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.Os 29.Dt REALHOSTNAME 3 30.Sh NAME 31.Nm realhostname 32.Nd "convert an IP number to the real host name" 33.Sh SYNOPSIS 34.Fd #include <sys/types.h> 35.Fd #include <netinet/in.h> 36.Fd #include <libutil.h> 37.Ft int 38.Fn realhostname "char *host" "size_t hsize" "const struct in_addr *ip" 39.Pp 40Link with 41.Va -lutil 42on the 43.Xr cc 1 44command line. 45.Sh DESCRIPTION 46The function 47.Fn realhostname 48converts 49.Ar ip 50to the corresponding host name. This is done by resolving 51.Ar ip 52to a host name and then ensuring that the host name resolves 53back to 54.Ar ip . 55.Pp 56.Ar host 57must point to a buffer of at least 58.Ar hsize 59bytes, and will always be written to by this function. 60.Pp 61If the name resolution doesn't work both ways or if the host name is longer 62than 63.Ar hsize 64bytes, 65.Xr inet_ntoa 3 66is used to convert 67.Ar ip 68to an ASCII form. 69.Pp 70If the string written to 71.Ar host 72is 73.Ar hsize 74bytes long, 75.Ar host 76will not be NUL terminated. 77.Sh RETURN VALUES 78.Fn realhostname 79will return one of the following constants which are defined in 80.Pa libutil.h : 81.Pp 82.Bl -tag -width XXX -offset XXX 83.It Li HOSTNAME_FOUND 84A valid host name was found. 85.It Li HOSTNAME_INCORRECTNAME 86A host name was found, but it did not resolve back to the passed 87.Ar ip . 88.Ar host 89now contains the numeric value of 90.Ar ip . 91.It Li HOSTNAME_INVALIDADDR 92.Ar ip 93could not be resolved. 94.Ar host 95now contains the numeric value of 96.Ar ip . 97.It Li HOSTNAME_INVALIDNAME 98A host name was found, but it could not be resolved back to any ip number. 99.Ar host 100now contains the numeric value of 101.Ar ip . 102.El 103.Sh SEE ALSO 104.Xr gethostbyaddr 3 , 105.Xr gethostbyname 3 , 106.Xr inet_ntoa 3 107