从C中的bin文件中删除记录

Question

我正在尝试从bin文件中删除记录。

我试图制作另一个指针，并制作一个临时文件以将数据写入其中，然后从临时文件中将数据写回原始文件。.我假设可能有一种更简单的方法。但是主要的问题是更改薪水功能的更改。

这是我到目前为止所做的。

因此，该程序的主要目标是，如果我输入额外的钱，那比门槛大，我应该删除记录。有什么建议我需要更改更新薪水功能？

    #define _CRT_SECURE_NO_WARNINGS
    #include <stdio.h>
    #include <stdlib.h>
    typedef struct employee
    {
        int  code;
        char  name[15];
        float  salary;
    } Employee;
    void create_bin(char *f, float* threshold);
    void updateSalary(char* filename, float threshold);
    void Display(char *fName);
    void main() {
        char filename[20] = "input.bin";
        float threshold;
        create_bin(filename,&threshold);
        Display(filename);
        updateSalary(filename, threshold);
        Display(filename);
        getch();
    }
    void create_bin(char *f,float* threshold){
        FILE *f_b;
        Employee emp1;
        int object=0,number,i=0;
        float amount;
        f_b = fopen(f, "wb+");
        if (!f_b) {
            printf("unable to open file");
        }
        printf("How many Employees?");
        scanf("%d",&number);
        for (i = 0; i < number; i++) {
            printf("Eneter employee Code:");
            scanf("%d",&emp1.code);
            rewind(stdin);
            puts("Enter name");
            gets(emp1.name);
            printf("Eneter employee Salary:");
            scanf("%f",&emp1.salary);
            rewind(stdin);
            object += fwrite(&emp1, sizeof(Employee), 1, f_b);
        }
        printf("Ente threshold:");
        scanf("%.2f",&amount);
        *threshold = amount;
        printf("Total elements in file %dn", object);
        fclose(f_b);
    }
    void updateSalary(char* filename, float threshold) 
    {
        float extra_money;
        int i = 1;
        Employee emp;
        FILE *f = fopen(filename,"rb+");
        FILE *f_temp = fopen("Final_file","wb+");
        if (!f)
        {
            printf("File not found!n");
            return 0;
        }
        if (!f_temp) {
            printf("File not found!n");
            return 0;
        }
        fread(&emp, sizeof(Employee), 1, f);
        while (!feof(f))
        {   
            printf("Enter how much money to add to #%d worker:",i++);
            rewind(stdin);
            scanf("%f",&extra_money);
                emp.salary+= extra_money;
                if (emp.salary <= threshold) {
                    fwrite(&emp, sizeof(Employee), 1, f_temp);
                }
                fread(&emp, sizeof(Employee), 1, f);
        }
        fread(&emp, sizeof(Employee), 1, f_temp);
        while (!feof(f_temp)) {
            fwrite(&emp, sizeof(Employee), 1,f);
            fread(&emp, sizeof(Employee), 1, f_temp);
        }
        fclose(f_temp);
        fclose(f);
    }
    void Display(char *fName)
    {
        Employee emp;
        FILE *f = fopen(fName, "rb");
        if (f)
        {
            fread(&emp, sizeof(emp), 1, f);
            while (!feof(f))
            {
                printf("%9d %15s %8.2fn", emp.code, emp.name, emp.salary);
                fread(&emp, sizeof(emp), 1, f);
            }
            fclose(f);
        }
    }

Answer 1

主要的问题是更改更新薪水功能。

遵循Scheff的好建议：将新文件重命名为原始文件的名称。要这样做，更改

        fread(&emp, sizeof(Employee), 1, f_temp);
        while (!feof(f_temp)) {
            fwrite(&emp, sizeof(Employee), 1,f);
            fread(&emp, sizeof(Employee), 1, f_temp);
        }
        fclose(f_temp);
        fclose(f);

to

        fclose(f_temp);
        fclose(f);
        rename(filename, "Backup_file");    // optional, or maybe remove(filename);
        rename("Final_file", filename);

除此之外，

        scanf("%.2f",&amount);

具有无效的转换规范；也许你的意思是

        scanf("%2f", &amount);