diff --git a/include/errno.h b/include/errno.h
index 7bd2284b9..4762f3d4e 100755
--- a/include/errno.h
+++ b/include/errno.h
@@ -73,6 +73,7 @@ extern int errno;		  /* place where the error numbers go */
 #define ENOLCK        (_SIGN 37)  /* no locks available */
 #define ENOSYS        (_SIGN 38)  /* function not implemented */
 #define ENOTEMPTY     (_SIGN 39)  /* directory not empty */
+#define ELOOP         (_SIGN 40)  /* too many levels of symlinks detected */
 
 /* The following errors relate to networking. */
 #define EPACKSIZE     (_SIGN 50)  /* invalid packet size for some protocol */
diff --git a/include/fcntl.h b/include/fcntl.h
index 78d511beb..2aa7cce69 100755
--- a/include/fcntl.h
+++ b/include/fcntl.h
@@ -64,4 +64,12 @@ _PROTOTYPE( int creat, (const char *_path, _mnx_Mode_t _mode)		);
 _PROTOTYPE( int fcntl, (int _filedes, int _cmd, ...)	  		);
 _PROTOTYPE( int open,  (const char *_path, int _oflag, ...) 		);
 
+/* For locking files. */
+#define LOCK_SH		F_RDLCK		/* Shared lock */
+#define LOCK_EX		F_WRLCK		/* Exclusive lock */
+#define LOCK_NB		0x0080		/* Do not block when locking */
+#define LOCK_UN		F_UNLCK		/* Unlock */
+
+_PROTOTYPE(  int flock, (int fd, int mode)				);
+
 #endif /* _FCNTL_H */
diff --git a/include/minix/callnr.h b/include/minix/callnr.h
index c8af59c2e..cb9891b69 100755
--- a/include/minix/callnr.h
+++ b/include/minix/callnr.h
@@ -39,9 +39,12 @@
 #define DUP		  41 
 #define PIPE		  42 
 #define TIMES		  43
+#define SYMLINK		  45
 #define SETGID		  46
 #define GETGID		  47
 #define SIGNAL		  48
+#define RDLNK		  49
+#define LSTAT		  50
 #define IOCTL		  54
 #define FCNTL		  55
 #define EXEC		  59
diff --git a/include/minix/const.h b/include/minix/const.h
index 3814621a3..6c9e1792a 100755
--- a/include/minix/const.h
+++ b/include/minix/const.h
@@ -96,6 +96,7 @@
 
 /* Flag bits for i_mode in the inode. */
 #define I_TYPE          0170000	/* this field gives inode type */
+#define I_SYMBOLIC_LINK 0120000	/* file is a symbolic link */
 #define I_REGULAR       0100000	/* regular file, not dir or special */
 #define I_BLOCK_SPECIAL 0060000	/* block special file */
 #define I_DIRECTORY     0040000	/* file is a directory */
@@ -119,6 +120,8 @@
 #define MAX_INODE_NR ((ino_t) 037777777777)	/* largest inode number */
 #define MAX_FILE_POS ((off_t) 037777777777)	/* largest legal file offset */
 
+#define MAX_SYM_LOOPS	8	/* how many symbolic links are recursed */
+
 #define NO_BLOCK              ((block_t) 0)	/* absence of a block number */
 #define NO_ENTRY                ((ino_t) 0)	/* absence of a dir entry */
 #define NO_ZONE                ((zone_t) 0)	/* absence of a zone number */
diff --git a/include/sys/stat.h b/include/sys/stat.h
index f586e459f..b08df5020 100755
--- a/include/sys/stat.h
+++ b/include/sys/stat.h
@@ -29,14 +29,14 @@ struct stat {
  * extensions such as S_IFREG != (mode_t) S_IFREG when ints are 32 bits.
  */
 #define S_IFMT  ((mode_t) 0170000)	/* type of file */
-#define S_IFLNK ((mode_t) 0120000)	/* symbolic link, not implemented */
+#define S_IFLNK ((mode_t) 0120000)	/* symbolic link */
 #define S_IFREG ((mode_t) 0100000)	/* regular */
-#define S_IFBLK 0060000		/* block special */
-#define S_IFDIR 0040000  	/* directory */
-#define S_IFCHR 0020000		/* character special */
-#define S_IFIFO 0010000		/* this is a FIFO */
-#define S_ISUID 0004000		/* set user id on execution */
-#define S_ISGID 0002000		/* set group id on execution */
+#define S_IFBLK ((mode_t) 0060000)	/* block special */
+#define S_IFDIR ((mode_t) 0040000)	/* directory */
+#define S_IFCHR ((mode_t) 0020000)	/* character special */
+#define S_IFIFO ((mode_t) 0010000)	/* this is a FIFO */
+#define S_ISUID ((mode_t) 0004000)	/* set user id on execution */
+#define S_ISGID ((mode_t) 0002000)	/* set group id on execution */
 				/* next is reserved for future use */
 #define S_ISVTX   01000		/* save swapped text even after use */
 
@@ -61,6 +61,7 @@ struct stat {
 #define S_ISDIR(m)	(((m) & S_IFMT) == S_IFDIR)	/* is a directory */
 #define S_ISCHR(m)	(((m) & S_IFMT) == S_IFCHR)	/* is a char spec */
 #define S_ISBLK(m)	(((m) & S_IFMT) == S_IFBLK)	/* is a block spec */
+#define S_ISLNK(m)	(((m) & S_IFMT) == S_IFLNK)	/* is a symlink */
 #define S_ISFIFO(m)	(((m) & S_IFMT) == S_IFIFO)	/* is a pipe/FIFO */
 #define S_ISLNK(m)      (((m) & S_IFMT) == S_IFLNK)     /* is a sym link */
 
diff --git a/include/unistd.h b/include/unistd.h
index 629ab534c..f05e94add 100755
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -182,8 +182,4 @@ _PROTOTYPE( int setgroups, (int ngroups, const gid_t *gidset)		);
 
 #endif
 
-_PROTOTYPE( int readlink, (const char *, char *, int));
-_PROTOTYPE( int getopt, (int, char **, char *));
-extern int optind, opterr, optopt;
-
 #endif /* _UNISTD_H */