Dont forget to #include <err.h>

usr.bin/tail/forward.c

@@ -50,6 +50,7 @@ static char sccsid[] = "@(#)forward.c	8.1 (Berkeley) 6/6/93";
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <err.h>
 #include "extern.h"
 
 static void rlines __P((FILE *, long, struct stat *));

usr.bin/tail/misc.c

@@ -45,6 +45,7 @@ static char sccsid[] = "@(#)misc.c	8.1 (Berkeley) 6/6/93";
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <err.h>
 #include "extern.h"
 
 void

usr.bin/tail/read.c

@@ -46,6 +46,7 @@ static char sccsid[] = "@(#)read.c	8.1 (Berkeley) 6/6/93";
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <err.h>
 #include "extern.h"
 
 /*

usr.bin/tail/reverse.c

@@ -48,6 +48,7 @@ static char sccsid[] = "@(#)reverse.c	8.1 (Berkeley) 6/6/93";
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <err.h>
 #include "extern.h"
 
 static void r_buf __P((FILE *));

usr.bin/tail/tail.c

@@ -51,6 +51,7 @@ static char sccsid[] = "@(#)tail.c	8.1 (Berkeley) 6/6/93";
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <err.h>
 #include "extern.h"
 
 int fflag, rflag, rval;