cmd/mesg/mesg.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*  Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */


/*
 * mesg -- set current tty to accept or
 *  forbid write permission.
 *
 *  mesg [-y | -n | y | n]
 *      y allow messages
 *      n forbid messages
 *  return codes
 *      0 if messages are ON or turned ON
 *      1 if messages are OFF or turned OFF
 *      2 if an error occurs
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <locale.h>
#include <libintl.h>
#include <sys/types.h>
#include <sys/stat.h>

static void error(const char *s);
static void newmode(mode_t m);
static void usage(void);

static char *tty;

int
main(int argc, char *argv[])
{
    int i, c, r = 0;
    int action = 0;
    struct stat sbuf;

    extern int optind;

    (void) setlocale(LC_ALL, "");
#if !defined(TEXT_DOMAIN)       /* Should be defined by cc -D */
#define TEXT_DOMAIN "SYS_TEST"  /* Use this only if it weren't */
#endif
    (void) textdomain(TEXT_DOMAIN);

    /*
     * Check stdin, stdout and stderr, in order, for a tty
     */
    for (i = 0; i <= 2; i++) {
        if ((tty = ttyname(i)) != NULL)
            break;
    }

    if (stat(tty, &sbuf) < 0)
        error("cannot stat");

    if (argc < 2) {
        if (sbuf.st_mode & (S_IWGRP | S_IWOTH)) {
            (void) printf("is y\n");
        } else {
            r = 1;
            (void) printf("is n\n");
        }
        exit(r);
    }

    while ((c = getopt(argc, argv, "yn")) != EOF) {
        switch (c) {
        case 'y':
            if (action > 0)
                usage();

            newmode(S_IRUSR | S_IWUSR | S_IWGRP);
            action++;
            break;

        case 'n':
            if (action > 0)
                usage();

            newmode(S_IRUSR | S_IWUSR);
            r = 1;
            action++;
            break;

        case '?':
            usage();
            break;
        }
    }

    /*
     * Required for POSIX.2
     */
    if (argc > optind) {
        if (action > 0)
            usage();

        switch (*argv[optind]) {
        case 'y':
            newmode(S_IRUSR | S_IWUSR | S_IWGRP);
            break;

        case 'n':
            newmode(S_IRUSR | S_IWUSR);
            r = 1;
            break;

        default:
            usage();
            break;
        }
    }

    return (r);
}

void
error(const char *s)
{
    (void) fprintf(stderr, "mesg: ");
    (void) fprintf(stderr, "%s\n", s);
    exit(2);
}

void
newmode(mode_t m)
{
    if (chmod(tty, m) < 0)
        error("cannot change mode");
}

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