.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "SETREUID" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" setreuid 
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.SH NAME
setreuid \- set real and effective user IDs
.SH SYNOPSIS
.LP
\fB#include <unistd.h>
.br
.sp
int setreuid(uid_t\fP \fIruid\fP\fB, uid_t\fP \fIeuid\fP\fB); \fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIsetreuid\fP() function shall set the real and effective user
IDs of the current process to the values specified by the
\fIruid\fP and \fIeuid\fP arguments. If \fIruid\fP or \fIeuid\fP is
-1, the corresponding effective or real user ID of the
current process shall be left unchanged.
.LP
A process with appropriate privileges can set either ID to any value.
An unprivileged process can only set the effective user ID
if the \fIeuid\fP argument is equal to either the real, effective,
or saved user ID of the process.
.LP
It is unspecified whether a process without appropriate privileges
is permitted to change the real user ID to match the current
real, effective, or saved set-user-ID of the process.
.SH RETURN VALUE
.LP
Upon successful completion, 0 shall be returned. Otherwise, -1 shall
be returned and \fIerrno\fP set to indicate the error.
.SH ERRORS
.LP
The \fIsetreuid\fP() function shall fail if:
.TP 7
.B EINVAL
The value of the \fIruid\fP or \fIeuid\fP argument is invalid or out-of-range.
.TP 7
.B EPERM
The current process does not have appropriate privileges, and either
an attempt was made to change the effective user ID to a
value other than the real user ID or the saved set-user-ID or an attempt
was made to change the real user ID to a value not
permitted by the implementation.
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.SS Setting the Effective User ID to the Real User ID
.LP
The following example sets the effective user ID of the calling process
to the real user ID, so that files created later will be
owned by the current user.
.sp
.RS
.nf

\fB#include <unistd.h>
#include <sys/types.h>
\&...
setreuid(getuid(), getuid());
\&...
\fP
.fi
.RE
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIgetegid\fP(), \fIgeteuid\fP(), \fIgetgid\fP(), \fIgetuid\fP(),
\fIsetegid\fP(), \fIseteuid\fP(), \fIsetgid\fP(), \fIsetregid\fP(),
\fIsetuid\fP(), the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, \fI<unistd.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .