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[linuxjm/LDP_man-pages.git] / draft / man3 / inet.3

.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\" and Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
.\"     <mtk.manpages@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\"     libc.info (from glibc distribution)
.\" Modified Sat Jul 24 19:12:00 1993 by Rik Faith <faith@cs.unc.edu>
.\" Modified Sun Sep  3 20:29:36 1995 by Jim Van Zandt <jrv@vanzandt.mv.com>
.\" Changed network into host byte order (for inet_network),
.\"     Andreas Jaeger <aj@arthur.rhein-neckar.de>, 980130.
.\" 2008-06-19, mtk
.\"     Describe the various address forms supported by inet_aton().
.\"     Clarify discussion of inet_lnaof(), inet_netof(), and inet_makeaddr().
.\"     Add discussion of Classful Addressing, noting that it is obsolete.
.\"     Added an EXAMPLE program.
.\"
.\" Japanese Version Copyright (c) 1998 Ueyama Rui
.\"         all rights reserved.
.\" Translated 1998-05-23, Ueyama Rui <rui@linux.or.jp>
.\" Updated & Modefied 1999-02-26, Shouichi Saito
.\" Updated 1999-12-26, Kentaro Shirakata <argrath@ub32.org>
.\" Updated 2005-10-04, Kentaro Shirakata <argrath@ub32.org>
.\" Updated 2007-05-01, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>, LDP v2.46
.\" Updated 2008-08-13, Akihiro MOTOKI, LDP v3.05
.\"
.\"WORD:        numbers-and-dots notation       ¿ôÃͤȥɥåȤˤè¤ëµ­Ë¡
.\"WORD:        dotted-decimal notation ¥É¥Ã¥È¶èÀÚ¤ê¤Î 10 ¿Ê¿ôµ­Ë¡
.\"WORD:        feature test macro      µ¡Ç½¸¡ºº¥Þ¥¯¥í
.\"
.TH INET 3  2008-06-19 "GNU" "Linux Programmer's Manual"
.\"O .SH NAME
.SH ̾Á°
.\"O inet_aton, inet_addr, inet_network, inet_ntoa, inet_makeaddr, inet_lnaof,
.\"O inet_netof \- Internet address manipulation routines
inet_aton, inet_addr, inet_network, inet_ntoa, inet_makeaddr, inet_lnaof,
inet_netof \- ¥¤¥ó¥¿¡¼¥Í¥Ã¥È¥¢¥É¥ì¥¹Áàºî¥ë¡¼¥Á¥ó
.\"O .SH SYNOPSIS
.SH ½ñ¼°
.nf
.B #include <sys/socket.h>
.B #include <netinet/in.h>
.B #include <arpa/inet.h>
.sp
.BI "int inet_aton(const char *" cp ", struct in_addr *" inp );
.sp
.BI "in_addr_t inet_addr(const char *" cp );
.sp
.BI "in_addr_t inet_network(const char *" cp );
.sp
.BI "char *inet_ntoa(struct in_addr " in );
.sp
.BI "struct in_addr inet_makeaddr(int " net ", int " host );
.sp
.BI "in_addr_t inet_lnaof(struct in_addr " in );
.sp
.BI "in_addr_t inet_netof(struct in_addr " in );
.fi
.sp
.in -4n
.\"O Feature Test Macro Requirements for glibc (see
.\"O .BR feature_test_macros (7)):
glibc ¸þ¤±¤Îµ¡Ç½¸¡ºº¥Þ¥¯¥í¤ÎÍ×·ï
.RB ( feature_test_macros (7)
»²¾È):
.in
.sp
.BR inet_aton (),
.BR inet_ntoa ():
_BSD_SOURCE || _SVID_SOURCE
.\"O .SH DESCRIPTION
.SH ÀâÌÀ
.\"O .BR inet_aton ()
.\"O converts the Internet host address \fIcp\fP from the
.\"O IPv4 numbers-and-dots notation into binary form (in network byte order)
.\"O and stores it in the structure that \fIinp\fP points to.
.\"O .BR inet_aton ()
.\"O returns nonzero if the address is valid, zero if not.
