1999-04-06 23:02:35 +00:00
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.\" Copyright (c) 1999 Brian Somers <brian@Awfulhak.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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1999-08-28 00:22:10 +00:00
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.\" $FreeBSD$
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1999-04-06 23:02:35 +00:00
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.\"
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.Dd April 6, 1999
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.Os
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.Dt REALHOSTNAME 3
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.Sh NAME
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.Nm realhostname
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.Nd "convert an IP number to the real host name"
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <netinet/in.h>
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.Fd #include <libutil.h>
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.Ft int
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.Fn realhostname "char *host" "size_t hsize" "const struct in_addr *ip"
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.Pp
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Link with
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.Va -lutil
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on the
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.Xr cc 1
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command line.
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.Sh DESCRIPTION
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The function
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.Fn realhostname
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converts
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.Ar ip
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to the corresponding host name. This is done by resolving
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.Ar ip
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to a host name and then ensuring that the host name resolves
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back to
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.Ar ip .
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.Pp
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.Ar host
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must point to a buffer of at least
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.Ar hsize
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bytes, and will always be written to by this function.
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.Pp
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If the name resolution doesn't work both ways or if the host name is longer
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than
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.Ar hsize
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bytes,
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.Xr inet_ntoa 3
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is used to convert
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.Ar ip
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1999-09-20 09:15:23 +00:00
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to an ASCII form.
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1999-04-06 23:02:35 +00:00
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.Pp
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If the string written to
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.Ar host
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is
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.Ar hsize
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bytes long,
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.Ar host
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will not be NUL terminated.
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.Sh RETURN VALUES
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.Fn realhostname
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will return one of the following constants which are defined in
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.Pa libutil.h :
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.Pp
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.Bl -tag -width XXX -offset XXX
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.It Li HOSTNAME_FOUND
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A valid host name was found.
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.It Li HOSTNAME_INCORRECTNAME
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A host name was found, but it did not resolve back to the passed
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.Ar ip .
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.Ar host
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now contains the numeric value of
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.Ar ip .
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.It Li HOSTNAME_INVALIDADDR
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.Ar ip
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could not be resolved.
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.Ar host
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now contains the numeric value of
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.Ar ip .
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.It Li HOSTNAME_INVALIDNAME
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A host name was found, but it could not be resolved back to any ip number.
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.Ar host
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now contains the numeric value of
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.Ar ip .
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.El
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.Sh SEE ALSO
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.Xr gethostbyaddr 3 ,
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.Xr gethostbyname 3 ,
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2000-01-25 14:52:10 +00:00
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.Xr inet_ntoa 3 ,
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.Xr realhostname_sa 3
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