.\" $OpenBSD: setreuid.2,v 1.7 2008/08/04 07:08:23 jmc 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. 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. .\" .\" @(#)setreuid.2 8.2 (Berkeley) 4/16/94 .\" .Dd $Mdocdate: August 4 2008 $ .Dt SETREUID 2 .Os .Sh NAME .Nm setreuid .Nd set real and effective user IDs .Sh SYNOPSIS .Fd #include .Ft int .Fn setreuid "uid_t ruid" "uid_t euid" .Sh DESCRIPTION The real and effective user IDs of the current process are set according to the arguments. The saved user ID will be set to the new value of the real user ID if a real user ID is specified and either the new real user ID value is different from the current value or the effective user ID is changed to a value other than the current saved user ID. .Pp Unprivileged users may change either user ID to the current value of the real, effective, or saved user ID. Only the superuser may make other changes. .Pp Supplying a value of -1 for either the real or effective user ID forces the system to substitute the current ID in place of the -1 parameter. .Pp The .Fn setreuid function was intended to allow swapping the real and effective user IDs in set-user-ID programs to temporarily relinquish the set-user-ID value. This purpose is now better served by the use of the .Xr seteuid 2 function. .Pp When setting the real and effective user IDs to the same value, the .Xr setuid 2 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 user ID to the real user ID was specified. .El .Sh SEE ALSO .Xr getuid 2 , .Xr seteuid 2 , .Xr setregid 2 , .Xr setresuid 2 , .Xr setuid 2 .Sh STANDARDS The .Fn setreuid function conforms to the .St -p1003.1-2001 and .St -xpg4.3 . specifications. .Pp Note, however, that prior to .St -p1003.1-2001 , the .Fn setreuid 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 setreuid 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 setreuid function predates .Tn POSIX saved user IDs. This implementation changes the saved user ID to the new value of the real user ID only if the real user ID is specified and either changed or the effective user ID is changed to a value other than the current saved user ID. Other implementations may behave differently.