C ++文件处理：ios :: ate无法正常工作

Question

在下面提到的代码中，当我应用ios :: out时它工作正常但是在ios :: ate的情况下不一样，它在文件中显示一些位置-1并且不能写入文件。

其次，peek（）函数在哪里使用。

代码：

int main ()

{
    char p[80];
    fstream file("text1.txt",ios::in|ios::ate);
    cout<<"Starting position of the file is "<<file.tellg()<<endl;
    getch();
    if(file.is_open())
        cout<<"file is open\n";
    else
        cout<<"file is not open\n";
    getch();
    file.seekp(0);
    while(file>>p)
    {
        cout<<p<<endl;
    }
    file.clear();
    if(file<<"Now if we add text to the file")//Not working
        cout<<"\n Data entry possible\n";
    else
        cout<<"\n Data entry not possible\n";
    file.flush();
    cout<<"\nThe current position of the file pointer is "<<file.tellg()<<endl;//Showing position -1
    file.clear();
    file.seekp(0);
    if(file.eof())
        cout<<"\n the eof\n";
    while(file>>p)
    {
        cout<<p<<endl;
    }
    file.close();
    return 0;
}

输出：

Starting position of the file is 30
file is open
Now
if
we
add
text
to
the
file

Data entry not possible

The current position of the file pointer is -1
Now
if
we
add
text
to
the
file

Answer 1

ate并不意味着out因此，如果您要写入文件，则仍需要使用out

fstream file("text1.txt",ios::in|ios::out|ios::ate);