getresuid - Man Page

get real, effective, and saved user/group IDs


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.

Return Value

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



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


None. These calls also appear on HP-UX and some of the BSDs.


Linux 2.1.44, glibc 2.3.2.

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)

Referenced By

auditctl(8), credentials(7), getgid(2), getuid(2), procenv(1), setresuid(2), syscalls(2).

The man pages getresgid(2), getresgid32(2) and getresuid32(2) are aliases of getresuid(2).

2023-10-31 Linux man-pages 6.7