(FILE *ptr)
{
    ogr_t record_prnt;
    char c;
    printf("%-13s%-13s%-13s%-13s%-13s%-13s\n", "RecordNo", "Name", "Surname", "StudentNum", "MidtermNote", "FinalNote");
    rewind(ptr);
    fread(&record_prnt, sizeof(ogr_t), 1, ptr);
    while (!feof(ptr))
    {
        if (record_prnt.kyt_no == 0)
        {
            record_prnt = { 0, 0, 0, 0, 0.0, "", "" };
        }
        else
        {
            printf("%-13d%-13s%-13s%-13d%-13d%-13d\n",
                record_prnt.kyt_no, record_prnt.ad,
                record_prnt.soyad, record_prnt.ogrno,
                record_prnt.vize, record_prnt.final);
        }
        fread(&record_prnt, sizeof(ogr_t), 1, ptr);
    }
    printf("press any key to contiue ...\n");
    if (c = _getche())
    {
        system("cls");
    }
}

按照用户选择的条件搜索特定记录。

void searchrecord(FILE *ptr)
{
    int request;
    int recnum;
    char name[20];
    ogr_t ogr;
    int mark;
    printf("Enter by what criteria do you want to search .\n\n"
        "1- By record num.\n"
        "2- By Name.\n"
        "3- By Grade.\n");
    scanf("%d", &request);
    system("cls");
    switch (request)
    {
    case 1:
        printf("Enter the record number .");
        scanf("%d", &recnum);
        fseek(ptr, (recnum - 1)*sizeof(ogr_t), SEEK_SET);
        fread(&ogr, sizeof(ogr_t), 1, ptr);
        printf("%-13s%-13s%-13s%-13s%-13s%-13s\n", "RecordNumber", "Name", "Surename", "StudentNum", "MidtermNote", "FinalNote");
        printf("%-13d%-13s%-13s%-13d%-13d%-13d\n", ogr.kyt_no, ogr.ad, ogr.soyad, ogr.ogrno, ogr.vize, ogr.final);
        break;
    case 2:
        printf("Enter the name of the student .\n ");
        scanf("%s",name);
        rewind(ptr);
        fread(&ogr, sizeof(ogr_t), 1, ptr);
        while (!feof(ptr))
        {
            if (strcmp(name, ogr.ad) == 0)
            {
                printf("%-13s%-13s%-13s%-13s%-13s%-13s\n", "RecordNumber", "Name", "Surename", "StudentNum", "MidtermNote", "FinalNote");
                printf("%-13d%-13s%-13s%-13d%-13d%-13d\n", ogr.kyt_no, ogr.ad, ogr.soyad, ogr.ogrno, ogr.vize, ogr.final);
            }
            fread(&ogr, sizeof(ogr_t), 1, ptr);
        }
        break;
    case 3:
        printf("Enter the Mark the you want to search for.\n ");
        scanf("%d",&mark);
        printf("The student that had higher than the mark that you've enterd are \n\n");
        rewind(ptr);
        fread(&ogr, sizeof(ogr_t), 1, ptr);
        while (!feof(ptr))
        {
            if (ogr.kyt_no!=0)
            {
                ogr.ort = ((ogr.final) + (ogr.vize)) / 2;
                if ((ogr.ort)>=mark)//print the records that have a higher averager than the mark.
                {
                    printf("%-13s%-13s%-13s%-13s%-13s%-13s\n", "RecordNumber", "Name", "Surename", "StudentNum", "MidtermNote", "FinalNote");
                    printf("%-13d%-13s%-13s%-13d%-13d%-13d\n", ogr.kyt_no, ogr.ad, ogr.soyad, ogr.ogrno, ogr.vize, ogr.final);
                }
            }
            fread(&ogr, sizeof(ogr_t), 1, ptr);
        }
        break;
    default:printf("Undefined choice.\n");
        break;
    }
}

程序结束。

Answer 1

在这种情况下，我要做的第一件事是......

Make sure for every fopen() call there is one fclose() call.

因此，在 createfile() 中，您以写入模式打开文件，并且不要关闭该文件。使用 rb+ 模式再次打开该文件，从而导致问题。

写入后，您应该在 createfile() 中关闭文件，这样您的代码就会像这样

void creatfile()
{
FILE *fp;
ogr_t bos_ogr = { 0, 0, 0, 0, 0.0, "", "" };
if ((fp = fopen("kayit.dat", "wb")) == NULL)
{
    printf("File was not opened");
}
else
{   //to create a file and initialize it with an empty 100 student record .
    for (int i = 0; i < 100; i++)
    {
        fwrite(&bos_ogr, sizeof(ogr_t), 1, fp);
    }//end for

    //Lets close the file         
    fclose(fp);
}
system("cls");
}