Provided by:
manpages-dev_2.17-1_all 
NAME
getresuid, getresgid - get real, effective and saved user or group ID
SYNOPSIS
#define _GNU_SOURCE
#include <unistd.h>
int getresuid(uid_t *ruid, uid_t *euid, uid_t *suid);
int getresgid(gid_t *rgid, gid_t *egid, gid_t *sgid);
DESCRIPTION
getresuid() and getresgid() (both introduced in Linux 2.1.44) get the
real UID, effective UID, and saved set-user-ID (resp. group ID’s) of
the current process.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is
set appropriately.
ERRORS
EFAULT One of the arguments specified an address outside the calling
program’s address space.
CONFORMING TO
This call is Linux-specific. The prototype is given by glibc since
version 2.3.2 provided _GNU_SOURCE is defined.
SEE ALSO
getuid(2), setresuid(2), setreuid(2), setuid(2)