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 #include <sys/types.h> 38 #include <sys/stat.h> 39 40 #include <err.h> 41 #include <stdio.h> 42 #include <stdlib.h> 43 #include <string.h> 44 #include <unistd.h> 45 46 static void usage(void) __dead2; 47 48 int 49 main(int argc, char *argv[]) 50 { 51 struct stat sb; 52 char *tty; 53 int ch; 54 55 while ((ch = getopt(argc, argv, "")) != -1) 56 switch (ch) { 57 case '?': 58 default: 59 usage(); 60 } 61 argc -= optind; 62 argv += optind; 63 64 if ((tty = ttyname(STDIN_FILENO)) == NULL && 65 (tty = ttyname(STDOUT_FILENO)) == NULL && 66 (tty = ttyname(STDERR_FILENO)) == NULL) 67 err(2, "ttyname"); 68 if (stat(tty, &sb) < 0) 69 err(2, "%s", tty); 70 71 if (*argv == NULL) { 72 if (sb.st_mode & S_IWGRP) { 73 (void)puts("is y"); 74 exit(0); 75 } 76 (void)puts("is n"); 77 exit(1); 78 } 79 80 switch (*argv[0]) { 81 case 'y': 82 if (chmod(tty, sb.st_mode | S_IWGRP) < 0) 83 err(2, "%s", tty); 84 exit(0); 85 case 'n': 86 if (chmod(tty, sb.st_mode & ~S_IWGRP) < 0) 87 err(2, "%s", tty); 88 exit(1); 89 } 90 91 usage(); 92 return(0); 93 } 94 95 static void 96 usage(void) 97 { 98 (void)fprintf(stderr, "usage: mesg [n | y]\n"); 99 exit(2); 100 } 101