File permissions are a crucial part of computer security and are organized in a hierarchical structure to control access to files and directories. The hierarchy typically involves users, groups, and others, each with their own set of permissions. Here’s an overview of the file permissions hierarchy:

User (Owner):

  • The user, also known as the owner, is the individual who owns the file or directory. The owner has the most control over the file, including the ability to read, write, and execute it.

Group:

  • A group is a collection of users. Files and directories can be assigned to a specific group, and all users within that group inherit the group’s permissions. This allows for easier management of permissions for multiple users.

Others (World):

  • The “others” category includes all users who are neither the owner nor members of the group. It represents the rest of the world. Permissions assigned to “others” apply to any user who doesn’t fall into the owner or group categories.

The typical file permissions are organized into three categories for each of the above entities (user, group, and others):

  • Read (r):
  • The read permission (represented by “r”) allows a user, group, or others to view the contents of a file or list the contents of a directory.
  • Write (w):
  • The write permission (represented by “w”) allows a user, group, or others to modify the contents of a file or create and delete files within a directory. For directories, the write permission allows adding, deleting, or renaming files within that directory.
  • Execute (x):
  • The execute permission (represented by “x”) allows a user, group, or others to run or execute a file. For directories, it permits users to access the directory and its contents.

File permissions are represented using a series of letters and dashes, such as “rw-r–r–,” which represents read and write permissions for the owner and read-only permissions for the group and others. Numeric values (octal notation) are also used to represent permissions, with values like 644 for the same set of permissions.

File permissions can be modified using commands like chmod in Unix-based systems or through file properties in graphical user interfaces. Properly configuring file permissions is essential for maintaining the security and integrity of a computer system, as it controls who can access and manipulate files and directories.