getresuid(2)                  System Calls Manual                 getresuid(2)

NAME
       getresuid, getresgid - get real, effective, and saved user/group IDs

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #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);

DESCRIPTION
       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.

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

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

STANDARDS
       POSIX.1-2024 XSI.

HISTORY
       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.

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

Linux man-pages 6.18              2026-02-08                      getresuid(2)