1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1987, 1993
5 * The Regents of the University of California. All rights reserved.
6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
8 * to the University of California by American Telephone and Telegraph
9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10 * the permission of UNIX System Laboratories, Inc.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37 #ifndef lint
38 static const char copyright[] =
39 "@(#) Copyright (c) 1987, 1993\n\
40 The Regents of the University of California. All rights reserved.\n";
41 #endif /* not lint */
42
43 #ifndef lint
44 #if 0
45 static char sccsid[] = "@(#)mesg.c 8.2 (Berkeley) 1/21/94";
46 #endif
47 #endif /* not lint */
48 #include <sys/cdefs.h>
49 #include <sys/types.h>
50 #include <sys/stat.h>
51
52 #include <err.h>
53 #include <stdio.h>
54 #include <stdlib.h>
55 #include <string.h>
56 #include <unistd.h>
57
58 static void usage(void);
59
60 int
main(int argc,char * argv[])61 main(int argc, char *argv[])
62 {
63 struct stat sb;
64 char *tty;
65 int ch;
66
67 while ((ch = getopt(argc, argv, "")) != -1)
68 switch (ch) {
69 case '?':
70 default:
71 usage();
72 }
73 argc -= optind;
74 argv += optind;
75
76 if ((tty = ttyname(STDIN_FILENO)) == NULL &&
77 (tty = ttyname(STDOUT_FILENO)) == NULL &&
78 (tty = ttyname(STDERR_FILENO)) == NULL)
79 err(2, "ttyname");
80 if (stat(tty, &sb) < 0)
81 err(2, "%s", tty);
82
83 if (*argv == NULL) {
84 if (sb.st_mode & S_IWGRP) {
85 (void)puts("is y");
86 exit(0);
87 }
88 (void)puts("is n");
89 exit(1);
90 }
91
92 switch (*argv[0]) {
93 case 'y':
94 if (chmod(tty, sb.st_mode | S_IWGRP) < 0)
95 err(2, "%s", tty);
96 exit(0);
97 case 'n':
98 if (chmod(tty, sb.st_mode & ~S_IWGRP) < 0)
99 err(2, "%s", tty);
100 exit(1);
101 }
102
103 usage();
104 return(0);
105 }
106
107 static void
usage(void)108 usage(void)
109 {
110 (void)fprintf(stderr, "usage: mesg [n | y]\n");
111 exit(2);
112 }
113