RAII example in modern C++ (example b)

CMakeLists.txt

cmake_minimum_required(VERSION 3.0.0)
project(raii_examples VERSION 0.1.0)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

add_executable(raii_2 raii_2.cpp)

raii_2.cpp

#include <fstream>
#include <memory>
#include <string_view>
#include <iostream>

void releaseFile(FILE *file)
{
    std::cout << "Closing the file" << std::endl;
    std::fclose(file);
}

using FileRaii = std::unique_ptr<std::FILE, decltype(&releaseFile)>;

FileRaii acquireFile(std::string_view filename)
{
    std::cout << "Opening the file" << std::endl;
    FileRaii my_file{std::fopen(filename.data(), "r"), &releaseFile};
    if (my_file == NULL)
    {
        throw std::runtime_error(std::strerror(errno));
    }
    return my_file;
}

int main()
{
    try
    {
        auto f = acquireFile("sample.txt");
        char line[255];
        fgets(line, sizeof(line), f.get());
        std::cout << line << std::endl;
    }
    catch (std::runtime_error &e)
    {
        std::cerr << e.what() << std::endl;
    }
    return 0;
}