std::filesystem::directory_entry:: is_symlink

#include <cstdio>
#include <cstring>
#include <filesystem>
#include <fstream>
#include <functional>
#include <iostream>
#include <memory>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <unistd.h>
namespace fs = std::filesystem;
void print_entry_type(const std::filesystem::directory_entry& entry)
{
    std::cout << entry.path() << ": ";
    if (!entry.exists())
        std::cout << "does not exist ";
    if (entry.is_block_file())
        std::cout << "is a block device ";
    if (entry.is_character_file())
        std::cout << "is a character device ";
    if (entry.is_directory())
        std::cout << "is a directory ";
    if (entry.is_fifo())
        std::cout << "is a named IPC pipe ";
    if (entry.is_regular_file())
        std::cout << "is a regular file ";
    if (entry.is_socket())
        std::cout << "is a named IPC socket ";
    if (entry.is_symlink())
        std::cout << "(a symlink)";
    if (entry.is_other())
        std::cout << "(an `other` file)";
    std::cout << '\n';
}
template<typename Type, typename Fun>
class scoped_cleanup
{
    std::unique_ptr<Type, std::function<void(const Type*)>> u;
public:
    scoped_cleanup(Type* ptr, Fun fun) : u{ptr, std::move(fun)} {}
};
int main()
{
    // 创建不同类型的文件
    std::filesystem::current_path(fs::temp_directory_path());
    const std::filesystem::path sandbox{"sandbox"};
    scoped_cleanup remove_all_at_exit{&sandbox, [](const fs::path* p)
    {
        std::cout << "cleanup: remove_all(" << *p << ")\n";
        fs::remove_all(*p);
    }};
    std::filesystem::create_directory(sandbox);
    std::ofstream{sandbox/"file"}; // 创建常规文件
    std::filesystem::create_directory(sandbox/"dir");
    mkfifo((sandbox/"pipe").string().data(), 0644);
    struct sockaddr_un addr; addr.sun_family = AF_UNIX;
    std::strcpy(addr.sun_path, (sandbox/"sock").string().data());
    int fd{socket(PF_UNIX, SOCK_STREAM, 0)};
    scoped_cleanup close_socket_at_exit{&fd, [](const int* f)
    {
        std::cout << "cleanup: close socket #" << *f << '\n';
        close(*f);
    }};
    bind(fd, reinterpret_cast<sockaddr*>(</