1.\" Copyright (c) 1999 Brian Somers <brian@Awfulhak.org> 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd April 6, 1999 28.Dt REALHOSTNAME 3 29.Os 30.Sh NAME 31.Nm realhostname 32.Nd "convert an IP number to the real host name" 33.Sh LIBRARY 34.Lb libutil 35.Sh SYNOPSIS 36.In sys/types.h 37.In netinet/in.h 38.In libutil.h 39.Ft int 40.Fn realhostname "char *host" "size_t hsize" "const struct in_addr *ip" 41.Sh DESCRIPTION 42The function 43.Fn realhostname 44converts 45.Ar ip 46to the corresponding host name. 47This is done by resolving 48.Ar ip 49to a host name and then ensuring that the host name resolves 50back to 51.Ar ip . 52.Pp 53.Ar host 54must point to a buffer of at least 55.Ar hsize 56bytes, and will always be written to by this function. 57.Pp 58If the name resolution does not work both ways or if the host name is longer 59than 60.Ar hsize 61bytes, 62.Xr inet_ntoa 3 63is used to convert 64.Ar ip 65to an ASCII form. 66.Pp 67If the string written to 68.Ar host 69is 70.Ar hsize 71bytes long, 72.Ar host 73will not be NUL terminated. 74.Sh RETURN VALUES 75The 76.Fn realhostname 77function will return one of the following constants which are defined in 78.In libutil.h : 79.Bl -tag -width XXX -offset XXX 80.It Li HOSTNAME_FOUND 81A valid host name was found. 82.It Li HOSTNAME_INCORRECTNAME 83A host name was found, but it did not resolve back to the passed 84.Ar ip . 85.Ar host 86now contains the numeric value of 87.Ar ip . 88.It Li HOSTNAME_INVALIDADDR 89.Ar ip 90could not be resolved. 91.Ar host 92now contains the numeric value of 93.Ar ip . 94.It Li HOSTNAME_INVALIDNAME 95A host name was found, but it could not be resolved back to any ip number. 96.Ar host 97now contains the numeric value of 98.Ar ip . 99.El 100.Sh SEE ALSO 101.Xr gethostbyaddr 3 , 102.Xr gethostbyname 3 , 103.Xr inet_ntoa 3 , 104.Xr realhostname_sa 3 105