Hard link

[1] This causes an alias effect: a process can open the file by any one of its paths and change its content.

For that reason, some file systems forbid the creation of additional hard links to directories.

(The OS may not to do so immediately, e.g., when there are outstanding file handles open, for performance reasons, or to enable the undelete command.)

[4] Mac OS X v10.5 (Leopard) and newer use hard links on directories for the Time Machine backup mechanism only.

The maximum number of hard links to a single file is limited by the size of the reference counter.

In some file systems, the number of hard links is limited more strictly by their on-disk format.

[7] On Linux Weekly News, Neil Brown criticized hard links as high-maintenance, since they complicate the design of programs that handle directory trees, including archivers and disk usage tools.

Brown notes that Plan 9 from Bell Labs, the intended successor to Unix, does not include the concept of a hard link.

[8] Windows NT 3.1 and later support hard links on the NTFS file system.

[9] Windows 2000 introduces a CreateHardLink() function to create hard links, but only for files, not directories.

To create hard links, end-users can use: To interrogate a file for its hard links, end-users can use: Unix-like emulation or compatibility software running on Microsoft Windows, such as Cygwin and Subsystem for UNIX-based Applications, allow the use of POSIX interfaces.