SETREGID(P) POSIX Programmer's Manual SETREGID(P)
setregid - set real and effective group IDs
int setregid(gid_t rgid, gid_t egid);
The setregid() function shall set the real and effective group IDs of the calling process.
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 call.
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.
Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno
set to indicate the error, and neither of the group IDs are changed.
The setregid() function shall fail if:
EINVAL The value of the rgid or egid argument is invalid or out-of-range.
EPERM 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.
The following sections are informative.
If a set-group-ID process sets its effective group ID to its real group ID, it can still
set its effective group ID back to the saved set-group-ID.
exec() , getegid() , geteuid() , getgid() , getuid() , setegid() , seteuid() , setgid() ,
setreuid() , setuid() , the Base Definitions volume of IEEE Std 1003.1-2001, <unistd.h>
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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 SETREGID(P)