basic_cmds/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
  39 #ifndef lint
  40 static 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
  47 static char sccsid[] = "@(#)mesg.c      8.2 (Berkeley) 1/21/94";
  48 #endif
  49 #endif /* not lint */
  50 #include <sys/cdefs.h>
  51 __RCSID("$FreeBSD: src/usr.bin/mesg/mesg.c,v 1.8 2002/09/04 23:29:04 dwmalone Exp $");
  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
  62 static void usage(void);
  63
  64 int
  65 main(int argc, char *argv[])
  66 {
  67         struct stat sb;
  68         char *tty;
  69         int ch;
  70
  71         while ((ch = getopt(argc, argv, "")) != -1)
  72                 switch (ch) {
  73                 case '?':
  74                 default:
  75                         usage();
  76                 }
  77 //      argc -= optind;
  78         argv += optind;
  79
  80         if ((tty = ttyname(STDIN_FILENO)) == NULL &&
  81             (tty = ttyname(STDOUT_FILENO)) == NULL &&
  82             (tty = ttyname(STDERR_FILENO)) == NULL)
  83                 err(2, "ttyname");
  84         if (stat(tty, &sb) < 0)
  85                 err(2, "%s", tty);
  86
  87         if (*argv == NULL) {
  88                 if (sb.st_mode & S_IWGRP) {
  89                         (void)puts("is y");
  90                         exit(0);
  91                 }
  92                 (void)puts("is n");
  93                 exit(1);
  94         }
  95
  96         switch (*argv[0]) {
  97         case 'y':
  98                 if (chmod(tty, sb.st_mode | S_IWGRP) < 0)
  99                         err(2, "%s", tty);
 100                 exit(0);
 101         case 'n':
 102                 if (chmod(tty, sb.st_mode & ~S_IWGRP) < 0)
 103                         err(2, "%s", tty);
 104                 exit(1);
 105         }
 106
 107         usage();
 108         return(0);
 109 }
 110
 111 static void
 112 usage(void)
 113 {
 114         (void)fprintf(stderr, "usage: mesg [y | n]\n");
 115         exit(2);
 116 }