std::ofstream, check if file exists before writing

Question

I am implementing file saving functionality within a Qt application using C++.

I am looking for a way to check to see if the selected file already exists be

Answer 1

With std::filesystem::exists of C++17:

#include  // C++17
#include 
namespace fs = std::filesystem;

int main()
{
    fs::path filePath("path/to/my/file.ext");
    std::error_code ec; // For using the noexcept overload.
    if (!fs::exists(filePath, ec) && !ec)
    {
        // Save to file, e.g. with std::ofstream file(filePath);
    }
    else
    {
        if (ec)
        {
            std::cerr << ec.message(); // Replace with your error handling.
        }
        else
        {
            std::cout << "File " << filePath << " does already exist.";
            // Handle overwrite case.
        }
    }
}

See also std::error_code.

In case you want to check if the path you are writing to is actually a regular file, use std::filesystem::is_regular_file.