NAME¶

std::filesystem::is_empty - std::filesystem::is_empty

Synopsis¶

Defined in header <filesystem>
bool is_empty( const std::filesystem::path& p ); (1) (since C++17)
bool is_empty( const std::filesystem::path& p, std::error_code& ec (2) (since C++17)
);

Checks whether the given path refers to an empty file or directory.

Parameters¶

p - path to examine
ec - error code to modify in case of error

Return value¶

true if the path indicated by p refers to an empty file or directory, false
otherwise. The non-throwing overload returns false if an error occurs.

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.

Example¶

// Run this code

#include <cstdio>
#include <filesystem>
#include <fstream>
#include <iostream>

int main()
{
namespace fs = std::filesystem;

const fs::path tmp_dir{fs::temp_directory_path()};
std::cout << std::boolalpha
<< "Temp dir: " << tmp_dir << '\n'
<< "is_empty(): " << fs::is_empty(tmp_dir) << '\n';

const fs::path tmp_name{tmp_dir / std::tmpnam(nullptr)};
std::cout << "Temp file: " << tmp_name << '\n';

std::ofstream file{tmp_name.string()};
std::cout << "is_empty(): " << fs::is_empty(tmp_name) << '\n';
file << "cppreference.com";
file.flush();
std::cout << "is_empty(): " << fs::is_empty(tmp_name) << '\n'
<< "file_size(): " << fs::file_size(tmp_name) << '\n';
file.close();
fs::remove(tmp_name);
}

Possible output:¶

Temp dir: "/tmp"
is_empty(): false
Temp file: "/tmp/fileCqd9DM"
is_empty(): true
is_empty(): false
file_size(): 16

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 3013 C++17 error_code overload marked noexcept but can noexcept removed
allocate memory

See also¶

status determines file attributes
symlink_status determines file attributes, checking the symlink target
(C++17) (function)
(C++17)
exists checks whether path refers to existing file system object
(C++17) (function)