What is a file system file permission?

File system file permissions refer to the access rights or permissions assigned to files and directories within a file system. These permissions determine who can read, write, or execute a file or directory, and are essential for maintaining security and controlling access to data.

In most file systems, file permissions are represented by a set of three types of permissions: read (r), write (w), and execute (x). These permissions can be assigned to three different categories of users: owner, group, and others.

1. Owner: The owner is the user who created the file or directory. The owner can modify the permissions, read, write, and execute the file or directory.

2. Group: A group is a collection of users who share common access rights. The group permissions apply to all users who belong to that specific group. Group members can have read, write, and execute permissions.

3. Others: Others refer to all users who are not the owner or part of the group. These permissions apply to everyone else. Others can have read, write, and execute permissions.

Each permission can be either granted or denied for each category of users. The permissions can be represented using numeric codes or symbolic notation.

Numeric codes:
- Read (r) permission is represented by the value 4.
- Write (w) permission is represented by the value 2.
- Execute (x) permission is represented by the value 1.

Symbolic notation:
- Read (r) permission is represented by the letter 'r'.
- Write (w) permission is represented by the letter 'w'.
- Execute (x) permission is represented by the letter 'x'.

For example, if a file has the permission set as 764, it means that the owner has read, write, and execute permissions (7 = 4 + 2 + 1), the group has read and write permissions (6 = 4 + 2), and others have read permissions (4 = 4).

File system file permissions play a crucial role in ensuring data security and privacy by controlling access to files and directories. They help prevent unauthorized access, accidental modifications, and maintain the integrity of the file system.