Why is this not producing a file in the current directory?

Question

I have some trouble with producing files in C++. I consulted this answer here but when I try using it, it doesn't produce a file. What I wrote:

//~/Documents/Test_CPP/ex2/main_2.cpp

#include <fstream>

int main()
{
    std::ofstream file("Hello.txt");
    // Hello.txt has been created here
}

I compile it with the command g++ main_2.cpp and run it with ./a.out. I don't really know what could go wrong here, except theorizing that the file might be produced not in the current directory but somewhere else. So I tried changing Hello.txt to ~/Documents/Test_CPP/ex2/Hello.txt, which doesn't change anything. What exactly am I doing wrong here?

"the file is not produced in the current directory but somewhere else" - where? — Jesper Juhl, Jan 11 '20 at 17:32
@JesperJuhl I thought it might be produced somewhere else, but I didn't know. So I tried giving it the full Path.. I'm sorry, but I don't think I understand your question correctly.. — Sito, Jan 11 '20 at 17:34
My question is very simple. You say the file is not created in the current working directory. So all I am asking is, where *is* the file created? — Jesper Juhl, Jan 11 '20 at 17:37
@JesperJuhl Ah, I'm sorry. It's not created at all.. At least I can't find it.. — Sito, Jan 11 '20 at 17:38
After you have answered Jesper's question, take a look at your second statement `~/Documnets/.../main_2.cpp` what are you doing there compared to `Hello.txt`? — picklepick, Jan 11 '20 at 17:39
Be careful with setting an existing file as an output file, because that file may then be overwritten! — Andreas Wenzel, Jan 11 '20 at 17:48
@rezi thank you for pointing that out.. I misspelled when writing the question, I did write `file(~/... /Hello. txt) ` — Sito, Jan 11 '20 at 17:52
@JesperJuhl I just tried searching for the file with `find / -name Hello.txt` and it really isn't anywhere on the machine. — Sito, Jan 11 '20 at 18:27
The code works for me. If the file doesn't exist, it's created, and if it does exist, it's emptied. Are you in a directory where you have permission to create files? (Try something like `echo "File Contents" > Hello.txt` from the Linux command line? Add error checking within your code to see if `file` is open?) — JaMiT, Jan 11 '20 at 19:56

score 0 · Answer 1 · answered Jan 11 '20 at 17:44

0

I have encountered this problem on macOS with Xcode if you use some IDEs you should point to build-dir.

answered Jan 11 '20 at 17:44

desperat0

56
6

and according to your second statement "I tried changing Hello.txt to ~/Documents/Test_CPP/ex2/main_2.cpp" you should fail here because file exist and already in use try "~/Documents/Test_CPP/ex2/test.txt" – desperat0 Jan 11 '20 at 17:47
I'm running everything from a Linux shell. – Sito Jan 11 '20 at 18:23
please point compiler version and Linux distributive type and kernel version – desperat0 Jan 11 '20 at 18:39
gcc 9.2.0, Manjaro, 4.19.56-1-surface – Sito Jan 11 '20 at 18:45

score 0 · Answer 2 · answered Jan 11 '20 at 20:33

My suggestion: use std::filesystem::current_path(). It will give full path to you elf\exe dir.

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


int main() {

    std::string file_name{"Hello.txt"};

    auto path{std::filesystem::current_path()};
    path = path / file_name;
    if (std::filesystem::exists(path)) {
        std::filesystem::remove(path);
    } 

    std::ofstream out_stream(path, std::ios::out);
    if (!out_stream.is_open()) {
        std::cerr << "Error open file" << std::endl;
        return -1;
    }

    out_stream << "test" << std::endl;

    out_stream.close();

    return 0;
}

d0rf47 · Answer 3 · 2020-01-11T17:58:59.133

-3

This can sometimes happen if you do not properly terminate the connection to the file

EG. file.close();

This must be done before the program terminates.

edited Jan 11 '20 at 17:58

answered Jan 11 '20 at 17:49

d0rf47

409
8
20

1

The `std::ofstream` destructor calls `close()` automatically. – JaMiT Jan 11 '20 at 19:42

Why is this not producing a file in the current directory?

3 Answers3