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std::filesy...t_write_time(3)  C++ Standard Libary std::filesy...t_write_time(3)

NAME
     std::filesystem::directory_entry::last_write_time - std::filesystem::direc-
     tory_entry::last_write_time

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&   (2)
     (since C++17)
	ec ) const noexcept;

	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.

Exceptions
	Any  overload not marked noexcept may throw std::bad_alloc if memory al-
     location
	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

      #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)

http://cppreference.com 	   2024.06.10	   std::filesy...t_write_time(3)
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