getuid, geteuid - get user identity
uid = getuid()
euid = geteuid()
The system call returns the real user ID of the current process, the
effective user ID.
The real user ID identifies the person who is logged in. The effective
user ID gives the process additional permissions during execution of
“set-user-ID” mode processes, which use to determine the real-user-id
of the process which invoked them.
Differs from the System V definition in that the return values are of
type int, instead of unsigned short.
When your program is compiled in POSIX mode, the and functions return a
value of type uid_t. The and functions return a value of type gid_t.
See Alsogetgid(2), setreuid(2)getuid(2)