1.\" Copyright (c) 1980, 1991, 1993, 1994 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)setreuid.2 8.2 (Berkeley) 4/16/94 29.\" $FreeBSD$ 30.\" 31.Dd February 8, 2001 32.Dt SETREUID 2 33.Os 34.Sh NAME 35.Nm setreuid 36.Nd set real and effective user ID's 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In unistd.h 41.Ft int 42.Fn setreuid "uid_t ruid" "uid_t euid" 43.Sh DESCRIPTION 44The real and effective user IDs of the 45current process are set according to the arguments. 46If 47.Fa ruid 48or 49.Fa euid 50is -1, the current uid is filled in by the system. 51Unprivileged users may change the real user 52ID to the effective user ID and vice-versa; only the super-user may 53make other changes. 54.Pp 55If the real user ID is changed (i.e.\& 56.Fa ruid 57is not -1) or the effective user ID is changed to something other than 58the real user ID, then the saved user ID will be set to the effective user ID. 59.Pp 60The 61.Fn setreuid 62system call has been used to swap the real and effective user IDs 63in set-user-ID programs to temporarily relinquish the set-user-ID value. 64This purpose is now better served by the use of the 65.Xr seteuid 2 66system call. 67.Pp 68When setting the real and effective user IDs to the same value, 69the standard 70.Fn setuid 71system call is preferred. 72.Sh RETURN VALUES 73.Rv -std setreuid 74.Sh ERRORS 75.Bl -tag -width Er 76.It Bq Er EPERM 77The current process is not the super-user and a change 78other than changing the effective user-id to the real user-id 79was specified. 80.El 81.Sh SEE ALSO 82.Xr getuid 2 , 83.Xr issetugid 2 , 84.Xr seteuid 2 , 85.Xr setuid 2 86.Sh HISTORY 87The 88.Fn setreuid 89system call appeared in 90.Bx 4.2 . 91