.\"O The address supplied in
.\"O .I cp
.\"O can have one of the following forms:
.BR inet_aton ()
¤Ï¡¢¥¤¥ó¥¿¡¼¥Í¥Ã¥È¥Û¥¹¥È¤Î¥¢¥É¥ì¥¹ \fIcp\fP ¤ò¡¢
IPv4 ¤Î¿ôÃͤȥɥåȤˤè¤ëɽµ­¤«¤é (¥Í¥Ã¥È¥ï¡¼¥¯¥Ð¥¤¥È¥ª¡¼¥À¤Î) ¥Ð¥¤¥Ê¥êÃͤØ
ÊÑ´¹¤·¡¢ÊÑ´¹·ë²Ì¤ò \fIinp\fP ¤¬»Ø¤·¤Æ¤¤¤ë¹½Â¤ÂΤ˳ÊǼ¤¹¤ë¡£
¥¢¥É¥ì¥¹¤¬Í­¸ú¤Ê¾ì¹ç 0 °Ê³°¤òÊÖ¤·¡¢¤½¤¦¤Ç¤Ê¤¤¾ì¹ç¤Ï 0 ¤òÊÖ¤¹¡£
.I cp
¤ÇÅϤ¹¥¢¥É¥ì¥¹¤È¤·¤Æ¡¢°Ê²¼¤Î·Á¼°¤òÍѤ¤¤ë¤³¤È¤¬¤Ç¤­¤ë¡£
.TP 10
.I a.b.c.d
.\"O Each of the four numeric parts specifies a byte of the address;
.\"O the bytes are assigned in left-to-right order to produce the binary address.
4 ¤Ä¤Î¿ô»ú¤Î¤½¤ì¤¾¤ì¤Ï¥¢¥É¥ì¥¹¤Î³Æ¥Ð¥¤¥È¤ò¼¨¤¹¡£
¤³¤ì¤é¤Î¥Ð¥¤¥È¤Ïº¸¤«¤é±¦¤Î½ç½ø¤Ç¥Ð¥¤¥Ê¥ê¥¢¥É¥ì¥¹¤Ë³ä¤êÅö¤Æ¤é¤ì¤ë¡£
.TP
.I a.b.c
.\"O Parts
.\"O .I a
.\"O and
.\"O .I b
.\"O specify the first two bytes of the binary address.
.\"O Part
.\"O .I c
.\"O is interpreted as a 16-bit value that defines the rightmost two bytes
.\"O of the binary address.
.\"O This notation is suitable for specifying (outmoded) Class B
.\"O network addresses.
.I a
¤È
.I b
¤Ï¥Ð¥¤¥Ê¥ê¥¢¥É¥ì¥¹¤ÎºÇ½é¤Î 2 ¥Ð¥¤¥È¤ò¼¨¤¹¡£
.I c
¤Ï 16 ¥Ó¥Ã¥ÈÃͤȲò¼á¤µ¤ì¡¢¥Ð¥¤¥Ê¥ê¥¢¥É¥ì¥¹¤Î±¦Â¦¤Î 2 ¥Ð¥¤¥È¤òɽ¤¹¡£
¤³¤Îɽµ­¤Ï¡¢(²áµî¤Î¤â¤Î¤È¤Ê¤Ã¤¿) ¥¯¥é¥¹ B ¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤ò
»ØÄꤹ¤ë¤Î¤ËŬ¤·¤Æ¤¤¤ë¡£
.TP
.I a.b
.\"O Part
.\"O .I a
.\"O specifies the first byte of the binary address.
.\"O Part
.\"O .I b
.\"O is interpreted as a 24-bit value that defines the rightmost three bytes
.\"O of the binary address.
.\"O This notation is suitable for specifying (outmoded) Class C
.\"O network addresses.
.I a
¤Ï¥Ð¥¤¥Ê¥ê¥¢¥É¥ì¥¹¤ÎºÇ½é¤Î¥Ð¥¤¥È¤ò¼¨¤¹¡£
.I b
¤Ï 24 ¥Ó¥Ã¥ÈÃͤȲò¼á¤µ¤ì¡¢¥Ð¥¤¥Ê¥ê¥¢¥É¥ì¥¹¤Î±¦Â¦¤Î 3 ¥Ð¥¤¥È¤òɽ¤¹¡£
¤³¤Îɽµ­¤Ï¡¢(²áµî¤Î¤â¤Î¤È¤Ê¤Ã¤¿) ¥¯¥é¥¹ C ¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤ò
»ØÄꤹ¤ë¤Î¤ËŬ¤·¤Æ¤¤¤ë¡£
.TP
.I a
.\"O The value
.\"O .I a
.\"O is interpreted as a 32-bit value that is stored directly
.\"O into the binary address without any byte rearrangement.
