Question

当我输入我想要的内容时，文件不会显示，但它也没有给我错误。

该文件是：

Account Name    Balance
100 Jones   24.98
200 Doe     345.67
300 White   0.00
400 Stone   -42.16
500 Rich    224.62

int main(void)
{
    int account;
    char name[30];
    float balance;
    int request;
    char singleline[150];
    FILE * fpointer;


    fpointer = fopen("acc.txt","r");
    while (!feof(fpointer))
    {
        fgets(singleline, 150, fpointer);
    }
    if ((fpointer= fopen("acc.txt", "r"))==NULL)
        printf("File could not be opened\n");
    else
    {
        printf("Enter Request\n"
               "1 - List accounts with zero balances\n"
               "2 - List accounts with credit balances\n"
               "3 -  List accounts with debit balances\n"
               "4 - Endof run\n");
        scanf("%d", &request);
        while (request !=4)
        {
            fscanf(fpointer,"%d%s%f", &account,name, &balance);
            switch(request)
            {
            case 1:
                printf("\nAccounts with zero balnces:\n");
                while(!feof(fpointer))
                {
                    if (balance ==0)
                        printf("%-10d%-13s%7.2f\n", account, name, balance);
                    fscanf(fpointer,"%d%s%f", &account,name, &balance);
                }
                break;
            case 2:
                printf("\nAccounts with credit balances:\n");
                while(!feof(fpointer))
                {
                    if (balance<0)
                        printf("%-10d%-13s%7.2f\n", account, name, balance);
                    fscanf(fpointer,"%d%s%f", &account,name, &balance);
                }
                break;
            case 3:
                printf("\nAccounts with debit balances:\n");
                while(!feof(fpointer))
                {
                    if (balance>0)
                        printf("%-10d%-13s%7.2f\n", account, name, balance);
                    fscanf(fpointer,"%d%s%f", &account,name, &balance);
                }
                break;
            }
            rewind (fpointer);
            printf("\n?" );
            scanf("%d",&request);
        }
        printf("End of run.\n");
    }
    fclose(fpointer);
    system("pause >nul");
    return 0;
}

Answer 1

您的代码存在很多问题，但最重要的是

你fopen()该文件什么都不做而且fclose()它没有，我认为在MS Windows计算机上你不能再fopen()，但你做了
你检查文件是否第二次没有打开，但不是第一次打开，所以就像你根本没有检查一样，此外，你继续fclose()文件后支票告诉你它没有打开。
while (!feof(file)) is always wrong.，因此您应该更改while循环的条件。

请注意，您在每个switch案例中都在重复代码，因此您应该考虑使用函数，这是修复所有问题的代码

#include <stdio.h>

int main(void)
{
    int   account;
    char  name[30];
    float balance;
    int   request;
    FILE *fpointer;


    if ((fpointer = fopen("acc.txt", "r")) == NULL)
        printf("File could not be opened\n");
    else
    {
        int  chr;
        char line[100];
        printf("Enter Request\n"
               "1 - List accounts with zero balances\n"
               "2 - List accounts with credit balances\n"
               "3 -  List accounts with debit balances\n"
               "4 - Endof run\n");
        scanf("%d", &request);       
        while ((request != 4) && (fgets(line, sizeof(line), fpointer) != NULL))
        {
            switch(request)
            {
            case 1:
                printf("\nAccounts with zero balnces:\n");
                while(fscanf(fpointer,"%d%s%f", &account, name, &balance) == 3)
                {
                    if (balance == 0)
                        printf("%-10d%-13s%7.2f\n", account, name, balance);
                }
                break;
            case 2:
                printf("\nAccounts with credit balances:\n");
                while(fscanf(fpointer,"%d%s%f", &account, name, &balance) == 3)
                {
                    if (balance < 0)
                        printf("%-10d%-13s%7.2f\n", account, name, balance);
                }
                break;
            case 3:
                printf("\nAccounts with debit balances:\n");
                while(fscanf(fpointer,"%d%s%f", &account, name, &balance) == 3)
                {
                    if (balance > 0)
                        printf("%-10d%-13s%7.2f\n", account, name, balance);
                }
                break;
            }
            rewind (fpointer);
            printf ("\n?" );

            while (((chr = getchar()) != EOF) && (chr != '\n'));
            scanf("%d", &request);
        }
        printf("End of run.\n");
        fclose (fpointer);
    }

    return 0;
}

Answer 2

切勿在循环条件中使用eof()。这是一种非常糟糕的做法。

这是一个你应该看一眼的参考资料：

Why is “while ( !feof (file) )” always wrong?

<强>解决方案：

首先将string从fpointer转移到临时变量并检查eof()，如果允许，则将该临时string放入所需的变量。

示例：

while(true){
    fgets(tmp, sizeof(tmp), fpointer);
    if(feof(fpointer)){ break;}
    text=tmp;
    }

文件无法在C中打开

2 个答案: