std::filesystem::path::append, std::filesystem::path::operator/=
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Filesystem library
std::filesystem::path
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| path& operator/=( const path& p ); |
(1) | (since C++17) |
| template< class Source > path& operator/=( const Source& source ); |
(2) | (since C++17) |
| template< class Source > path& append( const Source& source ); |
(3) | (since C++17) |
| template< class InputIt > path& append( InputIt first, InputIt last ); |
(4) | (since C++17) |
1) If p.is_absolute() || (p.has_root_name() && p.root_name() != root_name(), then replaces the current path with p as if by operator=(p) and finishes.
* Otherwise, if p.has_root_directory(), then removes any root directory and the entire relative path from the generic format pathname of *this.
* Otherwise, if has_filename() || (!has_root_directory() && is_absolute(), then appends
path::preferred_separator to the generic format of *this. * Either way, then appends the native format pathname of p, omitting any root-name from its generic format, to the native format of *this.
/ Where "/host" is a root-name path("/host") / "foo" / the result is "/host/foo" (appends with separator) path("/host/") / "foo" / the result is also "/host/foo" (appends without separator) / On POSIX, path("foo") / "" / the result is "foo/" (appends) path("foo") / "/bar"; / the result is "/bar" (replaces) / On Windows, path("foo") / "C:/bar"; / the result is "C:/bar" (replaces) path("foo") / "C:"; / the result is "C:" (replaces) path("C:") / ""; / the result is "C:" (appends, without separator) path("C:foo") / "/bar"; / yields "C:/bar" (removes relative path, then appends) path("C:foo") / "C:bar"; / yields "C:foo/bar" (appends, omitting p's root-name)
2,3) Same as (1), but accepts any std::basic_string, std::basic_string_view, null-terminated multicharacter string, or an input iterator pointing to a null-terminated multicharacter sequence. Equivalent to return operator/=(path(source));.
4) Same as (1), but accepts any iterator pair that designates a multicharacter string. Equivalent to return operator/=(path(first, last));.
(2) and (3) participate in overload resolution only if Source and path are not the same type, and either:
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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 | - | pathname 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.
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-The value type of InputIt must be one of the encoded character types (char, wchar_t, char16_t and char32_t).
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[edit] Return value
*this
[edit] Exceptions
May throw std::bad_alloc if memory allocation fails.
[edit] Notes
These functions effectively yield an approximation of the meaning of the argument path p in an environment where *this is the starting directory.
[edit] Example
The output is produced on Windows.
Run this code
#include <filesystem> #include <iostream> namespace fs = std::filesystem; int main() { fs::path p1 = "C:"; p1 /= "Users"; / does not insert a separator std::cout << "\"C:\" / \"Users\" == " << p1 << '\n'; p1 /= "batman"; / inserts fs::path::preferred_separator, '\' on Windows std::cout << "\"C:\" / \"Users\" / \"batman\" == " << p1 << '\n'; }
Possible output:
"C:" / "Users" == "C:Users" "C:" / "Users" / "batman" == "C:Users\\batman"
[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 3244 | C++17 | constraint that Source cannot be path was missing
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added |
[edit] See also
| concatenates two paths without introducing a directory separator (public member function) [edit] | |
| (C++17) |
concatenates two paths with a directory separator (function) [edit] |