ÃÍ
.I a
¤Ï 32 ¥Ó¥Ã¥ÈÃͤȲò¼á¤µ¤ì¡¢¥Ð¥¤¥È¤ÎºÆÇÛÃ֤ϹԤï¤ì¤º¡¢
¤½¤Î¤Þ¤Þ¥Ð¥¤¥Ê¥ê¥¢¥É¥ì¥¹¤È¤·¤Æ³ÊǼ¤µ¤ì¤ë¡£
.PP
.\"O In all of the above forms,
.\"O components of the dotted address can be specified in decimal,
.\"O octal (with a leading
.\"O .IR 0 ),
.\"O or hexadecimal, with a leading
.\"O .IR 0X ).
.\"O Addresses in any of these forms are collectively termed
.\"O .IR "IPV4 numbers-and-dots notation" .
.\"O The form that uses exactly four decimal numbers is referred to as
.\"O .IR "IPv4 dotted-decimal notation"
.\"O (or sometimes:
.\"O .IR "IPv4 dotted-quad notation" ).
¾åµ­¤ÎÁ´¤Æ¤Î·Á¼°¤Ç¡¢¥É¥Ã¥È¶èÀÚ¤ê¤Î¥¢¥É¥ì¥¹¤Î³ÆÍ×ÁǤϡ¢10 ¿Ê¿ô¡¢
8 ¿Ê¿ô (ÀèƬ¤Ë
.I 0
¤òÉÕ¤±¤ë)¡¢
16 ¿Ê¿ô (ÀèƬ¤Ë
.I 0X
¤òÉÕ¤±¤ë) ¤Ç»ØÄê¤Ç¤­¤ë¡£
¤³¤ì¤é¤Î·Á¼°¤Î¥¢¥É¥ì¥¹¤ò¤Þ¤È¤á¤Æ
.I "IPv4 ¤Î¿ôÃͤȥɥåȤˤè¤ëɽµ­ (IPv4 numbers-and-dots notation)"
¤È¸Æ¤Ö¡£
¤Þ¤¿¡¢10 ¿Ê¿ô 4 ¤Ä¤À¤±¤ò»È¤Ã¤¿·Á¼°¤ò
.I "IPv4 ¤Î¥É¥Ã¥È¶èÀÚ¤ê¤Î 10 ¿Ê¿ôɽµ­ (IPv4 dotted-decimal notation)"
¤È¸Æ¤Ö
.RI ( "IPv4 ¤Î¥É¥Ã¥È¶èÀÚ¤ê 4 ʬ³äɽµ­ (IPv4 dotted-decimal notation)"
¤È¸Æ¤Ö¤³¤È¤â¤¢¤ë)¡£
.PP
.\"O The
.\"O .BR inet_addr ()
.\"O function converts the Internet host address
.\"O \fIcp\fP from IPv4 numbers-and-dots notation into binary data in network
.\"O byte order.
.\"O If the input is invalid,
.\"O .B INADDR_NONE
.\"O (usually \-1) is returned.
.\"O Use of this function is problematic because \-1 is a valid address
.\"O (255.255.255.255).
.\"O Avoid its use in favor of
.\"O .BR inet_aton (),
.\"O .BR inet_pton (3),
.\"O or
.\"O .BR getaddrinfo (3)
.\"O which provide a cleaner way to indicate error return.
.BR inet_addr ()
´Ø¿ô¤Ï¡¢¥¤¥ó¥¿¡¼¥Í¥Ã¥È¥Û¥¹¥È¤Î¥¢¥É¥ì¥¹ \fIcp\fP ¤ò¡¢
IPv4 ¤Î¿ôÃͤȥɥåȤˤè¤ëɽµ­¤«¤é¥Í¥Ã¥È¥ï¡¼¥¯¥Ð¥¤¥È¥ª¡¼¥À¤Ç¤Î
¥Ð¥¤¥Ê¥êÃͤØÊÑ´¹¤·¤ÆÊÖ¤¹¡£
ÆþÎϤ¬ÉÔÀµ¤Ê¾ì¹ç¡¢
.B INADDR_NONE
(ÉáÄÌ¤Ï \-1) ¤òÊÖ¤¹¡£
\-1 ¤ÏÍ­¸ú¤Ê¥¢¥É¥ì¥¹ (255.255.255.255) ¤Ê¤Î¤Ç¡¢¤³¤Î´Ø¿ô¤ò»È¤¦¤È
ÌäÂê¤Ë¤Ê¤ë¤«¤â¤·¤ì¤Ê¤¤¡£
¤³¤Î´Ø¿ô¤ò»È¤¦¤Î¤ÏÈò¤±¡¢Âå¤ï¤ê¤Ë
.BR inet_aton (),
.BR inet_pton (3),
.BR getaddrinfo (3)
¤ò»È¤¦¤Î¤¬¤è¤¤¡£
¤³¤ì¤é¤Î´Ø¿ô¤ÎÊý¤¬¡¢¥¨¥é¡¼¤ÎÄÌÃΤ¬¤è¤ê¤­¤ì¤¤¤ÊÊýË¡¤Ç¹Ô¤ï¤ì¤ë¡£
.PP
.\"O The
.\"O .BR inet_network ()
.\"O function converts
.\"O .IR cp ,
.\"O a string in IPv4 numbers-and-dots notation,
.\"O into a number in host byte order suitable for use as an
.\"O Internet network address.
.\"O On success, the converted address is returned.
.\"O If the input is invalid, \-1 is returned.
.BR inet_network ()
´Ø¿ô¤Ï¡¢
IPv4 ¤Î¿ôÃͤȥɥåȤˤè¤ëɽµ­¤Îʸ»úÎó \fIcp\fP ¤ò¡¢
¥¤¥ó¥¿¡¼¥Í¥Ã¥È¥¢¥É¥ì¥¹¤È¤·¤Æ¤Î»ÈÍѤËŬ¤·¤¿
¥Û¥¹¥È¥Ð¥¤¥È¥ª¡¼¥À¤Î¿ôÃͤËÊÑ´¹¤¹¤ë¡£
À®¸ù¤¹¤ë¤È¡¢ÊÑ´¹¤µ¤ì¤¿¥¢¥É¥ì¥¹¤òÊÖ¤¹¡£
ÆþÎϤ¬ÉÔÀµ¤Ê¾ì¹ç¤Ï \-1 ¤òÊÖ¤¹¡£
.PP
.\"O The
.\"O .BR inet_ntoa ()
.\"O function converts the Internet host address
.\"O \fIin\fP, given in network byte order, to a string in IPv4
.\"O dotted-decimal notation.
.\"O The string is returned in a statically
.\"O allocated buffer, which subsequent calls will overwrite.
.BR inet_ntoa ()
´Ø¿ô¤Ï¡¢¥Í¥Ã¥È¥ï¡¼¥¯¥Ð¥¤¥È¥ª¡¼¥À¤ÇÅϤµ¤ì¤¿¥¤¥ó¥¿¡¼¥Í¥Ã¥È¥Û¥¹¥È¥¢¥É¥ì¥¹
\fIin\fP ¤ò¡¢ IPv4 ¤Î¥É¥Ã¥È¶èÀÚ¤ê¤Î 10 ¿Ê¿ôɽµ­¤Îʸ»úÎó¤ËÊÑ´¹¤¹¤ë¡£
ʸ»úÎó¤ÏÀÅŪ¤Ë³äÅö¤Æ¤é¤ì¤¿¥Ð¥Ã¥Õ¥¡¤Ë³ÊǼ¤µ¤ì¤ÆÊÖ¤µ¤ì¤ë¤Î¤Ç¡¢
¤³¤Î¸å¤Ç¤³¤Î´Ø¿ô¤òºÆÅٸƤӽФ¹¤Èʸ»úÎó¤Ï¾å½ñ¤­¤µ¤ì¤ë¡£
.PP
.\"O The
.\"O .BR inet_lnaof ()
.\"O function returns the local network address part
.\"O of the Internet address \fIin\fP.
.\"O The returned value is in host byte order.
