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localhostname.c revision 1.4 
      1 /*	$NetBSD: localhostname.c,v 1.4 1997/10/13 03:42:27 lukem Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1996 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Jason R. Thorpe.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #ifndef lint
     41 __RCSID("$NetBSD: localhostname.c,v 1.4 1997/10/13 03:42:27 lukem Exp $");
     42 #endif
     43 
     44 #include <sys/types.h>
     45 #include <err.h>
     46 #include <netdb.h>
     47 #include <stdio.h>
     48 #include <string.h>
     49 #include <unistd.h>
     50 
     51 #include "protos.h"
     52 
     53 void
     54 localhostname(buf, buflen)
     55 	char *buf;
     56 	size_t buflen;
     57 {
     58 	struct hostent *hp;
     59 	char hostname[MAXHOSTNAMELEN];
     60 	int i;
     61 
     62 	if (gethostname(hostname, sizeof(hostname)))
     63 		err(1, "gethostname");
     64 
     65 	memset(buf, 0, buflen);
     66 
     67 	/*
     68 	 * If hostname appears to be fully-qualified,
     69 	 * just return it.
     70 	 */
     71 	if (strchr(hostname, '.')) {
     72 		snprintf(buf, buflen, "%s", hostname);
     73 		return;
     74 	}
     75 
     76 	/*
     77 	 * Lookup the host.  Return the first name that appears
     78 	 * to be fully-qualified.
     79 	 */
     80 	hp = gethostbyname(hostname);
     81 	if (hp == NULL)
     82 		errx(1, "gethostbyname(%s) failed", hostname);
     83 
     84 	if (strchr(hp->h_name, '.')) {
     85 		snprintf(buf, buflen, "%s", hp->h_name);
     86 		return;
     87 	}
     88 
     89 	if (hp->h_aliases != NULL && hp->h_aliases[0] != NULL) {
     90 		for (i = 0; hp->h_aliases[i] != NULL; i++) {
     91 			if (strchr(hp->h_aliases[i], '.')) {
     92 				snprintf(buf, buflen, "%s", hp->h_aliases[i]);
     93 				return;
     94 			}
     95 		}
     96 	}
     97 
     98 	/*
     99 	 * As a last resort, just return hostname.
    100 	 */
    101 	snprintf(buf, buflen, "%s", hostname);
    102 }
    103