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.Dd February 8, 2001 29.Dt SETREUID 2 30.Os 31.Sh NAME 32.Nm setreuid 33.Nd set real and effective user ID's 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In unistd.h 38.Ft int 39.Fn setreuid "uid_t ruid" "uid_t euid" 40.Sh DESCRIPTION 41The real and effective user IDs of the 42current process are set according to the arguments. 43If 44.Fa ruid 45or 46.Fa euid 47is -1, the current uid is filled in by the system. 48Unprivileged users may change the real user 49ID to the effective user ID and vice-versa; only the super-user may 50make other changes. 51.Pp 52If the real user ID is changed (i.e.\& 53.Fa ruid 54is not -1) or the effective user ID is changed to something other than 55the real user ID, then the saved user ID will be set to the effective user ID. 56.Pp 57The 58.Fn setreuid 59system call has been used to swap the real and effective user IDs 60in set-user-ID programs to temporarily relinquish the set-user-ID value. 61This purpose is now better served by the use of the 62.Xr seteuid 2 63system call. 64.Pp 65When setting the real and effective user IDs to the same value, 66the standard 67.Fn setuid 68system call is preferred. 69.Sh RETURN VALUES 70.Rv -std setreuid 71.Sh ERRORS 72.Bl -tag -width Er 73.It Bq Er EPERM 74The current process is not the super-user and a change 75other than changing the effective user-id to the real user-id 76was specified. 77.El 78.Sh SEE ALSO 79.Xr getuid 2 , 80.Xr issetugid 2 , 81.Xr seteuid 2 , 82.Xr setuid 2 83.Sh HISTORY 84The 85.Fn setreuid 86system call appeared in 87.Bx 4.2 . 88