.BR inet_lnaof ()
´Ø¿ô¤Ï¡¢¥¤¥ó¥¿¡¼¥Í¥Ã¥È¥¢¥É¥ì¥¹ \fIin\fP ¤Î¥í¡¼¥«¥ë¥Í¥Ã¥È¥ï¡¼¥¯Éôʬ¤òÊÖ¤¹¡£
¤³¤ÎÊÖ¤êÃͤϥۥ¹¥È¥Ð¥¤¥È¥ª¡¼¥À¤Ç¤¢¤ë¡£
.PP
.\"O The
.\"O .BR inet_netof ()
.\"O function returns the network number part of
.\"O the Internet address \fIin\fP.
.\"O The returned value is in host byte order.
.BR inet_netof ()
´Ø¿ô¤Ï¡¢¥¤¥ó¥¿¡¼¥Í¥Ã¥È¥¢¥É¥ì¥¹ \fIin\fP ¤Î¥Í¥Ã¥È¥ï¡¼¥¯Éôʬ¤òÊÖ¤¹¡£
¤³¤ÎÊÖ¤êÃͤϥۥ¹¥È¥Ð¥¤¥È¥ª¡¼¥À¤Ç¤¢¤ë¡£
.PP
.\"O The
.\"O .BR inet_makeaddr ()
.\"O function is the converse of
.\"O .BR inet_netof ()
.\"O and
.\"O .BR inet_lnaof ().
.\"O It returns an Internet host address in network byte order,
.\"O created by combining the network number \fInet\fP
.\"O with the local address \fIhost\fP, both in
.\"O host byte order.
.BR inet_makeaddr ()
´Ø¿ô¤Ï
.BR inet_netof ()
¤È
.BR inet_lnaof ()
¤ÎµÕ¤Îµ¡Ç½¤ò»ý¤Ä¡£
¥Í¥Ã¥È¥ï¡¼¥¯ÈÖ¹æ \fInet\fP ¤È¡¢¥í¡¼¥«¥ë¥¢¥É¥ì¥¹ \fIhost\fP ¤ò
ÁȤ߹ç¤ï¤»¤ÆÀ¸À®¤·¤¿¡¢¥¤¥ó¥¿¡¼¥Í¥Ã¥È¥Û¥¹¥È¥¢¥É¥ì¥¹¤ò
¥Í¥Ã¥È¥ï¡¼¥¯¥Ð¥¤¥È¥ª¡¼¥À¤ÇÊÖ¤¹¡£
\fIhost\fP, \fInet\fP ¤Ï¤È¤â¤Ë¥Û¥¹¥È¥Ð¥¤¥È¥ª¡¼¥À¤Ç¤¢¤ë¡£
.PP
.\"O The structure \fIin_addr\fP as used in
.\"O .BR inet_ntoa (),
.\"O .BR inet_makeaddr (),
.\"O .BR inet_lnaof ()
.\"O and
.\"O .BR inet_netof ()
.\"O is defined in
.\"O .I <fnetinet/in.h>
.\"O as:
.BR inet_ntoa (),
.BR inet_makeaddr (),
.BR inet_lnaof (),
.BR inet_netof ()
¤Ç»ÈÍѤ¹¤ë¹½Â¤ÂÎ \fIin_addr\fP ¤Ï
.I <netinet/in.h>
¤Ç¼¡¤Î¤è¤¦¤ËÄêµÁ¤µ¤ì¤Æ¤¤¤ë:
.sp
.in +4n
.nf
typedef uint32_t in_addr_t;

struct in_addr {
    in_addr_t s_addr;
};
.fi
.in
.\"O .SH "CONFORMING TO"
.SH ½àµò
4.3BSD.
.\"O .BR inet_addr ()
.\"O and
.\"O .BR inet_ntoa ()
.\"O are specified in POSIX.1-2001.
.BR inet_addr (),
.BR inet_ntoa ()
¤Ï POSIX.1-2001 ¤Çµ¬Äꤵ¤ì¤Æ¤¤¤ë¡£
.\"O .BR inet_aton ()
.\"O is not specified in POSIX.1-2001, but is available on most systems.
