Understanding file protection

The owner attribute

Each file on the system has an owner. Generally, the creator of the file is also the owner. However, a file owner can generally reassign ownership rights using the chown(1) command.

If you own a file, you can decide who has the right to read it, write to it, or, if it is a program, to execute it. You can also restrict permissions for directories. When you grant execute permission for a directory, you allow the specified users to change directory to it and list its contents with the ls(1) command. Only the owner or a privileged user can define the following:

Because this type of access control is mediated at the discretion of the owner of the file, it is called Discretionary Access Control (DAC).
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UnixWare 7 Release 7.1.1 - 5 November 1999