std::experimental::filesystem::file_size

C++

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Language support library

Concepts library (C++20)

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Regular expressions library (C++11)

Atomic operations library (C++11)

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Filesystem library (C++17)

Technical Specifications

Technical specifications

Filesystem library (filesystem TS)

Library fundamentals (library fundamentals TS)

Library fundamentals 2 (library fundamentals 2 TS)

Extensions for parallelism (parallelism TS)

Extensions for parallelism 2 (parallelism TS v2)

Extensions for concurrency (concurrency TS)

Concepts (concepts TS)

Ranges (ranges TS)

Special mathematical functions (special math TR)

Filesystem library

Classes
filesystem::path filesystem::filesystem_error filesystem::directory_entry filesystem::directory_iterator filesystem::recursive_directory_iterator filesystem::file_status	filesystem::space_info filesystem::file_type filesystem::perms filesystem::copy_options filesystem::directory_options filesystem::file_time_type
Functions
filesystem::absolute filesystem::system_complete filesystem::canonical filesystem::copy filesystem::copy_file filesystem::copy_symlink filesystem::create_directory filesystem::create_directories filesystem::create_hard_link filesystem::create_symlink filesystem::create_directory_symlink filesystem::current_path filesystem::exists filesystem::equivalent	filesystem::file_size filesystem::hard_link_count filesystem::last_write_time filesystem::permissions filesystem::read_symlink filesystem::remove filesystem::remove_all filesystem::rename filesystem::resize_file filesystem::space filesystem::status filesystem::symlink_status filesystem::temp_directory_path
File types
filesystem::is_block_file filesystem::is_character_file filesystem::is_directory filesystem::is_empty filesystem::status_known	filesystem::is_fifo filesystem::is_other filesystem::is_regular_file filesystem::is_socket filesystem::is_symlink

Defined in header <experimental/filesystem>
std::uintmax_t file_size( const path& p ); std::uintmax_t file_size( const path& p, error_code& ec );	(1)	(filesystem TS)

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

Attempting to determine the size of a directory (as well as any other file that is not a regular file or a symlink) is treated as an error.

The non-throwing overload returns returns -1 on errors.

Parameters

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

Return value

The size of the file, in bytes.

Exceptions

The overload that does not take a error_code& parameter throws filesystem_error on underlying OS API errors, constructed with p as the first argument and the OS error code as the error code argument. std::bad_alloc may be thrown if memory allocation fails. The overload taking a 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. This overload has

noexcept specification:

noexcept

Example

Run this code

#include <iostream>
#include <fstream>
#include <experimental/filesystem>
namespace fs = std::experimental::filesystem;
int main()
{
    fs::path p = fs::current_path() / "example.bin";
    std::ofstream(p).put('a'); // create file of size 1
    std::cout << "File size = " << fs::file_size(p) << '\n';
    fs::remove(p);

    try {
        fs::file_size("/dev"); // attempt to get size of a directory
    } catch(fs::filesystem_error& e) {
        std::cout << e.what() << '\n';
    }        
}

Possible output:

File size = 1
filesystem error: cannot get file size: Is a directory [/dev]

See also

resize_file	changes the size of a regular file by truncation or zero-fill (function)
space	determines available free space on the file system (function)