Start option definition with: ``The following options are available''

Use .Ev for env variables.
Remove unused #includes, and sort others.

usr.bin/biff/biff.1

@@ -46,13 +46,12 @@
 informs the system whether you want to be notified when mail arrives
 during the current terminal session.
 .Pp
-Options supported by
-.Nm :
-.Bl -tag -width 4n
+The following options are available:
+.Bl -tag -width indent
 .It Cm n
-Disables notification.
+Disable notification.
 .It Cm y
-Enables notification.
+Enable notification.
 .El
 .Pp
 When mail notification is enabled, the header and first few lines of
@@ -68,11 +67,11 @@ to be executed at each login.
 .Nm Biff
 operates asynchronously.
 For synchronous notification use the
-.Ar MAIL
+.Ev MAIL
 variable of
 .Xr sh 1
 or the
-.Ar mail
+.Ev mail
 variable of
 .Xr csh 1 .
 .Sh SEE ALSO

usr.bin/biff/biff.c

@@ -46,14 +46,10 @@ static char sccsid[] = "@(#)biff.c	8.1 (Berkeley) 6/6/93";
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
-#include <sys/types.h>
 #include <sys/stat.h>
-#include <errno.h>
-#include <unistd.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
 #include <err.h>
+#include <stdio.h>
+#include <unistd.h>
 
 static void usage __P((void));