std::filesystem::path::append, std::filesystem::path::operator/=
From cppreference.com
< cpp | filesystem | path
|
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)
* 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 - std::iterator_traits < std::decay_t < >>::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
Parameters
| p | - | pathname to append |
| source | - | std::basic_string, std::basic_string_view |
| first, last | - | pair of LegacyInputIterator |
| 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
|
||
Return value
*this
Exceptions
May throw std::bad_alloc if memory allocation fails.
Notes
These functions effectively yield an approximation of the meaning of the argument path p in an environment where *this
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"
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 |
See also
| concatenates two paths without introducing a directory separator (public member function) |
|
|
(C++17)
|
concatenates two paths with a directory separator (function) |