How to open input file, C++ on visual studio community 2015?

问题

Does anyone know why the file isn't opening? I also tried just putting "infile.txt" and placing it in the folder of the program and also the debug folder but the ways I used to check for open error both triggered meaning that it could not open. I know I can hard code the location but I don't want to.

I heard you should do stringobj.c_str() but I don't know if that's accurate?

#include "stdafx.h"

#include <iostream>
#include <string>
#include <fstream>
using namespace std;

int main()
{
    ifstream infile;
    ofstream outfile;

    string fileloc = "infile.txt";

    infile.open(fileloc);


    if (!infile)
    {
        cout << "open fail 1" << endl;
    }

    bool fail = infile.fail();
    if (fail)
    {
        cout << "open fail 2";
    }

    return 0;
}

回答1:

Note that the directory structure (at least for VS2013) is

<base>
   - Solution Directory
     - Debug
     - Release
     - Project Directory
       - Debug
       - Release

The program by default runs in the project directory (even though it is built to the solution/debug directory).

If you accepted the default naming convention when starting your project, you should be putting your file in the "Projects\ConsoleApplication1\ConsoleApplication1" directory, not "Projects\ConsoleApplication1"

回答2:

Check your working directory in Project Settings -> Debugging. Make your file available there.

回答3:

First, the documentation for the signature of

std::ifstream::open( const char * filename, ios_base::openmode mode=ios_base::in)

does indicate it requires a const char *, exactly what std::string::c_str() provides. However, there is an overload for open which accepts a const str &, which means it works the same way for both on most implementations.

Otherwise, what you're grappling with is known as the current working directory (or cwd). Apparently you're not sure where THAT directory is. It may be different while you run the debugger on Visual Studio than it is when you run your program from the command line, and it may be different in various IDE's.

I'm not sure why you want to ensure your program only opens a file by name in the current directory, and not give the full path, but...

You may want to inquire what the current working directory is, so you can solve the mystery wherever you try this. In my Visual Studio 2015, the directory ends up being the directory ABOVE debug, but that depends entirely on how your project is configured, and we can't see that out here.

So, try:

std::string cwd = getcwd( NULL, 0 );

This requires a header <direct.h> on Windows in Visual Studio, but it will give you the directory you're trying to figure out.

回答4:

with

string fileloc = "infile.txt";

if you put infile.txt in the same folder of the cpp file, it should be fine.

btw I delete your first line

#include "stdafx.h"

I use cygwin console, may have minor diff

来源：https://stackoverflow.com/questions/32643393/how-to-open-input-file-c-on-visual-studio-community-2015

标签

c++

fstream