gno/usr.man/man2/setreuid.2

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.\"     @(#)setreuid.2	8.2 (Berkeley) 4/16/94
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.TH SETREUID 2 "16 January 1996" GNO "System Calls"
.SH NAME
.BR setreuid
\- set real and effective user ID
.SH SYNOPSIS
.br
#include <unistd.h>
.sp 1
int
\fBsetreuid\fR (uid_t \fIruid\fR, uid_t \fIeuid\fR);
.SH DESCRIPTION
The real and effective user IDs of the
current process are set according to the arguments.
If
.I ruid
or 
.I euid
is -1, the current uid is filled in by the system.
Unprivileged users may change the real user
ID to the effective user ID and vice-versa; only the super-user may
make other changes.
.LP
The
.BR setreuid 
function has been used to swap 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
.BR seteuid 
function (see
.BR setuid (2)).
.LP
When setting the real and effective user IDs to the same value,
the standard
.BR setuid 
function is preferred.
.SH RETURN VALUES
Upon successful completion, a value of 0 is returned.  Otherwise,
a value of -1 is returned and
.IR errno
is set to indicate the error.
.SH ERRORS
.RS
.IP \fBEPERM\fR
The current process is not the super-user and a change
other than changing the effective user-id to the real user-id
was specified.
.RE
.SH SEE ALSO
.BR getuid (2),
.BR seteuid (2),
.BR setuid (2)
.SH HISTORY
The
.BR setreuid
system call appeared in 4.2BSD.