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std::filesy...te_hard_link(3)  C++ Standard Libary std::filesy...te_hard_link(3)

NAME
     std::filesystem::create_hard_link - std::filesystem::create_hard_link

Synopsis
	Defined in header <filesystem>
	void  create_hard_link(  const std::filesystem::path& target, (1) (since
     C++17)
			       const std::filesystem::path& link );
	void create_hard_link( const std::filesystem::path& target,

			       const std::filesystem::path& link,    (2)  (since
     C++17)

			       std::error_code& ec ) noexcept;

	Creates  a  hard  link link with its target set to target as if by POSIX
     link(): the
	pathname target must exist.

	Once created, link and target are two logical names that  refer  to  the
     same file
	(they  are equivalent). Even if the original name target is deleted, the
     file
	continues to exist and is accessible as link.

Parameters
	target - path of the file or directory to link to
	link   - path of the new hard link
	ec     - out-parameter for error reporting in the non-throwing overload

Return value
	(none)

Exceptions
	Any overload not marked noexcept may throw std::bad_alloc if memory  al-
     location
	fails.

	1) Throws std::filesystem::filesystem_error on underlying OS API errors,
     constructed
	with  target  as  the first path argument, link as the second path argu-
     ment, and the OS
	error code as the error code argument.
	2) Sets a std::error_code& parameter to the OS API error code if  an  OS
     API call
	fails, and executes ec.clear() if no errors occur.

Notes
	Some  operating systems do not support hard links at all or support them
     only for
	regular files.

	Some file systems do not support hard links regardless of the  operating
     system: the
	FAT file system used on memory cards and flash drives, for example.

	Some file systems limit the number of links per file.

	Hardlinking to directories is typically restricted to the superuser.

	Hard links typically cannot cross filesystem boundaries.

	The  special  pathname dot (".") is a hard link to its parent directory.
     The special
	pathname dot-dot ".." is a hard link to the directory that is the parent
     of its
	parent.

Example
     // Run this code

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

      int main()
      {
	  fs::create_directories("sandbox/subdir");
	  std::ofstream("sandbox/a").put('a'); // create regular file
	  fs::create_hard_link("sandbox/a", "sandbox/b");
	  fs::remove("sandbox/a");
	  // read from the original file via surviving hard link
	  char c = std::ifstream("sandbox/b").get();
	  std::cout << c << '\n';
	  fs::remove_all("sandbox");
      }

Output:
      a

See also
	create_symlink
	create_directory_symlink creates a symbolic link
	(C++17) 		 (function)
	(C++17)
	hard_link_count 	 returns the number of hard links  referring  to
     the specific
	(C++17) 		 file
				 (function)

http://cppreference.com 	   2024.06.10	   std::filesy...te_hard_link(3)
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