getuid(2) System Calls Manual getuid(2)
NAME
getuid, geteuid - get user identity
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <unistd.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 and never modify errno.
STANDARDS
POSIX.1-2001, POSIX.1-2008, 4.3BSD.
NOTES
History
In UNIX V6 the getuid() call returned (euid << 8) + uid. UNIX V7 in-
troduced 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 ge-
teuid32(), 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
getresuid(2), setreuid(2), setuid(2), credentials(7)
Linux man-pages 6.03 2022-10-30 getuid(2)
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