.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" 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.\" manual page may be incorrect or out-of-date.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
.\" Modified Sat May 22 18:43:54 1993, David Metcalfe
.\" Modified Sun Jul 25 10:42:30 1993, Rik Faith (faith@cs.unc.edu)
.\" Modified Sun Feb 16 13:23:10 1997, Andries Brouwer (aeb@cwi.nl)
.\" Modified Mon Dec 21 14:49:33 1998, Andries Brouwer (aeb@cwi.nl)
.\" Modified Sat Aug 12 18:11:32 2000, Andries Brouwer (aeb@cwi.nl)
.\" Modified Sat May 19 23:37:50 2001, Andries Brouwer (aeb@cwi.nl)
.\"
.\" Japanese Version Copyright (c) 1998-2000 NAKANO Takeo all rights reserved.
.\" Translated Thu Apr 30 1998 by NAKANO Takeo <nakano@apm.seikei.ac.jp>
.\" Modified Sun Dec 6 by NAKANO Takeo
.\" Updated & Modified Thu Oct 12 1999 by NAKANO Takeo
.\" Updated & Modified Sun Jul  1 11:51:26 JST 2001
.\"         by Yuichi SATO <ysato@h4.dion.ne.jp>
.\" Updated & Modified Thu Jan  3 15:22:14 JST 2002 by Yuichi SATO
.\"
.TH GETHOSTBYNAME 3  2000-08-12 "BSD" "Linux Programmer's Manual"
.SH ̾
gethostbyname, gethostbyaddr, sethostent, endhostent, herror, hstrerror \- ͥåȥΥۥȤΥȥ 
.SH 
.nf
.B #include <netdb.h>
.B extern int h_errno;
.sp
.BI "struct hostent *gethostbyname(const char *" name );
.sp
.B #include <sys/socket.h> "      " /* for AF_INET */
.BI "struct hostent *gethostbyaddr(const char *" addr ,
.BI "  int " len ", int " type );
.sp
.BI "void sethostent(int " stayopen );
.sp
.B void endhostent(void);
.sp
.BI "void herror(const char *" s );
.sp
.BI "const char *hstrerror(int " err );
.sp 2
/* GNU extensions */
.br
.BI "struct hostent *gethostbyname2(const char *" name ", int " af );
.sp
.BI "int gethostbyname_r (const char *" name ,
.BI "  struct hostent *" ret ", char *" buf ", size_t " buflen ,
.BI "  struct hostent **" result ", int *" h_errnop );
.sp
.BI "int gethostbyname2_r (const char *" name ", int " af,
.BI "  struct hostent *" ret ", char *" buf ", size_t " buflen ,
.BI "  struct hostent **" result ", int *" h_errnop );
.fi
.SH 
.B gethostbyname()
ؿͿ줿ۥ̾
.I name
б빽¤
.I hostent
֤
.I name
ϥۥ̾ɥåȶڤ IPv4 ɥ쥹ڤ (ɥ
ȶڤǤפ⤷ʤ) IPv6 ɥ쥹Τ줫Ǥ롣 IPv6 
ɥ쥹εҤˤĤƤ RFC 1884 򻲹ͤˤƤۤ
.I name
 IPv4  IPv6 Υɥ쥹äˤϡ
̾ (lookup) ϹԤʤ
.BR gethostbyname ()
ñ
.I name
򤽤Τޤ
.I hostent
¤Τ
.I h_name
եɤ˥ԡ

.I name

.I struct in_addr
ɽǡƱ¤Τ
.I h_addr_list[0]
եɤơι¤Τ֤
.I name
ɥåȤǽλƤơĴĶѿ
.B HOSTALIASES
ꤵƤϡޤ
.B HOSTALIASES
ǻꤵƤե뤫
.I name
Υȥ꤬ (եΥեޥåȤˤĤƤ
.BR hostname (7)
򻲾ȤΤ)
.I name
ɥåȤǽλƤʤиߤΥɥᥤȤοƥɥᥤ󤬸롣
.PP
.B gethostbyaddr()
ؿͿ줿ۥȥɥ쥹
.I addr
(Ĺ \fIlen\fP  \fItype\fP) б빽¤
.I hostent
֤Ѥ뤳ȤΤǤ륿פ
.B AF_INET
ΤߤǤ롣
.PP
.B sethostent()
ؿϡ͡ॵСؤ³ͼꤹ롣
.I stayopen
 (1) ʤС͡ॵСؤ䤤碌ˤϡ³줿 TCP 
ȤѤϢ³䤤碌δ֤³ݻ롣ʤХ͡ॵС
ؤ䤤碌 UDP ǡѤ롣
.PP
.B endhostent()
ؿϥ͡ॵСؤ䤤碌Ѥ TCP ³Ѥλ롣
.PP
.B herror()
ؿ (⤦Ť) ϸߤ
.I h_errno
б륨顼å stderr ˽Ϥ롣
.PP
.B hsterror()
ؿ (⤦Ť) ϥ顼ֹ (ŵŪˤ \fIh_errno\fP) 
˼ꡢб륨顼åʸ֤
.PP
.BR gethostbyname ()

