Namespaces
Variants
Actions

std::filesystem::path::append, std::filesystem::path::operator/=

From cppreference.com
< cpp‎ | filesystem‎ | path
 
C++
 
Filesystem library
Classes
Functions
File types
 
std::filesystem::path
Member types
Member constants
Member functions
Path decomposition
Non-member functions
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
Helper classes
 
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:

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.
-
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

[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]
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/filesystem/path/append&oldid=158013"