--- /dev/null
+/* The <unistd.h> header contains a few miscellaneous manifest constants. */
+
+#ifndef _UNISTD_H
+#define _UNISTD_H
+
+/* Values used by access(). POSIX Table 2-6. */
+#define F_OK 0 /* test if file exists */
+#define X_OK 1 /* test if file is executable */
+#define W_OK 2 /* test if file is writable */
+#define R_OK 4 /* test if file is readable */
+
+/* Values used for whence in lseek(fd, offset, whence). POSIX Table 2-7. */
+#define SEEK_SET 0 /* offset is absolute */
+#define SEEK_CUR 1 /* offset is relative to current position */
+#define SEEK_END 2 /* offset is relative to end of file */
+
+/* This value is required by POSIX Table 2-8. */
+#define _POSIX_VERSION 198808L /* which standard is being conformed to */
+
+/* These three definitions are required by POSIX Sec. 8.2.1.2. */
+#define STDIN_FILENO 0 /* file descriptor for stdin */
+#define STDOUT_FILENO 1 /* file descriptor for stdout */
+#define STDERR_FILENO 2 /* file descriptor for stderr */
+
+/* NULL must be defined in <unistd.h> according to POSIX Sec. 2.8.1. */
+#define NULL ((void *)0)
+
+/* The following relate to configurable system variables. POSIX Table 4-2. */
+#define _SC_ARG_MAX 1
+#define _SC_CHILD_MAX 2
+#define _SC_CLOCKS_PER_SEC 3
+#define _SC_NGROUPS_MAX 4
+#define _SC_OPEN_MAX 5
+#define _SC_JOB_CONTROL 6
+#define _SC_SAVED_IDS 7
+#define _SC_VERSION 8
+
+/* The following relate to configurable pathname variables. POSIX Table 5-2. */
+#define _PC_LINK_MAX 1 /* link count */
+#define _PC_MAX_CANON 2 /* size of the canonical input queue */
+#define _PC_MAX_INPUT 3 /* type-ahead buffer size */
+#define _PC_NAME_MAX 4 /* file name size */
+#define _PC_PATH_MAX 5 /* pathname size */
+#define _PC_PIPE_BUF 6 /* pipe size */
+#define _PC_NO_TRUNC 7 /* treatment of long name components */
+#define _PC_VDISABLE 8 /* tty disable */
+#define _PC_CHOWN_RESTRICTED 9 /* chown restricted or not */
+
+/* POSIX defines several options that may be implemented or not, at the
+ * implementer's whim. This implementer has made the following choices:
+ *
+ * _POSIX_JOB_CONTROL not defined: no job control
+ * _POSIX_SAVED_IDS not defined: no saved uid/gid
+ * _POSIX_NO_TRUNC not defined: long path names are truncated
+ * _POSIX_CHOWN_RESTRICTED defined: you can't give away files
+ * _POSIX_VDISABLE defined: tty functions can be disabled
+ */
+#define _POSIX_CHOWN_RESTRICTED
+#define _POSIX_VDISABLE '\t' /* can't set any control char to tab */
+
+
+/* Function Prototypes. */
+#ifndef _ANSI_H
+#include <ansi.h>
+#endif
+
+_PROTOTYPE( void _exit, (int _status) );
+_PROTOTYPE( int access, (char *_path, int _amode) );
+_PROTOTYPE( int chdir, (char *_path) );
+_PROTOTYPE( int chown, (char *_path, int _owner, int _group) );
+_PROTOTYPE( int close, (int _fd) );
+_PROTOTYPE( char *ctermid, (char *_s) );
+_PROTOTYPE( char *cuserid, (char *_s) );
+_PROTOTYPE( int dup, (int _fd) );
+_PROTOTYPE( int dup2, (int _fd, int _fd2) );
+_PROTOTYPE( int execl, (char *_path, ...) );
+_PROTOTYPE( int execle, (char *_path, ...) );
+_PROTOTYPE( int execlp, (char *_file, ...) );
+_PROTOTYPE( int execv, (char *_path, char *_argv[]) );
+_PROTOTYPE( int execve, (char *_path, char *_argv[], char *_envp[]) );
+_PROTOTYPE( int execvp, (char *_file, char *_argv[]) );
+_PROTOTYPE( pid_t fork, (void) );
+_PROTOTYPE( long fpathconf, (int _fd, int _name) );
+_PROTOTYPE( char *getcwd, (char *_buf, int _size) );
+_PROTOTYPE( gid_t getegid, (void) );
+_PROTOTYPE( uid_t geteuid, (void) );
+_PROTOTYPE( gid_t getgid, (void) );
+_PROTOTYPE( int getgroups, (int _gidsetsize, gid_t _grouplist[]) );
+_PROTOTYPE( char *getlogin, (void) );
+_PROTOTYPE( pid_t getpgrp, (void) );
+_PROTOTYPE( pid_t getpid, (void) );
+_PROTOTYPE( pid_t getppid, (void) );
+_PROTOTYPE( uid_t getuid, (void) );
+_PROTOTYPE( unsigned int alarm, (unsigned int _seconds) );
+_PROTOTYPE( unsigned int sleep, (unsigned int _seconds) );
+_PROTOTYPE( int isatty, (int _fd) );
+_PROTOTYPE( int link, (const char *_path1, const char *_path2) );
+_PROTOTYPE( off_t lseek, (int _fd, off_t _offset, int _whence) );
+_PROTOTYPE( long pathconf, (char *_path, int _name) );
+_PROTOTYPE( int pause, (void) );
+_PROTOTYPE( int pipe, (int _fildes[2]) );
+_PROTOTYPE( int read, (int _fd, char *_buf, unsigned int _n) );
+_PROTOTYPE( int rmdir, (const char *_path) );
+_PROTOTYPE( int setgid, (int _gid) );
+_PROTOTYPE( int setpgid, (pid_t _pid, pid_t _pgid) );
+_PROTOTYPE( pid_t setsid, (void) );
+_PROTOTYPE( int setuid, (int _uid) );
+_PROTOTYPE( long sysconf, (int _name) );
+_PROTOTYPE( pid_t tcgetpgrp, (int _fd) );
+_PROTOTYPE( int tcsetpgrp, (int _fd, pid_t _pgrp_id) );
+_PROTOTYPE( char *ttyname, (int _fd) );
+_PROTOTYPE( int unlink, (const char *_path) );
+_PROTOTYPE( int write, (int _fd, char *_buf, unsigned int _n) );
+
+#ifdef _MINIX
+_PROTOTYPE( char *brk, (char *_addr) );
+_PROTOTYPE( int mknod, (const char *_name, int _mode, int _addr) );
+_PROTOTYPE( int mknod4, (const char *_name, int _mode, int _addr,
+ unsigned _size) );
+_PROTOTYPE( char *mktemp, (char *_template) );
+_PROTOTYPE( char *sbrk, (int _incr) );
+_PROTOTYPE( int chroot, (const char *_name) );
+_PROTOTYPE( int mount, (char *_spec, char *_name, int _flag));
+_PROTOTYPE( long ptrace, (int _req, int _pid, long _addr, long _data) );
+_PROTOTYPE( int stime, (long *top) );
+_PROTOTYPE( int sync, (void) );
+_PROTOTYPE( int umount, (const char *_name) );
+#endif
+
+#endif /* _UNISTD_H */