std::filesystem::path::concat, std::filesystem::path::operator+=
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Feature test macros (C++20)
Concepts library (C++20)
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Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Filesystem library
std::filesystem::path
Path decomposition Non-member functions
Helper classes
path::concatpath::operator+=
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
(C++26)
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+=( std::basic_string_view <value_type> str );
path& operator+=( const value_type* ptr );
(3)
(since C++17)
path& operator+=( value_type x );
(4)
(since C++17)
template< class CharT >
path& operator+=( CharT x );
(5)
(since C++17)
path& operator+=( CharT x );
template< class Source >
path& operator+=( const Source& source );
(6)
(since C++17)
path& operator+=( const Source& source );
template< class Source >
path& concat( const Source& source );
(7)
(since C++17)
path& concat( const Source& source );
template< class InputIt >
path& concat( InputIt first, InputIt last );
(8)
(since C++17)
path& concat( InputIt first, InputIt last );
Concatenates the current path and the argument
1-3,6,7) Appends path(p).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.
4,5) Same as return *this += std::basic_string_view (&x, 1);.
8) Same as return *this += path(first, last);.
(6) and (7) participate in overload resolution only if Source and path are not the same type, and either:
-
Sourceis a specialization of std::basic_string or std::basic_string_view , or - std::iterator_traits <std::decay_t <Source>>::value_type is valid and denotes a possibly const-qualified encoding character type (char, char8_t, (since C++20)char16_t, char32_t, or wchar_t).
[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
*this
[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
Run this code
#include <filesystem> #include <iostream> #include <string> int main() { std::filesystem::path p1; // an empty path p1 += "var"; // does not insert a separator std::cout << R"("" + "var" --> )" << p1 << '\n'; p1 += "lib"; // does not insert a separator std::cout << R"("var" + "lib" --> )" << p1 << '\n'; auto str = std::string {"1234567"}; p1.concat(std::begin (str) + 3, std::end (str) - 1); std::cout << "p1.concat --> " << p1 << '\n'; }
Output:
"" + "var" --> "var" "var" + "lib" --> "varlib" p1.concat --> "varlib456"
[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 |
| LWG 3244 | C++17 | constraint that Source cannot be path was missing
|
added |