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

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) First, appends the preferred directory separator to this, except if any of the following conditions is true:
* the separator would be redundant (*this already ends with a separator)
* *this is empty, or adding it would turn a relative path to an absolute path in some other way
* p is an empty path.
* p.native() begins with a directory separator.
Then, appends p.native() to the pathname maintained by *this
The behavior is undefined if p.has_root_name() is true.
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));

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 InputIterators that specify a multicharacter sequence that represents a path name
Type requirements
-InputIt must meet the requirements of InputIterator.
-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 filesystem_error on underlying OS API errors or std::bad_alloc if memory allocation fails.

Example

#include <iostream>
#include <filesystem>
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"

See also

concatenates two paths without introducing a directory separator
(public member function)
concatenates two paths with a directory separator
(function)

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