The setregid() function shall set the real and effective group IDs of the
If rgid is -1, the real group ID shall not be changed; if egid is
-1, the effective group ID shall not be changed.
The real and effective group IDs may be set to different values in the same
Only a process with appropriate privileges can set the real group ID and the
effective group ID to any valid value.
A non-privileged process can set either the real group ID to the saved
set-group-ID from one of the exec family of functions, or the effective
group ID to the saved set-group-ID or the real group ID.
Any supplementary group IDs of the calling process remain unchanged.
The value of the rgid or egid argument is
invalid or out-of-range.
The process does not have appropriate privileges and a
change other than changing the real group ID to the saved set-group-ID, or
changing the effective group ID to the real group ID or the saved
set-group-ID, was requested.
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