213 lines
6.6 KiB
Groff
213 lines
6.6 KiB
Groff
.\" $OpenBSD: inet_ntop.3,v 1.6 2022/09/11 06:38:10 jmc Exp $
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.\" $NetBSD: inet.3,v 1.7 1997/06/18 02:25:24 lukem Exp $
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.\"
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.\" Copyright (c) 1983, 1990, 1991, 1993
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.\" The Regents of the University of California. 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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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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.\" @(#)inet.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd $Mdocdate: September 11 2022 $
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.Dt INET_NTOP 3
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.Os
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.Sh NAME
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.Nm inet_ntop ,
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.Nm inet_pton
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.Nd convert Internet addresses between presentation and network formats
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.Sh SYNOPSIS
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.In sys/socket.h
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.In arpa/inet.h
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.Ft const char *
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.Fn inet_ntop "int af" "const void * restrict src" "char * restrict dst" "socklen_t size"
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.Ft int
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.Fn inet_pton "int af" "const char * restrict src" "void * restrict dst"
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.Sh DESCRIPTION
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The
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.Fn inet_pton
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function converts a presentation format address (that is, printable form
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as held in a character string) to network format (usually a
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.Vt struct in_addr
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or some other internal binary representation, in network byte order).
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It returns 1 if the address was valid for the specified address family;
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0 if the address wasn't parseable in the specified address family; or \-1
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if some system error occurred (in which case
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.Va errno
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will have been set).
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This function is presently valid for
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.Dv AF_INET
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and
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.Dv AF_INET6 .
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.Pp
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The function
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.Fn inet_ntop
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converts an address from network format to presentation format.
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It returns
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.Dv NULL
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if a system
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error occurs (in which case,
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.Va errno
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will have been set), or it returns a pointer to the destination string.
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.Pp
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All Internet addresses are returned in network
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order (bytes ordered from left to right).
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.Sh INTERNET ADDRESSES (IP VERSION 4)
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Values must be specified using the standard dot notation:
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.Bd -literal -offset indent
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a.b.c.d
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.Ed
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.Pp
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All four parts must be decimal numbers between 0 and 255, inclusive,
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and are assigned, from left to right,
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to the four bytes of an Internet address.
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Note that when an Internet address is viewed as a 32-bit integer
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quantity on a system that uses little-endian byte order
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(such as AMD64 or ARM processors)
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the bytes referred to above appear as
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.Dq Li d.c.b.a .
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That is, little-endian bytes are ordered from right to left.
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.Sh INTERNET ADDRESSES (IP VERSION 6)
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In order to support scoped IPv6 addresses,
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.Xr getaddrinfo 3
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and
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.Xr getnameinfo 3
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are recommended rather than the functions presented here.
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.Pp
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The presentation format of an IPv6 address is given in RFC 4291:
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.Pp
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There are three conventional forms for representing IPv6 addresses as
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text strings:
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.Bl -enum
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.It
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The preferred form is x:x:x:x:x:x:x:x, where the 'x's are the
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hexadecimal values of the eight 16-bit pieces of the address.
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Examples:
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.Bd -literal -offset indent
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FEDC:BA98:7654:3210:FEDC:BA98:7654:3210
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1080:0:0:0:8:800:200C:417A
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.Ed
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.Pp
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Note that it is not necessary to write the leading zeros in an
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individual field, but there must be at least one numeral in
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every field (except for the case described in 2.).
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.It
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Due to the method of allocating certain styles of IPv6
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addresses, it will be common for addresses to contain long
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strings of zero bits.
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In order to make writing addresses
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containing zero bits easier, a special syntax is available to
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compress the zeros.
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The use of
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.Dq \&:\&:
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indicates multiple groups
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of 16 bits of zeros.
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The
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.Dq \&:\&:
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can only appear once in an
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address.
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The
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.Dq \&:\&:
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can also be used to compress the leading and/or trailing zeros in an address.
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.Pp
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For example the following addresses:
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.Bd -literal -offset indent
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1080:0:0:0:8:800:200C:417A a unicast address
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FF01:0:0:0:0:0:0:43 a multicast address
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0:0:0:0:0:0:0:1 the loopback address
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0:0:0:0:0:0:0:0 the unspecified addresses
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.Ed
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.Pp
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may be represented as:
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.Bd -literal -offset indent
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1080::8:800:200C:417A a unicast address
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FF01::43 a multicast address
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::1 the loopback address
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:: the unspecified addresses
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.Ed
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.It
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An alternative form that is sometimes more convenient when
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dealing with a mixed environment of IPv4 and IPv6 nodes is
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x:x:x:x:x:x:d.d.d.d, where the 'x's are the hexadecimal values
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of the six high-order 16-bit pieces of the address, and the 'd's
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are the decimal values of the four low-order 8-bit pieces of the
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address (standard IPv4 representation).
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Examples:
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.Bd -literal -offset indent
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0:0:0:0:0:0:13.1.68.3
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0:0:0:0:0:FFFF:129.144.52.38
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.Ed
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.Pp
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or in compressed form:
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.Bd -literal -offset indent
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::13.1.68.3
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::FFFF:129.144.52.38
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.Ed
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.El
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.Sh SEE ALSO
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.Xr gethostbyname 3 ,
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.Xr inet_addr 3 ,
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.Xr inet_net_ntop 3 ,
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.Xr hosts 5
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.Sh STANDARDS
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The
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.Nm inet_ntop
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and
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.Nm inet_pton
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functions conform to the IETF IPv6 BSD API and address formatting
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specifications, as well as
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.St -p1003.1-2008 .
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.Sh HISTORY
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The
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.Nm inet_pton
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and
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.Nm inet_ntop
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functions appeared in BIND 4.9.4.
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.Sh CAVEATS
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Note that
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.Nm inet_pton
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does not accept 1-, 2-, or 3-part dotted addresses;
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all four parts must be specified and must be in decimal
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(and not octal or hexadecimal).
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This is a narrower input set than that accepted by
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.Nm inet_aton .
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.Pp
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.Rs
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.%A R. Gilligan
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.%A S. Thomson
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.%A J. Bound
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.%A J. McCann
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.%A W. Stevens
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.%D February 2003
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.%R RFC 3493
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.%T Basic Socket Interface Extensions for IPv6
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.Re
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.Pp
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.Rs
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.%A R. Hinden
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.%A S. Deering
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.%D February 2006
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.%R RFC 4291
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.%T IP Version 6 Addressing Architecture
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.Re
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