File Copying

This is a discussion on File Copying within the C++ Programming forums, part of the General Programming Boards category; Hi i am having a problem copying data from 1 file to another heres is my code. Code: #include <iostream> ...

  1. #1
    Registered User
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    Jan 2006
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    4

    File Copying

    Hi i am having a problem copying data from 1 file to another heres is my code.

    Code:
    #include <iostream>
    #include <fstream>
    
    using namespace std;
    
    void copyfiles(ifstream& copyfrom, ofstream& copyto);
    int main()
    {
    ofstream outfile;
    ifstream infile;
    
    infile.open("dates.txt");
    if (infile.fail())
    {
        cout << "cudnt open" <<endl;
            exit (1);
    }
    
    outfile.open("results.txt");
    if (outfile.fail())
    {
        cout << "cudnt open" <<endl;
            exit (1);
    }
    
    copyfiles(infile, outfile);
    cout<<"done"<<endl;
    
    infile.close();
    outfile.close();
    
    return 0;
    }
    
    void copyfiles(ifstream& copyfrom, ofstream& copyto)
    {
        int date;
        date = copyfrom.get();
        while ( ! copyfrom.eof())
        {
            copyto.put(date);
            date = copyfrom.get();
        }
        return;
    }
    I am supposed to be using a class to pass the data across and manipulate it on the way, but i need to understand how to do this first. It compiles fine, then when i run the program nothing happens. 'Result.txt' isnt even created. Cheers for your help.

  2. #2
    Registered User hk_mp5kpdw's Avatar
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    Jan 2002
    Location
    Northern Virginia/Washington DC Metropolitan Area
    Posts
    3,794
    First, define "nothing happens"... do you see any output at all?

    The eof test should not be used to control the loop these things are problematic when used in such a way. Several versions of the get function return a reference to the stream/file that can be tested directly to determine whether or not a value was read from said stream/file. I would suggest something more like this for the copyfiles function:

    Code:
    void copyfiles(ifstream& copyfrom, ofstream& copyto)
    {
        char date;
    
        while( !copyfrom.get(date) )
        {
            copyto.put(date);
        }
    
        return;
    }
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
    -Christopher Hitchens

  3. #3
    Registered User
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    Jan 2006
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    http://msdn.microsoft.com/library/de...s/copyfile.asp

    unless you absolutely need to bug yourself with a lot of issues (and you are coding for win32) one line of code is perfectly enough for you. I use API as much as i can for
    1. less work to be done.
    2. Already tested and documented functions.

  4. #4
    xhi
    xhi is offline
    !anExpert
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    >> It compiles fine, then when i run the program nothing happens. 'Result.txt' isnt even created.

    i tested it and it works as-is.. copies the file to results.txt..

    currently im on devc++ and winxp..

    thought youd like to know

  5. #5
    Advanced Novice linucksrox's Avatar
    Join Date
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    Location
    Michigan
    Posts
    198
    hk_mp5kpdw, i believe your solution should be
    Code:
    while (copyfrom.get(date))
    and you have a ! before the function call
    "What are all you parallelograms doing here?" - Peter Griffin (to Joe and his wheelchair buddies)

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