Explain the concept of file permissions.

File permissions refer to the access rights or restrictions that are assigned to files and directories in a file system. These permissions determine who can read, write, or execute a file, as well as who can access or modify a directory.

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

1. Owner Permissions: The owner of a file or directory is the user who created it. The owner permissions define what actions the owner can perform on the file or directory. The owner can have read, write, and execute permissions, allowing them to view, modify, and execute the file or directory.

2. Group Permissions: A group is a collection of users who share common access rights. The group permissions determine what actions the members of the group can perform on the file or directory. Similar to owner permissions, group permissions can include read, write, and execute permissions.

3. Other Permissions: Other permissions apply to all users who are not the owner or part of the group. These permissions define what actions other users can perform on the file or directory. Again, other permissions can include read, write, and execute permissions.

Each permission can be represented by a specific character or symbol:
- Read permission (r) allows a user to view the contents of a file or list the files in a directory.
- Write permission (w) allows a user to modify or delete a file, as well as create or delete files within a directory.
- Execute permission (x) allows a user to execute a file or access a directory.

Permissions can be assigned using numeric values or symbolic notation. Numeric values use a three-digit code (e.g., 755) to represent the permissions for owner, group, and others, respectively. Symbolic notation uses a combination of letters (e.g., rwxr-xr-x) to represent the permissions for owner, group, and others, respectively.

File permissions are crucial for maintaining security and controlling access to files and directories in a file system. They ensure that only authorized users can perform specific actions on files and directories, protecting sensitive data and preventing unauthorized modifications or access.