dirname

来源：https://stackoverflow.com/questions/3071665/getting-a-directory-name-from-a-filename

#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main()
{
    fs::path x{"/var/tmp/example.txt"};
    std::cout << x.parent_path().string() << std::endl;
    for(fs::path p : {"/var/tmp/example.txt", "/", "/var/tmp/."})
        std::cout << "The parent path of " << p
                  << " is " << p.parent_path() << '\n';
}

mkdir

来源：https://en.cppreference.com/w/cpp/filesystem/create_directory

bool create_directory( const std::filesystem::path& p );
(1) (since C++17)
bool create_directory( const std::filesystem::path& p, std::error_code& ec ) noexcept;
(2) (since C++17)
bool create_directory( const std::filesystem::path& p,
                       const std::filesystem::path& existing_p );
(3) (since C++17)
bool create_directory( const std::filesystem::path& p,
                       const std::filesystem::path& existing_p,
                       std::error_code& ec ) noexcept;
(4) (since C++17)
bool create_directories( const std::filesystem::path& p );
(5) (since C++17)
bool create_directories( const std::filesystem::path& p, std::error_code& ec );
(6) (since C++17)

• bool create_directory( const std::filesystem::path& p );
• bool create_directory( const std::filesystem::path& p, std::error_code& ec ) noexcept;
• bool create_directory( const std::filesystem::path& p, const std::filesystem::path& existing_p );
• bool create_directory( const std::filesystem::path& p, const std::filesystem::path& existing_p, std::error_code& ec ) noexcept;
• bool create_directories( const std::filesystem::path& p );
• bool create_directories( const std::filesystem::path& p, std::error_code& ec );

code

#include <cassert>
#include <cstdlib>
#include <filesystem>

int main()
{
    std::filesystem::current_path(std::filesystem::temp_directory_path());

    // Basic usage
    std::filesystem::create_directories("sandbox/1/2/a");
    std::filesystem::create_directory("sandbox/1/2/b");

    // Directory already exists (false returned, no error)
    assert(!std::filesystem::create_directory("sandbox/1/2/b"));

    // Permissions copying usage
    std::filesystem::permissions(
        "sandbox/1/2/b",
        std::filesystem::perms::others_all,
        std::filesystem::perm_options::remove
    );
    std::filesystem::create_directory("sandbox/1/2/c", "sandbox/1/2/b");

    std::system("ls -l sandbox/1/2");
    std::system("tree sandbox");
    std::filesystem::remove_all("sandbox");
}

读写文件

来源：https://stackoverflow.com/questions/38646062/c-high-performance-file-reading-and-writing-c14

写文件：

std::ofstream f("file.txt");
f.write(buffer.data(), buffer.size());

读文件：

std::string buffer;

std::ifstream f("file.txt");
f.seekg(0, std::ios::end);
buffer.resize(f.tellg());
f.seekg(0);
f.read(buffer.data(), buffer.size());