Description: A hard link is a directory entry that associates a name with a file in a file system. Unlike a symbolic link, which acts as a pointer to another file, a hard link creates a direct reference to the same inode in the file system. This means that both the hard link and the original file share the same content, so any changes made to one will be reflected in the other. Hard links are useful for file management as they allow multiple names for the same file without duplicating disk space. However, hard links cannot be created for directories (with some exceptions in specific file systems) or for files on different file systems. In many Unix-like operating systems, hard links are created using the ‘ln’ command without additional options, allowing users to establish multiple accesses to the same file efficiently and organized.
History: The concept of hard links dates back to the early file systems in Unix, which were developed in the 1970s. As operating systems evolved, the need for more efficient file management led to the implementation of this feature. Hard links became an integral part of file management in Unix-like systems, allowing users to create multiple accesses to the same file without taking up additional disk space.
Uses: Hard links are primarily used in Unix-like operating systems to facilitate file management. They allow users to create multiple names for the same file, which is useful in situations where the same content needs to be accessed from different locations without duplicating data. They are also used in scripts and applications that require references to files without worrying about the physical location of the file in the file system.
Examples: A practical example of a hard link would be creating an additional access to a configuration file in a Unix-like system. If a user has a file named ‘config.txt’ in ‘/etc/app/’, they can create a hard link in their home directory with the command ‘ln /etc/app/config.txt ~/config_hard.txt’. Now, both ‘/etc/app/config.txt’ and ‘~/config_hard.txt’ point to the same content, and any changes made to one will be reflected in the other.
