Question

I’ve been all over the ifstream questions here on SO and I’m still having trouble reading a simple text file. I’m working with Visual Studio 2008.

Here’s my code:

// CPPFileIO.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <fstream>
#include <conio.h>
#include <iostream>
#include <string>

using namespace std;


int _tmain(int argc, _TCHAR* argv[])
{

    ifstream infile;
    infile.open("input.txt", ifstream::in);

    if (infile.is_open())
    {
        while (infile.good())
            cout << (char) infile.get();
    }
    else
    {
        cout << "Unable to open file.";
    }
    infile.close();
    _getch();
    return 0;
}

I have confirmed that the input.txt file is in the correct “working directory” by checking the value of argv[0]. The Open method just won’t work.

I’m also having trouble debugging- should I not be able to set a watch on infile.good() or infile.is_open()? I keep getting

Error: member function not present.

EDIT: Updated code listing with full code from .CPP file.

UPDATE: The file was NOT in the Current Working Directory. This is the directory where the project file is located. Moved it there and it works when debugging in VS.NET.

Answer 1

Try using the bitwise OR operator when specifying the open mode.

infile.open ("input.txt", ios::ate | ios::in);

The openmode parameter is a bitmask. ios::ate is used to open the file for appending, and ios::in is used to open the file for reading input.

If you just want to read the file, you can probably just use:

infile.open ("input.txt", ios::in);

---

The default open mode for an ifstream is ios::in, so you can get rid of that altogether now. The following code is working for me using g++.

#include <iostream>
#include <fstream>
#include <cstdio>

using namespace std;

int main(int argc, char** argv) {
    ifstream infile;
    infile.open ("input.txt");

    if (infile)
    {
        while (infile.good())
            cout << (char) infile.get();
    }
    else
    {
        cout << "Unable to open file.";
    }
    infile.close();
    getchar();
    return 0;
}