Qt creator - problem with <fstream>

I'm using qt creator on MacOS and I have a problem with compiling my programs. Everytime I try to open txt file with:

fstream file;
file.open("test.txt");
if (file.good())

I get this in the console:

source /var/folders/qx/cpz2lwwx1pd9l1njfddzdxc80000gn/T/tmp6tPViX
Any ideas how to solve it ?

Enoizat (1343)

Step 1: improve the syntax:

1
2
3

std::fstream file("test.txt");
if ( file ) {
    ...

Step 2: check your file position.
Assuming your project name is “catsanddogs”, on your hd there should be a directory named “catsanddogs” which should contain a “catsanddogs.pro” file
and
another directory named “build-catsanddogs…”
where you should find both a “debug” and a “release” directories.

“test.txt”should be placed inside this directory.

Ganado (6811)

What is inside your actual if statement? There must be something.

If test.txt is an existing file, do ifstream instead of fstream.

And, do:

if (file)
{
    cout << "FILE OPENED\n";
}
else
{
    cout << "FILE NOT OPENED\n";
}

If it's not opening the file, then do the aforementioned troubleshooting steps.

On mac/linux/unix you can do system("pwd"); to have it print the current working directory. On Windows, you can do system("cd"); to have it print the current working directory.
Put the test.txt in that folder.

Last edited on

Enoizat (1343)

Ganado wrote:
on Windows, you can do system("cd"); to have it print the current working directory

Wasn’t it system("dir"); ?

Ganado (6811)

dir is the Windows sort-of equivalent to ls (shows you files/directories within the current directory)

Last edited on

againtry (2313)

I have no trouble with QtCreator - lucky me.

However, even though I haven't read it in great detail, this link might be of use
https://github.com/ocaml/opam/issues/3576

againtry (2313)

A bit further investigation confirms it's all to do with paths etc:

A simple 'fix' is to put the text file in some directory (here I put it in "/Users/againtry/" ) and call it up explicitly in the program as follows.

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

using namespace std;

int main()
{
    fstream file;
    file.open("/Users/againtry/test.txt");
    string line;

    cout << true << ' ' << file.good() << '\n';

    if (file.good() == true)
    {
        getline(file, line);

        cout << line << '\n';
        cout << "File is good\n";
    }
    else
        cout << "File is not good\n";

    cout << "Hello World!" << endl;
    return 0;
}


/Users/againtry/qtstuff_and_nonsense/build-untitled-Desktop_Qt_5_14_0_clang_64bit-Debug/untitled ; exit;
1 1
First line of text
File is good
Hello World!

keskiverto (10402)

If you use Qt Creator, do you use Qt as well?

Qt has QFile, QFileInfo, QDir, etc. Portable abstractions.

againtry (2313)

See: https://doc.qt.io/qt-5/qfile.html#setFileName

QFile and QFile::setFileName is essentially the same problem of clearly and explicitly defining, somehow or other, the path to the relevant file.

Last edited on

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Qt creator - problem with <fstream>

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