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 libutil.h 37.Ft int 38.Fn realhostname "char *host" "size_t hsize" "const struct in_addr *ip" 39.Sh DESCRIPTION 40The function 41.Fn realhostname 42converts 43.Ar ip 44to the corresponding host name. 45This is done by resolving 46.Ar ip 47to a host name and then ensuring that the host name resolves 48back to 49.Ar ip . 50.Pp 51.Ar host 52must point to a buffer of at least 53.Ar hsize 54bytes, and will always be written to by this function. 55.Pp 56If the name resolution does not work both ways or if the host name is longer 57than 58.Ar hsize 59bytes, 60.Xr inet_ntoa 3 61is used to convert 62.Ar ip 63to an ASCII form. 64.Pp 65If the string written to 66.Ar host 67is 68.Ar hsize 69bytes long, 70.Ar host 71will not be NUL terminated. 72.Sh RETURN VALUES 73The 74.Fn realhostname 75function will return one of the following constants which are defined in 76.In libutil.h : 77.Bl -tag -width XXX -offset XXX 78.It Li HOSTNAME_FOUND 79A valid host name was found. 80.It Li HOSTNAME_INCORRECTNAME 81A host name was found, but it did not resolve back to the passed 82.Ar ip . 83.Ar host 84now contains the numeric value of 85.Ar ip . 86.It Li HOSTNAME_INVALIDADDR 87.Ar ip 88could not be resolved. 89.Ar host 90now contains the numeric value of 91.Ar ip . 92.It Li HOSTNAME_INVALIDNAME 93A host name was found, but it could not be resolved back to any ip number. 94.Ar host 95now contains the numeric value of 96.Ar ip . 97.El 98.Sh SEE ALSO 99.Xr gethostbyaddr 3 , 100.Xr gethostbyname 3 , 101.Xr inet_ntoa 3 , 102.Xr realhostname_sa 3 103.Sh HISTORY 104The 105.Fn realhostname 106function first appeared in 107.Fx 3.2 . 108