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std::filesy...y::file_size(3) C++ Standard Libarystd::filesy...y::file_size(3)

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

Synopsis
	  std::uintmax_t file_size() const;				   (1)
       (since C++17)
	  std::uintmax_t  file_size( std::error_code& ec ) const noexcept; (2)
       (since C++17)

	  If the file size is cached  in  this	directory_entry,  returns  the
       cached value.
	  Otherwise, returns:

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

Parameters
	  ec - out-parameter for error reporting in the	non-throwing overload

Return value
	  The size of the referred-to filesystem object.

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 er-
       rors, 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
	  Prints  the  list of files in	a given	directory alongside with their
       sizes in	human
	  readable form.

       // Run this code

	#include <cmath>
	#include <cstdint>
	#include <filesystem>
	#include <iostream>

	struct HumanReadable
	{
	    std::uintmax_t size{};

	    template<typename Os> friend Os& operator<<(Os& os,	 HumanReadable
       hr)
	    {
		int i{};
		double mantissa	= hr.size;
		for (; mantissa	>= 1024.0; mantissa /= 1024.0, ++i)
		{}
		os << std::ceil(mantissa * 10.0) / 10.0	<< i["BKMGTPE"];
		return i ? os << "B (" << hr.size << ')' : os;
	    }
	};

	int main(int argc, const char* argv[])
	{
	    const auto dir = argc == 2 ? std::filesystem::path{argv[1]}
				       : std::filesystem::current_path();

	    for	(std::filesystem::directory_entry const& entry :
		 std::filesystem::directory_iterator(dir))
		if (entry.is_regular_file())
		    std::cout << entry.path().filename() << " size: "
			      << HumanReadable{entry.file_size()} << '\n';
	}

Possible output:
	"boost_1_73_0.tar.bz2" size: 104.2MB (109247910)
	"CppCon	2018 - Jon Kalb	Copy Elision.mp4" size:	15.7MB (16411990)
	"cppreference-doc-20190607.tar.xz" size: 6.3MB (6531336)
	"hana.hpp" size: 6.7KB (6807)

See also
	  file_size returns the	size of	a file
	  (C++17)   (function)

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

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