In this tutorial we discuss links, hard and soft, filesystems, and the important sort command. Sometimes you want to make a copy of a file without making a copy of it. That is, you would like a file to either have two different names, or to appear in two different directories, yet you do not want to waste disk space by having two separate, complete copies of the file. UNIX provides a command to allow this.
Directories are then just files that contain a list of names and links.
When a program or a command is given a filename, it looks up the name in the directory, gets the associated link, and then instructs the file system to retrieve the blocks from disk. Links are specified by large numbers, called i-node numbers. These i-node numbers are used in another table by UNIX to locate the actual disk blocks. This is the only way that you can discover if two names actually refer to the same file on disk. We would say that the file whose i-node is 91053 has two links to it.