.BR inet_aton ()
¤Ï POSIX.1-2001 ¤Çµ¬Äꤵ¤ì¤Æ¤¤¤Ê¤¤¤¬¡¢¤Û¤È¤ó¤É¤Î¥·¥¹¥Æ¥à¤ÇÍøÍѲÄǽ¤Ç¤¢¤ë¡£
.\"O .SH NOTES
.SH Ãí°Õ
.\"O On the i386 the host byte order is Least Significant Byte
.\"O first (little endian), whereas the network byte order, as used on the
.\"O Internet, is Most Significant Byte first (big endian).
i386 ¤Ç¤Ï¥Û¥¹¥È¥Ð¥¤¥È¥ª¡¼¥À¤Ï Least Significant Byte (LSB) first
(¥ê¥È¥ë¥¨¥ó¥Ç¥£¥¢¥ó) ¤À¤¬¡¢
¥¤¥ó¥¿¡¼¥Í¥Ã¥È¤Ç»È¤ï¤ì¤ë¥Í¥Ã¥È¥ï¡¼¥¯¥Ð¥¤¥È¥ª¡¼¥À¤Ï
Most Significant Byte (MSB) first (¥Ó¥Ã¥°¥¨¥ó¥Ç¥£¥¢¥ó)
¤Ç¤¢¤ëÅÀ¤ËÃí°Õ¤¹¤ë¤³¤È¡£

.\"O .BR inet_lnaof (),
.\"O .BR inet_netof (),
.\"O and
.\"O .BR inet_makeaddr ()
.\"O are legacy functions that assume they are dealing with
.\"O .IR "classful network addresses" .
.\"O Classful networking divides IPv4 network addresses into host and network
.\"O components at byte boundaries, as follows:
.BR inet_lnaof (),
.BR inet_netof (),
.BR inet_makeaddr ()
¤Ï²áµî¤Î̾»Ä¤Ç¤¢¤ê¡¢ÅϤµ¤ì¤¿¥¢¥É¥ì¥¹¤¬
.I "¥¯¥é¥¹¥Õ¥ë¡¦¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹ (classful network addresses)"
¤Ç¤¢¤ë¤È²¾Äꤷ¤Æ½èÍý¤ò¹Ô¤¦¡£
¥¯¥é¥¹¥Õ¥ë¡¦¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤Ç¤Ï¡¢°Ê²¼¤Ë¤¢¤ë¤è¤¦¤Ë¡¢
IPv4 ¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤ò¥Ð¥¤¥È¶­³¦¤Ç¥Í¥Ã¥È¥ï¡¼¥¯Éô¤È¥Û¥¹¥ÈÉô¤Ëʬ³ä¤¹¤ë¡£
.TP 10
Class A
.\"O This address type is indicated by the value 0 in the
.\"O most significant bit of the (network byte ordered) address.
.\"O The network address is contained in the most significant byte,
.\"O and the host address occupies the remaining three bytes.
(¥Í¥Ã¥È¥ï¡¼¥¯¥Ð¥¤¥È¥ª¡¼¥À¤Î) ¥¢¥É¥ì¥¹¤ÎºÇ¾å°Ì¥Ó¥Ã¥È¤¬ 0 ¤Î¾ì¹ç¡¢
¤³¤Î¥¢¥É¥ì¥¹¼ïÊ̤Ȥʤ롣¤³¤Î¥¢¥É¥ì¥¹¼ïÊ̤Ǥϡ¢
ºÇ¾å°Ì¥Ð¥¤¥È¤¬¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤òɽ¤·¡¢
»Ä¤ê¤Î 3 ¥Ð¥¤¥È¤¬¥Û¥¹¥È¥¢¥É¥ì¥¹¤òɽ¤¹¡£
.TP
Class B
.\"O This address type is indicated by the binary value 10 in the
.\"O most significant two bits of the address.
.\"O The network address is contained in the two most significant bytes,
.\"O and the host address occupies the remaining two bytes.
