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localhostname.c revision 1.2 
      1 /*	$NetBSD: localhostname.c,v 1.2 1997/07/18 21:57:00 thorpej 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 REGENTS OR CONTRIBUTORS BE
     30  * 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/types.h>
     40 #include <err.h>
     41 #include <netdb.h>
     42 #include <stdio.h>
     43 #include <string.h>
     44 #include <unistd.h>
     45 
     46 #include "protos.h"
     47 
     48 void
     49 localhostname(buf, buflen)
     50 	char *buf;
     51 	size_t buflen;
     52 {
     53 	struct hostent *hp;
     54 	char hostname[MAXHOSTNAMELEN];
     55 	int i;
     56 
     57 	if (gethostname(hostname, sizeof(hostname)))
     58 		err(1, "gethostname");
     59 
     60 	memset(buf, 0, buflen);
     61 
     62 	/*
     63 	 * If hostname appears to be fully-qualified,
     64 	 * just return it.
     65 	 */
     66 	if (strchr(hostname, '.')) {
     67 		snprintf(buf, buflen, "%s", hostname);
     68 		return;
     69 	}
     70 
     71 	/*
     72 	 * Lookup the host.  Return the first name that appears
     73 	 * to be fully-qualified.
     74 	 */
     75 	hp = gethostbyname(hostname);
     76 	if (hp == NULL)
     77 		errx(1, "gethostbyname(%s) failed", hostname);
     78 
     79 	if (strchr(hp->h_name, '.')) {
     80 		snprintf(buf, buflen, "%s", hp->h_name);
     81 		return;
     82 	}
     83 
     84 	if (hp->h_aliases != NULL && hp->h_aliases[0] != NULL) {
     85 		for (i = 0; hp->h_aliases[i] != NULL; i++) {
     86 			if (strchr(hp->h_aliases[i], '.')) {
     87 				snprintf(buf, buflen, "%s", hp->h_aliases[i]);
     88 				return;
     89 			}
     90 		}
     91 	}
     92 
     93 	/*
     94 	 * As a last resort, just return hostname.
     95 	 */
     96 	snprintf(buf, buflen, "%s", hostname);
     97 }
     98