getuid(2) - Linux manual page (original) (raw)

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](../man3/errno.3.html)_.

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)](../man2/syscall.2.html) for details regarding register mapping.

SEE ALSO top

   [getresuid(2)](../man2/getresuid.2.html), [setreuid(2)](../man2/setreuid.2.html), [setuid(2)](../man2/setuid.2.html), [credentials(7)](../man7/credentials.7.html)

COLOPHON top

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Linux man-pages 6.9.1 2024-05-02 getuid(2)

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