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. 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  * @(#) Copyright (c) 1987, 1993 The Regents of the University of California.  All rights reserved.
  39  * @(#)mesg.c   8.2 (Berkeley) 1/21/94
  40  * $FreeBSD: src/usr.bin/mesg/mesg.c,v 1.4 1999/08/28 01:03:59 peter Exp $
  41  * $DragonFly: src/usr.bin/mesg/mesg.c,v 1.5 2005/03/04 10:34:39 liamfoy Exp $
  42  */
  43
  44 #include <sys/types.h>
  45 #include <sys/stat.h>
  46
  47 #include <err.h>
  48 #include <stdio.h>
  49 #include <stdlib.h>
  50 #include <unistd.h>
  51
  52 static void usage(void);
  53
  54 int
  55 main(int argc, char **argv)
  56 {
  57         struct stat sb;
  58         char *tty;
  59         int ch;
  60
  61         while ((ch = getopt(argc, argv, "")) != -1)
  62                 switch (ch) {
  63                 case '?':
  64                 default:
  65                         usage();
  66                 }
  67         argc -= optind;
  68         argv += optind;
  69
  70         if ((tty = ttyname(STDIN_FILENO)) == NULL &&
  71             (tty = ttyname(STDOUT_FILENO)) == NULL &&
  72             (tty = ttyname(STDERR_FILENO)) == NULL)
  73                 err(2, "ttyname failed");
  74         if (stat(tty, &sb) < 0)
  75                 err(2, "%s", tty);
  76
  77         if (*argv == NULL) {
  78                 if (sb.st_mode & S_IWGRP) {
  79                         fprintf(stdout, "is y\n");
  80                         exit(0);
  81                 }
  82                 fprintf(stdout, "is n\n");
  83                 exit(1);
  84         }
  85
  86         switch (*argv[0]) {
  87         case 'y':
  88                 if (chmod(tty, sb.st_mode | S_IWGRP) < 0)
  89                         err(2, "%s", tty);
  90                 exit(0);
  91         case 'n':
  92                 if (chmod(tty, sb.st_mode & ~S_IWGRP) < 0)
  93                         err(2, "%s", tty);
  94                 exit(1);
  95         }
  96
  97         usage();
  98         return(0);
  99 }
 100
 101 static void
 102 usage(void)
 103 {
 104         fprintf(stderr, "usage: mesg [y | n]\n");
 105         exit(2);
 106 }