xref: /freebsd/bin/stty/util.c (revision c1d255d3)
1 /*-
2  * Copyright (c) 1991, 1993, 1994
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the University nor the names of its contributors
14  *    may be used to endorse or promote products derived from this software
15  *    without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  */
29 
30 #ifndef lint
31 #if 0
32 static char sccsid[] = "@(#)util.c	8.3 (Berkeley) 4/2/94";
33 #endif
34 #endif /* not lint */
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
37 
38 #include <sys/types.h>
39 #include <sys/stat.h>
40 
41 #include <err.h>
42 #include <unistd.h>
43 
44 #include "stty.h"
45 #include "extern.h"
46 
47 /*
48  * Gross, but since we're changing the control descriptor from 1 to 0, most
49  * users will be probably be doing "stty > /dev/sometty" by accident.  If 1
50  * and 2 are both ttys, but not the same, assume that 1 was incorrectly
51  * redirected.
52  */
53 void
54 checkredirect(void)
55 {
56 	struct stat sb1, sb2;
57 
58 	if (isatty(STDOUT_FILENO) && isatty(STDERR_FILENO) &&
59 	    !fstat(STDOUT_FILENO, &sb1) && !fstat(STDERR_FILENO, &sb2) &&
60 	    (sb1.st_rdev != sb2.st_rdev))
61 warnx("stdout appears redirected, but stdin is the control descriptor");
62 }
63