--- Net2/sys/errno.h	2018/04/24 18:03:58	1.1
+++ Net2/sys/errno.h	2018/04/24 18:16:22	1.1.1.2
@@ -30,9 +30,13 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)errno.h	7.13 (Berkeley) 2/19/91
+ *	from: @(#)errno.h	7.13 (Berkeley) 2/19/91
+ *	errno.h,v 1.3 1993/05/20 16:22:09 cgd Exp
  */
 
+#ifndef _SYS_ERRNO_H_
+#define _SYS_ERRNO_H_
+
 #ifndef KERNEL
 extern int errno;			/* global error number */
 #endif
@@ -151,3 +155,5 @@ extern int errno;			/* global error numb
 #define	ERESTART	-1		/* restart syscall */
 #define	EJUSTRETURN	-2		/* don't modify regs, just return */
 #endif
+
+#endif /* !_SYS_ERRNO_H_ */