GETIPNODEBYNAME(3) Linux Programmer's Manual GETIPNODEBYNAME(3)
NAME
getipnodebyname, getipnodebyaddr, freehostent - get network hostnames
and addresses
SYNOPSIS
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
struct hostent *getipnodebyname(const char *name, int af,
int flags, int *error_num);
struct hostent *getipnodebyaddr(const void *addr, size_t len,
int af, int *error_num);
void freehostent(struct hostent *ip);
DESCRIPTION
These functions are deprecated (and unavailable in glibc). Use getad-
drinfo(3) and getnameinfo(3) instead.
The getipnodebyname() and getipnodebyaddr() functions return the names
and addresses of a network host. These functions return a pointer to
the following structure:
struct hostent {
char *h_name;
char **h_aliases;
int h_addrtype;
int h_length;
char **h_addr_list;
};
These functions replace the gethostbyname(3) and gethostbyaddr(3) func-
tions, which could access only the IPv4 network address family. The
getipnodebyname() and getipnodebyaddr() functions can access multiple
network address families.
Unlike the gethostby functions, these functions return pointers to dy-
namically allocated memory. The freehostent() function is used to re-
lease the dynamically allocated memory after the caller no longer needs
the hostent structure.
getipnodebyname() arguments
The getipnodebyname() function looks up network addresses for the host
specified by the name argument. The af argument specifies one of the
following values:
AF_INET
The name argument points to a dotted-quad IPv4 address or a name
of an IPv4 network host.
AF_INET6
The name argument points to a hexadecimal IPv6 address or a name
of an IPv6 network host.
The flags argument specifies additional options. More than one option
can be specified by bitwise OR-ing them together. flags should be set
to 0 if no options are desired.
AI_V4MAPPED
This flag is used with AF_INET6 to request a query for IPv4 ad-
dresses instead of IPv6 addresses; the IPv4 addresses will be
mapped to IPv6 addresses.
AI_ALL This flag is used with AI_V4MAPPED to request a query for both
IPv4 and IPv6 addresses. Any IPv4 address found will be mapped
to an IPv6 address.
AI_ADDRCONFIG
This flag is used with 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 AI_V4MAPPED flag.
AI_DEFAULT
This flag is equivalent to (AI_ADDRCONFIG | AI_V4MAPPED).
getipnodebyaddr() arguments
The getipnodebyaddr() function looks up the name of the host whose net-
work address is specified by the addr argument. The af argument speci-
fies one of the following values:
AF_INET
The addr argument points to a struct in_addr and len must be set
to sizeof(struct in_addr).
AF_INET6
The addr argument points to a struct in6_addr and len must be
set to sizeof(struct in6_addr).
RETURN VALUE
NULL is returned if an error occurred, and error_num will contain an
error code from the following list:
HOST_NOT_FOUND
The hostname or network address was not found.
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 in-
formation only, or vice versa.
NO_RECOVERY
The domain name server returned a permanent failure response.
TRY_AGAIN
The domain name server returned a temporary failure response.
You might have better luck next time.
A successful query returns a pointer to a hostent structure that con-
tains the following fields:
h_name This is the official name of this network host.
h_aliases
This is an array of pointers to unofficial aliases for the same
host. The array is terminated by a null pointer.
h_addrtype
This is a copy of the af argument to getipnodebyname() or
getipnodebyaddr(). h_addrtype will always be AF_INET if the af
argument was AF_INET. h_addrtype will always be AF_INET6 if the
af argument was AF_INET6.
h_length
This field will be set to sizeof(struct in_addr) if h_addrtype
is AF_INET, and to sizeof(struct in6_addr) if h_addrtype is
AF_INET6.
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.
CONFORMING TO
RFC 2553.
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 dep-
recated.
SEE ALSO
getaddrinfo(3), getnameinfo(3), inet_ntop(3), inet_pton(3)
COLOPHON
This page is part of release 5.07 of the Linux 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/.
Linux 2017-09-15 GETIPNODEBYNAME(3)