gethostbyaddr man page on 4.4BSD

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GETHOSTBYNAME(3)	    BSD Programmer's Manual	      GETHOSTBYNAME(3)

     gethostbyname, gethostbyaddr, gethostent, sethostent, endhostent, herror
     - get network host entry

     #include <netdb.h>
     extern int h_errno;

     struct hostent *
     gethostbyname(char *name);

     struct hostent *
     gethostbyaddr(char *addr, int len, int type);

     struct hostent *

     sethostent(int stayopen);


     herror(char *string);

     The gethostbyname() and gethostbyaddr() functions each return a pointer
     to an object with the following structure describing an internet host
     referenced by name or by address, respectively.  This structure contains
     either the information obtained from the name server, named(8),  or bro-
     ken-out fields from a line in /etc/hosts. If the local name server is not
     running these routines do a lookup in /etc/hosts.

     struct  hostent {
	     char    *h_name;	     /* official name of host */
	     char    **h_aliases;    /* alias list */
	     int     h_addrtype;     /* host address type */
	     int     h_length;	     /* length of address */
	     char    **h_addr_list;  /* list of addresses from name server */
     #define h_addr  h_addr_list[0]  /* address, for backward compatibility */

     The members of this structure are:

     h_name	  Official name of the host.

     h_aliases	  A zero terminated array of alternate names for the host.

     h_addrtype	  The type of address being returned; currently always

     h_length	  The length, in bytes, of the address.

     h_addr_list  A zero terminated array of network addresses for the host.
		  Host addresses are returned in network byte order.

     h_addr	  The first address in h_addr_list; this is for backward com-

		  When using the nameserver, gethostbyname() will search for
		  the named host in the current domain and its parents unless
		  the name ends in a dot.  If the name contains no dot, and if
		  the environment variable ``HOSTALIASES'' contains the name
		  of an alias file, the alias file will first be searched for
		  an alias matching the input name.  See hostname(7) for the
		  domain search procedure and the alias file format.

		  The sethostent() function may be used to request the use of
		  a connected TCP socket for queries.  If the stayopen flag is
		  non-zero, this sets the option to send all queries to the
		  name server using TCP and to retain the connection after
		  each call to gethostbyname() or gethostbyaddr().  Otherwise,
		  queries are performed using UDP datagrams.

		  The endhostent() function closes the TCP connection.


     Error return status from gethostbyname() and gethostbyaddr() is indicated
     by return of a null pointer.  The external integer h_errno may then be
     checked to see whether this is a temporary failure or an invalid or un-
     known host.  The routine herror() can be used to print an error message
     describing the failure.  If its argument string is non-NULL, it is print-
     ed, followed by a colon and a space.  The error message is printed with a
     trailing newline.

     The variable h_errno can have the following values:

     HOST_NOT_FOUND  No such host is known.

     TRY_AGAIN	     This is usually a temporary error and means that the lo-
		     cal server did not receive a response from an authorita-
		     tive server.  A retry at some later time may succeed.

     NO_RECOVERY     Some unexpected server failure was encountered.  This is
		     a non-recoverable error.

     NO_DATA	     The requested name is valid but does not have an IP ad-
		     dress; this is not a temporary error.  This means that
		     the name is known to the name server but there is no ad-
		     dress associated with this name.  Another type of request
		     to the name server using this domain name will result in
		     an answer; for example, a mail-forwarder may be regis-
		     tered for this domain.

     resolver(3),  hosts(5),  hostname(7),  named(8)

     The gethostent() function is defined, and sethostent() and endhostent()
     are redefined, when libc(3) is built to use only the routines to lookup
     in /etc/hosts and not the name server.

     The gethostent() function reads the next line of /etc/hosts, opening the
     file if necessary.

     The sethostent() function opens and/or rewinds the file /etc/hosts. If
     the stayopen argument is non-zero, the file will not be closed after each
     call to gethostbyname() or gethostbyaddr().

     The endhostent() function closes the file.

     The herror() function appeared in 4.3BSD. The endhostent(),
     gethostbyaddr(), gethostbyname(), gethostent(), and sethostent() func-
     tions appeared in 4.2BSD.

     These functions use static data storage; if the data is needed for future
     use, it should be copied before any subsequent calls overwrite it.	 Only
     the Internet address format is currently understood.

4.2 Berkeley Distribution      February 27, 1995			     3

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