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/* Host name canonicalization
Copyright (C) 1995, 1996 Free Software Foundation, Inc.
Written by Miles Bader <miles@gnu.ai.mit.edu>
[This file is from sh-utils/lib; maybe something can be done to share them.]
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include <unistd.h>
#include <string.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
/* Returns the canonical hostname associated with HOST (allocated in a static
buffer), or 0 if it can't be determined. */
char *
canon_host (char *host)
{
struct hostent *he = gethostbyname (host);
if (he)
{
char *addr = 0;
/* Try and get an ascii version of the numeric host address. */
switch (he->h_addrtype)
{
case AF_INET:
addr = inet_ntoa (*(struct in_addr *)he->h_addr);
break;
}
if (addr && strcmp (he->h_name, addr) == 0)
/* gethostbyname() cheated! Lookup the host name via the address
this time to get the actual host name. */
he = gethostbyaddr (he->h_addr, he->h_length, he->h_addrtype);
if (he)
return he->h_name;
}
return 0;
}
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