1GETIPNODEBYNAME(3) Linux Programmer's Manual GETIPNODEBYNAME(3)
2
6 getipnodebyname, getipnodebyaddr, freehostent - get network hostnames
7 and addresses
8
10 #include <sys/types.h>
11 #include <sys/socket.h>
12 #include <netdb.h>
13 struct hostent *getipnodebyname(const char *name, int af,
15 int flags, int *error_num);
16 struct hostent *getipnodebyaddr(const void *addr, size_t len,
17 int af, int *error_num);
18 void freehostent(struct hostent *ip);
19
21 These functions are deprecated (and unavailable in glibc). Use getad‐
22 drinfo(3) and getnameinfo(3) instead.
23 The getipnodebyname() and getipnodebyaddr() functions return the names
25 and addresses of a network host. These functions return a pointer to
26 the following structure:
27 struct hostent {
29 char *h_name;
30 char **h_aliases;
31 int h_addrtype;
32 int h_length;
33 char **h_addr_list;
34 };
35 These functions replace the gethostbyname(3) and gethostbyaddr(3) func‐
37 tions, which could access only the IPv4 network address family. The
38 getipnodebyname() and getipnodebyaddr() functions can access multiple
39 network address families.
40 Unlike the gethostby functions, these functions return pointers to dy‐
42 namically allocated memory. The freehostent() function is used to re‐
43 lease the dynamically allocated memory after the caller no longer needs
44 the hostent structure.
45 getipnodebyname() arguments
47 The getipnodebyname() function looks up network addresses for the host
48 specified by the name argument. The af argument specifies one of the
49 following values:
50 AF_INET
52 The name argument points to a dotted-quad IPv4 address or a name
53 of an IPv4 network host.
54 AF_INET6
56 The name argument points to a hexadecimal IPv6 address or a name
57 of an IPv6 network host.
58 The flags argument specifies additional options. More than one option
60 can be specified by bitwise OR-ing them together. flags should be set
61 to 0 if no options are desired.
62 AI_V4MAPPED
64 This flag is used with AF_INET6 to request a query for IPv4 ad‐
65 dresses instead of IPv6 addresses; the IPv4 addresses will be
66 mapped to IPv6 addresses.
67 AI_ALL This flag is used with AI_V4MAPPED to request a query for both
69 IPv4 and IPv6 addresses. Any IPv4 address found will be mapped
70 to an IPv6 address.
71 AI_ADDRCONFIG
73 This flag is used with AF_INET6 to further request that queries
74 for IPv6 addresses should not be made unless the system has at
75 least one IPv6 address assigned to a network interface, and that
76 queries for IPv4 addresses should not be made unless the system
77 has at least one IPv4 address assigned to a network interface.
78 This flag may be used by itself or with the AI_V4MAPPED flag.
79 AI_DEFAULT
81 This flag is equivalent to (AI_ADDRCONFIG | AI_V4MAPPED).
82 getipnodebyaddr() arguments
84 The getipnodebyaddr() function looks up the name of the host whose net‐
85 work address is specified by the addr argument. The af argument speci‐
86 fies one of the following values:
87 AF_INET
89 The addr argument points to a struct in_addr and len must be set
90 to sizeof(struct in_addr).
91 AF_INET6
93 The addr argument points to a struct in6_addr and len must be
94 set to sizeof(struct in6_addr).
95
97 NULL is returned if an error occurred, and error_num will contain an
98 error code from the following list:
99 HOST_NOT_FOUND
101 The hostname or network address was not found.
102 NO_ADDRESS
104 The domain name server recognized the network address or name,
105 but no answer was returned. This can happen if the network host
106 has only IPv4 addresses and a request has been made for IPv6 in‐
107 formation only, or vice versa.
108 NO_RECOVERY
110 The domain name server returned a permanent failure response.
111 TRY_AGAIN
113 The domain name server returned a temporary failure response.
114 You might have better luck next time.
115 A successful query returns a pointer to a hostent structure that con‐
117 tains the following fields:
118 h_name This is the official name of this network host.
120 h_aliases
122 This is an array of pointers to unofficial aliases for the same
123 host. The array is terminated by a null pointer.
124 h_addrtype
126 This is a copy of the af argument to getipnodebyname() or
127 getipnodebyaddr(). h_addrtype will always be AF_INET if the af
128 argument was AF_INET. h_addrtype will always be AF_INET6 if the
129 af argument was AF_INET6.
130 h_length
132 This field will be set to sizeof(struct in_addr) if h_addrtype
133 is AF_INET, and to sizeof(struct in6_addr) if h_addrtype is
134 AF_INET6.
135 h_addr_list
137 This is an array of one or more pointers to network address
138 structures for the network host. The array is terminated by a
139 null pointer.
140
142 RFC 2553.
143
145 These functions were present in glibc 2.1.91-95, but were removed
146 again. Several UNIX-like systems support them, but all call them dep‐
147 recated.
148
150 getaddrinfo(3), getnameinfo(3), inet_ntop(3), inet_pton(3)
151
153 This page is part of release 5.13 of the Linux man-pages project. A
154 description of the project, information about reporting bugs, and the
155 latest version of this page, can be found at
156 https://www.kernel.org/doc/man-pages/.
157Linux 2021-03-22 GETIPNODEBYNAME(3)