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std::filesystem::directory_entry::file_size(3) C++ Standard Libary std::filesystem::directory_entry::file_size(3)


std::filesystem::directory_entry::file_size - std::filesystem::directory_entry::file_size


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

If the file size is cached in this directory_entry, returns the cached value.
Otherwise, returns std::filesystem::file_size(path()) or
std::filesystem::file_size(path(), ec), respectively.


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

Return value

The size of the referred-to filesystem object.


The overload that does not take a std::error_code& parameter throws
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. The overload
taking a std::error_code& parameter sets it to the OS API error code if an OS API
call fails, and executes ec.clear() if no errors occur. Any overload not marked
noexcept may throw std::bad_alloc if memory allocation fails.


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

// Run this code

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

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.; ++i) {
mantissa /= 1024.;
mantissa = std::ceil(mantissa * 10.) / 10.;
os << mantissa << "BKMGTPE"[i];
return i == 0 ? os : os << "B (" << hr.size << ')';

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)