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32 .\" From: @(#)gethostbyname.3 8.4 (Berkeley) 5/25/95
47 .Nd get network host entry
49 .Fd #include <netdb.h>
50 .Vt extern int h_errno;
52 .Fn gethostbyname "const char *name"
54 .Fn gethostbyname2 "const char *name" "int af"
56 .Fn gethostbyaddr "const char *addr" "int len" "int type"
60 .Fn sethostent "int stayopen"
64 .Fn herror "const char *string"
66 .Fn hstrerror "int err"
74 each return a pointer to an object with the
75 following structure describing an internet host
76 referenced by name or by address, respectively.
77 This structure contains either the information obtained from the name server,
79 or broken-out fields from a line in
81 If the local name server is not running these routines do a lookup in
85 char *h_name; /* official name of host */
86 char **h_aliases; /* alias list */
87 int h_addrtype; /* host address type */
88 int h_length; /* length of address */
89 char **h_addr_list; /* list of addresses from name server */
91 #define h_addr h_addr_list[0] /* address, for backward compatibility */
94 The members of this structure are:
95 .Bl -tag -width h_addr_list
97 Official name of the host.
99 A NULL-terminated array of alternate names for the host.
101 The type of address being returned; usually
104 The length, in bytes, of the address.
106 A NULL-terminated array of network addresses for the host.
107 Host addresses are returned in network byte order.
111 this is for backward compatibility.
114 When using the nameserver,
118 will search for the named host in the current domain and its parents
119 unless the name ends in a dot.
120 If the name contains no dot, and if the environment variable
122 contains the name of an alias file, the alias file will first be searched
123 for an alias matching the input name.
126 for the domain search procedure and the alias file format.
130 function is an evolution of
132 which is intended to allow lookups in address families other than
138 argument must be specified as
140 else the function will return
150 may be used to request the use of a connected
156 this sets the option to send all queries to the name server using
158 and to retain the connection after each call to
163 Otherwise, queries are performed using
176 function writes a message to the diagnostic output consisting of the
179 the constant string ": ", and a message corresponding to the value of
184 function returns a string which is the message text corresponding to the
189 .Bl -tag -width /etc/resolv.conf -compact
191 .It Pa /etc/host.conf
192 .It Pa /etc/resolv.conf
195 Error return status from
200 is indicated by return of a null pointer.
203 may then be checked to see whether this is a temporary failure
204 or an invalid or unknown host.
207 can be used to print an error message describing the failure.
212 it is printed, followed by a colon and a space.
213 The error message is printed with a trailing newline.
217 can have the following values:
218 .Bl -tag -width HOST_NOT_FOUND
219 .It Dv HOST_NOT_FOUND
220 No such host is known.
222 This is usually a temporary error
223 and means that the local server did not receive
224 a response from an authoritative server.
225 A retry at some later time may succeed.
227 Some unexpected server failure was encountered.
228 This is a non-recoverable error.
230 The requested name is valid but does not have an IP address;
231 this is not a temporary error.
232 This means that the name is known to the name server but there is no address
233 associated with this name.
234 Another type of request to the name server using this domain name
235 will result in an answer;
236 for example, a mail-forwarder may be registered for this domain.
254 is built to use only the routines to lookup in
256 and not the name server.
261 reads the next line of
263 opening the file if necessary.
268 opens and/or rewinds the file
272 argument is non-zero,
273 the file will not be closed after each call to
295 functions appeared in
299 function first appeared in bind-4.9.4.
301 These functions use static data storage;
302 if the data is needed for future use, it should be
303 copied before any subsequent calls overwrite it.
305 address format is currently understood.