'\" te
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.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
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.TH SETUID 2 "Jan 20, 2003"
.SH NAME
setuid, setegid, seteuid, setgid \- set user and group IDs
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <unistd.h>

\fBint\fR \fBsetuid\fR(\fBuid_t\fR \fIuid\fR);
.fi

.LP
.nf
\fBint\fR \fBsetgid\fR(\fBgid_t\fR \fIgid\fR);
.fi

.LP
.nf
\fBint\fR \fBseteuid\fR(\fBuid_t\fR \fIeuid\fR);
.fi

.LP
.nf
\fBint\fR \fBsetegid\fR(\fBgid_t\fR \fIegid\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBsetuid()\fR function sets the real user ID, effective user ID, and saved
user ID of the calling process. The \fBsetgid()\fR function sets the real group
ID, effective group ID, and saved group ID of the calling process. The
\fBsetegid()\fR and \fBseteuid()\fR functions set the effective group and user
IDs respectively for the calling process. See \fBIntro\fR(2) for more
information on real, effective, and saved user and group IDs.
.sp
.LP
At login time, the real user ID, effective user ID, and saved user ID of the
login process are set to the login ID of the user responsible for the creation
of the process. The same is true for the real, effective, and saved group IDs;
they are set to the group ID of the user responsible for the creation of the
process.
.sp
.LP
When a process calls one of the \fBexec\fR(2) family of functions to execute a
file (program), the user and/or group identifiers associated with the process
can change. If the file executed is a set-user-ID file, the effective and saved
user IDs of the process are set to the owner of the file executed. If the file
executed is a set-group-ID file, the effective and saved group IDs of the
process are set to the group of the file executed. If the file executed is not
a set-user-ID or set-group-ID file, the effective user \fBID\fR, saved user ID,
effective group ID, and saved group ID are not changed.
.sp
.LP
If the {\fBPRIV_PROC_SETID\fR} privilege is asserted in the effective set of
the process calling \fBsetuid()\fR, the real, effective, and saved user IDs are
set to the \fIuid\fR argument.  If the \fIuid\fR argument is 0 and none of the
saved, effective or real UID is 0, additional restrictions apply. See
\fBprivileges\fR(7).
.sp
.LP
If the {\fBPRIV_PROC_SETID\fR} privilege is not asserted in the effective set,
but \fIuid\fR is either the real user ID or the saved user ID of the calling
process, the effective user ID is set to \fIuid\fR.
.sp
.LP
If the {\fBPRIV_PROC_SETID\fR} privilege is asserted in the effective set of
the process calling \fBsetgid()\fR, the real, effective, and saved group IDs
are set to the \fIgid\fR argument.
.sp
.LP
If the {\fBPRIV_PROC_SETID\fR} privilege is not asserted in the effective set,
but \fIgid\fR is either the real group ID or the saved group ID of the calling
process, the effective group ID is set to \fIgid\fR.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is
returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBsetuid()\fR and \fBsetgid()\fR functions will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value of \fIuid\fR or \fIgid\fR is out of range.
.RE

.sp
.ne 2
.na
\fB\fBEPERM\fR\fR
.ad
.RS 10n
For \fBsetuid()\fR and \fBseteuid()\fR, the {\fBPRIV_PROC_SETID\fR} privilege
is not asserted in the effective set of the calling process and the \fIuid\fR
argument does not match either the real or saved user IDs, or an attempt is
made to change to UID 0 and none of the existing UIDs is 0, in which case
additional privileges are required.
.sp
For \fBsetgid()\fR and \fBsetegid()\fR, the {\fBPRIV_PROC_SETID\fR} privilege
is not asserted in the effective set and the \fIgid\fR argument does not match
either the real or saved group IDs.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	Async-Signal-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR Intro (2),
.BR exec (2),
.BR getgroups (2),
.BR getuid (2),
.BR stat.h (3HEAD),
.BR attributes (7),
.BR privileges (7),
.BR standards (7)