Use #include <unistd.h> rather than the explicit externs in the

example.  The externs haven't been needed in about 10 years, so
there's no reason to have them other than for hysterical raisins.  And
the California Rasins haven't been around for a long time...

lib/libc/stdlib/getopt.3

@@ -164,8 +164,7 @@ The
 function returns \-1 when the argument list is exhausted.
 .Sh EXAMPLES
 .Bd -literal -compact
-extern char *optarg;
-extern int optind;
+#include <unistd.h>
 int bflag, ch, fd;
 
 bflag = 0;