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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 $
34 .\" $DragonFly: src/lib/libc/net/gethostbyname.3,v 1.3 2006/11/18 00:01:21 swildner Exp $
48 .Nd get network host entry
53 .Vt extern int h_errno ;
55 .Fn gethostbyname "const char *name"
57 .Fn gethostbyname2 "const char *name" "int af"
59 .Fn gethostbyaddr "const char *addr" "int len" "int type"
63 .Fn sethostent "int stayopen"
67 .Fn herror "const char *string"
69 .Fn hstrerror "int err"
77 each return a pointer to an object with the
78 following structure describing an internet host
79 referenced by name or by address, respectively.
80 This structure contains either the information obtained from the name server,
82 or broken-out fields from a line in
84 If the local name server is not running these routines do a lookup in
88 char *h_name; /* official name of host */
89 char **h_aliases; /* alias list */
90 int h_addrtype; /* host address type */
91 int h_length; /* length of address */
92 char **h_addr_list; /* list of addresses from name server */
94 #define h_addr h_addr_list[0] /* address, for backward compatibility */
97 The members of this structure are:
98 .Bl -tag -width h_addr_list
100 Official name of the host.
103 .Dv NULL Ns -terminated
104 array of alternate names for the host.
106 The type of address being returned; usually
109 The length, in bytes, of the address.
112 .Dv NULL Ns -terminated
113 array of network addresses for the host.
114 Host addresses are returned in network byte order.
118 this is for backward compatibility.
121 When using the nameserver,
125 will search for the named host in the current domain and its parents
126 unless the name ends in a dot.
127 If the name contains no dot, and if the environment variable
129 contains the name of an alias file, the alias file will first be searched
130 for an alias matching the input name.
133 for the domain search procedure and the alias file format.
137 function is an evolution of
139 which is intended to allow lookups in address families other than
145 argument must be specified as
147 else the function will return
157 may be used to request the use of a connected
163 this sets the option to send all queries to the name server using
165 and to retain the connection after each call to
170 Otherwise, queries are performed using
183 function writes a message to the diagnostic output consisting of the
188 and a message corresponding to the value of
193 function returns a string which is the message text corresponding to the
198 .Bl -tag -width /etc/resolv.conf -compact
200 .It Pa /etc/host.conf
201 .It Pa /etc/resolv.conf
204 Error return status from
209 is indicated by return of a
214 may then be checked to see whether this is a temporary failure
215 or an invalid or unknown host.
218 can be used to print an error message describing the failure.
223 it is printed, followed by a colon and a space.
224 The error message is printed with a trailing newline.
228 can have the following values:
229 .Bl -tag -width HOST_NOT_FOUND
230 .It Dv HOST_NOT_FOUND
231 No such host is known.
233 This is usually a temporary error
234 and means that the local server did not receive
235 a response from an authoritative server.
236 A retry at some later time may succeed.
238 Some unexpected server failure was encountered.
239 This is a non-recoverable error.
241 The requested name is valid but does not have an IP address;
242 this is not a temporary error.
243 This means that the name is known to the name server but there is no address
244 associated with this name.
245 Another type of request to the name server using this domain name
246 will result in an answer;
247 for example, a mail-forwarder may be registered for this domain.
266 is built to use only the routines to lookup in
268 and not the name server.
273 reads the next line of
275 opening the file if necessary.
280 opens and/or rewinds the file
284 argument is non-zero,
285 the file will not be closed after each call to
307 functions appeared in
311 function first appeared in
315 These functions use static data storage;
316 if the data is needed for future use, it should be
317 copied before any subsequent calls overwrite it.
319 address format is currently understood.