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I/O files: reading, manipulating & outputting data

Pat (1)
I wish to input (read) the contents of the file called "numbers.dat" (that appears at the bottom of this writeup) into the file (sum.dat) following immediately here below; with the view of manipulating these contents and outputting the results within this file called "sum.dat". However, all my previous attempts have ended with: "Input file opening failed"!

I am using Code::Blocks 10.05 running on Windows.

I am unable to figure out why the input file fails to open. What is wrong here?

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#include <fstream>
#include <iostream>
#include <cstdlib>

int main()
{
    using namespace std;

    char in_file_name[16], out_file_name[16];
    ifstream in_stream;
    ofstream out_stream;

    cout << "Enter the input file name (maximum of 15 characters):\n";
    cin >> in_file_name;
    cout << "Enter the output file name (maximum of 15 characters):\n";
    cin >> out_file_name;
    cout << "I will read numbers from the file "
         << in_file_name << " and\n"
         << "place the sum in the file "
         << out_file_name << endl;

    in_stream.open(in_file_name);
    if (in_stream.fail ())
    {
        cout << "Input file opening failed.\n";
        exit(1);

        out_stream.open(out_file_name);
        if (out_stream.fail ())
        {
            cout << "Output file opening failed.\n";
            exit(1);
        }
        int first, second, third;
        in_stream >> first >> second >> third;

        out_stream << "The Sum of the first 3\n"
                   << "numbers in " << in_file_name << endl
                   << " is " << (first + second + third)
                   << endl;

        in_stream.close();
        out_stream.close();

        cout << " End of Program.\n";

    }

    return 0;
}

//Following is the file numbers.dat

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#include <fstream>
#include <string>
#include <iostream>
#include <cstdlib>

using namespace std;

int main()
{
    int num1, num2, num3, num4;
    string numbers;

    cout << "Enter the four numbers: " << endl;
    cin >> num1 >> num2 >> num3 >> num4;

    cout << "The numbers are: " << num1 << " "<< num2 << " " 
                                               << num3      << " " << num4;

    ofstream writer("numbers.dat");

    if(!writer)
    {
        cout << "Error opening file for output" << endl;
        return -1;
    }
    writer << numbers << endl;
    writer.close();

    return 0;
}
Last edited on
MikeyBoy (5631)
Please could you edit your post, and enclose your code in code tags? That would make it more readable. You can get code tags using the "<>" button to the right of the edit window. You'll probably need to reinstate your indentation, as it will have been lost.

The easier your code is to read, the more likely it is that people will take the time to read it and help you.
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