ssize_t read(int, void *, size_t);
int unlink(const char *);
ssize_t write(int, const void *, size_t);
int usleep(useconds_t);
unsigned sleep(unsigned);
int access(const char *, int);
unsigned alarm(unsigned);
int chdir(const char *);
int chown(const char *, uid_t, gid_t);
int close(int);
size_t confstr(int, char *, size_t);
void _exit(int);
pid_t fork(void);
NULL // Null pointer
SEEK_CUR // Set file offset to current plus offset.
SEEK_END // Set file offset to EOF plus offset.
SEEK_SET // Set file offset to offset.