Shared Files ( Acyclic Graph Directories )
Q Explain file sharing ? --- 3 Marks.
Ans : When multiple programmers work on a single project, they need to share files. Files associated with a project can be put in one subdirectory and these file can be selectively shared by many users.
Each user sharing a file will like to have that file in his own directory . A tree structure of directory does not allow sharing of files. The directory must be organized as directed a cyclic graph or AGD, rather than a tree.
It may be noted that shared file is not the same as two copies of the file with two copies of a file, if one user changes the file, the changes will not be visible in other’s copy. With a shared file, only one copy of the actual file exists. Shared files are implemented in UNIX using a link. A link is effectively a pointer to another file. If a directory entry is marked as link, then the name of the real file is included in the link information.
In UNIX, only the true owner of the file has a pointer to the i- node. Users who not I – node pointers when the owner removes the file, it is destroyed.
- WikiNote Foundation