NAME

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

Synopsis

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

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

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

// Run this code

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

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