RAII example using unique_ptr

CppUG_RAII_main.cpp

#include <cstdio>
#include <cstdlib>
#include <memory>

int main()
{
    auto file_open = [](const char* filename, const char* mode) -> FILE* 
    {
        return std::fopen(filename, mode);
    };

    auto file_deleter=[](FILE* file) {
        std::puts("Close file\n");
        std::fclose(file);
    };
    
    // Using a unique pointer and custom deleter (lamda)                                        
    std::unique_ptr<FILE, decltype(file_deleter)> fp{file_open("test.txt", "r"), 
                                                     file_deleter};
    if(!fp) {
        std::perror("File opening failed");
        return EXIT_FAILURE;
    }
 
    int c{};
    while ((c = std::fgetc(fp.get())) != EOF) {
       std::putchar(c);
    }
 
    if (std::ferror(fp.get())) {
        std::puts("I/O error when reading");
        return EXIT_FAILURE;
    } else if (std::feof(fp.get())) {
        std::puts("End of file reached successfully");
    }
}