xref: /freebsd/usr.bin/mesg/mesg.c (revision 5e3190f700637fcfc1a52daeaa4a031fdd2557c7)
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) __dead2;
59 
60 int
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
108 usage(void)
109 {
110 	(void)fprintf(stderr, "usage: mesg [n | y]\n");
111 	exit(2);
112 }
113