getuid(2)
Name
getuid, geteuid − get user identity
Syntax
#include <sys/types.h>
#include <unistd.h>
uid = getuid()
uid_t uid;
euid = geteuid()
uid_t euid;
Description
The getuid system call returns the real user ID of the current process, geteuid 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 getuid to determine the real-user-id of the process which invoked them.
Environment
System Five
Differs from the System V definition in that the return values are of type int, instead of unsigned short.
POSIX
When your program is compiled in POSIX mode, the getuid and geteuid functions return a value of type uid_t. The getgid and getegid functions return a value of type gid_t.