std::filesystem::path::extension

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Technical Specifications

Filesystem library

Classes
filesystem::path filesystem::filesystem_error filesystem::directory_entry filesystem::directory_iterator filesystem::recursive_directory_iterator filesystem::file_status	filesystem::space_info filesystem::file_type filesystem::perms filesystem::perm_options filesystem::copy_options filesystem::directory_options filesystem::file_time_type
Functions
filesystem::absolute filesystem::canonicalfilesystem::weakly_canonical filesystem::relativefilesystem::proximate filesystem::copy filesystem::copy_file filesystem::copy_symlink filesystem::create_directory filesystem::create_directories filesystem::create_hard_link filesystem::create_symlink filesystem::create_directory_symlink filesystem::current_path	filesystem::exists filesystem::equivalent filesystem::file_size filesystem::hard_link_count filesystem::last_write_time filesystem::permissions filesystem::read_symlink filesystem::remove filesystem::remove_all filesystem::rename filesystem::resize_file filesystem::space filesystem::status filesystem::symlink_status filesystem::temp_directory_path
File types
filesystem::is_block_file filesystem::is_character_file filesystem::is_directory filesystem::is_empty filesystem::status_known	filesystem::is_fifo filesystem::is_other filesystem::is_regular_file filesystem::is_socket filesystem::is_symlink

std::filesystem::path

Constants
path::native_formatpath::generic_formatpath::auto_format
Member functions
path::path path::~path path::operator= path::assign path::appendpath::operator /= path::concatpath::operator += path::clear path::make_preferred path::remove_filename path::replace_filename path::replace_extension path::swap path::compare path::beginpath::end	path::c_strpath::nativepath::operator string_type path::stringpath::u8stringpath::u16stringpath::u32stringpath::wstring path::generic_stringpath::generic_u8stringpath::generic_u16stringpath::generic_u32stringpath::generic_wstring path::lexically_normalpath::lexically_relativepath::lexically_proximate
Path decomposition
path::root_name path::root_directory path::root_path path::relative_path path::parent_path path::filename path::stem path::extension path::empty	path::has_root_pathpath::has_root_namepath::has_root_directorypath::has_relative_pathpath::has_parent_pathpath::has_filenamepath::has_stempath::has_extension path::is_absolutepath::is_relative
Non-member functions
swap(path)
hash_value
operator==operator!=operator<operator<=operator>operator>=
operator/
operator<<operator>>
u8path

path extension() const;		(since C++17)

Returns the extension of the filename component of the generic-format view of *this.

If the filename() component of the generic-format path contains a period (.), and is not one of the special filesystem elements dot or dot-dot, then the extension is the substring beginning at the rightmost period (including the period) and until the end of the pathname.

If the first character in the filename is a period, that period is ignored (a filename like ".profile" is not treated as an extension)

If the pathname is either . or .., or if filename() does not contain the . character, then empty path is returned.

Additional behavior may be defined by the implementations for file systems which append additional elements (such as alternate data streams or partitioned dataset names) to extensions.

Parameters

(none)

Return value

The extension of the current pathname or an empty path if there's no extension.

Exceptions

(none)

Notes

The extension as returned by this function includes a period to make it possible to distinguish the file that ends with a period (function returns ".") from a file with no extension (function returns "")

On a non-POSIX system, it is possible that p.stem()+p.extension() != p.filename() even though generic-format versions are the same.

Example

Run this code

#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;

int main()
{
    std::cout << fs::path("/foo/bar.txt").extension() << '\n'
              << fs::path("/foo/bar.").extension() << '\n'
              << fs::path("/foo/bar").extension() << '\n'
              << fs::path("/foo/bar.txt/bar.cc").extension() << '\n'
              << fs::path("/foo/bar.txt/bar.").extension() << '\n'
              << fs::path("/foo/bar.txt/bar").extension() << '\n'
              << fs::path("/foo/.").extension() << '\n'
              << fs::path("/foo/..").extension() << '\n'
              << fs::path("/foo/.hidden").extension() << '\n'
              << fs::path("/foo/..bar").extension() << '\n';
}

Output:

".txt"
"."
""
".cc"
"."
""
""
""
""
".bar"

See also

filename	returns the filename path component (public member function)
stem	returns the stem path component (public member function)
replace_extension	replaces the extension (public member function)
has_extension	checks if the corresponding path element is not empty (public member function)