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2019-03-06
Aliases: geteuid(2), geteuid(2), geteuid(2), geteuid(2), geteuid(2), geteuid(2), geteuid(2), geteuid(2), geteuid(2), geteuid(2), geteuid(2), geteuid(2), geteuid32(2), geteuid32(2), geteuid32(2), getuid32(2), getuid32(2), getuid32(2), getuid32(2), getuid32(2), getuid32(2), getuid32(2), getuid32(2), getuid32(2), getuid32(2)

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Manual pages about using GNU/Linux for development

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Linux kernel and C library user-space interface documentation

NAME

getuid, geteuid - get user identity

SYNOPSIS

#include <unistd.h>
#include <sys/types.h>
uid_t getuid(void);
uid_t geteuid(void);

DESCRIPTION

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

ERRORS

These functions are always successful.

CONFORMING TO

POSIX.1-2001, POSIX.1-2008, 4.3BSD.

NOTES

History

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.
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