The <sys/ipc.h> header is used by three mechanisms for XSI
interprocess communication (IPC): messages, semaphores, and shared memory. All
use a common structure type, ipc_perm, to pass information used in
determining permission to perform an IPC operation.
The ipc_perm structure shall contain the following members:
uid_t uid Owner's user ID.
gid_t gid Owner's group ID.
uid_t cuid Creator's user ID.
gid_t cgid Creator's group ID.
mode_t mode Read/write permission.
The uid_t, gid_t, mode_t, and key_t types shall be
defined as described in <sys/types.h> .
Definitions shall be provided for the following constants:
Create entry if key does not exist.
Fail if key exists.
Error if request must wait.
The following shall be declared as a function and may also be defined as a
macro. A function prototype shall be provided.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html