std::filesystem::hard_link_count (3) - Linux Manuals

std::filesystem::hard_link_count: std::filesystem::hard_link_count


std::filesystem::hard_link_count - std::filesystem::hard_link_count


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, (1) (since C++17)
std::error_code& ec ) noexcept;

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.


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

Return value

The number of hard links for p


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.


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