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32 .\" From: @(#)gethostbyname.3 8.4 (Berkeley) 5/25/95
33 .\" $FreeBSD: src/lib/libc/net/gethostbyname.3,v 1.12.2.7 2001/12/14 18:33:55 ru Exp $
47 .Nd get network host entry
52 .Vt extern int h_errno ;
54 .Fn gethostbyname "const char *name"
56 .Fn gethostbyname2 "const char *name" "int af"
58 .Fn gethostbyaddr "const char *addr" "int len" "int type"
62 .Fn sethostent "int stayopen"
66 .Fn herror "const char *string"
68 .Fn hstrerror "int err"
76 each return a pointer to an object with the
77 following structure describing an internet host
78 referenced by name or by address, respectively.
79 This structure contains either the information obtained from the name server,
81 or broken-out fields from a line in
83 If the local name server is not running these routines do a lookup in
87 char *h_name; /* official name of host */
88 char **h_aliases; /* alias list */
89 int h_addrtype; /* host address type */
90 int h_length; /* length of address */
91 char **h_addr_list; /* list of addresses from name server */
93 #define h_addr h_addr_list[0] /* address, for backward compatibility */
96 The members of this structure are:
97 .Bl -tag -width h_addr_list
99 Official name of the host.
102 .Dv NULL Ns -terminated
103 array of alternate names for the host.
105 The type of address being returned; usually
108 The length, in bytes, of the address.
111 .Dv NULL Ns -terminated
112 array of network addresses for the host.
113 Host addresses are returned in network byte order.
117 this is for backward compatibility.
120 When using the nameserver,
124 will search for the named host in the current domain and its parents
125 unless the name ends in a dot.
126 If the name contains no dot, and if the environment variable
128 contains the name of an alias file, the alias file will first be searched
129 for an alias matching the input name.
132 for the domain search procedure and the alias file format.
136 function is an evolution of
138 which is intended to allow lookups in address families other than
144 argument must be specified as
146 else the function will return
156 may be used to request the use of a connected
162 this sets the option to send all queries to the name server using
164 and to retain the connection after each call to
169 Otherwise, queries are performed using
182 function writes a message to the diagnostic output consisting of the
187 and a message corresponding to the value of
192 function returns a string which is the message text corresponding to the
197 .Bl -tag -width /etc/resolv.conf -compact
199 .It Pa /etc/host.conf
200 .It Pa /etc/resolv.conf
203 Error return status from
208 is indicated by return of a
213 may then be checked to see whether this is a temporary failure
214 or an invalid or unknown host.
217 can be used to print an error message describing the failure.
222 it is printed, followed by a colon and a space.
223 The error message is printed with a trailing newline.
227 can have the following values:
228 .Bl -tag -width HOST_NOT_FOUND
229 .It Dv HOST_NOT_FOUND
230 No such host is known.
232 This is usually a temporary error
233 and means that the local server did not receive
234 a response from an authoritative server.
235 A retry at some later time may succeed.
237 Some unexpected server failure was encountered.
238 This is a non-recoverable error.
240 The requested name is valid but does not have an IP address;
241 this is not a temporary error.
242 This means that the name is known to the name server but there is no address
243 associated with this name.
244 Another type of request to the name server using this domain name
245 will result in an answer;
246 for example, a mail-forwarder may be registered for this domain.
265 is built to use only the routines to lookup in
267 and not the name server.
272 reads the next line of
274 opening the file if necessary.
279 opens and/or rewinds the file
283 argument is non-zero,
284 the file will not be closed after each call to
306 functions appeared in
310 function first appeared in
314 These functions use static data storage;
315 if the data is needed for future use, it should be
316 copied before any subsequent calls overwrite it.
318 address format is currently understood.