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.Dd April 6, 1999 26.Dt REALHOSTNAME 3 27.Os 28.Sh NAME 29.Nm realhostname 30.Nd "convert an IP number to the real host name" 31.Sh LIBRARY 32.Lb libutil 33.Sh SYNOPSIS 34.In libutil.h 35.Ft int 36.Fn realhostname "char *host" "size_t hsize" "const struct in_addr *ip" 37.Sh DESCRIPTION 38The function 39.Fn realhostname 40converts 41.Ar ip 42to the corresponding host name. 43This is done by resolving 44.Ar ip 45to a host name and then ensuring that the host name resolves 46back to 47.Ar ip . 48.Pp 49.Ar host 50must point to a buffer of at least 51.Ar hsize 52bytes, and will always be written to by this function. 53.Pp 54If the name resolution does not work both ways or if the host name is longer 55than 56.Ar hsize 57bytes, 58.Xr inet_ntoa 3 59is used to convert 60.Ar ip 61to an ASCII form. 62.Pp 63If the string written to 64.Ar host 65is 66.Ar hsize 67bytes long, 68.Ar host 69will not be NUL terminated. 70.Sh RETURN VALUES 71The 72.Fn realhostname 73function will return one of the following constants which are defined in 74.In libutil.h : 75.Bl -tag -width XXX -offset XXX 76.It Li HOSTNAME_FOUND 77A valid host name was found. 78.It Li HOSTNAME_INCORRECTNAME 79A host name was found, but it did not resolve back to the passed 80.Ar ip . 81.Ar host 82now contains the numeric value of 83.Ar ip . 84.It Li HOSTNAME_INVALIDADDR 85.Ar ip 86could not be resolved. 87.Ar host 88now contains the numeric value of 89.Ar ip . 90.It Li HOSTNAME_INVALIDNAME 91A host name was found, but it could not be resolved back to any ip number. 92.Ar host 93now contains the numeric value of 94.Ar ip . 95.El 96.Sh SEE ALSO 97.Xr gethostbyaddr 3 , 98.Xr gethostbyname 3 , 99.Xr inet_ntoa 3 , 100.Xr realhostname_sa 3 101.Sh HISTORY 102The 103.Fn realhostname 104function first appeared in 105.Fx 3.2 . 106