std::filesystem::path::concat, std::filesystem::path::operator+=
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< 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) |
path& operator+=( value_type x ); | (4) | (since C++17) |
template<class CharT > path& operator+=( CharT x ); | (5) | (since C++17) |
template<class Source > path& operator+=(const Source& source ); | (6) | (since C++17) |
template<class Source > path& concat(const Source& source ); | (7) | (since C++17) |
template<class InputIt > path& concat( InputIt first, InputIt last ); | (8) | (since C++17) |
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).
Contents |
[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 separatorstd::cout<< R"("" + "var" --> )"<< p1 <<'\n'; p1 +="lib";// does not insert a separatorstd::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 |
[edit]See also
| appends elements to the path with a directory separator (public member function) | |
(C++17) | concatenates two paths with a directory separator (function) |
