1GETIPNODEBYNAME(3)       BSD Library Functions Manual       GETIPNODEBYNAME(3)
2

NAME

4     getipnodebyname, getipnodebyaddr — get network host entry
5     freehostent — free network host entry
6

SYNOPSIS

8     #include <netdb.h>
9
10     struct hostent *
11     getipnodebyname(const char *name, int af, int flags, int *error);
12
13     struct hostent *
14     getipnodebyaddr(const void *addr, size_t len, int af, int *error);
15
16     void
17     freehostent(struct hostent *he);
18

DESCRIPTION

20     Getipnodebyname(), and getipnodebyaddr() each return a pointer to a
21     hostent structure (see below) describing an internet host referenced by
22     name or by address, as the function names indicate.  This structure con‐
23     tains either the information obtained from the name server, or broken-out
24     fields from a line in /etc/hosts.  If the local name server is not run‐
25     ning, these routines do a lookup in /etc/hosts.
26
27           struct  hostent {
28                   char    *h_name;        /* official name of host */
29                   char    **h_aliases;    /* alias list */
30                   int     h_addrtype;     /* host address type */
31                   int     h_length;       /* length of address */
32                   char    **h_addr_list;  /* list of addresses from name server */
33           };
34
35           #define h_addr  h_addr_list[0]  /* address, for backward compatibility */
36
37     The members of this structure are:
38
39     h_name       Official name of the host.
40
41     h_aliases    A zero-terminated array of alternate names for the host.
42
43     h_addrtype   The type of address being returned.
44
45     h_length     The length, in bytes, of the address.
46
47     h_addr_list  A zero-terminated array of network addresses for the host.
48                  Host addresses are returned in network byte order.
49
50     h_addr       The first address in h_addr_list; this is for backward com‐
51                  patibility.
52
53     This structure should be freed after use by calling freehostent().
54
55     When using the nameserver, getiphostbyaddr() will search for the named
56     host in each parent domain given in the “search” directive of
57     resolv.conf(5) unless the name contains a dot (“.”).  If the name con‐
58     tains no dot, and if the environment variable HOSTALIASES contains the
59     name of an alias file, the alias file will first be searched for an alias
60     matching the input name.  See hostname(7) for the domain search procedure
61     and the alias file format.
62
63     Getiphostbyaddr() can be told to look for IPv4 addresses, IPv6 addresses
64     or both IPv4 and IPv6.  If IPv4 addresses only are to be looked up then
65     af should be set to AF_INET, otherwise it should be set to AF_INET6.
66
67     There are three flags that can be set
68
69     AI_V4MAPPED    Return IPv4 addresses if no IPv6 addresses are found.
70                    This flag is ignored unless af is AF_INET6.
71
72     AI_ALL         Return IPv4 addresses as well IPv6 addresses if
73                    AI_V4MAPPED is set.  This flag is ignored unless af is
74                    AF_INET6.
75
76     AI_ADDRCONFIG  Only return addresses of a given type if the system has an
77                    active interface with that type.
78