Very quick question about File I/O

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  1. #1
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    Very quick question about File I/O

    I have my program successfully writing to text files but when the program starts again, it deletes the text file and begins writing it fresh. I thought a solution would be to have the user input the file name they would like the program to create but I cannot figure out the correct syntax.

    Code:
    cout << "What do you want to call your file? eg. myfile.txt";
    char filename[256];
    cin >> filename;
    ofstream flout('filename');
    any help would be appreciated.
    Thanks!

  2. #2
    Registered User major_small's Avatar
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    Code:
    cout << "What do you want to call your file? eg. myfile.txt";
    char filename[256];
    cin >> filename;
    ofstream flout(filename,ios::app);
    that should do the trick
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  3. #3
    Registered User jlou's Avatar
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    I'd highly recommend:
    Code:
    cout << "What do you want to call your file? eg. myfile.txt";
    string filename;
    cin >> filename;
    ofstream flout(filename.c_str());
    To use the char[256] like you showed, you just need to remove the quotes around filename when creating the ofstream. However, I just happened to read in Josuttis' The C++ Standard Library that you should do this to avoid overwriting the char array:
    Code:
    cout << "What do you want to call your file? eg. myfile.txt";
    char filename[256];
    cin >> setw(sizeof(filename)) >> filename;
    ofstream flout(filename);
    EDIT: Didn't see major_small's post but I still think that the single quotes is the specific problem. The ios::app will let you append instead of overwrite if the chosen file already exists. And I still recommend the string instead of char[].
    Last edited by jlou; 09-09-2003 at 07:32 PM.

  4. #4
    Registered User major_small's Avatar
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    yeah, that's his problem if he wants the user to enter the filename, but the main problem was that the program would overwrite the file... this way it just adds to the end of the file..

    ios::nocreate //doesn't open file if it's not already there
    ios::app //adds to end of file
    ios::trunc //overwrites file
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    Thanks alot guys.
    I had filename without any quotes when I first created it but for some reason it wouldn't compile :/
    Screwy MSVC++

    oh, but I forgot to add that it does work now

  6. #6
    carry on JaWiB's Avatar
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    Josuttis' The C++ Standard Library
    Good book
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    I know them not: not therefore am I short
    Of knowing what I ought."
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