.\" Copyright 2000 Sam Varshavchik <mrsam@courier-mta.com>

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.\" References: RFC 2553

.TH GETIPNODEBYNAME 3 2017-09-15 "Linux" "Linux Programmer's Manual"

.SH NAME

getipnodebyname, getipnodebyaddr, freehostent \- get network

hostnames and addresses

.SH SYNOPSIS

.nf

.B #include <sys/types.h>

.B #include <sys/socket.h>

.B #include <netdb.h>

.PP

.BI "struct hostent *getipnodebyname(const char *" name ", int " af ,

.BI "                                int " flags ", int *" error_num );

.PP

.BI "struct hostent *getipnodebyaddr(const void *" addr ", size_t " len ,

.BI "                                int " af ", int *" "error_num" );

.PP

.BI "void freehostent(struct hostent *" "ip" );

.fi

.SH DESCRIPTION

These functions are deprecated (and unavailable in glibc).

Use

.BR getaddrinfo (3)

and

.BR getnameinfo (3)

instead.

.PP

The

.BR getipnodebyname ()

and

.BR getipnodebyaddr ()

functions return the names and addresses of a network host.

These functions return a pointer to the

following structure:

.PP

.in +4n

.EX

struct hostent {

    char  *h_name;

    char **h_aliases;

    int    h_addrtype;

    int    h_length;

    char **h_addr_list;

};

.EE

.in

.PP

These functions replace the

.BR gethostbyname (3)

and

.BR gethostbyaddr (3)

functions, which could access only the IPv4 network address family.

The

.BR getipnodebyname ()

and

.BR getipnodebyaddr ()

functions can access multiple network address families.

.PP

Unlike the

.B gethostby

functions,

these functions return pointers to dynamically allocated memory.

The

.BR freehostent ()

function is used to release the dynamically allocated memory

after the caller no longer needs the

.I hostent

structure.

.SS getipnodebyname() arguments

The

.BR getipnodebyname ()

function

looks up network addresses for the host

specified by the

.I name

argument.

The

.I af

argument specifies one of the following values:

.TP

.B AF_INET

The

.I name

argument points to a dotted-quad IPv4 address or a name

of an IPv4 network host.

.TP

.B AF_INET6

The

.I name

argument points to a hexadecimal IPv6 address or a name

of an IPv6 network host.

.PP

The

.I flags

argument specifies additional options.

More than one option can be specified by bitwise OR-ing

them together.

.I flags

should be set to 0

if no options are desired.

.TP

.B AI_V4MAPPED

This flag is used with

.B AF_INET6

to request a query for IPv4 addresses instead of

IPv6 addresses; the IPv4 addresses will

be mapped to IPv6 addresses.

.TP

.B AI_ALL

This flag is used with

.B AI_V4MAPPED

to request a query for both IPv4 and IPv6 addresses.

Any IPv4 address found will be mapped to an IPv6 address.

.TP

.B AI_ADDRCONFIG

This flag is used with

.B AF_INET6

to

further request that queries for IPv6 addresses should not be made unless

the system has at least one IPv6 address assigned to a network interface,

and that queries for IPv4 addresses should not be made unless the

system has at least one IPv4 address assigned to a network interface.

This flag may be used by itself or with the

.B AI_V4MAPPED

flag.

.TP

.B AI_DEFAULT

This flag is equivalent to

.BR "(AI_ADDRCONFIG | AI_V4MAPPED)" .

.SS getipnodebyaddr() arguments

The

.BR getipnodebyaddr ()

function

looks up the name of the host whose

network address is

specified by the

.I addr

argument.

The

.I af

argument specifies one of the following values:

.TP

.B AF_INET

The

.I addr

argument points to a

.I struct in_addr

and

.I len

must be set to

.IR "sizeof(struct in_addr)" .

.TP

.B AF_INET6

The

.I addr

argument points to a

.I struct in6_addr

and

.I len

must be set to

.IR "sizeof(struct in6_addr)" .

.SH RETURN VALUE

NULL is returned if an error occurred, and

.I error_num

will contain an error code from the following list:

.TP

.B HOST_NOT_FOUND

The hostname or network address was not found.

.TP

.B NO_ADDRESS

The domain name server recognized the network address or name,

but no answer was returned.

This can happen if the network host has only IPv4 addresses and

a request has been made for IPv6 information only, or vice versa.

.TP

.B NO_RECOVERY

The domain name server returned a permanent failure response.

.TP

.B TRY_AGAIN

The domain name server returned a temporary failure response.

You might have better luck next time.

.PP

A successful query returns a pointer to a

.I hostent

structure that contains the following fields:

.TP

.I h_name

This is the official name of this network host.

.TP

.I h_aliases

This is an array of pointers to unofficial aliases for the same host.

The array is terminated by a null pointer.

.TP

.I h_addrtype

This is a copy of the

.I af

argument to

.BR getipnodebyname ()

or

.BR getipnodebyaddr ().

.I h_addrtype

will always be

.B AF_INET

if the

.I af

argument was

.BR AF_INET .

.I h_addrtype

will always be

.B AF_INET6

if the

.I af

argument was

.BR AF_INET6 .

.TP

.I h_length

This field will be set to

.I sizeof(struct in_addr)

if

.I h_addrtype

is

.BR AF_INET ,

and to

.I sizeof(struct in6_addr)

if

.I h_addrtype

is

.BR AF_INET6 .

.TP

.I h_addr_list

This is an array of one or more pointers to network address structures for the

network host.

The array is terminated by a null pointer.

.SH CONFORMING TO

RFC\ 2553.

.\" Not in POSIX.1-2001.

.SH NOTES

These functions were present in glibc 2.1.91-95, but were

removed again.

Several UNIX-like systems support them, but all

call them deprecated.

.SH SEE ALSO

.BR getaddrinfo (3),

.BR getnameinfo (3),

.BR inet_ntop (3),

.BR inet_pton (3)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.