gid_t getegid(void);
int getgroups(int, gid_t []);
int setuid(uid_t);
-int setreuid(uid_t, uid_t);
int seteuid(uid_t);
int setgid(gid_t);
-int setregid(gid_t, gid_t);
int setegid(gid_t);
char *getlogin(void);
#define F_TEST 3
#if defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
+int setreuid(uid_t, uid_t);
+int setregid(gid_t, gid_t);
int lockf(int, int, off_t);
long gethostid(void);
int nice(int);