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std::filesystem::file_size

From cppreference.com
 
C++
 
Filesystem library
Classes
Functions
File types
 
Defined in header <filesystem>
std::uintmax_t file_size( const std::filesystem::path& p );
 (1) (since C++17)
std::uintmax_t file_size( const std::filesystem::path& p,
                          std::error_code& ec ) noexcept;
 (2) (since C++17)

If p does not exist, reports an error.

For a regular file p, returns the size determined as if by reading the st_size member of the structure obtained by POSIX stat (symlinks are followed).

The result of attempting to determine the size of a directory (as well as any other file that is not a regular file or a symlink) is implementation-defined.

The non-throwing overload returns static_cast<std::uintmax_t>(-1) on errors.

Contents

[edit] Parameters

p - path to examine
ec - out-parameter for error reporting in the non-throwing overload

[edit] Return value

The size of the file, in bytes.

[edit] 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.

[edit] Example

Run this code
#include <cmath>
#include <filesystem>
#include <fstream>
#include <iostream>
namespace fs = std::filesystem;
 
struct HumanReadable
{
    std::uintmax_t size{};
 
private:
    friend std::ostream& operator<<(