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.TH SETRESUID 2 2010-11-22 "Linux" "Linux Programmer's Manual"
.SH NAME
setresuid, setresgid \- set real, effective and saved user or group ID
.SH SYNOPSIS
.BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
.br
.B #include <unistd.h>
.sp
.BI "int setresuid(uid_t " ruid ", uid_t " euid ", uid_t " suid );
.br
.BI "int setresgid(gid_t " rgid ", gid_t " egid ", gid_t " sgid );
.SH DESCRIPTION
.BR setresuid ()
sets the real user ID, the effective user ID, and the
saved set-user-ID of the calling process.

Unprivileged user processes
may change the real UID,
effective UID, and saved set-user-ID, each to one of:
the current real UID, the current effective UID or the
current saved set-user-ID.

Privileged processes (on Linux, those having the \fBCAP_SETUID\fP capability)
may set the real UID, effective UID, and
saved set-user-ID to arbitrary values.

If one of the arguments equals \-1, the corresponding value is not changed.

Regardless of what changes are made to the real UID, effective UID,
and saved set-user-ID, the file system UID is always set to the same
value as the (possibly new) effective UID.

Completely analogously,
.BR setresgid ()
sets the real GID, effective GID, and saved set-group-ID
of the calling process (and always modifies the file system GID
to be the same as the effective GID),
with the same restrictions for unprivileged processes.
.SH "RETURN VALUE"
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EAGAIN
.I uid
does not match the current UID and this call would
bring that user ID over its
.B RLIMIT_NPROC
resource limit.
.TP
.B EPERM
The calling process is not privileged (did not have the \fBCAP_SETUID\fP
capability) and tried to change the IDs to values that are not permitted.
.SH VERSIONS
These calls are available under Linux since Linux 2.1.44.
.SH "CONFORMING TO"
These calls are nonstandard;
they also appear on HP-UX and some of the BSDs.
.SH NOTES
Under HP-UX and FreeBSD, the prototype is found in
.IR <unistd.h> .
Under Linux the prototype is provided by glibc since version 2.3.2.

The original Linux
.BR setresuid ()
and
.BR setresgid ()
system calls supported only 16-bit user and group IDs.
Subsequently, Linux 2.4 added
.BR setresuid32 ()
and
.BR setresgid32 (),
supporting 32-bit IDs.
The glibc
.BR setresuid ()
and
.BR setresgid ()
wrapper functions transparently deal with the variations across kernel versions.
.SH "SEE ALSO"
.BR getresuid (2),
.BR getuid (2),
.BR setfsgid (2),
.BR setfsuid (2),
.BR setreuid (2),
.BR setuid (2),
.BR capabilities (7),
.BR credentials (7)
.SH COLOPHON
This page is part of release 3.44 of the Linux
.I man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.