std::filesy...t_write_time(3)

🎀 NAME 🎀

okay so bestie, this is the std::filesy...t_write_time(3) page from the C++ Standard Libary manual, and it’s all about std::filesystem::directory_entry::last_write_time — literally the std::filesystem::directory_entry::last_write_time member function. periodt 💅

✨ Synopsis ✨

std::filesystem::file_time_type last_write_time() const;

(1) (since C++17)

std::filesystem::file_time_type last_write_time( std::error_code&
ec ) const noexcept;

(2) (since C++17)

If the last modification time is cached in this directory_entry, returns the cached value. Otherwise, returns:

1. std::filesystem::last_write_time(path()).
2. std::filesystem::last_write_time(path(), ec).

🌸 Parameters 🌸

• ec — out-parameter for error reporting in the non-throwing overload.

💖 Return value 💖

The last modification time for the referred-to filesystem object. iconic.

😭 Exceptions 😭

Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

1. Throws std::filesystem::filesystem_error on underlying OS API errors, constructed with p as the first path argument and the OS error code as the error code argument.
2. Sets a std::error_code& parameter to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur.

🧚 Example 🧚

// Run this code — no cap, go run it:

#include <chrono>
#include <ctime>
#include <filesystem>
#include <format>
#include <iostream>
#include <string>

std::string to_string(const std::filesystem::file_time_type& ftime)
{
#if __cpp_lib_format
    return std::format("{:%c}", ftime);
#else
    std::time_t cftime = std::chrono::system_clock::to_time_t(
        std::chrono::file_clock::to_sys(ftime));
    std::string str = std::asctime(std::localtime(&cftime));
    str.pop_back(); // rm the trailing '\n' put by `asctime`
    return str;
#endif
}

int main()
{
    auto dir = std::filesystem::current_path();
    using Entry = std::filesystem::directory_entry;
    for (Entry const& entry : std::filesystem::directory_iterator(dir))
        std::cout << to_string(entry.last_write_time()) << " : "
                  << entry.path().filename() << '\n';
}

🌈 Possible output 🌈

Wed Sep  6 13:37:13.960314156 2023 : "main.cpp"
Wed Sep  6 13:37:42.690271828 2023 : "a.out"

👀 See also 👀

• last_write_time gets or sets the time of the last data modification (C++17) (function).

source/version/date: http://cppreference.com, 2024.06.10, std::filesy...t_write_time(3) — bye bestie, u ate this page up 💖✨🎀