.\" Copyright (C) 1997 Andries Brouwer (aeb@cwi.nl)
.\" and Copyright (c) 2007, Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" Modified, 2003-05-26, Michael Kerrisk, <mtk.manpages@gmail.com>
.\"
.TH getresuid 2 2022-12-04 "Linux man-pages 6.03"
.SH NAME
getresuid, getresgid \- get real, effective, and saved user/group IDs
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
.B #include <unistd.h>
.PP
.BI "int getresuid(uid_t *" ruid ", uid_t *" euid ", uid_t *" suid );
.BI "int getresgid(gid_t *" rgid ", gid_t *" egid ", gid_t *" sgid );
.fi
.SH DESCRIPTION
.BR getresuid ()
returns the real UID, the effective UID, and the saved set-user-ID
of the calling process, in the arguments
.IR ruid ,
.IR euid ,
and
.IR suid ,
respectively.
.BR getresgid ()
performs the analogous task for the process's group IDs.
.SH RETURN VALUE
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EFAULT
One of the arguments specified an address outside the calling program's
address space.
.SH VERSIONS
These system calls were added on Linux 2.1.44.
.PP
The prototypes are given since glibc 2.3.2,
provided
.B _GNU_SOURCE
is defined.
.SH STANDARDS
These calls are nonstandard;
they also appear on HP-UX and some of the BSDs.
.SH NOTES
The original Linux
.BR getresuid ()
and
.BR getresgid ()
system calls supported only 16-bit user and group IDs.
Subsequently, Linux 2.4 added
.BR getresuid32 ()
and
.BR getresgid32 (),
supporting 32-bit IDs.
The glibc
.BR getresuid ()
and
.BR getresgid ()
wrapper functions transparently deal with the variations across kernel versions.
.SH SEE ALSO
.BR getuid (2),
.BR setresuid (2),
.BR setreuid (2),
.BR setuid (2),
.BR credentials (7)