std::errc

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

void print_error(const std::string& details, std::error_code error_code)
{
    std::string value_name;
    if (error_code == std::errc::invalid_argument)
        value_name = "std::errc::invalid_argument";
    if (error_code == std::errc::no_such_file_or_directory)
        value_name = "std::errc::no_such_file_or_directory";
    if (error_code == std::errc::is_a_directory)
        value_name = "std::errc::is_a_directory";
    if (error_code == std::errc::permission_denied)
        value_name = "std::errc::permission_denied";
    std::cout << details << ": \"" << error_code.message() << "\" ("
              << value_name << ") \n";
}

void print_errno(const std::string& details, int errno_value = errno)
{
    print_error(details, std::make_error_code(std::errc(errno_value)));
}

int main()
{
    //  
    try
    {
        std::thread().detach();
    }
    catch (const std::system_error& e)
    {
        print_error("   ", e.code());
    }
    
    //   
    {
        std::ifstream nofile(" ");
        if (!nofile.is_open())
        {
            print_errno("     ");
        }
    }
    
    //     
    {
        std::filesystem::create_directory("dir");
        std::ifstream dir_stream("dir");
        [[maybe_unused]] char c = dir_stream.get();
        if (!dir_stream.good())
        {
            print_errno("    ");
        }
    }
    
    //       
    {
        {
            std::fstream new_file("readonly-file", std::ios::out);
        }
        std::filesystem::permissions("readonly-file", std::filesystem::perms::owner_read);
        std::fstream write_readonly("readonly-file", std::ios::out);
        if (!write_readonly.is_open())
        {
            print_errno("       ");
        }
    }
}