operator<<,>> (std::filesystem::path)

From cppreference.com
template < class CharT, class Traits >

friend std:: basic_ostream < CharT,Traits > &

operator << ( std:: basic_ostream < CharT,Traits > & os, const path & p ) ;
(1) (since C++17)
template < class CharT, class Traits >

friend std:: basic_istream < CharT,Traits > &

operator >> ( std:: basic_istream < CharT,Traits > & is, path & p ) ;
(2) (since C++17)

Performs stream input or output on the path p . std:: quoted is used so that spaces do not cause truncation when later read by stream input operator.

These function templates are not visible to ordinary unqualified or qualified lookup , and can only be found by argument-dependent lookup when std::filesystem::path is an associated class of the arguments. This prevents undesirable conversions in the presence of a using namespace std :: filesystem ; using-directive .

Parameters

os - stream to perform output on
is - stream to perform input on
p - path to insert or extract

Return value

1) os
2) is

Exceptions

May throw implementation-defined exceptions.

Possible implementation

operator<<
template<class CharT, class Traits>
friend std::basic_ostream<CharT,Traits>&
    operator<<(std::basic_ostream<CharT,Traits>& os, const path& p)
{
    os << std::quoted(p.string<CharT,Traits>());
    return os;
}
operator>>
template<class CharT, class Traits>
friend std::basic_istream<CharT,Traits>&
    operator>>(std::basic_istream<CharT,Traits>& is, path& p)
{
    std::basic_string<CharT, Traits> t;
    is >> std::quoted(t);
    p = t;
    return is;
}

Example

#include <filesystem>
#include <iostream>
 
int main()
{
    std::cout << std::filesystem::current_path() << '\n';
    std::cout << std::filesystem::temp_directory_path() << '\n';
}

Possible output:

"/home/user"
"/tmp"

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 2989 C++17 allowed insertion of everything convertible to path in the presence of a using-directive made hidden friend