int     access (const char *path, int amode);
int     chdir (const char *path);
int     chmod (const char *path, mode_t mode);
int     chown (const char *path, uid_t owner, gid_t group);
int     close (int fildes);
int     closedir (DIR *dirp);
int     creat (const char *path, mode_t mode);
int     dup (int fildes);
int     dup2 (int fildes, int fildes2);
int     execl *const char *path, const char *arg, ...);
int     execle (const char *path, const char *arg, ...);
int     execlp (const char *file, const char *arg, ...);
int     execv (const char *path, char *const argv[]);
int     execve (const char *path, char *const argv[], char *const envp[]);
int     execvp (const char *file, const char *arg, ...);
void    _exit (int status);
int     fcntl (int fildes, int cmd, ...);
pid_t   fork (void);
int     fstat (int fildes, struct stat *buf);
char    *getcwd (char *buf, size_t size);
gid_t   getegid (void);
char    *getenv (const char *name);
uid_t   geteuid (void);
gid_t   getgid (void);
struct group    *getgrgid (gid_t gid);
struct group    *getgrnam (const char *name);
int     getgroups (int gidsetsize, gid_t grouplist[]);
char    *getlogin (void);
pid_t   getpgrp (void);
pid_t   getpid (void);
pid_t   getppid (void);
uid_t   getuid (void);
int     kill (pid_t pid, int sig);
int     link (const char *existing, const char *new);
off_t   lseek (int fildes, off_t offset, int whence);
int     mkdir (const char *path, mode_t mode);
int     mkfifo (const char *path, mode_t mode);
int     open (const char *path, int oflag, ...);
DIR     *opendir (const char *dirname);
int     pause (void);
int     pipe (int fildes[2]);
ssize_t read (int fildes, void *buf, size_t nbyte);
struct dirent   *readdir (DIR *dirp);
int     rename (const char *old, const char *new);
void    rewinddir (DIR *dirp);
int     rmdir (const char *path);
int     setgid (gid_t gid);
int     setpgid (pid_t pid, pid_t pgid);
pid_t   setsid (void);
int     setuid (uid_t uid);
int     sigaction (int sig, const struct sigaction *act, 
                   struct sigaction *oact);
int     sigaddset (sigset_t *set, int signo);
int     sigdelset (sigset_t *set, int signo);
int     sigemptyset (sigset_t *set);
int     sigfillset (sigset_t *set);
int     sigismember (const sigset_t *set, int signo);
void    siglongjmp (sigjmp_buf env, int val);
int     sigpending (const sigset_t *sigmask);
int     sigprocmask (int how, const sigset_t *set, sigset_t *oset);
int     sigsetjmp (sigjmp_buf env, int savemask);
int     sigsuspend (const sigset_t *sigmask);
unsigned int    sleep (unsigned int seconds);
int     stat (const char *path, struct stat *buf);
time_t  time (time_t *tloc);
clock_t times (struct tms *buffer);
char    *ttyname (int fildes);
void    tzset (void);
mode_t  umask (mode_t cmask);
int     uname (struct utsname *name);
int     unlink (const char *path);
int     utime (const char *path, const struct utimbuf *times);
int     watipid (pid_t pid, int *stat_loc, int options);
ssize_t write (int fildes, const void *buf, size_t nbyte);
