gno/usr.man/man2/setuid.2

.\" Copyright (c) 1983, 1991, 1993
.\"	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. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. 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.
.\"
.\"     @(#)setuid.2	8.1 (Berkeley) 6/4/93
.\"
.TH SETUID 2 "16 January 1996" GNO "System Calls"
.SH NAME
.BR setuid ,
.BR seteuid ,
.BR setgid ,
.BR setegid ,
\- set user and group ID
.SH SYNOPSIS
#include <sys/types.h>
.br
#include <unistd.h>
.sp 1
int
\fBsetuid\fR (uid_t \fIuid\fR);
.br
int
\fBseteuid\fR (uid_t \fIeuid\fR);
.br
int
\fBsetgid\fR (gid_t \fIgid\fR);
.br
int
\fBsetegid\fR (gid_t \fIegid\fR);
.SH DESCRIPTION
The
.BR setuid 
function
sets the real and effective
user IDs and the saved set-user-ID of the current process
to the specified value.
The
.BR setuid 
function is permitted if the specified ID is equal to the real user ID
of the process, or if the effective user ID is that of the super user.
.LP
The
.BR setgid 
function
sets the real and effective
group IDs and the saved set-group-ID of the current process
to the specified value.
The
.BR setgid 
function is permitted if the specified ID is equal to the real group ID
of the process, or if the effective user ID is that of the super user.
.LP
The
.BR seteuid 
function
sets the effective user ID (group ID) of the
current process.
The effective user ID may be set to the value
of the real user ID or the saved set-user-ID (see
.BR intro (2)
and
.BR execve (2));
in this way, the effective user ID of a set-user-ID executable
may be toggled by switching to the real user ID, then re-enabled
by reverting to the set-user-ID value.
Similarly, the effective group ID may be set to the value
of the real group ID or the saved set-user-ID.
.LP
.SH RETURN VALUES
Upon success, these functions return 0;
otherwise \-1 is returned.
.LP
If the user is not the super user, or the uid
specified is not the real, effective ID, or saved ID,
these functions return \-1.
.SH SEE ALSO
.BR getuid (2),
.BR getgid (2)
.SH STANDARDS
The
.BR setuid 
and
.BR setgid 
functions are compliant with the
POSIX 1003.1-88
specification with _POSIX_SAVED_IDS not defined.
The
.BR seteuid 
and
.BR setegid 
functions are extensions based on the POSIX
concept of _POSIX_SAVED_IDS,
and have been proposed for a future revision of the standard.