mesg.c revision 96093 
1/*
2 * Copyright (c) 1987, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 *    must display the following acknowledgement:
20 *	This product includes software developed by the University of
21 *	California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 *    may be used to endorse or promote products derived from this software
24 *    without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 */
38
39#ifndef lint
40static const char copyright[] =
41"@(#) Copyright (c) 1987, 1993\n\
42	The Regents of the University of California.  All rights reserved.\n";
43#endif /* not lint */
44
45#ifndef lint
46#if 0
47static char sccsid[] = "@(#)mesg.c	8.2 (Berkeley) 1/21/94";
48#endif
49static const char rcsid[] =
50  "$FreeBSD: head/usr.bin/mesg/mesg.c 96093 2002-05-06 04:33:04Z tjr $";
51#endif /* not lint */
52
53#include <sys/types.h>
54#include <sys/stat.h>
55
56#include <err.h>
57#include <stdio.h>
58#include <stdlib.h>
59#include <string.h>
60#include <unistd.h>
61
62static void usage(void);
63
64int
65main(argc, argv)
66	int argc;
67	char *argv[];
68{
69	struct stat sb;
70	char *tty;
71	int ch;
72
73	while ((ch = getopt(argc, argv, "")) != -1)
74		switch (ch) {
75		case '?':
76		default:
77			usage();
78		}
79	argc -= optind;
80	argv += optind;
81
82	if ((tty = ttyname(STDIN_FILENO)) == NULL &&
83	    (tty = ttyname(STDOUT_FILENO)) == NULL &&
84	    (tty = ttyname(STDERR_FILENO)) == NULL)
85		err(2, "ttyname");
86	if (stat(tty, &sb) < 0)
87		err(2, "%s", tty);
88
89	if (*argv == NULL) {
90		if (sb.st_mode & S_IWGRP) {
91			(void)puts("is y");
92			exit(0);
93		}
94		(void)puts("is n");
95		exit(1);
96	}
97
98	switch (*argv[0]) {
99	case 'y':
100		if (chmod(tty, sb.st_mode | S_IWGRP) < 0)
101			err(2, "%s", tty);
102		exit(0);
103	case 'n':
104		if (chmod(tty, sb.st_mode & ~S_IWGRP) < 0)
105			err(2, "%s", tty);
106		exit(1);
107	}
108
109	usage();
110	return(0);
111}
112
113static void
114usage()
115{
116	(void)fprintf(stderr, "usage: mesg [y | n]\n");
117	exit(2);
118}
119