std::filesystem::path::concat, std::filesystem::path::operator+=

path& operator+=( const path& p );	(1)	(since C++17)
path& operator+=( const string_type& str ); path& operator+=( std::basic_string_view<value_type> str );	(2)	(since C++17)
path& operator+=( const value_type* ptr );	(3)	(since C++17)
path& operator+=( value_type x );	(4)	(since C++17)
template< class Source > path& operator+=( const Source& source );	(5)	(since C++17)
template< class CharT > path& operator+=( CharT x );	(6)	(since C++17)
template< class Source > path& concat( const Source& source );	(7)	(since C++17)
template< class InputIt > path& concat( InputIterator first, InputIterator last );	(8)	(since C++17)

Concatenates the current path and the argument

1-7) Appends path(other).native() to the pathname stored in *this in the native format. This directly manipulates the value of native() and may not be portable between operating systems.

8) Same as return *this += path(first, last)

Parameters

p	-	path to append
str	-	string or string view to append
ptr	-	pointer to the beginning of a null-terminated string to append
x	-	single character to append
source	-	std::basic_string, std::basic_string_view, null-terminated multicharacter string, or an input iterator pointing to a null-terminated multicharacter sequence, which represents a path name (either in portable or in native format)
first, last	-	pair of LegacyInputIterators that specify a multicharacter sequence that represents a path name
Type requirements
- `InputIt` must meet the requirements of LegacyInputIterator.
- The value type of `InputIt` must be one of the encoded character types (char, wchar_t, char16_t and char32_t)
- `CharT` must be one of the encoded character types (char, wchar_t, char16_t and char32_t)

Return value

*this

Exceptions

May throw std::bad_alloc if memory allocation fails.

Notes

Unlike with append() or operator/=, additional directory separators are never introduced.

Example

Run this code

#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main() {
    fs::path p1; // empty path
    p1 += "var"; // does not insert a separator
    std::cout << "\"\" + \"var\" == " << p1 << '\n';
    p1 += "lib"; // does not insert a separator
    std::cout << "\"\" + \"var\" + \"lib\" == " << p1 << '\n';
}

Output:

"" + "var" == "var"
"" + "var" + "lib" == "varlib"

Language
Standard Library Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications