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att
GitHub Repository: att/ast
 Path: blob/master/src/cmd/std/mesg.c
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/***********************************************************************

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*                                                                      *

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*               This software is part of the ast package               *

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*          Copyright (c) 1989-2011 AT&T Intellectual Property          *

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*                      and is licensed under the                       *

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*                 Eclipse Public License, Version 1.0                  *

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*                    by AT&T Intellectual Property                     *

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*                                                                      *

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*                A copy of the License is available at                 *

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*          http://www.eclipse.org/org/documents/epl-v10.html           *

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*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *

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*                                                                      *

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*              Information and Software Systems Research               *

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*                            AT&T Research                             *

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*                           Florham Park NJ                            *

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*                                                                      *

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*                 Glenn Fowler <[email protected]>                  *

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*                                                                      *

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***********************************************************************/

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#pragma prototyped

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/*

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 * mesg.c

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 * Written by David Korn

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 * Thu Aug 15 15:25:29 EDT 1996

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 */

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static const char usage[] =

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"[-?\n@(#)$Id: mesg (AT&T Research) 1999-04-28 $\n]"

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USAGE_LICENSE

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"[+NAME?mesg - permit or deny messages to the terminal]"

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"[+DESCRIPTION?\bmesg\b controls whether other users are allowed to send"

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"	messages via \bwrite\b(1), \btalk\b(1) or other commands to the"

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"	terminal device. The terminal device affected is determined by"

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"	searching for the first terminal in the sequence of devices"

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"	associated with standard input, standard output and standard error,"

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"	respectively. With no arguments, \bmesg\b reports the current state"

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"	without changing it. Processes with appropriate privileges may be"

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"	able to send messages to the terminal independent of the"

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"	current state.]"

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"\n"

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"\n[ y | n ]\n"

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"\n"

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"[+OPERANDS?The following operands are supported:]{"

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"	[+y?Grant permission to other users to send messages to the terminal.]"

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"	[+n?Deny permission to other users to send messages to the terminal.]"

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"}"

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"[+SEE ALSO?\btalk\b(1), \bwrite\b(1)]"

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;

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#include	<cmd.h>

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#include	<ls.h>

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static int mesg(int  mode)

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{

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	struct stat statb;

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	char *tty = ttyname(2);

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	if(!tty)

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		tty = ttyname(0);

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	if(!tty)

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		tty = ttyname(1);

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	if(!tty)

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		error(ERROR_exit(1),"cannot find terminal");

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	if(stat(tty,&statb)<0)

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		error(ERROR_system(1),"%s: cannot stat",tty);

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	switch(mode)

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	{

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	    case 'n':

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	    case 'y':

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		if(mode=='y')

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			statb.st_mode |= S_IWGRP;

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		else

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			statb.st_mode &= ~S_IWGRP;

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		if(chmod(tty, statb.st_mode) < 0)

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			error(ERROR_system(1),"%s: cannot stat",tty);

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		break;

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	    case 0:

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		sfprintf(sfstdout,"%c\n",(statb.st_mode&S_IWGRP)?'y':'n');

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	}

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	return((statb.st_mode&S_IWGRP)==0);

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}

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int

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main(int argc, char *argv[])

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{

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	register int n;

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	NoP(argc);

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	error_info.id = "mesg";

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	for (;;)

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	{

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		switch (optget(argv, usage))

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		{

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		case ':':

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			error(2, "%s", opt_info.arg);

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			break;

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		case '?':

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			error(ERROR_usage(2), "%s", opt_info.arg);

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			break;

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		}

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		break;

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	}

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	argv += opt_info.index;

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	n = 0;

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	if(error_info.errors || (*argv && (n= **argv) !='y' && n!='n'))

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		error(ERROR_usage(2), "%s", optusage(NiL));

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	return mesg(n);

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}

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