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

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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.

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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.

File I/O with fstream

re: File I/O with fstream

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