ifstream::open not working in Visual Studio debug mode

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;
}

Answer 2

Sometimes Visual Studio puts your exe file away from your source code. By default VS may only look for the file starting from your exe file. This process is a simple step for getting the input txt file from the same directory as your source code. Should you not want to fix your IDE setup.

using namespace std;

ifstream infile;

string path = __FILE__; //gets source code path, include file name
path = path.substr(0,1+path.find_last_of('\\')); //removes file name
path+= "input.txt"; //adds input file to path

infile.open(path);

Hopefully this helps other people for a quick solution. It took me a while to find this setup myself.

Answer 3

I've found two problems in your code:

a) syntax error in "ios::ate || ios::in" => should be "ios::ate | ios::in"

b) "ios::ate" sets the cursor to the end of file - so you get nothing when you start reading

So just remove "ios::ate" and you are fine :)

ciao, Chris

Answer 4

If you use the default Vs code setup, place the text file that you want to read from in the same folder as your executable, I know it is not pretty but yeah it works

Answer 5

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

|| is the logical or operator, not the bitwise operator (as Bill The Lizzard said).

so i guess you are doing the equivalent to:

infile.open ("input.txt", true);

(assuming neither ios::ate or ios::in are 0)

Answer 6

Try using:

ifstream fStm("input.txt", ios::ate | ios::in);

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."

and the proper includes:

#include <fstream> 

etc.