我试图通过在Employee.Firstname的第一个字节上用'*'标记二进制文件来删除Employee，但是如果文件上有多个雇员，我尝试通过标记来删除第二个雇员用“ *”删除它时，只会用“ *”标记第一个Employee.Firstname的第一个字节。
这是我写入文件的方式：
struct EmployeeInformation{
char Firstname[32];
char Lastname[32];
char Address[32];
char ID[8];
char Duration[8];
}
struct EmployeeInformation Employee;
void AddEmployee()
{
FILE *fd;
printf("\n\n>>Add Employee<<\n");
//I use fgets and get all Employee info I just didn't include it for reading purposes.
if((fd = fopen(BINARY_FILE, "ab+")) == NULL)
{
printf("Error in opening file.\n\n");
getchar();
}
else
{
//Write Employee to file.
fwrite(&Employee, sizeof(Employee), 1, fd);
printf("\nEmployee Added!\n\n");
}
fclose(fd);
}
这是删除员工的代码。
void DeleteEmployee()
{
FILE *fd;
char EmployeeID[8];
long Pos = 0;
fpos_t pos;
printf("\n>>Delete Employee<<\n");
//Ask user for ID of employee they wish to delete.
printf("Employee ID:");
fgets(EmployeeID, 6, stdin);
if ((fd = fopen(BINARY_FILE, "rb+")) == NULL)
{
printf("Error, Cannot Open File.\n");
}
else
{
while(fread(&Employee, sizeof(struct EmployeeInformation), 1, fd) != 0)
{
if(strcmp(EmployeeID, Employee.ID) == 0)
{
//Employee Found
printf("Employee Found!\n");
//Get Current Position in file.
Pos = fgetpos(fd, &pos);
//Go to that Postion.
fseek(fd, Pos, SEEK_SET);
//Mark for deletion with '*'
fputc('*', fd);
printf("Firstname: %s\n",Employee.Firstname);
}
else
{
printf("Employe Not Found!\n\n");
}
}
}
fclose(fd);
}
您所获得的位置fgetpos是您刚刚阅读的记录之后。您需要fgetpos在进行读取sizeof(struct EmployeeInformation)之前先调用，或者在之前从该位置减去fseek。当您向后搜索然后写入一个字节时，还会弄乱当前位置。最后，fgetpos不返回您认为的结果；替换为ftell。
我建议这样做：
long int pos = ftell(fd);
while(fread(&Employee, sizeof(struct EmployeeInformation), 1, fd) != 0)
{
if(strcmp(EmployeeID, Employee.ID) == 0)
{
//Employee Found
printf("Employee Found!\n");
//Go to the BEGINNING of the record
fseek(fd, pos, SEEK_SET);
//Mark for deletion with '*'
fputc('*', fd);
printf("Firstname: %s\n",Employee.Firstname);
//Now position back to the end of the record (-1 because we advanced 1
//byte when we did fputc() above
fseek(pd, pos+sizeof(struct EmployeeInformation)-1, SEEK_SET);
}
else
{
printf("Employe Not Found!\n\n");
}
//We should now be at the beginning of the next record - mark the position
pos = ftell(fd);
}
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