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+.\" $OpenBSD: setregid.2,v 1.1 2003/01/31 21:47:46 millert Exp $
+.\"
+.\" Copyright (c) 1980, 1991, 1993, 1994
+.\"	The Regents of the University of California.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"	This product includes software developed by the University of
+.\"	California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"     @(#)setregid.2	8.2 (Berkeley) 4/16/94
+.\"
+.Dd January 29, 2003
+.Dt SETREGID 2
+.Os
+.Sh NAME
+.Nm setregid
+.Nd set real and effective group IDs
+.Sh SYNOPSIS
+.Fd #include <unistd.h>
+.Ft int
+.Fn setregid "gid_t rgid" "gid_t egid"
+.Sh DESCRIPTION
+The real and effective group IDs 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
+Unprivileged users may change either group ID to the current value
+of the real, effective, or saved group ID.
+Only the superuser may make other changes.
+.Pp
+Supplying a value of -1 for either the real or effective
+group ID forces the system to substitute the current
+ID in place of the -1 parameter.
+.Pp
+The
+.Fn setregid
+function was intended to allow swapping 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, the
+.Fn setgid
+function is preferred.
+.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 superuser 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 setresgid 2 ,
+.Xr setuid 2
+.Sh STANDARDS
+The
+.Fn setregid
+function conforms to the
+.St -p1003.1-01
+and
+.St -xpg4.3 .
+specifications.
+.Pp
+Note, however, that prior to
+.St -p1003.1-01 ,
+the
+.Fn setregid
+function was not a part of the
+.St -p1003.1
+specification.
+As a result, it may not be implemented on all systems.
+.Sh HISTORY
+The
+.Fn setregid
+function call appeared in
+.Bx 4.2 .
+A semantically different version appeared in
+.Bx 4.4 .
+The current version, with the original semantics restored, appeared in
+.Ox 3.3 .
+.Sh CAVEATS
+The
+.Fn setregid
+function predates
+.Tn POSIX
+saved group IDs.
+This implementation changes the saved group ID to the new value of
+the effective group ID if the real group ID is changed.
+Other implementations may behave differently.