getuid, geteuid - get user identity
#include <unistd.h>
#include <sys/types.h>
uid_t getuid(void);
uid_t geteuid(void);
getuid() returns the real user ID of the calling process.
geteuid() returns the effective user ID of the calling process.
These functions are always successful.
POSIX.1-2001, POSIX.1-2008, 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.
getresuid(2),
setreuid(2),
setuid(2),
credentials(7)