.BR gethostbyaddr ()
ˤäƼ¹Ԥɥᥤ̾䤤碌Ǥϡ͡ॵС
.BR named (8)
.I /etc/hosts
Υǡԡ
Network Information Service (NIS ޤ YP)
Τ줫뤤Ϥ٤ƤѤ롣
.I /etc/host.conf

.I order
ԤƤ˰¸ (ܤ
.BR resolv+ (8)
򸫤)
ǥեȤǤϤޤ
.B named (8)
䤤碌
.I /etc/hosts
롣
.PP
.I hostent
¤Τ
.I <netdb.h>
ǰʲΤ褦Ƥ:
.sp
.RS
.nf
.ne 7
.ta 8n 16n 32n
struct hostent {
	char	*h_name;		/* official name of host */
	char	**h_aliases;		/* alias list */
	int	h_addrtype;		/* host address type */
	int	h_length;		/* length of address */
	char	**h_addr_list;		/* list of addresses */
}
#define h_addr	h_addr_list[0]		/* for backward compatibility */
.ta
.fi
.RE
.PP
.I hostent
¤ΤΥФϰʲ̤ꡣ
.TP
.I h_name
ۥȤ̾ (official name)
.TP
.I h_aliases
ۥȤ̾ʤ 0 ǽü롣
.TP
.I h_addrtype
ɥ쥹ΥסߤϤ٤
.B AF_INET
Ǥ롣
.TP
.I h_length
Хñ̤ɽɥ쥹Ĺ
.TP
.I h_addr_list
ۥȤΥͥåȥɥ쥹ͥåȥХȥɽ 
0 ǽü롣
.TP
.I h_addr
.I h_addr_list
κǽΥɥ쥹ȤθߴݤĤΤΤǤ롣
.SH ֤
.B gethostbyname()

.B gethostbyaddr()
ؿ
.I hostent
¤Τ֤顼ä NULL ݥ󥿤֤顼κݤˤ
.I h_errno
ѿ顼ֹݻ롣
.SH 顼
.I h_errno
ѿϰʲͤꤦ롣
.TP
.B HOST_NOT_FOUND
ꤷۥȤĤʤ
.TP
.B NO_ADDRESS " ޤ " NO_DATA
ꤷ̾ͭ IP ɥ쥹äƤʤ
.TP
.B NO_RECOVERY
͡ॵСǽʥ顼ä
.TP
.B TRY_AGAIN
aurhoritative ʥ͡ॵСǰŪʥ顼ä֤򤪤
⤦ٻȡ
.SH ե
.TP
.I /etc/host.conf
̾ե
.TP
.I /etc/hosts
ۥȤΥǡ١ե
.SH 
BSD 4.3.
.SH 
SUS-v2 ϥХ¿
.B gethostbyaddr()

.I len
ѥ᡼
.I size_t
ȤƤ롣
(ϸǡ
.I size_t
ǤϤʤ
.I int
ǤʤФʤʤ
POSIX 1003.1-2001 ǤϤ
.I socklen_t
ȤƤ뤬 OK)
.LP
.BR gethostbyname ()

.BR gethostbyaddr ()
ؿŪǡؤΥݥ󥿤֤
Υݥ󥿤ϡθθƤӽФǾ񤭤뤫⤷ʤ
.I hostent
¤Τϥݥ󥿤ޤǤΤǡ¤ΤΥԡǤԽʬǤ롣
- 꿼ԡɬפǤ롣
.LP
glibc2 ˤ
.B gethostbyname2()
⤢ꡢ
.B gethostbyname()
Ʊ褦ư뤬
ϥɥ쥹°륢ɥ쥹եߥ꡼ꤹ뤳ȤǤ롣
.LP
glibc2 ˤϥꥨȥ (reentrant) 
.B gethostbyname_r()

.B gethostbyname2_r()
⤢롣
δؿϡ 0 ֤Ԥ 0 ʳ֤
ߤΤȤθƤӽФη̤ϥɥ쥹
.I ret
ι¤Τ˳Ǽ롣
ƤӽФθ塢Ԥ
.RI * result
 NULL ˤʤꡢ
.RI * result
̤ؤ
­ǡĹ
.I buflen
ΥХåե
.I buf
˳Ǽ롣
(Хåե硢δؿ
.B ERANGE
֤)
ѿ
.I h_errno
ѹʤ顼ֹǼѿΥɥ쥹
.I h_errnop 
Ϥ롣
.PP
POSIX 1003.1-2001 
.B gethostbyaddr()

.B gethostbyname()
ΤΤȤ
.sp
.nf
.BI "struct hostent *getipnodebyaddr (const void *restrict " addr ,
.BI "  socklen_t " len ", int " type ", int *restrict " error_num );
.sp
.BI "struct hostent *getipnodebyname (const char *" name ,
.BI "  int " type ", int " flags ", int *" error_num );
.sp
ƳƤ롣
.SH Ϣ
.BR resolver (3),
.BR hosts (5),
.BR hostname (7),
.BR resolv+ (8),
.BR named (8)