c++ - 此代码可以正常编译，但未创建文件？请指出错误

Question

我只是开始文件处理，开始编写代码来创建，使用二进制文件进行读写，我将结构传递给它并尝试运行它，但是我发现未在目录中创建代码中指定的任何文件虽然代码编译良好。

#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;
struct Student
{
    char name[20];
    int student_id;
    char department[20];
    char address[30];
};
ostream & operator <<(ostream &out,Student &s1)
{
    out<<"Name: "<<s1.name<<endl;
    out<<"Student Id: "<<s1.student_id<<endl;
    out<<"Department: "<<s1.department<<endl;
    out<<"Address: "<<s1.address<<endl;
}
int main()
{
    Student s1;
    strcpy(s1.name, "Sandeep");
    s1.student_id = 1;
    strcpy(s1.department,"BCT");
    strcpy(s1.address, "New Baneshwor,Kathmandu");
    fstream file;  //file part
    file.open("Student.dat",ios::in | ios::out |ios::binary); //create a file
    file.write((char*)(&s1),sizeof(Student)); //write to it
    if(file.is_open())
    {
        cout<<"nice"; //check if it's open(code not running)
    }
    file.seekg(0);
    file.read((char*)(&s1),sizeof(Student)); //read from a file just created
    cout<<s1;
    if(file.fail())
    {
        cout<<"Cannot create file"; //check if file is not created
    }
    file.close();

}

Answer 1

因为您使用ios::in | ios::out，所以该文件必须已经存在。你可以做:

file.open("Student.dat", ios::in | ios::out | ios::binary);
if ( !file.is_open() ) {
   file.clear();
   file.open("Student.dat", ios::out | ios::binary );
   file.close();
   file.open("Student.dat", ios::in | ios::out | ios::binary);
}

无耻被盗 from here