1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 * Copyright 2022 Oxide Computer Company
26 */
27
28 /* Copyright (c) 1988 AT&T */
29 /* All Rights Reserved */
30
31 #pragma weak _isatty = isatty
32
33 #include "lint.h"
34 #include <sys/types.h>
35 #include <sys/termio.h>
36 #include <errno.h>
37 #include <unistd.h>
38
39 /*
40 * Returns 1 iff file is a tty
41 */
42 int
isatty(int f)43 isatty(int f)
44 {
45 struct termio tty;
46
47 if (ioctl(f, TCGETA, &tty) < 0) {
48 /*
49 * POSIX stipulates that systems may return an error here and if
50 * they do, it should either be EBADF or ENOTTY. In general, we
51 * assume that a driver that receives this ioctl is not going to
52 * return EBADF say due to an fd that's not open with the right
53 * mode and will instead return something else. It is possible
54 * to get many other errors here and we assume anything else
55 * that's returned means it's not a TTY and thus transform that.
56 *
57 * In the past, errno was preserved around this, which was
58 * incorrect because that meant that on failure there was no way
59 * to know whether it was meaningful or not. As pretty much
60 * every other system always returns an errno and there are
61 * consumers in the wild which assume they'll get something, we
62 * opt to always return an error.
63 */
64 if (errno != EBADF) {
65 errno = ENOTTY;
66 }
67 return (0);
68 }
69 return (1);
70 }
71