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getipnodebyname(3)
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getipnodebyname, getipnodebyaddr, freehostent - get network host names
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);
The getipnodebyname(3) and getipnodebyaddr(3) 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 only access the IPv4 network address family. The
getipnodebyname(3) and getipnodebyaddr(3) functions can access multiple
network address families.
Unlike the gethostby functions, these functions return pointers to
dynamically allocated memory. The freehostent(3) function is used to
release the dynamically allocated memory after the caller no longer
needs the hostent structure.
getipnodebyname parameters
The getipnodebyname(3) function looks up network addresses for the host
specified by the name parameter. The af parameter specifies one of the
following values:
AF_INET [Toc] [Back]
The name parameter points to a dotted-quad IPv4 address or a
name of an IPv4 network host.
AF_INET6 [Toc] [Back]
The name parameter points to a hexadecimal IPv6 address or a
name of an IPv6 network host.
The flags parameter specifies additional options. More than one option
can be specified by logically OR-ing them together. flags should be
set to 0 if no options are desired.
AI_V4MAPPED [Toc] [Back]
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 [Toc] [Back]
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_ALL This flag is equivalent to (AI_ADDRCONFIG | AI_V4MAPPED).
getipnodebyaddr parameters
The getipnodebyaddr(3) function looks up the name of the host whose
network address is specified by the addr parameter. The af parameter
specifies one of the following values:
AF_INET [Toc] [Back]
The addr parameter points to a struct in_addr and len must be
set to sizeof(struct in_addr).
AF_INET6 [Toc] [Back]
The addr parameter points to a struct in6_addr and len must be
set to sizeof(struct in6_addr).
A null pointer is returned if an error occurred, and error_num will
contain an error code from the following list:
HOST_NOT_FOUND [Toc] [Back]
The host name or network address was not found.
NO_ADDRESS [Toc] [Back]
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 [Toc] [Back]
The domain name server returned a permanent failure response.
TRY_AGAIN [Toc] [Back]
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 parameter to getipnodebyname(3) or
getipnodebyaddr(3). h_addrtype will always be AF_INET if the af
parameter was AF_INET. h_addrtype will always be AF_INET6 if
the af parameter 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.
getaddrinfo(3), inet_ntop(3), inet_pton(3)
Linux Man Page 2000-12-18 getipnodebyname(3)
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