std::filesystem::is_empty
From cppreference.com
< cpp | filesystem
Defined in header <filesystem> | ||
bool is_empty(conststd::filesystem::path& p ); | (1) | (since C++17) |
bool is_empty(conststd::filesystem::path& p, std::error_code& ec ); | (2) | (since C++17) |
Checks whether the given path refers to an empty file or directory.
Contents |
[edit]Parameters
| p | - | path to examine |
| ec | - | error code to modify in case of error |
[edit]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.
[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 <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
[edit]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 allocate memory | noexcept removed |
[edit]See also
(C++17)(C++17) | determines file attributes determines file attributes, checking the symlink target (function) |
(C++17) | checks whether path refers to existing file system object (function) |
