std::filesystem::hard_link_count

C++

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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

Defined in header <filesystem>
std::uintmax_t hard_link_count( const std::filesystem::path& p ); std::uintmax_t hard_link_count( const std::filesystem::path& p, std::error_code& ec ) noexcept;	(1)	(since C++17)

Returns the number of hard links for the filesystem object identified by path p.

The non-throwing overload returns static_cast<uintmax_t>(-1) on errors.

Parameters

p	-	path to examine
ec	-	out-parameter for error reporting in the non-throwing overload

Return value

The number of hard links for p

Exceptions

The overload that does not take a std::error_code& parameter throws filesystem_error on underlying OS API errors, constructed with p as the first path argument and the OS error code as the error code argument. The overload taking a std::error_code& parameter sets it to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur. Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

Example

Run this code

#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main()
{
    // On a POSIX-style filesystem, each directory has at least 2 hard links:
    // itself and the special member pathname "."
    fs::path p = fs::current_path();
    std::cout << "Number of hard links for current path is "
              << fs::hard_link_count(p) << '\n';

    // each ".." is a hard link to the parent directory, so the total number
    // of hard links for any directory is 2 plus number of direct subdirectories
    p = fs::current_path() / ".."; // each dot-dot is a hard link to parent
    std::cout << "Number of hard links for .. is "
              << fs::hard_link_count(p) << '\n';
}

Possible output:

Number of hard links for current path is 2
Number of hard links for .. is 3

See also

create_hard_link (C++17)	creates a hard link (function)
hard_link_count	returns the number of hard links referring to the file to which the directory entry refers (public member function of std::filesystem::directory_entry)