| path filename() const; | (since C++17) | 
Returns the generic-format filename component of the path.
Equivalent to relative_path().empty() ? path() : *--end().
(none).
The filename identified by the path.
May throw implementation-defined exceptions.
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
 
int main()
{
    std::cout 
        << fs::path( "/foo/bar.txt" ).filename() << '\n'
        << fs::path( "/foo/.bar"    ).filename() << '\n'
        << fs::path( "/foo/bar/"    ).filename() << '\n'
        << fs::path( "/foo/."       ).filename() << '\n'
        << fs::path( "/foo/.."      ).filename() << '\n'
        << fs::path( "."            ).filename() << '\n'
        << fs::path( ".."           ).filename() << '\n'
        << fs::path( "/"            ).filename() << '\n'
        << fs::path( "//host"       ).filename() << '\n';
}Output:
"bar.txt" ".bar" "" "." ".." "." ".." "" "host"
| returns the file extension path component (public member function) | |
| returns the stem path component (filename without the final extension) (public member function) | |
| replaces the last path component with another path (public member function) | |
| checks if the corresponding path element is not empty (public member function) | 
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    https://en.cppreference.com/w/cpp/filesystem/path/filename