# std::filesystem::directory_entry::file_size

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< cpp‎ | filesystem‎ | directory entry

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

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.

### Parameters

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

### Return value

The size of the referred-to filesystem object.

### Exceptions

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.

### Example

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 (C++17) | returns the size of a file (function)

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