/*
 * Copyright (c) 1987, 1993
 *	The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char copyright[] =
"@(#) Copyright (c) 1987, 1993\n\
	The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)mesg.c	8.2 (Berkeley) 01/21/94";
#endif /* not lint */

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

#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

int
main(argc, argv)
	int argc;
	char *argv[];
{
	struct stat sb;
	char *tty;
	int ch;

	while ((ch = getopt(argc, argv, "")) != EOF)
		switch (ch) {
		case '?':
		default:
			goto usage;
		}
	argc -= optind;
	argv += optind;

	if ((tty = ttyname(STDERR_FILENO)) == NULL)
		err(1, "ttyname");
	if (stat(tty, &sb) < 0)
		err(1, "%s", tty);

	if (*argv == NULL) {
		if (sb.st_mode & S_IWGRP) {
			(void)fprintf(stderr, "is y\n");
			exit(0);
		}
		(void)fprintf(stderr, "is n\n");
		exit(1);
	}

	switch (*argv[0]) {
	case 'y':
		if (chmod(tty, sb.st_mode | S_IWGRP) < 0)
			err(1, "%s", tty);
		exit(0);
	case 'n':
		if (chmod(tty, sb.st_mode & ~S_IWGRP) < 0)
			err(1, "%s", tty);
		exit(1);
	}

usage:	(void)fprintf(stderr, "usage: mesg [y | n]\n");
	exit(2);
}