Unix-like operating systems are by nature multi-user, which means that more than one user can be operating the computer at the same time.

For example, if the computer is attached to a local network or the Internet, remote users can log in via a secure shell and operate the computer.

In order to make this practical, a method had to be devised to protect the users from each other, as after all, we wouldn't want the actions of one user to crash the computer, nor would we allow one user to interfere with the files belonging to another user.

File permissions

File permissions, also called file mode, refers to the settings that determine who can read, write, and execute a particular file or directory.

These permissions apply to three groups of users on the system, including:

• The owner, which is the user who owns the file/directory.

• The group, which is a group of users who share certain permissions on the file/directory.

• The others, which are all the other users who are not the owner nor part of the specified group.

For each user entity in the aforementioned order, permissions are represented by a set of three characters called the symbolic notation:

rwx rwx rwx