File I/O with fstream

[emaghero]

Greetings and Salutations,

I have started using the fstream class in C++ to create text files for input and output. Whenever I try to instantiate an fstream object using the following code

fstream data("c:\\sine.txt",ios_base::in|ios_base::out);
    if(!data){
        cerr<<"Failed to open data\n";
    }
    data.close();
 

The error message is always returned. The header file fstream is included. However, if I first instantiate an ofstream object, close that object and then instantiate the fstream object given above no errors occur.

ofstream data_one("c:\\sine.txt");
    if(!data_one){
        cerr<<"Failed to open data_one\n";
    }
    data_one.close();
 
fstream data("c:\\sine.txt",ios_base::in|ios_base::out);
    if(!data){
        cerr<<"Failed to open data\n";
    }
    data.close();
 

I find this very peculiar. Can anybody explain to me why this is happening, and how it can be remedied. I would be very grateful.

[horace1]

if you open an fstream with ios::in (for reading) and the file does not exist you will get an error. Try checking if the files exists if so open it for read/write if not create it with ofstream (as in your example), close it, then open if for read/write.