getresuid, getresgid

Standard C library (libc, -lc)

#define _GNU_SOURCE         /* See feature_test_macros(7) */
#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);

getresuid() returns the real UID, the effective UID, and the saved set-user-ID of the calling process, in the arguments ruid, euid, and suid, respectively. getresgid() performs the analogous task for the process's group IDs.

On success, zero is returned. On error, -1 is returned, and errno is set to indicate the error.

EFAULT

One of the arguments specified an address outside the calling program's address space.

POSIX.1-2024 XSI.

Linux 2.1.44, glibc 2.3.2, POSIX.1-2024 XSI.

The original Linux getresuid() and getresgid() system calls supported only 16-bit user and group IDs. Subsequently, Linux 2.4 added getresuid32() and getresgid32(), supporting 32-bit IDs. The glibc getresuid() and getresgid() wrapper functions transparently deal with the variations across kernel versions.

getuid(2), setresuid(2), setreuid(2), setuid(2), credentials(7)