std::filesystem::path::append, std::filesystem::path::operator/=
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Filesystem library
std::filesystem::path
Path decomposition Non-member functions
Helper classes
path::appendpath::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)
template< class Source >
path& operator/=( const Source& source );
(2)
(since C++17)
path& operator/=( const Source& source );
template< class Source >
path& append( const Source& source );
(3)
(since C++17)
path& append( const Source& source );
template< class InputIt >
path& append( InputIt first, InputIt last );
(4)
(since C++17)
path& append( InputIt first, InputIt last );
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:
-
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
-
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.
-The value type of
InputIt 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
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
|
added |