/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>

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

static void usage(void) __dead2;

int
main(int argc, char *argv[])
{
        int ch, sflag, dflag;
        char hostname[MAXHOSTNAMELEN], *hostp, *p;

        sflag = 0;
        dflag = 0;
        while ((ch = getopt(argc, argv, "fsd")) != -1)
                switch (ch) {
                case 'f':
                        /*
                         * On Linux, "hostname -f" prints FQDN.
                         * BSD "hostname" always prints FQDN by
                         * default, so we accept but ignore -f.
                         */
                        break;
                case 's':
                        sflag = 1;
                        break;
                case 'd':
                        dflag = 1;
                        break;
                case '?':
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (argc > 1 || (sflag && dflag))
                usage();

        if (*argv) {
                if (sethostname(*argv, (int)strlen(*argv)))
                        err(1, "sethostname");
        } else {
                hostp = hostname;
                if (gethostname(hostname, (int)sizeof(hostname)))
                        err(1, "gethostname");
                if (sflag) {
                        p = strchr(hostname, '.');
                        if (p != NULL)
                                *p = '\0';
                } else if (dflag) {
                        p = strchr(hostname, '.');
                        if (p != NULL)
                                hostp = p + 1;
                }
                (void)printf("%s\n", hostp);
        }
        exit(0);
}

static void
usage(void)
{

        (void)fprintf(stderr, "usage: hostname [-f] [-s | -d] [name-of-host]\n");
        exit(1);
}