.\"	$NetBSD: setregid.2,v 1.7 1997/09/20 04:16:40 mikel Exp $
.\"
.\" Copyright (c) 1996 Charles M. Hannum.  All rights reserved.
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.\"     from: @(#)setregid.2	6.4 (Berkeley) 3/10/91
.\"
.Dd June 23, 1996
.Dt SETREGID 2
.Os BSD 4.2
.Sh NAME
.Nm setregid
.Nd set real and effective group ID's
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fn setregid "int rgid" "int egid"
.Sh DESCRIPTION
The real and effective group ID's of the
current process are set according to the arguments.  If the real group ID
is changed, the saved group ID is changed to the new value of the effective
group ID.
.Pp
If
.Fa rgid
or
.Fa egid
is -1, the current gid is filled in by the system.
Unprivileged users may change the real group
ID to the effective group ID, and may change the effective group ID to the
real group ID or the saved group ID; only the super-user may
make other changes.
.Pp
The 
.Fn setregid
function has been used to swap the real and effective group
IDs in set-group-ID programs to temporarily relinquish the set-group-ID
value.  This purpose is now better served by the use of the
.Fn setegid
function (see
.Xr setuid 2 ).
.Pp
When setting the real and effective group IDs to the same value, this
function is equivalent to the
.Fn setgid
function.
When setting only the effective group ID, this function is equivalent to
the
.Fn setegid
function.
.Sh RETURN VALUES
Upon successful completion, a value of 0 is returned.  Otherwise,
a value of -1 is returned and
.Va errno
is set to indicate the error.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EPERM
The current process is not the super-user and a change
other than changing the effective group-id to the real group-id
was specified.
.El
.Sh SEE ALSO
.Xr getgid 2 ,
.Xr setegid 2 ,
.Xr setgid 2 ,
.Xr setuid 2
.Sh HISTORY
The
.Fn setregid
function call appeared in
.Bx 4.2
and was dropped in
.Bx 4.4 .
It was reimplemented in
.Nx 1.2
in a way compatible with
.Bx 4.3 ,
SunOS and Linux.