The link utility is a Unixcommand line program that creates a hard link from an existing directory entry to a new directory entry. It does no more than call the link() system function. It does not perform error checking before attempting to create the link. It returns an exit status that indicates whether the link was created (0 if successful, >0 if an error occurred). Creating a link to a directory entry that is itself a directory requires elevated privileges.
The ln command is more commonly used as it provides more features: it can create both hard links and symbolic links, and has error checking.