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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
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GETIPNODEBYNAME(3) Linux Programmer's Manual GETIPNODEBYNAME(3)
getipnodebyname, getipnodebyaddr, freehostent - get network hostnames
and addresses
#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);
These functions are deprecated (and unavailable in glibc). Use
getaddrinfo(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)
functions, which could access only the IPv4 network address family.
The getipnodebyname() and getipnodebyaddr() functions can access mul‐
tiple network address families.
Unlike the gethostby functions, these functions return pointers to
dynamically allocated memory. The freehostent() function is used to
release 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
addresses 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 sys‐
tem has at least one IPv6 address assigned to a network inter‐
face, 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
network address is specified by the addr argument. The af argument
specifies 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).
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 information 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
contains 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.
RFC 2553.
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.
getaddrinfo(3), getnameinfo(3), inet_ntop(3), inet_pton(3)
This page is part of release 4.15 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)
Copyright and license for this manual page
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