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

< cpp‎ | filesystem‎ | path
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)
template< class Source >
path& operator+=( const Source& source );
(4) (since C++17)
template< class Source >
path& concat( const Source& source );
(5) (since C++17)
path& operator+=( value_type x );
(6) (since C++17)
template< class CharT >
path& operator+=( CharT x );
(7) (since C++17)
template< class InputIt >
path& concat( InputIterator first, InputIterator last );
(8) (since C++17)

Concatenates the current path and the argument

1-5) 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.
6-7) Same as return *this += std::basic_string_view(&x, 1);
8) Same as return *this += path(first, last);


[edit] 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)

[edit] Return value


[edit] Exceptions

May throw std::bad_alloc if memory allocation fails.

[edit] Notes

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

[edit] Example

#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';


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

[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 3055 C++17 the specification of concatenating a single character was ill-formed made well-formed

[edit] See also

appends elements to the path with a directory separator
(public member function) [edit]
concatenates two paths with a directory separator
(function) [edit]