Added example of how to tell various FreeBSD versions apart.

svn path=/head/; revision=2006

share/examples/FreeBSD_version/FreeBSD_version.c

@@ -0,0 +1,17 @@
+#if __FreeBSD__ == 0		/* 1.0 did not define __FreeBSD__ */
+#define __FreeBSD_version 199401
+#elif __FreeBSD__ == 1		/* 1.1 defined it to be 1 */
+#define __FreeBSD_version 199405
+#else				/* 2.0 and higher define it to be 2 */
+#include <osreldate.h>		/* and this works */
+#endif
+
+int main(void) { 
+  extern int getosreldate(void);
+  printf("Compilation release date: %d\n", __FreeBSD_version);
+#if __FreeBSD_version >= 199408
+  printf("Execution environment release date: %d\n", getosreldate());
+#else
+  printf("Execution environment release date: can't tell\n");
+#endif
+}

share/examples/FreeBSD_version/Makefile

@@ -0,0 +1,8 @@
+#	$Id$
+
+PROG=	FreeBSD_version
+NOMAN=
+
+install:
+
+.include <bsd.prog.mk>

share/examples/FreeBSD_version/README

@@ -0,0 +1,4 @@
+This is an example of how to determine the version of FreeBSD that
+a program was compiled on, and maybe running on (if 2.0 or better).
+
+This program is in the public domain.

share/examples/Makefile

@@ -1,10 +1,10 @@
-#	$Id$
+#	$Id: Makefile,v 1.1 1994/08/09 18:25:36 wollman Exp $
 #
 # Doing a make install builds /usr/share/examples
 #
 all clean cleandir depend lint tags:
 
-DIRS=sunrpc etc
+DIRS=sunrpc etc FreeBSD_version
 
 # Define SHARED to indicate whether you want symbolic links to the system
 # source (``symlinks''), or a separate copy (``copies''); (latter useful