usr.bin/mesg/mesg.c

   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. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  * @(#) Copyright (c) 1987, 1993 The Regents of the University of California.  All rights reserved.
  35  * @(#)mesg.c   8.2 (Berkeley) 1/21/94
  36  * $FreeBSD: src/usr.bin/mesg/mesg.c,v 1.4 1999/08/28 01:03:59 peter Exp $
  37  * $DragonFly: src/usr.bin/mesg/mesg.c,v 1.5 2005/03/04 10:34:39 liamfoy Exp $
  38  */
  39
  40 #include <sys/types.h>
  41 #include <sys/stat.h>
  42
  43 #include <err.h>
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include <unistd.h>
  47
  48 static void usage(void);
  49
  50 int
  51 main(int argc, char **argv)
  52 {
  53         struct stat sb;
  54         char *tty;
  55         int ch;
  56
  57         while ((ch = getopt(argc, argv, "")) != -1)
  58                 switch (ch) {
  59                 case '?':
  60                 default:
  61                         usage();
  62                 }
  63         argc -= optind;
  64         argv += optind;
  65
  66         if ((tty = ttyname(STDIN_FILENO)) == NULL &&
  67             (tty = ttyname(STDOUT_FILENO)) == NULL &&
  68             (tty = ttyname(STDERR_FILENO)) == NULL)
  69                 err(2, "ttyname failed");
  70         if (stat(tty, &sb) < 0)
  71                 err(2, "%s", tty);
  72
  73         if (*argv == NULL) {
  74                 if (sb.st_mode & S_IWGRP) {
  75                         fprintf(stdout, "is y\n");
  76                         exit(0);
  77                 }
  78                 fprintf(stdout, "is n\n");
  79                 exit(1);
  80         }
  81
  82         switch (*argv[0]) {
  83         case 'y':
  84                 if (chmod(tty, sb.st_mode | S_IWGRP) < 0)
  85                         err(2, "%s", tty);
  86                 exit(0);
  87         case 'n':
  88                 if (chmod(tty, sb.st_mode & ~S_IWGRP) < 0)
  89                         err(2, "%s", tty);
  90                 exit(1);
  91         }
  92
  93         usage();
  94         return(0);
  95 }
  96
  97 static void
  98 usage(void)
  99 {
 100         fprintf(stderr, "usage: mesg [y | n]\n");
 101         exit(2);
 102 }