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std::filesystem:: remove, std::filesystem:: remove_all

From cppreference.net
C++
Filesystem library
Classes
Functions
File types
Defined in header <filesystem>
bool remove ( const std:: filesystem :: path & p ) ;
(1) (since C++17)
bool remove ( const std:: filesystem :: path & p, std:: error_code & ec ) noexcept ;
(2) (since C++17)
(3) (since C++17)
(4) (since C++17)
1,2) The file or empty directory identified by the path p is deleted as if by the POSIX remove . Symlinks are not followed (symlink is removed, not its target).
3,4) Deletes the contents of p (if it is a directory) and the contents of all its subdirectories, recursively, then deletes p itself as if by repeatedly applying the POSIX remove . Symlinks are not followed (symlink is removed, not its target).

Contents

Parameters

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

Return value

1,2) true if the file was deleted, false if it did not exist. The overload that takes error_code& argument returns false on errors.
3,4) Returns the number of files and directories that were deleted (which may be zero if p did not exist to begin with). The overload that takes error_code& argument returns static_cast < std:: uintmax_t > ( - 1 ) on error.

Exceptions

Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

1,3) 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.
2,4) 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.

Notes

On POSIX systems, this function typically calls unlink and rmdir as needed, on Windows DeleteFileW and RemoveDirectoryW .

If p did not exist, this function returns false and does not report an error.

Example

Run this code 
#include <cstdint>
#include <filesystem>
#include <fstream>
#include <iostream>
int main()
{
    namespace fs = std::filesystem;
    std::cout << std::boolalpha;
    fs::path tmp{std::filesystem::temp_directory_path()};
    const auto O_O{"O_O"};
    std::ofstream{tmp / O_O} << O_O; // creates file containing O_O
    std::cout << "remove(): " << fs::remove(tmp / O_O) << '\n'; // success
    std::cout << "remove(): " << fs::remove(tmp / O_O) << '\n'; // fail
    std::filesystem::create_directories(tmp / "abcdef/example");
    const std::uintmax_t n{fs::remove_all(tmp / "abcdef")};
    std::cout << "remove_all(): " << n << " files or directories\n";
}

Possible output: 

remove(): true
remove(): false
remove_all(): 2 files or directories

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 3014 C++17 error_code overload of remove_all marked noexcept but can allocate memory noexcept removed

See also

erases a file
(function)