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,
                                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

#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

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

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