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[unix-history] / usr / src / usr.bin / mesg / mesg.c

/*
* Copyright (c) 1987 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley.  The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/

#ifndef lint
char copyright[] =
"@(#) Copyright (c) 1987 Regents of the University of California.\n\
All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)mesg.c      4.5 (Berkeley) %G%";
#endif /* not lint */

/*
* mesg -- set current tty to accept or
*      forbid write permission.
*
*      mesg [y] [n]
*              y allow messages
*              n forbid messages
*/

#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>

static char *tty;

main(argc, argv)
       int argc;
       char **argv;
{
       struct stat sbuf;
       char *ttyname();

       if (!(tty = ttyname(2))) {
               fputs("mesg: not a device in /dev.\n", stderr);
               exit(-1);
       }
       if (stat(tty, &sbuf) < 0) {
               perror("mesg");
               exit(-1);
       }
       if (argc < 2) {
               if (sbuf.st_mode & 020) {
                       fputs("is y\n", stderr);
                       exit(0);
               }
               fputs("is n\n", stderr);
               exit(1);
       }
#define OTHER_WRITE     020
       switch(*argv[1]) {
       case 'y':
               newmode(sbuf.st_mode | OTHER_WRITE);
               exit(0);
       case 'n':
               newmode(sbuf.st_mode &~ OTHER_WRITE);
               exit(1);
       default:
               fputs("usage: mesg [y] [n]\n", stderr);
               exit(-1);
       }
       /*NOTREACHED*/
}

static
newmode(m)
       u_short m;
{
       if (chmod(tty, m) < 0) {
               perror("mesg");
               exit(-1);
       }
}