getuid - Man Page

Standard C library (libc, -lc)

#include <unistd.h>

uid_t getuid(void);
uid_t geteuid(void);

getuid() returns the real user ID of the calling process.

geteuid() returns the effective user ID of the calling process.

These functions are always successful and never modify errno.

POSIX.1-2008.

POSIX.1-2001, 4.3BSD.

In UNIX V6 the getuid() call returned (euid << 8) + uid. UNIX V7 introduced separate calls getuid() and geteuid().

The original Linux getuid() and geteuid() system calls supported only 16-bit user IDs. Subsequently, Linux 2.4 added getuid32() and geteuid32(), supporting 32-bit IDs. The glibc getuid() and geteuid() wrapper functions transparently deal with the variations across kernel versions.

On Alpha, instead of a pair of getuid() and geteuid() system calls, a single getxuid() system call is provided, which returns a pair of real and effective UIDs. The glibc getuid() and geteuid() wrapper functions transparently deal with this. See syscall(2) for details regarding register mapping.

getresuid(2), setreuid(2), setuid(2), credentials(7)

ch-image(1), credentials(7), getlogin(3), getresuid(2), homectl(1), importctl(1), journalctl(1), localectl(1), lockfile-progs(1), loginctl(1), machinectl(1), mksh(1), oksh(1), oping(8), pam_close_session(3), pam_open_session(3), portablectl(1), procenv(1), ps(1), seteuid(2), setpgid(2), setresuid(2), setreuid(2), setuid(2), signal-safety(7), strace(1), stress-ng(1), syscalls(2), systemctl(1), systemd(1), systemd-analyze(1), systemd-inhibit(1), systemd-nspawn(1), systemd-tmpfiles(8), systemd-vmspawn(1), timedatectl(1), userdbctl(1), user_namespaces(7).

The man pages geteuid(2), geteuid32(2) and getuid32(2) are aliases of getuid(2).