Index: usr.bin/tty/tty.c
===================================================================
--- usr.bin/tty/tty.c
+++ usr.bin/tty/tty.c
@@ -44,6 +44,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <sysexits.h>
 #include <unistd.h>
 
 static void usage(void);
@@ -63,17 +64,18 @@
 		case '?':
 		default:
 			usage();
+			/* NOTREACHED */
 		}
 
-	t = ttyname(0);
+	t = ttyname(STDIN_FILENO);
 	if (!sflag)
 		puts(t ? t : "not a tty");
-	exit(t ? 0 : 1);
+	exit(t ? EXIT_SUCCESS : EXIT_FAILURE);
 }
 
 static void
 usage(void)
 {
-	fprintf(stderr, "usage: tty [-s]\n");
-	exit(2);
+	fprintf(stderr, "usage: %s [-s]\n", getprogname());
+	exit(EX_USAGE);
 }