(¥Í¥Ã¥È¥ï¡¼¥¯¥Ð¥¤¥È¥ª¡¼¥À¤Î) ¥¢¥É¥ì¥¹¤Î¾å°Ì¦ 2 ¥Ó¥Ã¥È¤¬¥Ð¥¤¥Ê¥êÃͤÇ
10 ¤Î¾ì¹ç¡¢¤³¤Î¥¢¥É¥ì¥¹¼ïÊ̤Ȥʤ롣¤³¤Î¥¢¥É¥ì¥¹¼ïÊ̤Ǥϡ¢
¾å°Ì 2 ¥Ð¥¤¥È¤¬¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤òɽ¤·¡¢
»Ä¤ê¤Î 2 ¥Ð¥¤¥È¤¬¥Û¥¹¥È¥¢¥É¥ì¥¹¤òɽ¤¹¡£
.TP
Class C
.\"O This address type is indicated by the binary value 110 in the
.\"O most significant three bits of the address.
.\"O The network address is contained in the three most significant bytes,
.\"O and the host address occupies the remaining byte.
(¥Í¥Ã¥È¥ï¡¼¥¯¥Ð¥¤¥È¥ª¡¼¥À¤Î) ¥¢¥É¥ì¥¹¤Î¾å°Ì¦ 3 ¥Ó¥Ã¥È¤¬¥Ð¥¤¥Ê¥êÃͤÇ
110 ¤Î¾ì¹ç¡¢¤³¤Î¥¢¥É¥ì¥¹¼ïÊ̤Ȥʤ롣¤³¤Î¥¢¥É¥ì¥¹¼ïÊ̤Ǥϡ¢
¾å°Ì 3 ¥Ð¥¤¥È¤¬¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤òɽ¤·¡¢
»Ä¤ê¤Î 1 ¥Ð¥¤¥È¤¬¥Û¥¹¥È¥¢¥É¥ì¥¹¤òɽ¤¹¡£
.PP
.\"O Classful network addresses are now obsolete,
.\"O having been superseded by Classless Inter-Domain Routing (CIDR),
.\"O which divides addresses into network and host components at
.\"O arbitrary bit (rather than byte) boundaries.
¥¯¥é¥¹¥Õ¥ë¡¦¥Í¥Ã¥È¥ï¡¼¥¯¥¢¥É¥ì¥¹¤Ï¸½ºß¤Ç¤ÏÇѻߤµ¤ì¡¢
¥¯¥é¥¹¥ì¥¹¡¦¥É¥á¥¤¥ó´Ö¥ë¡¼¥Á¥ó (CIDR) ¤Ë¼è¤Ã¤ÆÂå¤ï¤é¤ì¤¿¡£
CIDR ¤Ç¤Ï¡¢¥¢¥É¥ì¥¹¤òǤ°Õ¤Î¥Ó¥Ã¥È¶­³¦ (¥Ð¥¤¥È¶­³¦¤Ç¤Ï¤Ê¤¤) ¤Ç
¥Í¥Ã¥È¥ï¡¼¥¯Éô¤È¥Û¥¹¥ÈÉô¤Ëʬ³ä¤¹¤ë¡£
.\"O .SH EXAMPLE
.SH Îã
.\"O An example of the use of
.\"O .BR inet_aton ()
.\"O and
.\"O .BR inet_ntoa ()
.\"O is shown below.
.\"O Here are some example runs:
°Ê²¼¤Ï
.BR inet_aton ()
¤È
.BR inet_ntoa ()
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.in +4n
.nf

.RB "$" " ./a.out 226.000.000.037" "      # Last byte is in octal"
226.0.0.31
.RB "$" " ./a.out 0x7f.1         " "      # First byte is in hex"
127.0.0.1
.fi
.in
.\"O .SS Program source
.SS ¥×¥í¥°¥é¥à¤Î¥½¡¼¥¹
\&
.nf
#define _BSD_SOURCE
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char *argv[])
{
    struct in_addr addr;

    if (argc != 2) {
        fprintf(stderr, "%s <dotted\-address>\\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    if (inet_aton(argv[1], &addr) == 0) {
        perror("inet_aton");
        exit(EXIT_FAILURE);
    }

    printf("%s\\n", inet_ntoa(addr));
    exit(EXIT_SUCCESS);
}
.fi
.\"O .SH "SEE ALSO"
.SH ´ØÏ¢¹àÌÜ
.BR byteorder (3),
.BR getaddrinfo (3),
.BR gethostbyname (3),
.BR getnameinfo (3),
.BR getnetent (3),
.BR inet_ntop (3),
.BR inet_pton (3),
.BR hosts (5),
.BR networks (5)