The concept of a link in UNIX is for file sharing. A link file is created by the system when a symbolic link is created to an existing file. The link file points to the existing file, which allows the users to rename an existing file and share it without duplicating its contents.
As introduced in Section 6.1.4, for the kernel, every file has one inode, but it may have several names of links, all of which map into the inode.
The concept of the symbolic link in UNIX is a creation of BSD but is presently available on almost all versions of UNIX (Ousterhout et al 1985; Quarterman et al 1985). The symbolic link is also called soft link. A symbolic
link may be a file containing the pathname of another file or directory, and it can cross file system boundaries.
In contrast to soft link, it is a hard link.
There are two typical hard links:
- one is written as '.'; the other is '..' .
- '.' in a directory is a hard link to the directory itself, and '..' of the directory is a hard link to its parent directory.