getuid(2) — Linux manual page

getuid(2)                  System Calls Manual                  getuid(2)

NAME         top

       getuid, geteuid - get user identity

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <unistd.h>

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

DESCRIPTION         top

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

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

ERRORS         top

       These functions are always successful and never modify errno.

STANDARDS         top

       POSIX.1-2008.

HISTORY         top

       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.

SEE ALSO         top

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

COLOPHON         top

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Linux man-pages 6.15            2025-05-17                      getuid(2)

Pages that refer to this page: groups(1@@shadow-utils),  homectl(1),  importctl(1),  journalctl(1),  localectl(1),  loginctl(1),  machinectl(1),  portablectl(1),  ps(1),  strace(1),  systemctl(1),  systemd(1),  systemd-analyze(1),  systemd-inhibit(1),  systemd-nspawn(1),  systemd-vmspawn(1),  timedatectl(1),  updatectl(1),  userdbctl(1),  getresuid(2),  seteuid(2),  setpgid(2),  setresuid(2),  setreuid(2),  setuid(2),  syscalls(2),  getlogin(3),  id_t(3type),  pam_close_session(3),  pam_open_session(3),  sysexits.h(3head),  credentials(7),  signal-safety(7),  user_namespaces(7),  systemd-tmpfiles(8)

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