Each MPE/iX user has an associated user
ID (UID). The UID is a string (in the form
user.account) and a corresponding integer value.
Additionally, one or more users can be organized into groups
(distinct from MPE groups) to simplify
file sharing. Each group has an associated group ID
(GID). The GID is a string (in the form account) with
a corresponding integer value.
UIDs and GIDs are used in conjunction with other security
mechanisms to control access to objects. Objects are entities that contain or receive information, such as files, directories, and devices.
A process is a program that is currently being executed. Every process has a UID, one or more GIDs, an optional file mode creation mask (specifies which permissions should not be granted), and a set of capabilities (for example, SM, AL, GL, ND, SF, etc.). MPE/iX Release 5.0 only supports one GID per process.
When files or directories are created, they are assigned their parent directory's GID and the UID of the process creating them. File and directory UIDs and GIDs can be changed using the chown() function available through the MPE/iX shell.
