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getuid(2) — Linux manual page

getuid(2)                  System Calls Manualgetuid(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 modifyerrno.

STANDARDS        top

       POSIX.1-2008.

HISTORY        top

       POSIX.1-2001, 4.3BSD.       In UNIX V6 thegetuid() call returned(euid << 8) + uid.  UNIX V7       introduced separate callsgetuid() andgeteuid().       The original Linuxgetuid() andgeteuid() system calls supported       only 16-bit user IDs.  Subsequently, Linux 2.4 addedgetuid32()       andgeteuid32(), supporting 32-bit IDs.  The glibcgetuid() andgeteuid() wrapper functions transparently deal with the variations       across kernel versions.       On Alpha, instead of a pair ofgetuid() andgeteuid() system       calls, a singlegetxuid() system call is provided, which returns a       pair of real and effective UIDs.  The glibcgetuid() andgeteuid()       wrapper functions transparently deal with this.  Seesyscall(2)       for details regarding register mapping.

SEE ALSO        top

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

COLOPHON        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17getuid(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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